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Divya K, Thangaraj M, Krishna Radhika N. CRISPR/Cas9: an advanced platform for root and tuber crops improvement. Front Genome Ed 2024; 5:1242510. [PMID: 38312197 PMCID: PMC10836405 DOI: 10.3389/fgeed.2023.1242510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 12/26/2023] [Indexed: 02/06/2024] Open
Abstract
Root and tuber crops (RTCs), which include cassava, potato, sweet potato, and yams, principally function as staple crops for a considerable fraction of the world population, in addition to their diverse applications in nutrition, industry, and bioenergy sectors. Even then, RTCs are an underutilized group considering their potential as industrial raw material. Complexities in conventional RTC improvement programs curb the extensive exploitation of the potentials of this group of crop species for food, energy production, value addition, and sustainable development. Now, with the advent of whole-genome sequencing, sufficient sequence data are available for cassava, sweet potato, and potato. These genomic resources provide enormous scope for the improvement of tuber crops, to make them better suited for agronomic and industrial applications. There has been remarkable progress in RTC improvement through the deployment of new strategies like gene editing over the last decade. This review brings out the major areas where CRISPR/Cas technology has improved tuber crops. Strategies for genetic transformation of RTCs with CRISPR/Cas9 constructs and regeneration of edited lines and the bottlenecks encountered in their establishment are also discussed. Certain attributes of tuber crops requiring focus in future research along with putative editing targets are also indicated. Altogether, this review provides a comprehensive account of developments achieved, future lines of research, bottlenecks, and major experimental concerns regarding the establishment of CRISPR/Cas9-based gene editing in RTCs.
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Affiliation(s)
- K Divya
- ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, India
| | | | - N Krishna Radhika
- ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, India
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Ntui VO, Tripathi JN, Kariuki SM, Tripathi L. Cassava molecular genetics and genomics for enhanced resistance to diseases and pests. MOLECULAR PLANT PATHOLOGY 2024; 25:e13402. [PMID: 37933591 PMCID: PMC10788594 DOI: 10.1111/mpp.13402] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 10/16/2023] [Accepted: 10/17/2023] [Indexed: 11/08/2023]
Abstract
Cassava (Manihot esculenta) is one of the most important sources of dietary calories in the tropics, playing a central role in food and economic security for smallholder farmers. Cassava production is highly constrained by several pests and diseases, mostly cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). These diseases cause significant yield losses, affecting food security and the livelihoods of smallholder farmers. Developing resistant varieties is a good way of increasing cassava productivity. Although some levels of resistance have been developed for some of these diseases, there is observed breakdown in resistance for some diseases, such as CMD. A frequent re-evaluation of existing disease resistance traits is required to make sure they are still able to withstand the pressure associated with pest and pathogen evolution. Modern breeding approaches such as genomic-assisted selection in addition to biotechnology techniques like classical genetic engineering or genome editing can accelerate the development of pest- and disease-resistant cassava varieties. This article summarizes current developments and discusses the potential of using molecular genetics and genomics to produce cassava varieties resistant to diseases and pests.
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Affiliation(s)
| | | | | | - Leena Tripathi
- International Institute of Tropical AgricultureNairobiKenya
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3
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Nishiguchi M, Ali ME, Kaya T, Kobayashi K. Plant virus disease control by vaccination and transgenic approaches: Current status and perspective. PLANT RNA VIRUSES 2023:373-424. [DOI: 10.1016/b978-0-323-95339-9.00028-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Chikoti PC, Tembo M. Expansion and impact of cassava brown streak and cassava mosaic diseases in Africa: A review. FRONTIERS IN SUSTAINABLE FOOD SYSTEMS 2022. [DOI: 10.3389/fsufs.2022.1076364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Africa produces over half of global cassava; however, the continent's average yield is below the potential yields achieved under experimental conditions. Many factors contributing to low yield include lack of quality varieties, poor soils, limited access to capital, competition for labor, as well as pests and diseases. Plant diseases are the major biotic constraints to cassava production and have caused considerable food insecurity in Africa. Although there has been some level of disease management which has contributed to the increase in cassava production, the two viral diseases: cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) still claim between 30–40% and upto 70%, respectively of Africa's cassava harvest. Given the importance of the two diseases in Africa, we review the expansion of CBSD and CMD; impacts of the two diseases on food security and how they can be managed. We provide insights in the spread of the two diseases, management efforts, and future directions.
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Voloudakis AE, Kaldis A, Patil BL. RNA-Based Vaccination of Plants for Control of Viruses. Annu Rev Virol 2022; 9:521-548. [PMID: 36173698 DOI: 10.1146/annurev-virology-091919-073708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Plant viruses cause nearly half of the emerging plant diseases worldwide, contributing to 10-15% of crop yield losses. Control of plant viral diseases is mainly accomplished by extensive chemical applications targeting the vectors (i.e., insects, nematodes, fungi) transmitting these viruses. However, these chemicals have a significant negative effect on human health and the environment. RNA interference is an endogenous, cellular, sequence-specific RNA degradation mechanism in eukaryotes induced by double-stranded RNA molecules that has been exploited as an antiviral strategy through transgenesis. Because genetically modified crop plants are not accepted for cultivation in several countries globally, there is an urgent demand for alternative strategies. This has boosted research on exogenous application of the RNA-based biopesticides that are shown to exhibit significant protective effect against viral infections. Such environment-friendly and efficacious antiviral agents for crop protection will contribute to global food security, without adverse effects on human health.
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Affiliation(s)
- Andreas E Voloudakis
- Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece;
| | - Athanasios Kaldis
- Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece;
| | - Basavaprabhu L Patil
- Division of Basic Sciences, ICAR-Indian Institute of Horticultural Research, Bengaluru, Karnataka State, India
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Bocos-Asenjo IT, Niño-Sánchez J, Ginésy M, Diez JJ. New Insights on the Integrated Management of Plant Diseases by RNA Strategies: Mycoviruses and RNA Interference. Int J Mol Sci 2022; 23:9236. [PMID: 36012499 PMCID: PMC9409477 DOI: 10.3390/ijms23169236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 08/09/2022] [Accepted: 08/15/2022] [Indexed: 11/25/2022] Open
Abstract
RNA-based strategies for plant disease management offer an attractive alternative to agrochemicals that negatively impact human and ecosystem health and lead to pathogen resistance. There has been recent interest in using mycoviruses for fungal disease control after it was discovered that some cause hypovirulence in fungal pathogens, which refers to a decline in the ability of a pathogen to cause disease. Cryphonectria parasitica, the causal agent of chestnut blight, has set an ideal model of management through the release of hypovirulent strains. However, mycovirus-based management of plant diseases is still restricted by limited approaches to search for viruses causing hypovirulence and the lack of protocols allowing effective and systemic virus infection in pathogens. RNA interference (RNAi), the eukaryotic cell system that recognizes RNA sequences and specifically degrades them, represents a promising. RNA-based disease management method. The natural occurrence of cross-kingdom RNAi provides a basis for host-induced gene silencing, while the ability of most pathogens to uptake exogenous small RNAs enables the use of spray-induced gene silencing techniques. This review describes the mechanisms behind and the potential of two RNA-based strategies, mycoviruses and RNAi, for plant disease management. Successful applications are discussed, as well as the research gaps and limitations that remain to be addressed.
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Affiliation(s)
- Irene Teresa Bocos-Asenjo
- Department of Plant Production and Forest Resources, University of Valladolid, 34004 Palencia, Spain
- iuFOR-Sustainable Forest Management Research Institute, University of Valladolid-INIA, 34004 Palencia, Spain
| | - Jonatan Niño-Sánchez
- Department of Plant Production and Forest Resources, University of Valladolid, 34004 Palencia, Spain
- iuFOR-Sustainable Forest Management Research Institute, University of Valladolid-INIA, 34004 Palencia, Spain
| | - Mireille Ginésy
- Department of Plant Production and Forest Resources, University of Valladolid, 34004 Palencia, Spain
- iuFOR-Sustainable Forest Management Research Institute, University of Valladolid-INIA, 34004 Palencia, Spain
| | - Julio Javier Diez
- Department of Plant Production and Forest Resources, University of Valladolid, 34004 Palencia, Spain
- iuFOR-Sustainable Forest Management Research Institute, University of Valladolid-INIA, 34004 Palencia, Spain
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Comparative evaluation of resistance to potato virus Y (PVY) in three different RNAi-based transgenic potato plants. Transgenic Res 2022; 31:313-323. [PMID: 35262867 DOI: 10.1007/s11248-022-00302-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 02/24/2022] [Indexed: 10/18/2022]
Abstract
Small interfering RNAs (siRNAs) produced from template double-stranded RNAs (dsRNAs) can activate the immune system in transgenic plants by detecting virus transcripts to degrade. In the present study, an RNA interference (RNAi) gene silencing mechanism was used for the development of transgenic potato plants resistant to potato virus Y (PVY), the most harmful viral disease. Three RNAi gene constructs were designed based on the coat protein (CP) and the untranslated region parts of the PVY genome, being highly conserved among all strains of the PVY viruses. Transgenic potato plants were generated using Agrobacterium containing pCAMRNAiCP, pCAMRNAiUR, and pCAMRNAiCP-UR constructs. The transgene insertions were confirmed by molecular analysis containing polymerase chain reaction (PCR) and southern blotting. The resistance of transgenic plants to PVY virus was determined using bioassay and evaluating the amount of viral RNA in plants by RT-PCR, dot blotting of PVY coating protein, and enzyme-linked immunosorbent assay (ELISA). Bioassay analysis revealed that more than 67% of transgenic potato plants were resistant to PVY compared with the non-transgenic plants, which showed viral disease symptoms. No phenotypic abnormalities were observed in transgenic plants. Out of six lines in southern blot analysis, four lines had one copy of the transgene and two lines had two copies of the target genes. No correlation was detected between the copy number of the genes and the resistance level of the plant to PVY. Transgenic lines obtained from all three constructs indicated more or less similar levels of resistance against viral infection; however, CP-UR lines exhibited relatively high resistance followed by CP and UR expressing lines, respectively. Meanwhile, some lines showed a delay in symptoms 35 days after infection which were classified as susceptible.
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Mero HR, Lyantagaye SL, Bongcam-Rudloff E. Cassava Brown Streak Viruses express second 6-kilodalton (6K2) protein with varied polarity and three dimensional (3D) structures: Basis for trait discrepancy between the virus species. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2022; 98:105219. [PMID: 35066168 DOI: 10.1016/j.meegid.2022.105219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 12/15/2021] [Accepted: 01/17/2022] [Indexed: 10/19/2022]
Abstract
Cassava Brown Streak Virus (CBSV) and Ugandan Cassava Brown Streak Virus (UCBSV) are the two among six virus species speculated to cause the most catastrophic Brown Streak Disease of Cassava (CBSD) in Africa and Asia. Cassava Brown Streak Virus (CBSV) is hard to breed resistance for compared to Ugandan Cassava Brown Streak Virus (UCBSV) species. This is exemplified by incidences of CBSV species rather than UCBSV species in elite breeding line, KBH 2006/0026 at Bagamoyo, Tanzania. It is not yet understood as to why CBSV species could breakdown CBSD-resistance in the KBH 2006/0026 unlike the UCBSV species. This marks the first in silico study conducted to understand molecular basis for the trait discrepancy between CBSV and UCBSV species from structural biology view point. Following ab initio modelling and analysis of physical-chemical properties of second 6-kilodalton (6K2) protein encoded by CBSV and UCBSV species, using ROBETTA server and Protein Parameters tool, respectively we report that; three dimensional (3D) structures and polarity of the protein differs significantly between the two virus species. (95% and 5%) and (85% and 15%) strains of 20 CBSV and 20 UCBSV species respectively, expressed the protein in homo-trimeric and homo-tetrameric forms, correspondingly. 95% and 85% of studied strain population of the two virus species expressed hydrophilic and hydrophobic 6K2, respectively. Based on findings of the curent study, we hypothesize that; (i) The hydrophilic 6K2 expressed by the CBSV species, favour its faster systemic movement via vascular tissues of cassava host and hence result into higher tissue titres than the UCBSV species encoding hydrophobic form of the protein. t and (ii) The hydrophilic 6K2 expressed byCBSV species have additional interaction advantage with Nuclear Inclusion b protease domain (NIb) and Viral genome-linked protein (VPg), components of Virus Replication Complex (VRC) and hence contributing to faster replication of viral genome than the hydrophobic 6K2 expressed by the UCBSV species. Experimental studies are needed to resolve the 3D structures of the 6K2, VPg and NIb and comprehend complex molecular interactions between them. We suggest that, the 6K2 gene should be targeted for improvement of RNA interference (RNAi)-directed transgenesis of virus-resistant cassava as a more effective way to control the CBSD besides breeding.
