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Wei L, Chen B, Li X, Shi H, Xie S, Hu H, Chen W, Wei L, Wang X, Chen C. The HOG-pathway related AaOS1 leads to dicarboximide-resistance in field strains of Alternaria alternata and contributes, together with the Aafhk1, to mycotoxin production and virulence. PEST MANAGEMENT SCIENCE 2024; 80:2937-2949. [PMID: 38297826 DOI: 10.1002/ps.8002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 01/27/2024] [Accepted: 02/01/2024] [Indexed: 02/02/2024]
Abstract
BACKGROUND Garlic leaf spot (GLS) caused by Alternaria alternata is one of the main diseases in the garlic production areas, and its management heavily relies on dicarboximide fungicides. However, the efficacy of dicarboximides against the GLS disease has decreased year on year. RESULTS In the present study, 10 of 148 A. alternata strains separated from Jiangsu Province were moderately resistant (MR) to a dicarboximide fungicide procymidone (ProMR). Positive cross-resistance was observed between Pro and iprodione (Ipro) or fludioxonil (Fld), but not between Pro and fluazinam or azoxystrobin. Mutations at AaOS1, but not Aafhk1, were confirmed to confer the Pro resistance by constructing replacement mutants, whereas mutations at both AaOS1 and Aafhk1 decreased the gene expression level of AapksI, as well as the ability to produce mycotoxin AOH (polyketide-derived alternariol) and virulence. Additionally, more genes (AaOS1 and Aafhk1) harboring the mutations experienced a larger biological fitness penalty. CONCLUSION To our knowledge, this is the first report on Pro resistance selected in garlic fields, and mutations at AaOS1 of A. alternata causing a decreased ability to produce the mycotoxin AOH. © 2024 Society of Chemical Industry.
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Affiliation(s)
- Lingling Wei
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Bin Chen
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Xiujuan Li
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Haiping Shi
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Shuai Xie
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Hao Hu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Wenchan Chen
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Lihui Wei
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Xiaoyu Wang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Changjun Chen
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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Detection and Molecular Phylogenetic-Morphometric Characterization of Rhizoctonia tuliparum, Causal Agent of Gray Bulb Rot of Tulips and Bulbous Iris. J Fungi (Basel) 2022; 8:jof8020163. [PMID: 35205917 PMCID: PMC8880388 DOI: 10.3390/jof8020163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 01/31/2022] [Accepted: 02/03/2022] [Indexed: 11/17/2022] Open
Abstract
Gray bulb rot of tulips and bulbous iris is caused by the soil-borne fungal pathogen, Rhizoctonia tuliparum (Rtul). Sclerotia present in infected bulbs, as well as overwintering sclerotia in soil and field debris, are the primary sources of infection. A method for accurate and sensitive detection of Rtul from soil and infected bulbs, and estimation of inoculum threshold levels, is needed for the management of disease caused by this pathogen. We designed a unique set of primers targeting the ITS2 region of the Rtul genome and developed a highly sensitive quantitative PCR (qPCR)-based method for Rtul identification using these primers, where the threshold of detection was approximately 1 fg Rtul DNA. The assay was more sensitive with sclerotia collected from the field (natural) than with those grown in the lab, and more sensitive with natural-light than natural-dark sclerotia. Also, the detection method was more sensitive when sclerotia were extracted from soil than from bulb tissue. The qPCR method was highly specific, as no PCR amplification was detected when genomic DNA from 62 non-Rtul Rhizoctonia isolates from a wide range of anastomosis groups were tested. To understand the evolutionary relationships and genomic diversity of Rtul, we performed phylogenetics of the ITS1-5.8S-ITS2 region and ITS2-molecular morphometric characterization (MMC) of Rtul isolates. The three Rtul isolates whose ITS sequences were available in GenBank formed a distinct phylogenetic clade with Ceratobasidium anceps as the nearest relative. Furthermore, MMC analysis revealed genetic divergence among these three Rtul isolates.
