1
|
How virulent are emerging maize-infecting mastreviruses? Arch Virol 2021; 166:955-959. [PMID: 33502595 DOI: 10.1007/s00705-020-04906-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 10/15/2020] [Indexed: 10/22/2022]
Abstract
Maize streak disease (MSD) is one of the most significant biotic constraints on the production of Africa's most important cereal crop. Until recently, the only virus known to cause severe MSD was the A-strain of maize streak virus (MSV/A), a member of the genus Mastrevirus, family Geminiviridae. However, over the past decade, two other mastreviruses, MSV/C and maize streak Réunion virus (MSRV), have been repeatedly found in the absence of MSV/A in maize plants displaying severe MSD symptoms. Here, we report on infectious clones of MSV/C and MSRV and test their ability to cause severe MSD symptoms. Although cloned MSV/C and MSRV genomes could cause systemic symptomatic infections in MSD-sensitive maize genotypes, these infections yielded substantially milder symptoms than those observed in the field. The MSV/C and MSRV isolates that we have examined are therefore unlikely to cause severe MSD on their own. Furthermore, mixed infections of MSRV and MSV/C with other mild MSV strains also consistently yielded mild MSD symptoms. It is noteworthy that MSRV produces distinctive striate symptoms in maize that are similar in pattern, albeit not in severity, to those seen in the field, showing that this virus may contribute to the severe MSD symptoms seen in the field. Therefore, despite not fulfilling Koch's postulates for MSV/C and MSRV as causal agents of severe MSD, we cannot exclude the possibility that these viruses could be contributing to currently emerging maize diseases.
Collapse
|
2
|
Monjane AL, Dellicour S, Hartnady P, Oyeniran KA, Owor BE, Bezuidenhout M, Linderme D, Syed RA, Donaldson L, Murray S, Rybicki EP, Kvarnheden A, Yazdkhasti E, Lefeuvre P, Froissart R, Roumagnac P, Shepherd DN, Harkins GW, Suchard MA, Lemey P, Varsani A, Martin DP. Symptom evolution following the emergence of maize streak virus. eLife 2020; 9:51984. [PMID: 31939738 PMCID: PMC7034976 DOI: 10.7554/elife.51984] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/14/2020] [Indexed: 11/24/2022] Open
Abstract
For pathogens infecting single host species evolutionary trade-offs have previously been demonstrated between pathogen-induced mortality rates and transmission rates. It remains unclear, however, how such trade-offs impact sub-lethal pathogen-inflicted damage, and whether these trade-offs even occur in broad host-range pathogens. Here, we examine changes over the past 110 years in symptoms induced in maize by the broad host-range pathogen, maize streak virus (MSV). Specifically, we use the quantified symptom intensities of cloned MSV isolates in differentially resistant maize genotypes to phylogenetically infer ancestral symptom intensities and check for phylogenetic signal associated with these symptom intensities. We show that whereas symptoms reflecting harm to the host have remained constant or decreased, there has been an increase in how extensively MSV colonizes the cells upon which transmission vectors feed. This demonstrates an evolutionary trade-off between amounts of pathogen-inflicted harm and how effectively viruses position themselves within plants to enable onward transmission.