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Affiliation(s)
- Herieth Rhodes Mero
- University of Dar es Salaam, Mkwawa University College of Education (MUCE), P. O. Box 2513, Iringa, Tanzania; Swedish University of Agricultural Sciences (SLU), SLU-Global Bioinformatics Centre, Department of Animal Breeding and Genetics, P. 0. BOX 7054, 750 07 Uppsala, Sweden.
| | | | - Erik Bongcam-Rudloff
- Swedish University of Agricultural Sciences (SLU), SLU-Global Bioinformatics Centre, Department of Animal Breeding and Genetics, P. 0. BOX 7054, 750 07 Uppsala, Sweden
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Kaur R, Choudhury A, Chauhan S, Ghosh A, Tiwari R, Rajam MV. RNA interference and crop protection against biotic stresses. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2021; 27:2357-2377. [PMID: 34744371 PMCID: PMC8526635 DOI: 10.1007/s12298-021-01064-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 08/14/2021] [Accepted: 09/07/2021] [Indexed: 05/26/2023]
Abstract
RNA interference (RNAi) is a universal phenomenon of RNA silencing or gene silencing with broader implications in important physiological and developmental processes of most eukaryotes, including plants. Small RNA (sRNA) are the critical drivers of the RNAi machinery that ensures down-regulation of the target genes in a homology-dependent manner and includes small-interfering RNAs (siRNAs) and micro RNAs (miRNAs). Plant researchers across the globe have exploited the powerful technique of RNAi to execute targeted suppression of desired genes in important crop plants, with an intent to improve crop protection against pathogens and pests for sustainable crop production. Biotic stresses cause severe losses to the agricultural productivity leading to food insecurity for future generations. RNAi has majorly contributed towards the development of designer crops that are resilient towards the various biotic stresses such as viruses, bacteria, fungi, insect pests, and nematodes. This review summarizes the recent progress made in the RNAi-mediated strategies against these biotic stresses, along with new insights on the future directions in research involving RNAi for crop protection.
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Affiliation(s)
- Ranjeet Kaur
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
| | - Aparajita Choudhury
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
| | - Sambhavana Chauhan
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
| | - Arundhati Ghosh
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
| | - Ruby Tiwari
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
| | - Manchikatla Venkat Rajam
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021 India
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Mero HR, Lyantagaye SL, Bongcam-Rudloff E. Why has permanent control of cassava brown streak disease in Sub-Saharan Africa remained a dream since the 1930s? INFECTION GENETICS AND EVOLUTION 2021; 94:105001. [PMID: 34271188 DOI: 10.1016/j.meegid.2021.105001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/07/2021] [Accepted: 07/11/2021] [Indexed: 10/20/2022]
Abstract
Effective control of ipomoviruses that cause cassava brown streak disease (CBSD) in Africa has remained problematic despite eight remarkable decades (1930-2021) of research efforts. Molecular mechanisms underlying resistance breakdown in genetically improved cassava are still unknown. The vast genetic diversity of cassava brown streak viruses, which is crucial for the improvement of routine reverse transcription polymerase chain reaction (RT-qPCR) assays in CBSD-endemic regions of Africa, is controversial and underrepresented. From a molecular epidemiology viewpoint, this review discusses the reasons for why permanent control of CBSD is difficult in the modern era, even with the presence of diverse in silico and omics tools, recombinant DNA, and high throughput next-generation sequencing technologies. Following an extensive nucleotide data search in the National Centre for Biotechnology Information (NCBI) database and a literature review in PubMed and Scopus, we report that genomic data of 87.62% (474/541) strains of cassava brown streak virus are missing due to poor sequencing capacity in Africa. The evolution dynamics of viral virulence and pathogenicity has not yet been fully explored from the available 67 (12.38%) genomic sequences, owing to poor bioinformatics capacity. Tanzania and Zambia have the highest and lowest disease inoculum pressure, correspondingly. Knowledge gaps in molecular biology and the overall molecular pathogenesis of CBSD viruses impede effective disease control in Africa. Recommendations for possible solutions to the research questions, controversies, and hypotheses raised in this study serve as a roadmap for the invention of more effective CBSD control methods.
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Affiliation(s)
- Herieth Rhodes Mero
- University of Dar es Salaam, Mkwawa University College of Education (MUCE), Department of Biological Sciences, P. O. BOX 2513, Iringa, Tanzania.; Swedish University of Agricultural Sciences (SLU), SLU-Global Bioinformatics Centre, Department of Animal Breeding and Genetics, PO Box 7054 750 07, Uppsala, Sweden.
| | | | - Erik Bongcam-Rudloff
- Swedish University of Agricultural Sciences (SLU), SLU-Global Bioinformatics Centre, Department of Animal Breeding and Genetics, PO Box 7054 750 07, Uppsala, Sweden
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Ozimati AA, Esuma W, Alicai T, Jannink JL, Egesi C, Kawuki R. Outlook of Cassava Brown Streak Disease Assessment: Perspectives of the Screening Methods of Breeders and Pathologists. FRONTIERS IN PLANT SCIENCE 2021; 12:648436. [PMID: 34290720 PMCID: PMC8288188 DOI: 10.3389/fpls.2021.648436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 05/31/2021] [Indexed: 06/13/2023]
Abstract
Cassava production and productivity in Eastern, Central, and Southern Africa are ravaged by cassava brown streak disease (CBSD), causing yield losses of up to 100% when susceptible varieties are grown. Efforts to develop CBSD-resistant clones are underway. However, the methods for screening CBSD resistance currently vary between breeders and pathologists, with the limited empirical data to support their choices. In this study, we used the empirical CBSD foliar and root necrosis data from two breeding populations, termed cycle zero (C0) and cycle one (C1), to assess and compare the effectiveness of the CBSD screening methods of breeders vs. pathologists. On the one hand, the estimates of broad-sense heritability (H 2) for the CBSD root necrosis assessment of breeder ranged from 0.15 to 0.87, while for the assessment method of pathologists, H 2 varied from 0.00 to 0.71 in C0 clones. On the other hand, the marker-based heritability estimates (h 2) for C0 ranged from 0.00 to 0.70 for the assessment method of breeders and from 0.00 to 0.63 for the assessment method of pathologists. For cycle one (C1) population, where both foliar and root necrosis data were analyzed for clones assessed at clonal evaluation trials (CETs) and advanced yield trials (AYTs), H 2 varied from 0.10 to 0.59 for the assessment method of breeders, while the H 2 values ranged from 0.09 to 0.35 for the CBSD computation method of pathologists. In general, higher correlations were recorded for foliar severity from the assessment method of breeders (r = 0.4, p ≤ 0.01 for CBSD3s and r = 0.37, p ≤ 0.01 for CBSD6s) in C1 clones evaluated at both clonal and advanced breeding stages than from the approach of pathologists. Ranking of top 10 C1 clones by their indexed best linear unbiased predictors (BLUPs) for CBSD foliar and root necrosis showed four overlapping clones between clonal and advanced selection stages for the method of breeders; meanwhile, only a clone featured in both clonal and advanced selection stages from the CBSD assessment method of pathologists. Overall, the CBSD assessment method of breeders was more effective than the assessment method of pathologists, and thus, it justifies its continued use in CBSD resistance breeding.
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Affiliation(s)
- Alfred A. Ozimati
- Root Crops Program, National Crops Resources Research Institute (NaCRRI), Kampala, Uganda
| | - Williams Esuma
- Root Crops Program, National Crops Resources Research Institute (NaCRRI), Kampala, Uganda
| | - Titus Alicai
- Root Crops Program, National Crops Resources Research Institute (NaCRRI), Kampala, Uganda
| | - Jean-Luc Jannink
- College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, United States
| | - Chiedozie Egesi
- College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, United States
| | - Robert Kawuki
- Root Crops Program, National Crops Resources Research Institute (NaCRRI), Kampala, Uganda
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Abstract
Root rot diseases remain a major global threat to the productivity of agricultural crops. They are usually caused by more than one type of pathogen and are thus often referred to as a root rot complex. Fungal and oomycete species are the predominant participants in the complex, while bacteria and viruses are also known to cause root rot. Incorporating genetic resistance in cultivated crops is considered the most efficient and sustainable solution to counter root rot, however, resistance is often quantitative in nature. Several genetics studies in various crops have identified the quantitative trait loci associated with resistance. With access to whole genome sequences, the identity of the genes within the reported loci is becoming available. Several of the identified genes have been implicated in pathogen responses. However, it is becoming apparent that at the molecular level, each pathogen engages a unique set of proteins to either infest the host successfully or be defeated or contained in attempting so. In this review, a comprehensive summary of the genes and the potential mechanisms underlying resistance or susceptibility against the most investigated root rots of important agricultural crops is presented.
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Kapazoglou A, Tani E, Avramidou EV, Abraham EM, Gerakari M, Megariti S, Doupis G, Doulis AG. Epigenetic Changes and Transcriptional Reprogramming Upon Woody Plant Grafting for Crop Sustainability in a Changing Environment. FRONTIERS IN PLANT SCIENCE 2021; 11:613004. [PMID: 33510757 PMCID: PMC7835530 DOI: 10.3389/fpls.2020.613004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/10/2020] [Indexed: 05/07/2023]
Abstract
Plant grafting is an ancient agricultural practice widely employed in crops such as woody fruit trees, grapes, and vegetables, in order to improve plant performance. Successful grafting requires the interaction of compatible scion and rootstock genotypes. This involves an intricate network of molecular mechanisms operating at the graft junction and associated with the development and the physiology of the scion, ultimately leading to improved agricultural characteristics such as fruit quality and increased tolerance/resistance to abiotic and biotic factors. Bidirectional transfer of molecular signals such as hormones, nutrients, proteins, and nucleic acids from the rootstock to the scion and vice versa have been well documented. In recent years, studies on rootstock-scion interactions have proposed the existence of an epigenetic component in grafting reactions. Epigenetic changes such as DNA methylation, histone modification, and the action of small RNA molecules are known to modulate chromatin architecture, leading to gene expression changes and impacting cellular function. Mobile small RNAs (siRNAs) migrating across the graft union from the rootstock to the scion and vice versa mediate modifications in the DNA methylation pattern of the recipient partner, leading to altered chromatin structure and transcriptional reprogramming. Moreover, graft-induced DNA methylation changes and gene expression shifts in the scion have been associated with variations in graft performance. If these changes are heritable they can lead to stably altered phenotypes and affect important agricultural traits, making grafting an alternative to breeding for the production of superior plants with improved traits. However, most reviews on the molecular mechanisms underlying this process comprise studies related to vegetable grafting. In this review we will provide a comprehensive presentation of the current knowledge on the epigenetic changes and transcriptional reprogramming associated with the rootstock-scion interaction focusing on woody plant species, including the recent findings arising from the employment of advanced-omics technologies as well as transgrafting methodologies and their potential exploitation for generating superior quality grafts in woody species. Furthermore, will discuss graft-induced heritable epigenetic changes leading to novel plant phenotypes and their implication to woody crop improvement for yield, quality, and stress resilience, within the context of climate change.