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Singh V, Lakshman DK, Roberts DP, Ismaiel A, Hooda KS, Gogoi R. Morphopathological and Molecular Morphometric Characterization of Waitea circinata var. prodigus Causing a Novel Sheath Spot Disease of Maize in India. PLANT DISEASE 2022; 106:526-534. [PMID: 34261356 DOI: 10.1094/pdis-05-21-0951-re] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Maize brown sheath spot (MBSS), a new disease of maize, was discovered while surveying for maize leaf and sheath blight diseases in the Indian states of Assam, Jharkhand, Meghalaya, Manipur, and Odisha. Maize is the third most important cereal after rice and wheat in India. Unlike banded leaf and sheath blight disease caused by Rhizoctonia solani, MBSS symptoms on maize were discrete and limited to sheaths only. Symptoms of MBSS in the field were initially water-soaked necrotic lesions of 1 to 2 cm in diameter on the lowermost leaf sheaths, which then progressed to the upper sheaths. Lesions coalesced and covered approximately 2 to 5% of the sheath area. Infected dried lower leaves were shed, whereas infected upper leaves remained on the stem. The pathogen was isolated, characterized morphologically, pathologically, and molecularly, and identified as Waitea circinata var. prodigus, a basidiomycete known to cause basal leaf blight of seashore paspalum. The internal transcribed spacer (ITS) sequence 2 (ITS2) of rDNA from MBSS isolates formed a well supported clade with known W. circinata var. prodigus isolates. Molecular morphometric analysis of the ITS2 regions of the five known varieties of W. circinata detected distinguishing variations in GC content, compensatory base changes (CBCs), hemi- CBCs, indels, and altered base-pairing of helices. Variation in these characteristics may indicate that varieties are distinct biological species within W. circinata sensu lato. The geographical distribution and potential impacts of MBSS on the maize crop in India necessitate further investigations of pathogen identification and disease management.
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Affiliation(s)
- Vimla Singh
- Department of Botany and Plant Physiology, Chaudhary Charan Singh Haryana Agricultural University, Regional Research Station, Karnal 132001, India
| | - Dilip K Lakshman
- Sustainable Agricultural Systems Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705, U.S.A
| | - Daniel P Roberts
- Sustainable Agricultural Systems Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705, U.S.A
| | - Adnan Ismaiel
- Sustainable Agricultural Systems Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705, U.S.A
| | - K S Hooda
- Germplasm Evaluation Division, Indian Council of Agricultural Research, National Bureau of Plant Genetic Resources, New Delhi 110012, India
| | - Robin Gogoi
- Division of Plant Pathology, Indian Council of Agricultural Research, Indian Agricultural Research Institute, New Delhi 110012, India
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Wang M, Van Vleet S, McGee R, Paulitz T, Porter L, Schroeder K, Vandemark G, Chen W. Chickpea Seed Rot and Damping-Off Caused by Metalaxyl-Resistant Pythium ultimum and Its Management with Ethaboxam. PLANT DISEASE 2021; 105:1728-1737. [PMID: 33118871 DOI: 10.1094/pdis-08-20-1659-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Metalaxyl and its isomer mefenoxam have been the primary fungicides used as seed treatments in managing Pythium seed rot and damping-off of chickpea (Cicer arietinum). However, outbreaks of seed rot and damping-off of metalaxyl-treated chickpea seeds were found in the dryland agriculture regions of southeastern Washington and northern Idaho. Pythium spp. isolated from rotten seeds and associated soils showed high levels of resistance to metalaxyl. Large proportions (31 to 91%) of Pythium isolates resistant to metalaxyl were detected in areas where severe chickpea damping-off occurred and were observed in commercial chickpea fields over several years. All metalaxyl-resistant (MR) isolates were identified as Pythium ultimum var. ultimum. The metalaxyl resistance trait measured by EC50 values was stable over 10 generations in the absence of metalaxyl, and no observable fitness costs were associated with metalaxyl resistance. Under controlled conditions, metalaxyl treatments failed to protect chickpea seeds from seed rot and damping-off after inoculation with MR Pythium isolates. In culture, ethaboxam inhibited mycelial growth of both MR and metalaxyl-sensitive isolates. Greenhouse and field tests showed that ethaboxam is effective in managing MR Pythium. Ethaboxam in combination with metalaxyl is commonly applied as seed treatments in commercial chickpea production.