Collapse
Affiliation(s)
- Adérito L Monjane
- Fish Health Research Group, Norwegian Veterinary Institute, Oslo, Norway.,Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Simon Dellicour
- Department of Microbiology, Immunology and Transplantation, Rega Institute, Laboratory for Clinical and Epidemiological Virology, KU Leuven - University of Leuven, Leuven, Belgium.,Spatial Epidemiology Laboratory (SpELL), Université Libre de Bruxelles, Brussels, Belgium
| | - Penelope Hartnady
- Computational Biology Division, Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| | - Kehinde A Oyeniran
- Computational Biology Division, Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| | - Betty E Owor
- Department of Agricultural Production, School of Agricultural Sciences, Makerere University, Kampala, Uganda
| | - Marion Bezuidenhout
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Daphné Linderme
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Rizwan A Syed
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Lara Donaldson
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Shane Murray
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Edward P Rybicki
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Anders Kvarnheden
- Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Elham Yazdkhasti
- Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | | | - Rémy Froissart
- University of Montpellier, Centre National de la Recherche Scientifique (CNRS), Institut de recherche pour le développement (IRD), UMR 5290, Maladie Infectieuses & Vecteurs: Écologie, Génétique Évolution & Contrôle" (MIVEGEC), Montpellier, France
| | - Philippe Roumagnac
- CIRAD, BGPI, Montpellier, France.,BGPI, INRA, CIRAD, SupAgro, Univ Montpellier, Montpellier, France
| | - Dionne N Shepherd
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa.,Research Office, University of Cape Town, Cape Town, South Africa
| | - Gordon W Harkins
- South African Medical Research Council Bioinformatics Unit, South African National Bioinformatics Institute, University of the Western Cape, Bellville, South Africa
| | - Marc A Suchard
- Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Philippe Lemey
- Department of Microbiology, Immunology and Transplantation, Rega Institute, Laboratory for Clinical and Epidemiological Virology, KU Leuven - University of Leuven, Leuven, Belgium
| | - Arvind Varsani
- The Biodesign Center for Fundamental and Applied Microbiomics, Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, United States.,Structural Biology Research Unit, Department of Integrative Biomedical Sciences, University of Cape Town, Cape Town, South Africa
| | - Darren P Martin
- Computational Biology Division, Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| |
Collapse
|
3
|
Diagnostics of Seed-Borne Plant Pathogens for Safe Introduction and Healthy Conservation of Plant Genetic Resources. Fungal Biol 2016. [DOI: 10.1007/978-3-319-27312-9_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
4
|
Shepherd DN, Dugdale B, Martin DP, Varsani A, Lakay FM, Bezuidenhout ME, Monjane AL, Thomson JA, Dale J, Rybicki EP. Inducible resistance to maize streak virus. PLoS One 2014; 9:e105932. [PMID: 25166274 PMCID: PMC4148390 DOI: 10.1371/journal.pone.0105932] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 07/28/2014] [Indexed: 11/18/2022] Open
Abstract
Maize streak virus (MSV), which causes maize streak disease (MSD), is the major viral pathogenic constraint on maize production in Africa. Type member of the Mastrevirus genus in the family Geminiviridae, MSV has a 2.7 kb, single-stranded circular DNA genome encoding a coat protein, movement protein, and the two replication-associated proteins Rep and RepA. While we have previously developed MSV-resistant transgenic maize lines constitutively expressing "dominant negative mutant" versions of the MSV Rep, the only transgenes we could use were those that caused no developmental defects during the regeneration of plants in tissue culture. A better transgene expression system would be an inducible one, where resistance-conferring transgenes are expressed only in MSV-infected cells. However, most known inducible transgene expression systems are hampered by background or "leaky" expression in the absence of the inducer. Here we describe an adaptation of the recently developed INPACT system to express MSV-derived resistance genes in cell culture. Split gene cassette constructs (SGCs) were developed containing three different transgenes in combination with three different promoter sequences. In each SGC, the transgene was split such that it would be translatable only in the presence of an infecting MSV's replication associated protein. We used a quantitative real-time PCR assay to show that one of these SGCs (pSPLITrepIII-Rb-Ubi) inducibly inhibits MSV replication as efficiently as does a constitutively expressed transgene that has previously proven effective in protecting transgenic maize from MSV. In addition, in our cell-culture based assay pSPLITrepIII-Rb-Ubi inhibited replication of diverse MSV strains, and even, albeit to a lesser extent, of a different mastrevirus species. The application of this new technology to MSV resistance in maize could allow a better, more acceptable product.