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Affiliation(s)
- Aliki Kapazoglou
- Department of Vitis, Institute of Olive Tree, Subtropical Crops and Viticulture (IOSV), Hellenic Agricultural Organization-Demeter (HAO-Demeter), Athens, Greece
| | - Eleni Tani
- Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece
| | - Evangelia V. Avramidou
- Laboratory of Forest Genetics and Biotechnology, Institute of Mediterranean Forest Ecosystems, Athens, Hellenic Agricultural Organization-Demeter (HAO-Demeter), Athens, Greece
| | - Eleni M. Abraham
- Laboratory of Range Science, Faculty of Forestry and Natural Environment, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Maria Gerakari
- Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece
| | - Stamatia Megariti
- Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece
| | - Georgios Doupis
- Department of Viticulture, Vegetable Crops, Floriculture and Plant Protection, Institute of Olive Tree, Sub-Tropical Crops and Viticulture, Hellenic Agricultural Organization-Demeter (HAO-Demeter) (fr. NAGREF), Heraklion, Greece
| | - Andreas G. Doulis
- Department of Viticulture, Vegetable Crops, Floriculture and Plant Protection, Institute of Olive Tree, Sub-Tropical Crops and Viticulture, Hellenic Agricultural Organization-Demeter (HAO-Demeter) (fr. NAGREF), Heraklion, Greece
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Jekayinoluwa T, Tripathi L, Tripathi JN, Ntui VO, Obiero G, Muge E, Dale J. RNAi technology for management of banana bunchy top disease. Food Energy Secur 2020; 9:e247. [PMID: 33381301 PMCID: PMC7757248 DOI: 10.1002/fes3.247] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 08/13/2020] [Accepted: 08/16/2020] [Indexed: 12/15/2022] Open
Abstract
Banana bunchy top disease (BBTD) is one of the world's most destructive viral diseases of banana and plantain, causing up to 100% yield loss in severe cases. The disease is vectored by banana aphids (Pentalonia nigronervosa) and carried long distances through the movement of infected plant materials. The banana aphids harboring banana bunchy top virus (BBTV) present in banana producing regions are the sole vector and the most efficient method of transmitting the virus to the healthy plants. Controlling the spread of BBTD has been very challenging since no known banana germplasm is immune to BBTV. The disease can be managed with the use of virus-free planting material and roguing. However, once BBTD is established in the field, it is very difficult to eradicate or manage it. Therefore, a more sustainable way of controlling the disease is developing host plant resistance against the virus and the vector. Biotechnological strategies via RNA interference (RNAi) could be used to target the banana aphid as well as BBTV to reduce virus-associated yield losses of banana and plantain, which feed over 500 million people around the world. This review discusses the status of BBTD and perspectives on effective RNAi technologies for controlling BBTV and the vector, banana aphid, transmitting the virus as sustainable management of the disease.
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Affiliation(s)
- Temitope Jekayinoluwa
- International Institute of Tropical AgricultureNairobiKenya
- Center for Biotechnology and BioinformaticsUniversity of NairobiNairobiKenya
| | - Leena Tripathi
- International Institute of Tropical AgricultureNairobiKenya
| | | | | | - George Obiero
- Center for Biotechnology and BioinformaticsUniversity of NairobiNairobiKenya
| | - Edward Muge
- Department of BiochemistryUniversity of NairobiNairobiKenya
| | - James Dale
- Queensland University of TechnologyBrisbaneQldAustralia
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15
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Shirima RR, Legg JP, Maeda DG, Tumwegamire S, Mkamilo G, Mtunda K, Kulembeka H, Ndyetabula I, Kimata BP, Matondo DG, Ceasar G, Mushi E, Sichalwe K, Kanju E. Genotype by environment cultivar evaluation for cassava brown streak disease resistance in Tanzania. Virus Res 2020; 286:198017. [PMID: 32461191 PMCID: PMC7450270 DOI: 10.1016/j.virusres.2020.198017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/17/2020] [Accepted: 05/05/2020] [Indexed: 10/25/2022]
Abstract
Cassava brown steak disease (CBSD), caused by Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), is the most important biotic constraint to cassava production in East and Central Africa. Concerted efforts are required to prevent further spread into West Africa as well as to reduce losses in areas already affected. The study reported here was part of a five-country (Kenya, Malawi, Mozambique, Tanzania and Uganda) programme that aimed to identify superior cassava cultivars resistant to CBSD and to disseminate them widely in the region. Seventeen tissue-cultured and virus-tested cultivars were evaluated in Tanzania across nine sites with diverse CBSD inoculum conditions. Experiments were planted using an alpha-lattice design and assessments were made of surrounding inoculum pressure, CBSD foliar and root incidence and root yield at harvest. There were large differences in CBSD infection between sites, with greatest spread recorded from the north-western Lake (Victoria) zone. Differences were driven by Bemisia tabaci whitefly vector abundance and CBSD inoculum pressure. Both CBSV and UCBSV were almost equally represented in cassava fields surrounding experimental plots, although CBSV predominated in the north-west whilst UCBSV was more frequent in coastal and southern sites. However, the incidence of CBSV was much greater than that of UCBSV in initially virus-free experimental plots, suggesting that CBSV is more virulent. Cultivars could be categorised into three groups based on the degree of CBSD symptom expression in shoots and roots. The seven cultivars (F10_30R2, Eyope, Mkumba, Mkuranga1, Narocass1, Nase3 and Orera) in the most resistant category each had shoot and root incidences of less than 20%. Fresh root yield differed between sites and cultivars, but there was no genotype by environment interaction for this trait, probably attributable to the large fertility and soil moisture differences between sites. Susceptible cultivars and the local check performed well in the absence of CBSD pressure, highlighting the importance of exploiting quality and yield traits of local landraces in breeding programmes. Overall, our results emphasized the importance of applying a balanced strategy for CBSD management. This should use both improved and local germplasm resources to generate high yielding cultivars for specific end-user traits, and combine the deployment of improved cultivars with phytosanitary control measures including the use of healthy planting material and planting during periods of reduced CBSD infection.
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Affiliation(s)
| | | | | | | | | | - Kiddo Mtunda
- Tanzania Agricultural Research Institute, Tumbi, Tanzania
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16
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Screening for Resistance in Farmer-Preferred Cassava Cultivars from Ghana to a Mixed Infection of CBSV and UCBSV. PLANTS 2020; 9:plants9081026. [PMID: 32823622 PMCID: PMC7465500 DOI: 10.3390/plants9081026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/06/2020] [Accepted: 08/10/2020] [Indexed: 12/02/2022]
Abstract
Cassava brown streak disease (CBSD) caused by the Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) is a threat to cassava production in Africa. The potential spread of CBSD into West Africa is a cause for concern, therefore screening for resistance in farmer-preferred genotypes is crucial for effective control and management. We multiplied a selection of eleven cassava cultivars grown by farmers in Ghana to test their response to a mixed infection of CBSV (TAZ-DES-01) and UCBSV (TAZ-DES-02) isolates using a stringent top-cleft graft inoculation method. Virus titers were quantified in the inoculated scions and cuttings propagated from the inoculated scions to assess virus accumulation and recovery. All cultivars were susceptible to the mixed infection although their response and symptom development varied. In the propagated infected scions, CBSV accumulated at higher titers in leaves of eight of the eleven cultivars. Visual scoring of storage roots from six-month-old virus-inoculated plants revealed the absence of CBSD-associated necrosis symptoms and detectable titers of CBSVs in the cultivar, IFAD. Although all eleven cultivars supported the replication of CBSV and UCBSV in their leaves, the absence of virus replication and CBSD-associated symptoms in the roots of some cultivars could be used as criteria to rapidly advance durable CBSD tolerance using breeding and genetic engineering approaches.
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17
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Rodrigues TB, Petrick JS. Safety Considerations for Humans and Other Vertebrates Regarding Agricultural Uses of Externally Applied RNA Molecules. FRONTIERS IN PLANT SCIENCE 2020; 11:407. [PMID: 32391029 PMCID: PMC7191066 DOI: 10.3389/fpls.2020.00407] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 03/20/2020] [Indexed: 05/13/2023]
Abstract
The potential of double-stranded RNAs (dsRNAs) for use as topical biopesticides in agriculture was recently discussed during an OECD (Organisation for Economic Co-operation and Development) Conference on RNA interference (RNAi)-based pesticides. Several topics were presented and these covered different aspects of RNAi technology, its application, and its potential effects on target and non-target organisms (including both mammals and non-mammals). This review presents information relating to RNAi mechanisms in vertebrates, the history of safe RNA consumption, the biological barriers that contribute to the safety of its consumption, and effects related to humans and other vertebrates as discussed during the conference. We also review literature related to vertebrates exposed to RNA molecules and further consider human health safety assessments of RNAi-based biopesticides. This includes possible routes of exposure other than the ingestion of potential residual material in food and water (such as dermal and inhalation exposures during application in the field), the implications of different types of formulations and RNA structures, and the possibility of non-specific effects such as the activation of the innate immune system or saturation of the RNAi machinery.
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Affiliation(s)
| | - Jay S. Petrick
- Bayer Crop Science, Chesterfield, MO, United States
- *Correspondence: Jay S. Petrick,
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18
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Abstract
Manihot esculenta Crantz (cassava) is a food crop originating from South America grown primarily for its starchy storage roots. Today, cassava is grown in the tropics of South America, Africa, and Asia with an estimated 800 million people relying on it as a staple source of calories. In parts of sub-Saharan Africa, cassava is particularly crucial for food security. Cassava root starch also has use in the pharmaceutical, textile, paper, and biofuel industries. Cassava has seen strong demand since 2000 and production has increased consistently year-over-year, but potential yields are hampered by susceptibility to biotic and abiotic stresses. In particular, bacterial and viral diseases can cause severe yield losses. Of note are cassava bacterial blight (CBB), cassava mosaic disease (CMD), and cassava brown streak disease (CBSD), all of which can cause catastrophic losses for growers. In this article, we provide an overview of the major microbial diseases of cassava, discuss current and potential future efforts to engineer new sources of resistance, and conclude with a discussion of the regulatory hurdles that face biotechnology.
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Affiliation(s)
- Z J Daniel Lin
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA
| | - Nigel J Taylor
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA
| | - Rebecca Bart
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA
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19
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Catch Me If You Can! RNA Silencing-Based Improvement of Antiviral Plant Immunity. Viruses 2019; 11:v11070673. [PMID: 31340474 PMCID: PMC6669615 DOI: 10.3390/v11070673] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 07/11/2019] [Accepted: 07/17/2019] [Indexed: 12/27/2022] Open
Abstract
Viruses are obligate parasites which cause a range of severe plant diseases that affect farm productivity around the world, resulting in immense annual losses of yield. Therefore, control of viral pathogens continues to be an agronomic and scientific challenge requiring innovative and ground-breaking strategies to meet the demands of a growing world population. Over the last decade, RNA silencing has been employed to develop plants with an improved resistance to biotic stresses based on their function to provide protection from invasion by foreign nucleic acids, such as viruses. This natural phenomenon can be exploited to control agronomically relevant plant diseases. Recent evidence argues that this biotechnological method, called host-induced gene silencing, is effective against sucking insects, nematodes, and pathogenic fungi, as well as bacteria and viruses on their plant hosts. Here, we review recent studies which reveal the enormous potential that RNA-silencing strategies hold for providing an environmentally friendly mechanism to protect crop plants from viral diseases.
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20
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Saggaf MH, Ndunguru J, Tairo F, Sseruwagi P, Ascencio-Ibáñez JT, Kilalo D, Miano DW. Immunohistochemical localization of Cassava brown streak virus and its morphological effect on cassava leaves. PHYSIOLOGICAL AND MOLECULAR PLANT PATHOLOGY 2019; 105:67-76. [PMID: 31007375 PMCID: PMC6472608 DOI: 10.1016/j.pmpp.2018.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/26/2018] [Accepted: 06/08/2018] [Indexed: 05/24/2023]
Abstract
The localization of Cassava brown streak virus (CBSV) in cassava (Manihot esculenta) leaf tissues was determined and cellular morphological changes in CBSV-infected tissues were evaluated. CBSV-symptomatic leaves were screened with CBSV-specific primers using reverse-transcriptase polymerase chain reaction. Immunohistochemical reactions showed precipitation in CBSV-infected but not CBSV-free tissues, demonstrating successful localization of CBSV. Microscopic inspection showed significantly larger (P < 0.001) midribs in CBSV-infected compared with control (uninfected) leaves. Viral accumulation occurred in middle and lower but rarely in young upper leaves. This immunohistochemical method for virus localization will be invaluable for efficient screening of CBSV and for breeding resistant cassava.