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Affiliation(s)
- Moying Wang
- Washington State University, Pullman, WA 99164
| | | | - Rebecca McGee
- Washington State University, Pullman, WA 99164
- U.S. Department of Agriculture-Agricultural Research Service and Washington State University, Pullman, WA 99164
| | - Timothy Paulitz
- Washington State University, Pullman, WA 99164
- U.S. Department of Agriculture-Agricultural Research Service and Washington State University, Pullman, WA 99164
| | - Lyndon Porter
- Washington State University, Pullman, WA 99164
- U.S. Department of Agriculture-Agricultural Research Service and Washington State University, Prosser, WA 99350
| | | | - George Vandemark
- Washington State University, Pullman, WA 99164
- U.S. Department of Agriculture-Agricultural Research Service and Washington State University, Pullman, WA 99164
| | - Weidong Chen
- Washington State University, Pullman, WA 99164
- U.S. Department of Agriculture-Agricultural Research Service and Washington State University, Pullman, WA 99164
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Muzhinji N, Woodhall JW, Truter M, van der Waals JE. Variation in Fungicide Sensitivity Among Rhizoctonia Isolates Recovered from Potatoes in South Africa. PLANT DISEASE 2018; 102:1520-1526. [PMID: 30673418 DOI: 10.1094/pdis-09-17-1470-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Rhizoctonia is a major pathogen of potato causing substantial yield losses worldwide. Control of Rhizoctonia diseases is based predominantly on the application of fungicides. However, little is known about the fungicide response variability of different Rhizoctonia anastomosis groups associated with potato diseases in South Africa. A total of 131 Rhizoctonia isolates were obtained from potato growing regions of South Africa from 2012 to 2014 and evaluated for sensitivity to fungicides in vitro and in vivo. The fungicides comprised six chemical formulations and one bio-fungicide representing seven Fungicide Resistance Action Committee groups. All Rhizoctonia anastomosis groups were sensitive to tolclofos-methyl (EC50: 0.001 to 0.098 μg a.i. ml-1) and fludioxonil (EC50: 0.06 to 0.09 μg a.i. ml-1) and showed variation in sensitivity to pencycuron, iprodione, benomyl, and Bacillus subtilis QST 713. However, for azoxystrobin, Rhizoctonia isolates exhibited variable sensitivity ranging from sensitivity (EC50: <0.09 μg a.i. ml-1) to insensitivity with EC50 values exceeding 5 μg a.i. ml-1. In greenhouse and field trials, tolclofos-methyl and fludioxonil exhibited significantly greater control of stem and black scurf whereas azoxystrobin was the least effective. This work demonstrated variable sensitivity within and among anastomosis groups of R. solani and binucleate Rhizoctonia to different fungicides. Information on fungicide sensitivity of Rhizoctonia isolates is crucial in the development of effective Rhizoctonia control strategies and facilitates monitoring of fungicide insensitive isolates in the pathogen population.
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Affiliation(s)
- N Muzhinji
- Department of Plant and Soil Sciences, University of Pretoria, Hatfield, Pretoria 0001, South Africa
| | - J W Woodhall
- University of Idaho, Parma Research and Extension Center, Parma, ID 83660
| | - M Truter
- Agricultural Research Council-Vegetable and Ornamental Plants, Pretoria, 0001, South Africa
| | - J E van der Waals
- Department of Plant and Soil Sciences, University of Pretoria, Hatfield, Pretoria 0001, South Africa
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Blanco AJV, Costa MO, Silva RDN, Albuquerque FSD, Melo ATDO, Lopes FAC, Steindorff AS, Barbosa ET, Ulhoa CJ, Lobo Junior M. Diversity and Pathogenicity of Rhizoctonia Species from the Brazilian Cerrado. PLANT DISEASE 2018; 102:773-781. [PMID: 30673401 DOI: 10.1094/pdis-05-17-0721-re] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Eighty-one Rhizoctonia-like isolates were identified based on morphology and nuclei-staining methods from natural and agricultural soils of the Cerrado (Brazilian savanna). The nucleotide similarity analysis of ITS1-5.8S-ITS2 regions identified 14 different taxa, with 39.5% of isolates assigned to Waitea circinata (zeae, oryzae, and circinata varieties), while 37.0% belonged to Thanatephorus cucumeris anastomosis groups (AGs) AG1-IB, AG1-ID, AG1-IE, AG4-HGI, and AG4-HGIII. Ceratobasidium spp. AG-A, AG-F, AG-Fa, AG-P, and AG-R comprised 23.5%. Rhizoctonia zeae (19.8%), R. solani AG1-IE (18.6%), and binucleate Rhizoctonia AG-A (8.6%) were the most frequent anamorphic states found. Root rot severity caused by the different taxa varied from low to high on common beans, and tended to be low to average in maize. Twenty-two isolates were pathogenic to both hosts, suggesting difficulties in managing Rhizoctonia root rots with crop rotation. These results suggest that cropping history affects the geographical arrangement of AGs, with a prevalence of AG1 in the tropical zone from central to north Brazil while the AG4 group was most prevalent from central to subtropical south. W. circinata var. zeae was predominant in soils under maize production. To our knowledge, this is the first report on the occurrence of W. circinata var. circinata in Brazil.