Collapse
Affiliation(s)
- Dionne N. Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
- * E-mail:
| | - Benjamin Dugdale
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - Darren P. Martin
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
- Centre for High-Performance Computing, Rosebank, Cape Town, South Africa
| | - Arvind Varsani
- School of Biological Sciences and Biomolecular Interaction Centre, University of Canterbury, Christchurch, New Zealand
- Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
- Electron Microscope Unit, Division of Medical Biochemistry, Department of Clinical Laboratory Sciences, University of Cape Town, Observatory, Cape Town, South Africa
| | - Francisco M. Lakay
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
| | - Marion E. Bezuidenhout
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
| | - Adérito L. Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| | - Jennifer A. Thomson
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
| | - James Dale
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - Edward P. Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| |
Collapse
|
5
|
Monjane AL, Martin DP, Lakay F, Muhire BM, Pande D, Varsani A, Harkins G, Shepherd DN, Rybicki EP. Extensive recombination-induced disruption of genetic interactions is highly deleterious but can be partially reversed by small numbers of secondary recombination events. J Virol 2014; 88:7843-51. [PMID: 24789787 PMCID: PMC4097777 DOI: 10.1128/jvi.00709-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 04/22/2014] [Indexed: 01/12/2023] Open
Abstract
Although homologous recombination can potentially provide viruses with vastly more evolutionary options than are available through mutation alone, there are considerable limits on the adaptive potential of this important evolutionary process. Primary among these is the disruption of favorable coevolved genetic interactions that can occur following the transfer of foreign genetic material into a genome. Although the fitness costs of such disruptions can be severe, in some cases they can be rapidly recouped by either compensatory mutations or secondary recombination events. Here, we used a maize streak virus (MSV) experimental model to explore both the extremes of recombination-induced genetic disruption and the capacity of secondary recombination to adaptively reverse almost lethal recombination events. Starting with two naturally occurring parental viruses, we synthesized two of the most extreme conceivable MSV chimeras, each effectively carrying 182 recombination breakpoints and containing thorough reciprocal mixtures of parental polymorphisms. Although both chimeras were severely defective and apparently noninfectious, neither had individual movement-, encapsidation-, or replication-associated genome regions that were on their own "lethally recombinant." Surprisingly, mixed inoculations of the chimeras yielded symptomatic infections with viruses with secondary recombination events. These recombinants had only 2 to 6 breakpoints, had predominantly inherited the least defective of the chimeric parental genome fragments, and were obviously far more fit than their synthetic parents. It is clearly evident, therefore, that even when recombinationally disrupted virus genomes have extremely low fitness and there are no easily accessible routes to full recovery, small numbers of secondary recombination events can still yield tremendous fitness gains. Importance: Recombination between viruses can generate strains with enhanced pathological properties but also runs the risk of producing hybrid genomes with decreased fitness due to the disruption of favorable genetic interactions. Using two synthetic maize streak virus genome chimeras containing alternating genome segments derived from two natural viral strains, we examined both the fitness costs of extreme degrees of recombination (both chimeras had 182 recombination breakpoints) and the capacity of secondary recombination events to recoup these costs. After the severely defective chimeras were introduced together into a suitable host, viruses with between 1 and 3 secondary recombination events arose, which had greatly increased replication and infective capacities. This indicates that even in extreme cases where recombination-induced genetic disruptions are almost lethal, and 91 consecutive secondary recombination events would be required to reconstitute either one of the parental viruses, moderate degrees of fitness recovery can be achieved through relatively small numbers of secondary recombination events.
Collapse
Affiliation(s)
- Adérito L Monjane
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Darren P Martin
- Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Francisco Lakay
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Brejnev M Muhire
- Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Daniel Pande
- Department of Botany and Horticulture, Maseno University, Maseno, Kenya
| | - Arvind Varsani
- School of Biological Sciences and Biomolecular Interaction Centre, University of Canterbury, Christchurch, New Zealand Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA Electron Microscope Unit, Division of Medical Biochemistry, Department of Clinical Laboratory Sciences, University of Cape Town, Cape Town, South Africa
| | - Gordon Harkins
- South African National Bioinformatics Institute, MRC Unit for Bioinformatics Capacity Development, University of the Western Cape, Bellville, South Africa
| | - Dionne N Shepherd
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa
| | - Edward P Rybicki
- Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| |
Collapse
|
6
|