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Affiliation(s)
- Maliha H. Saggaf
- Mikocheni Agricultural Research Institute, P.O. Box, 6226, Dar-es-Salaam, Tanzania
| | - Joseph Ndunguru
- Mikocheni Agricultural Research Institute, P.O. Box, 6226, Dar-es-Salaam, Tanzania
| | - Fred Tairo
- Mikocheni Agricultural Research Institute, P.O. Box, 6226, Dar-es-Salaam, Tanzania
| | - Peter Sseruwagi
- Mikocheni Agricultural Research Institute, P.O. Box, 6226, Dar-es-Salaam, Tanzania
| | | | - Dora Kilalo
- University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
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21
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Sharma S, Kumar G, Dasgupta I. Simultaneous resistance against the two viruses causing rice tungro disease using RNA interference. Virus Res 2018; 255:157-164. [PMID: 30031045 DOI: 10.1016/j.virusres.2018.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/14/2018] [Accepted: 07/17/2018] [Indexed: 02/09/2023]
Abstract
Rice tungro is the most important viral disease affecting rice in South and Southeast Asia, caused by two viruses rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV). Transgenic resistance using RNA-interference (RNAi) has been reported individually against RTBV and RTSV earlier. Here we report the development of transgenic rice plants expressing RNAi against both RTBV and RTSV simultaneously. A DNA construct carrying 300 bp of RTBV DNA and 300 bp of RTSV cDNA were cloned as the two arms in hairpin orientation in a binary plasmid background to generate RNAi against both viruses simultaneously. Transgenic rice plants were raised using the above construct and their resistance against RTBV and RTSV was quantified at the T1 plants. Levels of both the viral nucleic acids showed a fall of 100- to 500-fold in the above plants, compared with the non-transgenic controls, coupled with the amelioration of stunting. The transgenic plants also retained higher chlorophyll levels than the control non-transgenic plants after infection with RTBV and RTSV. Small RNA analysis of virus inoculated transgenic plants indicated the presence of 21 nt and 22 nt siRNAs specific to RTBV and RTSV. The evidence points towards an active RNAi mechanism leading to resistance against the tungro viruses in the plants analysed.
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Affiliation(s)
- Shweta Sharma
- Department of Plant Molecular Biology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Gaurav Kumar
- Department of Plant Molecular Biology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Indranil Dasgupta
- Department of Plant Molecular Biology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India.
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22
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Hummel AW, Chauhan RD, Cermak T, Mutka AM, Vijayaraghavan A, Boyher A, Starker CG, Bart R, Voytas DF, Taylor NJ. Allele exchange at the EPSPS locus confers glyphosate tolerance in cassava. PLANT BIOTECHNOLOGY JOURNAL 2018; 16:1275-1282. [PMID: 29223136 PMCID: PMC5999311 DOI: 10.1111/pbi.12868] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 11/22/2017] [Accepted: 12/03/2017] [Indexed: 05/20/2023]
Abstract
Effective weed control can protect yields of cassava (Manihot esculenta) storage roots. Farmers could benefit from using herbicide with a tolerant cultivar. We applied traditional transgenesis and gene editing to generate robust glyphosate tolerance in cassava. By comparing promoters regulating expression of transformed 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) genes with various paired amino acid substitutions, we found that strong constitutive expression is required to achieve glyphosate tolerance during in vitro selection and in whole cassava plants. Using strategies that exploit homologous recombination (HR) and nonhomologous end-joining (NHEJ) DNA repair pathways, we precisely introduced the best-performing allele into the cassava genome, simultaneously creating a promoter swap and dual amino acid substitutions at the endogenous EPSPS locus. Primary EPSPS-edited plants were phenotypically normal, tolerant to high doses of glyphosate, with some free of detectable T-DNA integrations. Our methods demonstrate an editing strategy for creating glyphosate tolerance in crop plants and demonstrate the potential of gene editing for further improvement of cassava.
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Affiliation(s)
- Aaron W. Hummel
- Department of Genetics, Cell Biology, & Development and Center for Genome EngineeringUniversity of MinnesotaMinneapolisMNUSA
- Present address:
KWS Gateway Research CenterSt. LouisMOUSA
| | | | - Tomas Cermak
- Department of Genetics, Cell Biology, & Development and Center for Genome EngineeringUniversity of MinnesotaMinneapolisMNUSA
- Present address:
Inari Agriculture Inc200 Sidney StSuite 340, CambridgeMA 02139USA
| | - Andrew M. Mutka
- Donald Danforth Plant Science CenterSt. LouisMOUSA
- Present address:
Elemental EnzymesSt. LouisMOUSA
| | - Anupama Vijayaraghavan
- Donald Danforth Plant Science CenterSt. LouisMOUSA
- Present address:
MonsantoSt. LouisMOUSA
| | - Adam Boyher
- Donald Danforth Plant Science CenterSt. LouisMOUSA
| | - Colby G. Starker
- Department of Genetics, Cell Biology, & Development and Center for Genome EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - Rebecca Bart
- Donald Danforth Plant Science CenterSt. LouisMOUSA
| | - Daniel F. Voytas
- Department of Genetics, Cell Biology, & Development and Center for Genome EngineeringUniversity of MinnesotaMinneapolisMNUSA
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23
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Tomlinson KR, Bailey AM, Alicai T, Seal S, Foster GD. Cassava brown streak disease: historical timeline, current knowledge and future prospects. MOLECULAR PLANT PATHOLOGY 2018; 19:1282-1294. [PMID: 28887856 PMCID: PMC5947582 DOI: 10.1111/mpp.12613] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 09/07/2017] [Accepted: 09/07/2017] [Indexed: 05/09/2023]
Abstract
Cassava is the second most important staple food crop in terms of per capita calories consumed in Africa and holds potential for climate change adaptation. Unfortunately, productivity in East and Central Africa is severely constrained by two viral diseases: cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). CBSD was first reported in 1936 from northeast Tanzania. For approximately 70 years, CBSD was restricted to coastal East Africa and so had a relatively low impact on food security compared with CMD. However, at the turn of the 21st century, CBSD re-emerged further inland, in areas around Lake Victoria, and it has since spread through many East and Central African countries, causing high yield losses and jeopardizing the food security of subsistence farmers. This recent re-emergence has attracted intense scientific interest, with studies shedding light on CBSD viral epidemiology, sequence diversity, host interactions and potential sources of resistance within the cassava genome. This review reflects on 80 years of CBSD research history (1936-2016) with a timeline of key events. We provide insights into current CBSD knowledge, management efforts and future prospects for improved understanding needed to underpin effective control and mitigation of impacts on food security.
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Affiliation(s)
| | - Andy M. Bailey
- School of Biological SciencesUniversity of BristolBristolBS8 1TQUK
| | - Titus Alicai
- National Crops Resources Research InstituteKampala 7084Uganda
| | - Sue Seal
- Natural Resources InstituteUniversity of GreenwichChatham MaritimeKent ME4 4TBUK
| | - Gary D. Foster
- School of Biological SciencesUniversity of BristolBristolBS8 1TQUK
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24
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Utsumi Y, Utsumi C, Tanaka M, Ha VT, Matsui A, Takahashi S, Seki M. Formation of friable embryogenic callus in cassava is enhanced under conditions of reduced nitrate, potassium and phosphate. PLoS One 2017; 12:e0180736. [PMID: 28806727 PMCID: PMC5555663 DOI: 10.1371/journal.pone.0180736] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 06/20/2017] [Indexed: 01/22/2023] Open
Abstract
Agrobacterium-mediated transformation is an important research tool for the genetic improvement of cassava. The induction of friable embryogenic callus (FEC) is considered as a key step in cassava transformation. In the present study, the media composition was optimized for enhancing the FEC induction, and the effect of the optimized medium on gene expression was evaluated. In relative comparison to MS medium, results demonstrated that using a medium with reducing nutrition (a 10-fold less concentration of nitrogen, potassium, and phosphate), the increased amount of vitamin B1 (10 mg/L) and the use of picrolam led to reprogram non-FEC to FEC. Gene expression analyses revealed that FEC on modified media increased the expression of genes related to the regulation of polysaccharide biosynthesis and breakdown of cell wall components in comparison to FEC on normal CIM media, whereas the gene expression associated with energy flux was not dramatically altered. It is hypothesized that we reprogram non-FEC to FEC under low nitrogen, potassium and phosphate and high vitamin B1. These findings were more effective in inducing FEC formation than the previous protocol. It might contribute to development of an efficient transformation strategy in cassava.
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Affiliation(s)
- Yoshinori Utsumi
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
| | - Chikako Utsumi
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology (JST), 4-1-8 Honcho, Kawaguchi, Saitama, Japan
| | - Maho Tanaka
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
| | - Vu The Ha
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
| | - Akihiro Matsui
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
| | - Satoshi Takahashi
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
| | - Motoaki Seki
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology (JST), 4-1-8 Honcho, Kawaguchi, Saitama, Japan
- Kihara Institute for Biological Research, Yokohama City University, 641–12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, Japan
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25
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Abstract
Cassava is the fourth largest source of calories in the world but is subject to economically important yield losses due to viral diseases, including cassava brown streak disease and cassava mosaic disease. Cassava mosaic disease occurs in sub-Saharan Africa and the Asian subcontinent and is associated with nine begomovirus species, whereas cassava brown streak disease has to date been reported only in sub-Saharan Africa and is caused by two distinct ipomovirus species. We present an overview of key milestones and their significance in the understanding and characterization of these two major diseases as well as their associated viruses and whitefly vector. New biotechnologies offer a wide range of opportunities to reduce virus-associated yield losses in cassava for farmers and can additionally enable the exploitation of this valuable crop for industrial purposes. This review explores established and new technologies for genetic manipulation to achieve desired traits such as virus resistance.
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Affiliation(s)
- Chrissie Rey
- School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2000, South Africa;
| | - Hervé Vanderschuren
- AgroBioChem Department, Gembloux Agro-Bio Tech, University of Liège, 5030 Gembloux, Belgium;
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26
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Fondong VN. The Search for Resistance to Cassava Mosaic Geminiviruses: How Much We Have Accomplished, and What Lies Ahead. FRONTIERS IN PLANT SCIENCE 2017; 8:408. [PMID: 28392798 PMCID: PMC5365051 DOI: 10.3389/fpls.2017.00408] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 03/09/2017] [Indexed: 05/23/2023]
Abstract
The cassava mosaic disease (CMD), which occurs in all cassava growing regions of Africa and the Indian subcontinent, is caused by cassava mosaic geminiviruses (CMGs). CMGs are considered to be the most damaging vector-borne plant pathogens. So far, the most successful approach used to control these viruses has been the transfer of a polygenic recessive resistance locus, designated CMD1, from wild cassava to cassava cultivars. Further progress in harnessing natural resistance to contain CMGs has come from the discovery of the dominant monogenic resistance locus, CMD2, in some West African cassava cultivars. CMD2 has been combined with CMD1 through genetic crosses. Because of the limitations of the cassava breeding approach, especially with regard to time required to produce a variety and the loss of preferred agronomic attributes, efforts have been directed toward the deployment of genetic engineering approaches. Most of these approaches have been centered on RNA silencing strategies, developed mainly in the model plant Nicotiana benthamiana. Early RNA silencing platforms assessed for CMG resistance have been use of viral genes for co-suppression, antisense suppression or for hairpin RNAs-mediated gene silencing. Here, progress and challenges in the deployment of these approaches in the control of CMGs are discussed. Novel functional genomics approaches with potential to overcome some of the drawbacks of the current strategies are also discussed.
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Affiliation(s)
- Vincent N. Fondong
- Department of Biological Sciences, Delaware State UniversityDover, DE, USA
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27
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Wagaba H, Beyene G, Aleu J, Odipio J, Okao-Okuja G, Chauhan RD, Munga T, Obiero H, Halsey ME, Ilyas M, Raymond P, Bua A, Taylor NJ, Miano D, Alicai T. Field Level RNAi-Mediated Resistance to Cassava Brown Streak Disease across Multiple Cropping Cycles and Diverse East African Agro-Ecological Locations. FRONTIERS IN PLANT SCIENCE 2017; 7:2060. [PMID: 28127301 PMCID: PMC5226948 DOI: 10.3389/fpls.2016.02060] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 12/23/2016] [Indexed: 05/24/2023]
Abstract
Cassava brown streak disease (CBSD) presents a serious threat to cassava production in East and Central Africa. Currently, no cultivars with high levels of resistance to CBSD are available to farmers. Transgenic RNAi technology was employed to combat CBSD by fusing coat protein (CP) sequences from Ugandan cassava brown streak virus (UCBSV) and Cassava brown streak virus (CBSV) to create an inverted repeat construct (p5001) driven by the constitutive Cassava vein mosaic virus promoter. Twenty-five plant lines of cultivar TME 204 expressing varying levels of small interfering RNAs (siRNAs) were established in confined field trials (CFTs) in Uganda and Kenya. Within an initial CFT at Namulonge, Uganda, non-transgenic TME 204 plants developed foliar and storage root CBSD incidences at 96-100% by 12 months after planting. In contrast, 16 of the 25 p5001 transgenic lines showed no foliar symptoms and had less than 8% of their storage roots symptomatic for CBSD. A direct positive correlation was seen between levels of resistance to CBSD and expression of transgenic CP-derived siRNAs. A subsequent CFT was established at Namulonge using stem cuttings from the initial trial. All transgenic lines established remained asymptomatic for CBSD, while 98% of the non-transgenic TME 204 stake-derived plants developed storage roots symptomatic for CBSD. Similarly, very high levels of resistance to CBSD were demonstrated by TME 204 p5001 RNAi lines grown within a CFT over a full cropping cycle at Mtwapa, coastal Kenya. Sequence analysis of CBSD causal viruses present at the trial sites showed that the transgenic lines were exposed to both CBSV and UCBSV, and that the sequenced isolates shared >90% CP identity with transgenic CP sequences expressed by the p5001 inverted repeat expression cassette. These results demonstrate very high levels of field resistance to CBSD conferred by the p5001 RNAi construct at diverse agro-ecological locations, and across the vegetative cropping cycle.