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Affiliation(s)
- Angel José Vieira Blanco
- Goiás Federal Institute of Education, Science and Technology - Campus Inhumas, Inhumas, GO, Brazil 75400-000
| | - Marília Oliveira Costa
- Goiás Federal Institute of Education, Science and Technology - Campus Inhumas, Inhumas, GO, Brazil 75400-000
| | - Roberto do Nascimento Silva
- Department of Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, SP, Brazil 14049-900
| | | | | | | | - Andrei Stecca Steindorff
- Department of Cell Biology, Biological Sciences Institute, Brasília University Campus Darcy Ribeiro, Brasília, DF, Brazil, 70910-900
| | - Elder Tadeu Barbosa
- Brazilian Agricultural Research Corporation, Embrapa Arroz e Feijão, Santo Antônio de Goiás, GO, Brazil, 75375-000
| | - Cirano José Ulhoa
- Biological Sciences Institute, Biochemistry and Molecular Biology Department, Goiás Federal University, Campus Samambaia, Goiânia, GO, Brazil, 74690-900
| | - Murillo Lobo Junior
- Brazilian Agricultural Research Corporation, Embrapa Arroz e Feijão, Santo Antônio de Goiás, GO, Brazil, 75375-000
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Koehler AM, Shew HD. Seasonal dynamics and fungicide sensitivity of organisms causing brown patch of tall fescue in North Carolina. Mycologia 2017; 109:667-675. [PMID: 29020516 DOI: 10.1080/00275514.2017.1377587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Brown patch, caused by multiple species of Rhizoctonia and Rhizoctonia-like fungi, is the most severe summer disease of tall fescue in home lawns across the southeastern United States. Home lawns were surveyed in central North Carolina from 2013 to 2015 to determine the organisms present during typical epidemics of brown patch in tall fescue. Isolates of Rhizoctonia and Rhizoctonia-like fungi were obtained by sampling 147 locations in July 2013 and May and July 2014. In addition, 11 sites were sampled once a week for 12 consecutive weeks from late May to the end of July 2015. All isolates were identified to species and anastomosis group with nuc rDNA internal transcribed spacer (ITS) sequence analysis. Isolations from brown patch lesions in May 2014 predominately yielded Ceratobasidium cereale (77% of the organisms recovered), whereas the organisms recovered in July 2013 and 2014 were R. solani AG 2-2-IIIB (44%), R. solani AG 1-IB (37%), and R. zeae (14%). In 2015, Ceratobasidium cereale was isolated from all 11 locations in May but was replaced by Rhizoctonia species in June and July. Sensitivity of the May 2014 isolates to multiple concentrations of the fungicides azoxystrobin, flutolanil, fluxapyroxad, and propiconazole was compared with sensitivity of isolates collected in 2003, to determine whether multiple years of exposure to fungicides applied for brown patch control had altered fungicide sensitivity. Historical isolates of R. solani, which had never been exposed to fungicide applications for brown patch control, were also included for comparison. Mean EC50 values (concentration of fungicide needed to inhibit mycelial growth by 50%) varied across fungicides and species, but no resistance was observed, and there was no apparent shift in sensitivity over the years. An additional 94 isolates from 2015 were screened against azoxystrobin, flutolanil, fluxapyroxad, and propiconazole, and fungicide insensitivity was not observed.
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Affiliation(s)
- Alyssa M Koehler
- a Department of Entomology and Plant Pathology , North Carolina State University , Raleigh , North Carolina 27695
| | - H David Shew
- a Department of Entomology and Plant Pathology , North Carolina State University , Raleigh , North Carolina 27695
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Ajayi-Oyetunde OO, Butts-Wilmsmeyer CJ, Bradley CA. Sensitivity of Rhizoctonia solani to Succinate Dehydrogenase Inhibitor and Demethylation Inhibitor Fungicides. PLANT DISEASE 2017; 101:487-495. [PMID: 30677351 DOI: 10.1094/pdis-07-16-1015-re] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Soybean seedling diseases are caused by Rhizoctonia solani and can be managed with seed-applied fungicides that belong to different chemistry classes. To provide a benchmark for assessing a decline in sensitivities to these fungicide classes, R. solani isolates collected prior to 2001 were evaluated for their sensitivities to succinate dehydrogenase inhibitor (SDHI) (penflufen and sedaxane) and demethylation inhibitor (DMI) fungicides (ipconazole and prothioconazole). The effective concentration of each fungicide that reduced mycelial growth by 50% (EC50) was determined in vitro and compared with those of isolates recovered after 2011 from soybean plants with damping off and hypocotyl and root rot symptoms across different soybean-growing regions in the United States and Canada. All isolates, regardless of collection date, were extremely sensitive (EC50 < 1 μg/ml) to the SDHI fungicides but were either extremely sensitive or moderately sensitive (1 ≤ EC50 ≤ 10 μg/ml) to the DMI fungicides. For all four active ingredients, variation in sensitivities was observed within and among the different anastomosis groups composing both isolate groups. Isolates collected after 2011, which also had varying in vitro sensitivities, were further evaluated for in vivo sensitivity to the four fungicides in the greenhouse. In vitro fungicide sensitivity did not always coincide with fungicide efficacy in vivo because all isolates tested, regardless of in vitro sensitivity, were effectively controlled by the application of the seed treatment fungicides in the greenhouse. Overall, our results indicate no shift in sensitivity to the fungicide classes evaluated, although considerable variability in the sensitivities of the two groups of isolates examined was present. Based on this research, continued monitoring of fungicide sensitivities of R. solani populations should occur to determine whether sensitivities become further reduced in the future.
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Affiliation(s)
| | | | - Carl A Bradley
- Department of Crop Sciences, University of Illinois, Urbana 61801
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