Monjane AL, Pande D, Lakay F, Shepherd DN, van der Walt E, Lefeuvre P, Lett JM, Varsani A, Rybicki EP, Martin DP. Adaptive evolution by recombination is not associated with increased mutation rates in Maize streak virus. BMC Evol Biol 2012; 12:252. [PMID: 23268599 PMCID: PMC3556111 DOI: 10.1186/1471-2148-12-252] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Accepted: 12/12/2012] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Single-stranded (ss) DNA viruses in the family Geminiviridae are proving to be very useful in real-time evolution studies. The high mutation rate of geminiviruses and other ssDNA viruses is somewhat mysterious in that their DNA genomes are replicated in host nuclei by high fidelity host polymerases. Although strand specific mutation biases observed in virus species from the geminivirus genus Mastrevirus indicate that the high mutation rates in viruses in this genus may be due to mutational processes that operate specifically on ssDNA, it is currently unknown whether viruses from other genera display similar strand specific mutation biases. Also, geminivirus genomes frequently recombine with one another and an alternative cause of their high mutation rates could be that the recombination process is either directly mutagenic or produces a selective environment in which the survival of mutants is favoured. To investigate whether there is an association between recombination and increased basal mutation rates or increased degrees of selection favoring the survival of mutations, we compared the mutation dynamics of the MSV-MatA and MSV-VW field isolates of Maize streak virus (MSV; Mastrevirus), with both a laboratory constructed MSV recombinant, and MSV recombinants closely resembling MSV-MatA. To determine whether strand specific mutation biases are a general characteristic of geminivirus evolution we compared mutation spectra arising during these MSV experiments with those arising during similar experiments involving the geminivirus Tomato yellow leaf curl virus (Begomovirus genus). RESULTS Although both the genomic distribution of mutations and the occurrence of various convergent mutations at specific genomic sites indicated that either mutation hotspots or selection for adaptive mutations might elevate observed mutation rates in MSV, we found no association between recombination and mutation rates. Importantly, when comparing the mutation spectra of MSV and TYLCV we observed similar strand specific mutation biases arising predominantly from imbalances in the complementary mutations G → T: C → A. CONCLUSIONS While our results suggest that recombination does not strongly influence mutation rates in MSV, they indicate that high geminivirus mutation rates are at least partially attributable to increased susceptibility of all geminivirus genomes to oxidative damage while in a single stranded state.
Collapse
Affiliation(s)
- Adérito L Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Monjane AL, van der Walt E, Varsani A, Rybicki EP, Martin DP. Recombination hotspots and host susceptibility modulate the adaptive value of recombination during maize streak virus evolution. BMC Evol Biol 2011; 11:350. [PMID: 22136133 PMCID: PMC3280948 DOI: 10.1186/1471-2148-11-350] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/02/2011] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Maize streak virus -strain A (MSV-A; Genus Mastrevirus, Family Geminiviridae), the maize-adapted strain of MSV that causes maize streak disease throughout sub-Saharan Africa, probably arose between 100 and 200 years ago via homologous recombination between two MSV strains adapted to wild grasses. MSV recombination experiments and analyses of natural MSV recombination patterns have revealed that this recombination event entailed the exchange of the movement protein - coat protein gene cassette, bounded by the two genomic regions most prone to recombination in mastrevirus genomes; the first surrounding the virion-strand origin of replication, and the second around the interface between the coat protein gene and the short intergenic region. Therefore, aside from the likely adaptive advantages presented by a modular exchange of this cassette, these specific breakpoints may have been largely predetermined by the underlying mechanisms of mastrevirus recombination. To investigate this hypothesis, we constructed artificial, low-fitness, reciprocal chimaeric MSV genomes using alternating genomic segments from two MSV strains; a grass-adapted MSV-B, and a maize-adapted MSV-A. Between them, each pair of reciprocal chimaeric genomes represented all of the genetic material required to reconstruct - via recombination - the highly maize-adapted MSV-A genotype, MSV-MatA. We then co-infected a selection of differentially MSV-resistant maize genotypes with pairs of reciprocal chimaeras to determine the efficiency with which recombination would give rise to high-fitness progeny genomes resembling MSV-MatA. RESULTS Recombinants resembling MSV-MatA invariably arose in all of our experiments. However, the accuracy and efficiency with which the MSV-MatA genotype was recovered across all replicates of each experiment depended on the MSV susceptibility of the maize genotypes used and the precise positions - in relation to known recombination hotspots - of the breakpoints required to re-create MSV-MatA. Although the MSV-sensitive maize genotype gave rise to the greatest variety of recombinants, the measured fitness of each of these recombinants correlated with their similarity to MSV-MatA. CONCLUSIONS The mechanistic predispositions of different MSV genomic regions to recombination can strongly influence the accessibility of high-fitness MSV recombinants. The frequency with which the fittest recombinant MSV genomes arise also correlates directly with the escalating selection pressures imposed by increasingly MSV-resistant maize hosts.