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Affiliation(s)
- Henry Wagaba
- National Crops Resources Research InstituteKampala, Uganda
| | - Getu Beyene
- Donald Danforth Plant Science CenterSt. Louis, MO, USA
| | - Jude Aleu
- National Crops Resources Research InstituteKampala, Uganda
| | - John Odipio
- National Crops Resources Research InstituteKampala, Uganda
- Donald Danforth Plant Science CenterSt. Louis, MO, USA
| | | | | | - Theresia Munga
- Kenya Agricultural and Livestock Research OrganizationNairobi, Kenya
| | | | | | | | | | - Anton Bua
- National Crops Resources Research InstituteKampala, Uganda
| | | | - Douglas Miano
- Department of Plant Science and Crop Protection, University of NairobiNairobi, Kenya
| | - Titus Alicai
- National Crops Resources Research InstituteKampala, Uganda
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Beyene G, Chauhan RD, Wagaba H, Moll T, Alicai T, Miano D, Carrington JC, Taylor NJ. Loss of CMD2-mediated resistance to cassava mosaic disease in plants regenerated through somatic embryogenesis. MOLECULAR PLANT PATHOLOGY 2016; 17:1095-110. [PMID: 26662210 PMCID: PMC5021159 DOI: 10.1111/mpp.12353] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 11/30/2015] [Accepted: 12/07/2015] [Indexed: 05/11/2023]
Abstract
Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are the two most important viral diseases affecting cassava production in Africa. Three sources of resistance are employed to combat CMD: polygenic recessive resistance, termed CMD1, the dominant monogenic type, named CMD2, and the recently characterized CMD3. The farmer-preferred cultivar TME 204 carries inherent resistance to CMD mediated by CMD2, but is highly susceptible to CBSD. Selected plants of TME 204 produced for RNA interference (RNAi)-mediated resistance to CBSD were regenerated via somatic embryogenesis and tested in confined field trials in East Africa. Although micropropagated, wild-type TME 204 plants exhibited the expected levels of resistance, all plants regenerated via somatic embryogenesis were found to be highly susceptible to CMD. Glasshouse studies using infectious clones of East African cassava mosaic virus conclusively demonstrated that the process of somatic embryogenesis used to regenerate cassava caused the resulting plants to become susceptible to CMD. This phenomenon could be replicated in the two additional CMD2-type varieties TME 3 and TME 7, but the CMD1-type cultivar TMS 30572 and the CMD3-type cultivar TMS 98/0505 maintained resistance to CMD after passage through somatic embryogenesis. Data are presented to define the specific tissue culture step at which the loss of CMD resistance occurs and to show that the loss of CMD2-mediated resistance is maintained across vegetative generations. These findings reveal new aspects of the widely used technique of somatic embryogenesis, and the stability of field-level resistance in CMD2-type cultivars presently grown by farmers in East Africa, where CMD pressure is high.
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Affiliation(s)
- Getu Beyene
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO, 63132, USA
| | - Raj Deepika Chauhan
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO, 63132, USA
| | - Henry Wagaba
- National Crops Resources Research Institute, Namulonge, P. O. Box 7084, Kampala, Uganda
| | - Theodore Moll
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO, 63132, USA
| | - Titus Alicai
- National Crops Resources Research Institute, Namulonge, P. O. Box 7084, Kampala, Uganda
| | - Douglas Miano
- University of Nairobi, P. O. Box 29053, Nairobi, post code 00625, Kenya
| | - James C Carrington
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO, 63132, USA
| | - Nigel J Taylor
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO, 63132, USA
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29
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Chavarriaga-Aguirre P, Brand A, Medina A, Prías M, Escobar R, Martinez J, Díaz P, López C, Roca WM, Tohme J. The potential of using biotechnology to improve cassava: a review. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY. PLANT : JOURNAL OF THE TISSUE CULTURE ASSOCIATION 2016; 52:461-478. [PMID: 27818605 PMCID: PMC5071364 DOI: 10.1007/s11627-016-9776-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 07/06/2016] [Indexed: 05/26/2023]
Abstract
The importance of cassava as the fourth largest source of calories in the world requires that contributions of biotechnology to improving this crop, advances and current challenges, be periodically reviewed. Plant biotechnology offers a wide range of opportunities that can help cassava become a better crop for a constantly changing world. We therefore review the state of knowledge on the current use of biotechnology applied to cassava cultivars and its implications for breeding the crop into the future. The history of the development of the first transgenic cassava plant serves as the basis to explore molecular aspects of somatic embryogenesis and friable embryogenic callus production. We analyze complex plant-pathogen interactions to profit from such knowledge to help cassava fight bacterial diseases and look at candidate genes possibly involved in resistance to viruses and whiteflies-the two most important traits of cassava. The review also covers the analyses of main achievements in transgenic-mediated nutritional improvement and mass production of healthy plants by tissue culture and synthetic seeds. Finally, the perspectives of using genome editing and the challenges associated to climate change for further improving the crop are discussed. During the last 30 yr, great advances have been made in cassava using biotechnology, but they need to scale out of the proof of concept to the fields of cassava growers.
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Affiliation(s)
- Paul Chavarriaga-Aguirre
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Alejandro Brand
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Adriana Medina
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Mónica Prías
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Roosevelt Escobar
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Juan Martinez
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
| | - Paula Díaz
- Biology Department, Universidad Nacional de Colombia, Carrera 30 No. 45-03. Edificio 421, Bogotá, Colombia
| | - Camilo López
- Biology Department, Universidad Nacional de Colombia, Carrera 30 No. 45-03. Edificio 421, Bogotá, Colombia
| | - Willy M Roca
- International Potato Center-CIP, Av. La Molina 1895, Lima 12, P.O. Box 1558, Lima, Perú
| | - Joe Tohme
- Agrobiodiversity Research Area, International Center for tropical Agriculture-CIAT, AA 6713 Cali, Colombia
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Wagaba H, Patil BL, Mukasa S, Alicai T, Fauquet CM, Taylor NJ. Artificial microRNA-derived resistance to Cassava brown streak disease. J Virol Methods 2016; 231:38-43. [PMID: 26912232 PMCID: PMC4819903 DOI: 10.1016/j.jviromet.2016.02.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 12/08/2015] [Accepted: 02/08/2016] [Indexed: 11/23/2022]
Abstract
Artificial miRNAs (amiRNA) were generated targeting conserved sequences within the genomes of the two causal agents of Cassava brown streak disease (CBSD): Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). Transient expression studies on ten amiRNAs targeting 21nt conserved sequences of P1(CBSV and UCBSV), P3(CBSV and UCBSV), CI(UCBSV), NIb(CBSV and UCBSV), CP(UCBSV) and the un-translated region (3'-UTR) were tested in Nicotiana benthamiana. Four out of the ten amiRNAs expressed the corresponding amiRNA at high levels. Transgenic N. benthamiana plants were developed for the four amiRNAs targeting the P1 and NIb genes of CBSV and the P1 and CP genes of UCBSV and shown to accumulate miRNA products. Transgenic plants challenged with CBSV and UCBSV isolates showed resistance levels that ranged between ∼20-60% against CBSV and UCBSV and correlated with expression levels of the transgenically derived miRNAs. MicroRNAs targeting P1 and NIb of CBSV showed protection against CBSV and UCBSV, while amiRNAs targeting the P1 and CP of UCBSV showed protection against UCBSV but were less efficient against CBSV. These results indicate a potential application of amiRNAs for engineering resistance to CBSD-causing viruses in cassava.
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Affiliation(s)
- Henry Wagaba
- National Crops Resources Research Institute, Namulonge, P.O. Box 7084, Kampala, Uganda; Makerere University, P.O. Box 7062, University Rd, Kampala, Uganda
| | - Basavaprabhu L Patil
- ICAR-National Research Center on Plant Biotechnology, IARI, Pusa Campus, New Delhi 110012, India
| | - Settumba Mukasa
- Makerere University, P.O. Box 7062, University Rd, Kampala, Uganda
| | - Titus Alicai
- National Crops Resources Research Institute, Namulonge, P.O. Box 7084, Kampala, Uganda
| | - Claude M Fauquet
- Centro Internacional de Agricultura Tropical, Cali, Apartado Aéreo 6713, Cali, Colombia
| | - Nigel J Taylor
- Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO 63132, USA.
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Ogwok E, Ilyas M, Alicai T, Rey MEC, Taylor NJ. Comparative analysis of virus-derived small RNAs within cassava (Manihot esculenta Crantz) infected with cassava brown streak viruses. Virus Res 2016; 215:1-11. [PMID: 26811902 PMCID: PMC4796025 DOI: 10.1016/j.virusres.2016.01.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 01/18/2016] [Accepted: 01/21/2016] [Indexed: 01/02/2023]
Abstract
The 21-nt virus-derived small RNAs were predominant, followed by the 22-nt class. Susceptible cassava genotypes accumulated higher CBSV- than UCBSV-derived small RNA. Tolerant cassava genotype accumulated high CBSV- and low UCBSV-derived small RNAs. AGO2, DCL2 and DCL4 were differentially regulated in CBSV/UCBSV-infected plants. CBSV and UCBSV interact differently in the same host genetic background
Infection of plant cells by viral pathogens triggers RNA silencing, an innate antiviral defense mechanism. In response to infection, small RNAs (sRNAs) are produced that associate with Argonaute (AGO)-containing silencing complexes which act to inactivate viral genomes by posttranscriptional gene silencing (PTGS). Deep sequencing was used to compare virus-derived small RNAs (vsRNAs) in cassava genotypes NASE 3, TME 204 and 60444 infected with the positive sense single-stranded RNA (+ssRNA) viruses cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), the causal agents of cassava brown streak disease (CBSD). An abundance of 21–24 nt vsRNAs was detected and mapped, covering the entire CBSV and UCBSV genomes. The 21 nt vsRNAs were most predominant, followed by the 22 nt class with a slight bias toward sense compared to antisense polarity, and a bias for adenine and uracil bases present at the 5′-terminus. Distribution and frequency of vsRNAs differed between cassava genotypes and viral genomes. In susceptible genotypes TME 204 and 60444, CBSV-derived sRNAs were seen in greater abundance than UCBSV-derived sRNAs. NASE 3, known to be resistant to UCBSV, accumulated negligible UCBSV-derived sRNAs but high populations of CBSV-derived sRNAs. Transcript levels of cassava homologues of AGO2, DCL2 and DCL4, which are central to the gene-silencing complex, were found to be differentially regulated in CBSV- and UCBSV-infected plants across genotypes, suggesting these proteins play a role in antiviral defense. Irrespective of genotype or viral pathogen, maximum populations of vsRNAs mapped to the cytoplasmic inclusion, P1 and P3 protein-encoding regions. Our results indicate disparity between CBSV and UCBSV host-virus interaction mechanisms, and provide insight into the role of virus-induced gene silencing as a mechanism of resistance to CBSD.