Collapse
Affiliation(s)
- Adérito L Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa
| | | | - Arvind Varsani
- Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
- Electron Microscope Unit, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa
| | - Edward P Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa
- Computational Biology Group, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, 7925, Cape Town, South Africa
| | - Darren P Martin
- Computational Biology Group, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, 7925, Cape Town, South Africa
- Centre for High-Performance Computing, Rosebank, Cape Town, South Africa
| |
Collapse
|
8
|
Shepherd DN, Martin DP, Van Der Walt E, Dent K, Varsani A, Rybicki EP. Maize streak virus: an old and complex 'emerging' pathogen. MOLECULAR PLANT PATHOLOGY 2010; 11:1-12. [PMID: 20078771 PMCID: PMC6640477 DOI: 10.1111/j.1364-3703.2009.00568.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
UNLABELLED Maize streak virus (MSV; Genus Mastrevirus, Family Geminiviridae) occurs throughout Africa, where it causes what is probably the most serious viral crop disease on the continent. It is obligately transmitted by as many as six leafhopper species in the Genus Cicadulina, but mainly by C. mbila Naudé and C. storeyi. In addition to maize, it can infect over 80 other species in the Family Poaceae. Whereas 11 strains of MSV are currently known, only the MSV-A strain is known to cause economically significant streak disease in maize. Severe maize streak disease (MSD) manifests as pronounced, continuous parallel chlorotic streaks on leaves, with severe stunting of the affected plant and, usuallly, a failure to produce complete cobs or seed. Natural resistance to MSV in maize, and/or maize infections caused by non-maize-adapted MSV strains, can result in narrow, interrupted streaks and no obvious yield losses. MSV epidemiology is primarily governed by environmental influences on its vector species, resulting in erratic epidemics every 3-10 years. Even in epidemic years, disease incidences can vary from a few infected plants per field, with little associated yield loss, to 100% infection rates and complete yield loss. TAXONOMY The only virus species known to cause MSD is MSV, the type member of the Genus Mastrevirus in the Family Geminiviridae. In addition to the MSV-A strain, which causes the most severe form of streak disease in maize, 10 other MSV strains (MSV-B to MSV-K) are known to infect barley, wheat, oats, rye, sugarcane, millet and many wild, mostly annual, grass species. Seven other mastrevirus species, many with host and geographical ranges partially overlapping those of MSV, appear to infect primarily perennial grasses. PHYSICAL PROPERTIES MSV and all related grass mastreviruses have single-component, circular, single-stranded DNA genomes of approximately 2700 bases, encapsidated in 22 x 38-nm geminate particles comprising two incomplete T = 1 icosahedra, with 22 pentameric capsomers composed of a single 32-kDa capsid protein. Particles are generally stable in buffers of pH 4-8. DISEASE SYMPTOMS In infected maize plants, streak disease initially manifests as minute, pale, circular spots on the lowest exposed portion of the youngest leaves. The only leaves that develop symptoms are those formed after infection, with older leaves remaining healthy. As the disease progresses, newer leaves emerge containing streaks up to several millimetres in length along the leaf veins, with primary veins being less affected than secondary or tertiary veins. The streaks are often fused laterally, appearing as narrow, broken, chlorotic stripes, which may extend over the entire length of severely affected leaves. Lesion colour generally varies from white to yellow, with some virus strains causing red pigmentation on maize leaves and abnormal shoot and flower bunching in grasses. Reduced photosynthesis and increased respiration usually lead to a reduction in leaf length and plant height; thus, maize plants infected at an early stage become severely stunted, producing undersized, misshapen cobs or giving no yield at all. Yield loss in susceptible maize is directly related to the time of infection: infected seedlings produce no yield or are killed, whereas plants infected at later times are proportionately less affected. DISEASE CONTROL Disease avoidance can be practised by only planting maize during the early season when viral inoculum loads are lowest. Leafhopper vectors can also be controlled with insecticides such as carbofuran. However, the development and use of streak-resistant cultivars is probably the most effective and economically viable means of preventing streak epidemics. Naturally occurring tolerance to MSV (meaning that, although plants become systemically infected, they do not suffer serious yield losses) has been found, which has primarily been attributed to a single gene, msv-1. However, other MSV resistance genes also exist and improved resistance has been achieved by concentrating these within individual maize genotypes. Whereas true MSV immunity (meaning that plants cannot be symptomatically infected by the virus) has been achieved in lines that include multiple small-effect resistance genes together with msv-1, it has proven difficult to transfer this immunity into commercial maize genotypes. An alternative resistance strategy using genetic engineering is currently being investigated in South Africa. USEFUL WEBSITES http://www.mcb.uct.ac.za/MSV/mastrevirus.htm; http://www.danforthcenter.org/iltab/geminiviridae/geminiaccess/mastrevirus/Mastrevirus.htm.