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Affiliation(s)
- Emmanuel Ogwok
- National Crops Resources Research Institute, Namulonge, P.O Box 7084, Kampala, Uganda; Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA; School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, P.O Wits 2050, Johannesburg, South Africa
| | - Muhammad Ilyas
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
| | - Titus Alicai
- National Crops Resources Research Institute, Namulonge, P.O Box 7084, Kampala, Uganda
| | - Marie E C Rey
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, P.O Wits 2050, Johannesburg, South Africa
| | - Nigel J Taylor
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
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Beyene G, Chauhan RD, Ilyas M, Wagaba H, Fauquet CM, Miano D, Alicai T, Taylor NJ. A Virus-Derived Stacked RNAi Construct Confers Robust Resistance to Cassava Brown Streak Disease. FRONTIERS IN PLANT SCIENCE 2016; 7:2052. [PMID: 28149300 PMCID: PMC5241307 DOI: 10.3389/fpls.2016.02052] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 12/22/2016] [Indexed: 05/17/2023]
Abstract
Cassava brown streak disease (CBSD) threatens food and economic security for smallholder farmers throughout East and Central Africa, and poses a threat to cassava production in West Africa. CBSD is caused by two whitefly-transmitted virus species: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) (Genus: Ipomovirus, Family Potyviridae). Although varying levels of tolerance have been achieved through conventional breeding, to date, effective resistance to CBSD within East African cassava germplasm has not been identified. RNAi technology was utilized to integrate CBSD resistance into the Ugandan farmer-preferred cassava cultivar TME 204. Transgenic plant lines were generated expressing an inverted repeat construct (p5001) derived from coat-protein (CP) sequences of CBSV and UCBSV fused in tandem. Northern blots using probes specific for each CP sequence were performed to characterize 169 independent transgenic lines for accumulation of CP-derived siRNAs. Transgenic plant lines accumulating low, medium and high levels of siRNAs were bud graft challenged with the virulent CBSV Naliendele isolate alone or in combination with UCBSV. Resistance to CBSD in the greenhouse directly correlated to levels of CP-derived siRNAs as determined by visual assessment of leaf and storage root symptoms, and RT-PCR diagnosis for presence of the pathogens. Low expressing lines were found to be susceptible to CBSV and UCBSV, while medium to high accumulating plant lines were resistant to both virus species. Absence of detectable virus in the best performing p5001 transgenic lines was further confirmed by back-inoculation via sap or graft challenge to CBSD susceptible Nicotiana benthamiana and cassava cultivar 60444, respectively. Data presented shows robust resistance of transgenic p5001 TME 204 lines to both CBSV and UCBSV under greenhouse conditions. Levels of resistance correlated directly with levels of transgene derived siRNA expression such that the latter can be used as predictor of resistance to CBSD.
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Affiliation(s)
- Getu Beyene
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. LouisMO, USA
| | - Raj Deepika Chauhan
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. LouisMO, USA
| | - Muhammad Ilyas
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. LouisMO, USA
- School of Plant Sciences, University of Arizona, TucsonAZ, USA
| | - Henry Wagaba
- National Crops Resources Research InstituteKampala, Uganda
| | - Claude M. Fauquet
- Global Cassava Partnership for the 21st Century, International Center for Tropical AgricultureCali, Colombia
| | - Douglas Miano
- Department of Plant Science and Crop Protection, University of NairobiNairobi, Kenya
| | - Titus Alicai
- National Crops Resources Research InstituteKampala, Uganda
| | - Nigel J. Taylor
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. LouisMO, USA
- *Correspondence: Nigel J. Taylor,
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33
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Patil BL, Legg JP, Kanju E, Fauquet CM. Cassava brown streak disease: a threat to food security in Africa. J Gen Virol 2015; 96:956-68. [PMID: 26015320 DOI: 10.1099/vir.0.000014] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cassava brown streak disease (CBSD) has emerged as the most important viral disease of cassava (Manihot esculenta) in Africa and is a major threat to food security. CBSD is caused by two distinct species of ipomoviruses, Cassava brown streak virus and Ugandan cassava brown streak virus, belonging to the family Potyviridae. Previously, CBSD was reported only from the coastal lowlands of East Africa, but recently it has begun to spread as an epidemic throughout the Great Lakes region of East and Central Africa. This new spread represents a major threat to the cassava-growing regions of West Africa. CBSD-resistant cassava cultivars are being developed through breeding, and transgenic RNA interference-derived field resistance to CBSD has also been demonstrated. This review aims to provide a summary of the most important studies on the aetiology, epidemiology and control of CBSD and to highlight key research areas that need prioritization.
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Affiliation(s)
- Basavaprabhu L Patil
- National Research Centre on Plant Biotechnology, IARI, Pusa Campus, New Delhi 110012, India
| | - James P Legg
- International Institute of Tropical Agriculture, PO Box 34441, Dar-Es-Salaam, Tanzania
| | - Edward Kanju
- International Institute of Tropical Agriculture, PO Box 34441, Dar-Es-Salaam, Tanzania
| | - Claude M Fauquet
- Centro Internacional de Agricultura Tropical, Apartado Aéreo 6713, Cali, Colombia
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Abstract
Transgenic resistance to plant viruses is an important technology for control of plant virus infection, which has been demonstrated for many model systems, as well as for the most important plant viruses, in terms of the costs of crop losses to disease, and also for many other plant viruses infecting various fruits and vegetables. Different approaches have been used over the last 28 years to confer resistance, to ascertain whether particular genes or RNAs are more efficient at generating resistance, and to take advantage of advances in the biology of RNA interference to generate more efficient and environmentally safer, novel "resistance genes." The approaches used have been based on expression of various viral proteins (mostly capsid protein but also replicase proteins, movement proteins, and to a much lesser extent, other viral proteins), RNAs [sense RNAs (translatable or not), antisense RNAs, satellite RNAs, defective-interfering RNAs, hairpin RNAs, and artificial microRNAs], nonviral genes (nucleases, antiviral inhibitors, and plantibodies), and host-derived resistance genes (dominant resistance genes and recessive resistance genes), and various factors involved in host defense responses. This review examines the above range of approaches used, the viruses that were tested, and the host species that have been examined for resistance, in many cases describing differences in results that were obtained for various systems developed in the last 20 years. We hope this compilation of experiences will aid those who are seeking to use this technology to provide resistance in yet other crops, where nature has not provided such.
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Affiliation(s)
| | - Peter Palukaitis
- Department of Horticultural Sciences, Seoul Women's University, Seoul, Republic of Korea.
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35
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Patil BL, Legg JP, Kanju E, Fauquet CM. Cassava brown streak disease: a threat to food security in Africa. J Gen Virol 2015. [DOI: 10.1099/jgv.0.000014] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- Basavaprabhu L. Patil
- National Research Centre on Plant Biotechnology, IARI, Pusa Campus, New Delhi 110012, India
| | - James P. Legg
- International Institute of Tropical Agriculture, PO Box 34441, Dar-Es-Salaam, Tanzania
| | - Edward Kanju
- International Institute of Tropical Agriculture, PO Box 34441, Dar-Es-Salaam, Tanzania
| | - Claude M. Fauquet
- Centro Internacional de Agricultura Tropical, Apartado Aéreo 6713, Cali, Colombia
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Ntui VO, Kong K, Khan RS, Igawa T, Janavi GJ, Rabindran R, Nakamura I, Mii M. Resistance to Sri Lankan cassava mosaic virus (SLCMV) in genetically engineered cassava cv. KU50 through RNA silencing. PLoS One 2015; 10:e0120551. [PMID: 25901740 PMCID: PMC4406713 DOI: 10.1371/journal.pone.0120551] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 02/05/2015] [Indexed: 11/18/2022] Open
Abstract
Cassava ranks fifth among the starch producing crops of the world, its annual bioethanol yield is higher than for any other crop. Cassava cultivar KU50, the most widely grown cultivar for non-food purposes is susceptible to Sri Lankan cassava mosaic virus (SLCMV). The objective of this work was to engineer resistance to SLCMV by RNA interference (RNAi) in order to increase biomass yield, an important aspect for bioethanol production. Here, we produced transgenic KU50 lines expressing dsRNA homologous to the region between the AV2 and AV1 of DNA A of SLCMV. High level expression of dsRNA of SLCMV did not induce any growth abnormality in the transgenic plants. Transgenic lines displayed high levels of resistance to SLCMV compared to the wild-type plants and no virus load could be detected in uninoculated new leaves of the infected resistant lines after PCR amplification and RT-PCR analysis. The agronomic performance of the transgenic lines was unimpaired after inoculation with the virus as the plants presented similar growth when compared to the mock inoculated control plants and revealed no apparent reduction in the amount and weight of tubers produced. We show that the resistance is correlated with post-transcriptional gene silencing because of the production of transgene specific siRNA. The results demonstrate that transgenic lines exhibited high levels of resistance to SLCMV. This resistance coupled with the desirable yield components in the transgenic lines makes them better candidates for exploitation in the production of biomass as well as bioethanol.
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Affiliation(s)
- Valentine Otang Ntui
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
- Department of Genetics/Biotechnology, Faculty of Science, University of Calabar, Calabar, Nigeria
- * E-mail:
| | - Kynet Kong
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
- Cambodia Agricultural Research and Development Institute, Phnom Penh, Cambodia
| | - Raham Sher Khan
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
- Department of Biotechnology, Abdul Wali Khan University, Mardan, Pakistan
| | - Tomoko Igawa
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
| | - Gnanaguru Janaky Janavi
- Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, India
| | - Ramalingam Rabindran
- Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, India
| | - Ikuo Nakamura
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
| | - Masahiro Mii
- Laboratory of Plant Cell Technology, Graduate School of Horticulture, Chiba University, Chiba, Japan
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Albacete A, Martínez-Andújar C, Martínez-Pérez A, Thompson AJ, Dodd IC, Pérez-Alfocea F. Unravelling rootstock×scion interactions to improve food security. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:2211-26. [PMID: 25754404 PMCID: PMC4986720 DOI: 10.1093/jxb/erv027] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 12/12/2014] [Accepted: 01/08/2015] [Indexed: 05/19/2023]
Abstract
While much recent science has focused on understanding and exploiting root traits as new opportunities for crop improvement, the use of rootstocks has enhanced productivity of woody perennial crops for centuries. Grafting of vegetable crops has developed very quickly in the last 50 years, mainly to induce shoot vigour and to overcome soil-borne diseases in solanaceous and cucurbitaceous crops. In most cases, such progress has largely been due to empirical interactions between farmers, gardeners, and botanists, with limited insights into the underlying physiological mechanisms. Only during the last 20 years has science realized the potential of this old activity and studied the physiological and molecular mechanisms involved in rootstock×scion interactions, thereby not only explaining old phenomena but also developing new tools for crop improvement. Rootstocks can contribute to food security by: (i) increasing the yield potential of elite varieties; (ii) closing the yield gap under suboptimal growing conditions; (iii) decreasing the amount of chemical (pesticides and fertilizers) contaminants in the soil; (iv) increasing the efficiency of use of natural (water and soil) resources; (v) generating new useful genotypic variability (via epigenetics); and (vi) creating new products with improved quality. The potential of grafting is as broad as the genetic variability able to cross a potential incompatibility barrier between the rootstock and the scion. Therefore, understanding the mechanisms underlying the phenotypic variability resulting from rootstock×scion×environment interactions will certainly contribute to developing and exploiting rootstocks for food security.
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Affiliation(s)
- Alfonso Albacete
- Departamento de Nutrición Vegetal, CEBAS-CSIC, Campus Universitario de Espinardo, 25, E-30100 Murcia, Spain
| | - Cristina Martínez-Andújar
- Departamento de Nutrición Vegetal, CEBAS-CSIC, Campus Universitario de Espinardo, 25, E-30100 Murcia, Spain
| | - Ascensión Martínez-Pérez
- Departamento de Nutrición Vegetal, CEBAS-CSIC, Campus Universitario de Espinardo, 25, E-30100 Murcia, Spain
| | - Andrew J Thompson
- School of Energy, Environment and Agrifood, Cranfield University, Bedfordshire MK43 0AL, UK
| | - Ian C Dodd
- Lancaster Environment Centre, University of Lancaster, Lancaster LA1 4YQ, UK
| | - Francisco Pérez-Alfocea
- Departamento de Nutrición Vegetal, CEBAS-CSIC, Campus Universitario de Espinardo, 25, E-30100 Murcia, Spain
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Legg JP, Lava Kumar P, Makeshkumar T, Tripathi L, Ferguson M, Kanju E, Ntawuruhunga P, Cuellar W. Cassava virus diseases: biology, epidemiology, and management. Adv Virus Res 2015; 91:85-142. [PMID: 25591878 DOI: 10.1016/bs.aivir.2014.10.001] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cassava (Manihot esculenta Crantz.) is the most important vegetatively propagated food staple in Africa and a prominent industrial crop in Latin America and Asia. Its vegetative propagation through stem cuttings has many advantages, but deleteriously it means that pathogens are passed from one generation to the next and can easily accumulate, threatening cassava production. Cassava-growing continents are characterized by specific suites of viruses that affect cassava and pose particular threats. Of major concern, causing large and increasing economic impact in Africa and Asia are the cassava mosaic geminiviruses that cause cassava mosaic disease in Africa and Asia and cassava brown streak viruses causing cassava brown streak disease in Africa. Latin America, the center of origin and domestication of the crop, hosts a diverse set of virus species, of which the most economically important give rise to cassava frog skin disease syndrome. Here, we review current knowledge on the biology, epidemiology, and control of the most economically important groups of viruses in relation to both farming and cultural practices. Components of virus control strategies examined include: diagnostics and surveillance, prevention and control of infection using phytosanitation, and control of disease through the breeding and promotion of varieties that inhibit virus replication and/or movement. We highlight areas that need further research attention and conclude by examining the likely future global outlook for virus disease management in cassava.
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Affiliation(s)
- James P Legg
- International Institute of Tropical Agriculture (IITA), Dar es Salaam, Tanzania.
| | - P Lava Kumar
- International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - T Makeshkumar
- Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram, India
| | - Leena Tripathi
- International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
| | - Morag Ferguson
- International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
| | - Edward Kanju
- International Institute of Tropical Agriculture (IITA), Dar es Salaam, Tanzania
| | | | - Wilmer Cuellar
- Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia
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Nicaise V. Crop immunity against viruses: outcomes and future challenges. FRONTIERS IN PLANT SCIENCE 2014; 5:660. [PMID: 25484888 PMCID: PMC4240047 DOI: 10.3389/fpls.2014.00660] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/04/2014] [Indexed: 05/02/2023]
Abstract
Viruses cause epidemics on all major cultures of agronomic importance, representing a serious threat to global food security. As strict intracellular pathogens, they cannot be controlled chemically and prophylactic measures consist mainly in the destruction of infected plants and excessive pesticide applications to limit the population of vector organisms. A powerful alternative frequently employed in agriculture relies on the use of crop genetic resistances, approach that depends on mechanisms governing plant-virus interactions. Hence, knowledge related to the molecular bases of viral infections and crop resistances is key to face viral attacks in fields. Over the past 80 years, great advances have been made on our understanding of plant immunity against viruses. Although most of the known natural resistance genes have long been dominant R genes (encoding NBS-LRR proteins), a vast number of crop recessive resistance genes were cloned in the last decade, emphasizing another evolutive strategy to block viruses. In addition, the discovery of RNA interference pathways highlighted a very efficient antiviral system targeting the infectious agent at the nucleic acid level. Insidiously, plant viruses evolve and often acquire the ability to overcome the resistances employed by breeders. The development of efficient and durable resistances able to withstand the extreme genetic plasticity of viruses therefore represents a major challenge for the coming years. This review aims at describing some of the most devastating diseases caused by viruses on crops and summarizes current knowledge about plant-virus interactions, focusing on resistance mechanisms that prevent or limit viral infection in plants. In addition, I will discuss the current outcomes of the actions employed to control viral diseases in fields and the future investigations that need to be undertaken to develop sustainable broad-spectrum crop resistances against viruses.
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Affiliation(s)
- Valérie Nicaise
- Fruit Biology and Pathology, Virology Laboratory, Institut National de la Recherche Agronomique, University of BordeauxUMR 1332, Villenave d’Ornon, France
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Maruthi MN, Bouvaine S, Tufan HA, Mohammed IU, Hillocks RJ. Transcriptional response of virus-infected cassava and identification of putative sources of resistance for cassava brown streak disease. PLoS One 2014; 9:e96642. [PMID: 24846209 PMCID: PMC4028184 DOI: 10.1371/journal.pone.0096642] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 04/08/2014] [Indexed: 02/02/2023] Open
Abstract
Cassava (Manihot esculenta) is a major food staple in sub-Saharan Africa, which is severely affected by cassava brown streak disease (CBSD). The aim of this study was to identify resistance for CBSD as well as to understand the mechanism of putative resistance for providing effective control for the disease. Three cassava varieties; Kaleso, Kiroba and Albert were inoculated with cassava brown streak viruses by grafting and also using the natural insect vector the whitefly, Bemisia tabaci. Kaleso expressed mild or no disease symptoms and supported low concentrations of viruses, which is a characteristic of resistant plants. In comparison, Kiroba expressed severe leaf but milder root symptoms, while Albert was susceptible with severe symptoms both on leaves and roots. Real-time PCR was used to estimate virus concentrations in cassava varieties. Virus quantities were higher in Kiroba and Albert compared to Kaleso. The Illumina RNA-sequencing was used to further understand the genetic basis of resistance. More than 700 genes were uniquely overexpressed in Kaleso in response to virus infection compared to Albert. Surprisingly, none of them were similar to known resistant gene orthologs. Some of the overexpressed genes, however, belonged to the hormone signalling pathways and secondary metabolites, both of which are linked to plant resistance. These genes should be further characterised before confirming their role in resistance to CBSD.
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Affiliation(s)
- M. N. Maruthi
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
| | - Sophie Bouvaine
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
| | - Hale A. Tufan
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
| | - Ibrahim U. Mohammed
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
| | - Rory J. Hillocks
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
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Abstract
Whiteflies are a key pest of crops in open-field production throughout the tropics and subtropics. This is due in large part to the long and diverse list of devastating plant viruses transmitted by these vectors. Open-field production provides many challenges to manage these viruses and in many cases adequate management has not been possible. Diseases caused by whitefly-transmitted viruses have become limiting factors in open-field production of a wide range of crops, i.e., bean golden mosaic disease in beans, tomato yellow leaf curl disease in tomato, cassava mosaic disease and cassava brown streak disease in cassava, and cotton leaf crumple disease in cotton. While host resistance has proven to be the most cost-effective management solution, few examples of host resistance have been developed to date. The main strategy to limit the incidence of virus-infected plants has been the application of insecticides to reduce vector populations aided to some extent by the use of selected cultural practices. However, due to concerns about the effect of insecticides on pollinators, consumer demand for reduced pesticide use, and the ability of the whitefly vectors to develop insecticide-resistance, there is a growing need to develop and deploy strategies that do not rely on insecticides. The reduction in pesticide use will greatly increase the need for genetic resistance to more viruses in more crop plants. Resistance combined with selected IPM strategies could become a viable means to increase yields in crops produced in open fields despite the presence of whitefly-transmitted viruses.
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Odipio J, Ogwok E, Taylor NJ, Halsey M, Bua A, Fauquet CM, Alicai T. RNAi-derived field resistance to Cassava brown streak disease persists across the vegetative cropping cycle. GM CROPS & FOOD 2014; 5:16-9. [PMID: 24296511 PMCID: PMC5033198 DOI: 10.4161/gmcr.26408] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/03/2013] [Accepted: 09/07/2013] [Indexed: 11/19/2022]
Abstract
A confined field trial was established to determine durability of RNAi-mediated resistance to Cassava brown streak disease (CBSD). Stem cuttings were obtained from field-grown cassava plants of cv 60444 transgenic for construct p718, consisting of an 894 bp inverted repeat sequence from the Ugandan Cassava brown streak virus (UCBSV) coat protein. Plants were established from three transgenic lines previously shown to provide complete resistance to UCBSV and differing levels of protection to the non-homologous virus species Cassava brown streak virus (CBSV), and grown for 11 months. CBSD symptoms were observed on shoots and storage roots of all non-transgenic cv 60444 control plants and transgenic lines p718-002 and p718-005, but not on p718-001. RT-PCR diagnostic showed tissues of plant lines p718-002 and p718-005 to be infected with CBSV, but free of UCBSV. All leaves and roots of p718-001 plants were to carry no detectable levels of either pathogen. Plants of cv 60444 in this field trial showed severe cassava mosaic disease symptoms, indicating that presence of replicating geminiviruses did not cause significant suppression of RNAi-mediated resistance to CBSD. Resistance to CBSD across a vegetative cropping cycle confirms earlier field data, and provides an important step in proof of concept for application of RNAi technology to control of CBSD under conditions encountered in farmers' fields.
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Affiliation(s)
- John Odipio
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
| | - Emmanuel Ogwok
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Nigel J Taylor
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Mark Halsey
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Anton Bua
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
| | - Claude M Fauquet
- Centro Internacional de Agricultura Tropical; Cali-Palmira; Cali, Colombia
| | - Titus Alicai
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
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Nyaboga E, Njiru J, Nguu E, Gruissem W, Vanderschuren H, Tripathi L. Unlocking the potential of tropical root crop biotechnology in east Africa by establishing a genetic transformation platform for local farmer-preferred cassava cultivars. FRONTIERS IN PLANT SCIENCE 2013; 4:526. [PMID: 24400011 PMCID: PMC3872047 DOI: 10.3389/fpls.2013.00526] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 12/06/2013] [Indexed: 05/12/2023]
Abstract
Cassava genetic transformation capacity is still mostly restricted to advanced laboratories in the USA, Europe and China; and its implementation and maintenance in African laboratories has remained scarce. The impact of transgenic technologies for genetic improvement of cassava will depend largely on the transfer of such capabilities to researchers in Africa, where cassava has an important socioeconomic niche. A major constraint to the development of genetic transformation technologies for cassava improvement has been the lack of an efficient and robust transformation and regeneration system. Despite the success achieved in genetic modification of few cassava cultivars, including the model cultivar 60444, transgenic cassava production remains difficult for farmer-preferred cultivars. In this study, a protocol for cultivar 60444 developed at ETH Zurich was successfully implemented and optimized to establish transformation of farmer-preferred cassava cultivars popular in east Africa. The conditions for production and proliferation of friable embryogenic calli (FEC) and Agrobacterium-mediated transformation were optimized for three east African farmer-preferred cultivars (Ebwanatereka, Kibandameno and Serere). Our results demonstrated transformation efficiencies of about 14-22 independent transgenic lines per 100 mg of FEC for farmer-preferred cultivars in comparison to 28 lines per 100 mg of the model cultivar 60444. The presence, integration and expression of the transgenes were confirmed by PCR, Southern blot analysis and histochemical GUS assay. This study reports the establishment of a cassava transformation platform at International Institute of Tropical Agriculture (IITA) hosted by Biosciences eastern and central Africa (BecA) hub in Kenya and provides the basis for transferring important traits such as virus resistance and prolonged shelf-life to farmer-preferred cultivars in east Africa. We anticipate that such platform will also be instrumental to transfer technologies to national agricultural research systems (NARS) in sub-Saharan Africa.
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Affiliation(s)
- Evans Nyaboga
- International Institute of Tropical AgricultureNairobi, Kenya
- Department of Biology, Plant Biotechnology, Eidgenössische Technische HochschuleZurich, Switzerland
- Department of Biochemistry, University of NairobiNairobi, Kenya
| | - Joshua Njiru
- International Institute of Tropical AgricultureNairobi, Kenya
| | - Edward Nguu
- Department of Biochemistry, University of NairobiNairobi, Kenya
| | - Wilhelm Gruissem
- Department of Biology, Plant Biotechnology, Eidgenössische Technische HochschuleZurich, Switzerland
| | - Herve Vanderschuren
- Department of Biology, Plant Biotechnology, Eidgenössische Technische HochschuleZurich, Switzerland
| | - Leena Tripathi
- International Institute of Tropical AgricultureNairobi, Kenya
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Wagaba H, Beyene G, Trembley C, Alicai T, Fauquet CM, Taylor NJ. Efficient transmission of cassava brown streak disease viral pathogens by chip bud grafting. BMC Res Notes 2013; 6:516. [PMID: 24314370 PMCID: PMC3896733 DOI: 10.1186/1756-0500-6-516] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 11/08/2013] [Indexed: 11/21/2022] Open
Abstract
Background Techniques to study plant viral diseases under controlled growth conditions are required to fully understand their biology and investigate host resistance. Cassava brown streak disease (CBSD) presents a major threat to cassava production in East Africa. No infectious clones of the causal viruses, Cassava brown streak virus (CBSV) or Ugandan cassava brown streak virus (UCBSV) are available, and mechanical transmission to cassava is not effective. An improved method for transmission of the viruses, both singly and as co-infections has been developed using bud grafts. Findings Axillary buds from CBSD symptomatic plants infected with virulent isolates of CBSV and UCBSV were excised and grafted onto 6–8 week old greenhouse-grown, disease-free cassava plants of cultivars Ebwanateraka, TME204 and 60444. Plants were assessed visually for development of CBSD symptoms and by RT-PCR for presence of the viruses in leaf and storage root tissues. Across replicated experiments, 70-100% of plants inoculated with CBSV developed CBSD leaf and stem symptoms 2–6 weeks after bud grafting. Infected plants showed typical, severe necrotic lesions in storage roots at harvest 12–14 weeks after graft inoculation. Sequential grafting of buds from plants infected with UCBSV followed 10–14 days later by buds carrying CBSV, onto the same test plant, resulted in 100% of the rootstocks becoming co-infected with both pathogens. This dual transmission rate was greater than that achieved by simultaneous grafting with UCBSV and CBSV (67%), or when grafting first with CBSV followed by UCBSV (17%). Conclusions The bud grafting method described presents an improved tool for screening cassava germplasm for resistance to CBSD causal viruses, and for studying pathogenicity of this important disease. Bud grafting provides new opportunities compared to previously reported top and side grafting systems. Test plants can be inoculated as young, uniform plants of a size easily handled in a small greenhouse or large growth chamber and can be inoculated in a controlled manner with CBSV and UCBSV, either singly or together. Disease symptoms develop rapidly, allowing better studies of interactions between these viral pathogens, their movement within shoot and root systems, and how they induce their destructive disease symptoms.
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Affiliation(s)
| | | | | | | | | | - Nigel J Taylor
- Donald Danforth Plant Science Center, 975 N, Warson Rd, St Louis, MO, USA.
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Transgenic accumulation of a defective cucumber mosaic virus (CMV) replicase derived double stranded RNA modulates plant defence against CMV strains O and Y in potato. Transgenic Res 2013; 22:1191-205. [PMID: 23748933 DOI: 10.1007/s11248-013-9721-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 05/31/2013] [Indexed: 10/26/2022]
Abstract
Cucumber mosaic virus is an important plant pathogen with a broad host range encompassing many plant species. This study demonstrates the production of transgenic potato lines exhibiting complete resistance to cucumber mosaic virus strain O and Y by post transcriptional gene silencing. Two constructs were used, one, pEKH2IN2CMVai, contains inverted repeat of 1,138 bp fragment of a defective CMV replicase gene derived from RNA2 of cucumber mosaic virus strain O (CMV-O), while the other, TRV-based VIGS vector (pTRV2CMVai), contains the same fragment of the replicase gene, but without inverted repeat. These constructs were used to produce transgenic potato lines of cultivar 'Danshaku', a susceptible genotype to CMV. Transgenic lines derived from pEKH2IN2CMVai accumulated small interfering RNA (siRNA) before and after virus challenge, whereas those derived from pTRV2CMVai showed siRNA expression after virus challenge. When transgenic lines were challenged with CMV-O or CMV-Y, four lines exhibited complete (100%) resistance to both strains, whereas the other lines had high levels of resistance. Infectivity of CMV-O was lower than that of CMV-Y in the highly resistant plants. There were no significant differences with regard to resistance between plants derived from pEKH2IN2CMVai and those obtained from pTRV2CMVai. The presence of CMV-specific siRNA in the resistant phenotypes indicates that the resistance was acquired through RNA silencing.
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46
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Ogwok E, Odipio J, Halsey M, Gaitán-Solís E, Bua A, Taylor NJ, Fauquet CM, Alicai T. Transgenic RNA interference (RNAi)-derived field resistance to cassava brown streak disease. MOLECULAR PLANT PATHOLOGY 2012; 13:1019-31. [PMID: 22845735 PMCID: PMC6638741 DOI: 10.1111/j.1364-3703.2012.00812.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cassava brown streak disease (CBSD), caused by the Ipomoviruses Cassava brown streak virus (CBSV) and Ugandan Cassava brown streak virus (UCBSV), is considered to be an imminent threat to food security in tropical Africa. Cassava plants were transgenically modified to generate small interfering RNAs (siRNAs) from truncated full-length (894-bp) and N-terminal (402-bp) portions of the UCBSV coat protein (ΔCP) sequence. Seven siRNA-producing lines from each gene construct were tested under confined field trials at Namulonge, Uganda. All nontransgenic control plants (n = 60) developed CBSD symptoms on aerial tissues by 6 months after planting, whereas plants transgenic for the full-length ΔCP sequence showed a 3-month delay in disease development, with 98% of clonal replicates within line 718-001 remaining symptom free over the 11-month trial. Reverse transcriptase-polymerase chain reaction (RT-PCR) diagnostics indicated the presence of UCBSV within the leaves of 57% of the nontransgenic controls, but in only two of 413 plants tested (0.5%) across the 14 transgenic lines. All transgenic plants showing CBSD were PCR positive for the presence of CBSV, except for line 781-001, in which 93% of plants were confirmed to be free of both pathogens. At harvest, 90% of storage roots from nontransgenic plants were severely affected by CBSD-induced necrosis. However, transgenic lines 718-005 and 718-001 showed significant suppression of disease, with 95% of roots from the latter line remaining free from necrosis and RT-PCR negative for the presence of both viral pathogens. Cross-protection against CBSV by siRNAs generated from the full-length UCBSV ΔCP confirms a previous report in tobacco. The information presented provides proof of principle for the control of CBSD by RNA interference-mediated technology, and progress towards the potential control of this damaging disease.
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Affiliation(s)
- Emmanuel Ogwok
- National Crops Resources Research Institute, Namulonge, Kampala, Uganda
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47
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Vanderschuren H, Moreno I, Anjanappa RB, Zainuddin IM, Gruissem W. Exploiting the combination of natural and genetically engineered resistance to cassava mosaic and cassava brown streak viruses impacting cassava production in Africa. PLoS One 2012; 7:e45277. [PMID: 23049780 PMCID: PMC3458115 DOI: 10.1371/journal.pone.0045277] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 08/15/2012] [Indexed: 11/18/2022] Open
Abstract
Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are currently two major viral diseases that severely reduce cassava production in large areas of Sub-Saharan Africa. Natural resistance has so far only been reported for CMD in cassava. CBSD is caused by two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). A sequence of the CBSV coat protein (CP) highly conserved between the two virus species was used to demonstrate that a CBSV-CP hairpin construct sufficed to generate immunity against both viral species in the cassava model cultivar (cv. 60444). Most of the transgenic lines showed high levels of resistance under increasing viral loads using a stringent top-grafting method of inoculation. No viral replication was observed in the resistant transgenic lines and they remained free of typical CBSD root symptoms 7 month post-infection. To generate transgenic cassava lines combining resistance to both CBSD and CMD the hairpin construct was transferred to a CMD-resistant farmer-preferred Nigerian landrace TME 7 (Oko-Iyawo). An adapted protocol allowed the efficient Agrobacterium-based transformation of TME 7 and the regeneration of transgenic lines with high levels of CBSV-CP hairpin-derived small RNAs. All transgenic TME 7 lines were immune to both CBSV and UCBSV infections. Further evaluation of the transgenic TME 7 lines revealed that CBSD resistance was maintained when plants were co-inoculated with East African cassava mosaic virus (EACMV), a geminivirus causing CMD. The innovative combination of natural and engineered virus resistance in farmer-preferred landraces will be particularly important to reducing the increasing impact of cassava viral diseases in Africa.
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Affiliation(s)
- Hervé Vanderschuren
- Department of Biology, Plant Biotechnology, ETH Zurich, Zurich, Switzerland.
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48
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Soler N, Plomer M, Fagoaga C, Moreno P, Navarro L, Flores R, Peña L. Transformation of Mexican lime with an intron-hairpin construct expressing untranslatable versions of the genes coding for the three silencing suppressors of Citrus tristeza virus confers complete resistance to the virus. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:597-608. [PMID: 22405601 DOI: 10.1111/j.1467-7652.2012.00691.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Citrus tristeza virus (CTV), the causal agent of the most devastating viral disease of citrus, has evolved three silencing suppressor proteins acting at intra- (p23 and p20) and/or intercellular level (p20 and p25) to overcome host antiviral defence. Previously, we showed that Mexican lime transformed with an intron-hairpin construct including part of the gene p23 and the adjacent 3' untranslated region displays partial resistance to CTV, with a fraction of the propagations from some transgenic lines remaining uninfected. Here, we transformed Mexican lime with an intron-hairpin vector carrying full-length, untranslatable versions of the genes p25, p20 and p23 from CTV strain T36 to silence the expression of these critical genes in CTV-infected cells. Three transgenic lines presented complete resistance to viral infection, with all their propagations remaining symptomless and virus-free after graft inoculation with CTV-T36, either in the nontransgenic rootstock or in the transgenic scion. Accumulation of transgene-derived siRNAs was necessary but not sufficient for CTV resistance. Inoculation with a divergent CTV strain led to partially breaking the resistance, thus showing the role of sequence identity in the underlying mechanism. Our results are a step forward to developing transgenic resistance to CTV and also show that targeting simultaneously by RNA interference (RNAi) the three viral silencing suppressors appears critical for this purpose, although the involvement of concurrent RNAi mechanisms cannot be excluded.
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Affiliation(s)
- Nuria Soler
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias-IVIA, Valencia, Spain
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Taylor NJ, Halsey M, Gaitán-Solís E, Anderson P, Gichuki S, Miano D, Bua A, Alicai T, Fauquet CM. The VIRCA Project: virus resistant cassava for Africa. GM CROPS & FOOD 2012; 3:93-103. [PMID: 22572842 DOI: 10.4161/gmcr.19144] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The VIRCA (Virus Resistant Cassava for Africa) project is a collaborative program between the Donald Danforth Plant Science Center, USA the National Crops Resources Research Institute, Uganda and the Kenya Agricultural Research Institute, Kenya. VIRCA is structured to include all aspects of the intellectual property, technology, regulatory, biosafety, quality control, communication and distribution components required for a GM crop development and delivery process. VIRCA's goal is to improve cassava for resistance to the viral diseases cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) using pathogen-derived RNAi technology, and to field test, obtain regulatory approval for and deliver these products to small landholder farmers. During Phase I of the project, proof of concept was achieved by production and testing of virus resistant plants under greenhouse and confined field trials in East Africa. In VIRCA Phase II, two farmer-preferred varieties will be modified for resistance to CBSD and CMD, and lead events identified after molecular and field screening. In addition to delivery of royalty-free improved planting materials for farmers, VIRCA capacity building activities are enhancing indigenous capability for crop biotechnology in East Africa.
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Affiliation(s)
- Nigel J Taylor
- Donald Danforth Plant Science Center, St. Louis, MO, USA
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50
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Haroldsen VM, Szczerba MW, Aktas H, Lopez-Baltazar J, Odias MJ, Chi-Ham CL, Labavitch JM, Bennett AB, Powell ALT. Mobility of Transgenic Nucleic Acids and Proteins within Grafted Rootstocks for Agricultural Improvement. FRONTIERS IN PLANT SCIENCE 2012; 3:39. [PMID: 22645583 PMCID: PMC3355758 DOI: 10.3389/fpls.2012.00039] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 02/17/2012] [Indexed: 05/03/2023]
Abstract
Grafting has been used in agriculture for over 2000 years. Disease resistance and environmental tolerance are highly beneficial traits that can be provided through use of grafting, although the mechanisms, in particular for resistance, have frequently been unknown. As information emerges that describes plant disease resistance mechanisms, the proteins, and nucleic acids that play a critical role in disease management can be expressed in genetically engineered (GE) plant lines. Utilizing transgrafting, the combination of a GE rootstock with a wild-type (WT) scion, or the reverse, has the potential to provide pest and pathogen resistance, impart biotic and abiotic stress tolerance, or increase plant vigor and productivity. Of central importance to these potential benefits is the question of to what extent nucleic acids and proteins are transmitted across a graft junction and whether the movement of these molecules will affect the efficacy of the transgrafting approach. Using a variety of specific examples, this review will report on the movement of organellar DNA, RNAs, and proteins across graft unions. Attention will be specifically drawn to the use of small RNAs and gene silencing within transgrafted plants, with a particular focus on pathogen resistance. The use of GE rootstocks or scions has the potential to extend the horticultural utility of grafting by combining this ancient technique with the molecular strategies of the modern era.
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Affiliation(s)
| | - Mark W. Szczerba
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Hakan Aktas
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
- Department of Horticulture, Faculty of Agriculture, University of Suleyman DemirelIsparta, Turkey
| | - Javier Lopez-Baltazar
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
- Instituto Tecnologico del Valle de OaxacaOaxaca, Mexico
| | - Mar Joseph Odias
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | | | - John M. Labavitch
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Alan B. Bennett
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Ann L. T. Powell
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
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