Collapse
Affiliation(s)
- Dionne N Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, PB Rondebosch, 7701, South Africa.
| | | | | | | | | | | |
Collapse
|
9
|
Harkins GW, Martin DP, Duffy S, Monjane AL, Shepherd DN, Windram OP, Owor BE, Donaldson L, van Antwerpen T, Sayed RA, Flett B, Ramusi M, Rybicki EP, Peterschmitt M, Varsani A. Dating the origins of the maize-adapted strain of maize streak virus, MSV-A. J Gen Virol 2009; 90:3066-3074. [PMID: 19692547 PMCID: PMC2885043 DOI: 10.1099/vir.0.015537-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Maize streak virus (MSV), which causes maize streak disease (MSD), is one of the most serious biotic threats to African food security. Here, we use whole MSV genomes sampled over 30 years to estimate the dates of key evolutionary events in the 500 year association of MSV and maize. The substitution rates implied by our analyses agree closely with those estimated previously in controlled MSV evolution experiments, and we use them to infer the date when the maize-adapted strain, MSV-A, was generated by recombination between two grass-adapted MSV strains. Our results indicate that this recombination event occurred in the mid-1800s, ∼20 years before the first credible reports of MSD in South Africa and centuries after the introduction of maize to the continent in the early 1500s. This suggests a causal link between MSV recombination and the emergence of MSV-A as a serious pathogen of maize.
Collapse
Affiliation(s)
- Gordon W Harkins
- South African National Bioinformatics Institute, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
| | - Darren P Martin
- Centre for High-Performance Computing, Rosebank, Cape Town, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| | - Siobain Duffy
- Department of Ecology, Evolution and Natural Resources, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901 USA
| | - Aderito L Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Dionne N Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Oliver P Windram
- Warwick Systems Biology Centre, University of Warwick, Wellesbourne CV35 9EF, UK
| | - Betty E Owor
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Lara Donaldson
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Tania van Antwerpen
- South African Sugarcane Research Institute, Mount Edgecombe, KwaZulu Natal, South Africa
| | - Rizwan A Sayed
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Bradley Flett
- Crop Protection, ARC-Grain Crops Institute, Potchefstroom 2520, South Africa
| | - Moses Ramusi
- Crop Protection, ARC-Grain Crops Institute, Potchefstroom 2520, South Africa
| | - Edward P Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, South Africa
| | - Michel Peterschmitt
- CIRAD, UMR BGPI, TA A54/K, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France
| | - Arvind Varsani
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.,Electron Microscope Unit, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
| |
Collapse
|
10
|
Martin DP, Shepherd DN. The epidemiology, economic impact and control of maize streak disease. Food Secur 2009. [DOI: 10.1007/s12571-009-0023-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
11
|
van der Walt E, Rybicki EP, Varsani A, Polston JE, Billharz R, Donaldson L, Monjane AL, Martin DP. Rapid host adaptation by extensive recombination. J Gen Virol 2009; 90:734-746. [PMID: 19218220 PMCID: PMC2885065 DOI: 10.1099/vir.0.007724-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Accepted: 11/18/2008] [Indexed: 11/25/2022] Open
Abstract
Experimental investigations into virus recombination can provide valuable insights into the biochemical mechanisms and the evolutionary value of this fundamental biological process. Here, we describe an experimental scheme for studying recombination that should be applicable to any recombinogenic viruses amenable to the production of synthetic infectious genomes. Our approach is based on differences in fitness that generally exist between synthetic chimaeric genomes and the wild-type viruses from which they are constructed. In mixed infections of defective reciprocal chimaeras, selection strongly favours recombinant progeny genomes that recover a portion of wild-type fitness. Characterizing these evolved progeny viruses can highlight both important genetic fitness determinants and the contribution that recombination makes to the evolution of their natural relatives. Moreover, these experiments supply precise information about the frequency and distribution of recombination breakpoints, which can shed light on the mechanistic processes underlying recombination. We demonstrate the value of this approach using the small single-stranded DNA geminivirus, maize streak virus (MSV). Our results show that adaptive recombination in this virus is extremely efficient and can yield complex progeny genomes comprising up to 18 recombination breakpoints. The patterns of recombination that we observe strongly imply that the mechanistic processes underlying rolling circle replication are the prime determinants of recombination breakpoint distributions found in MSV genomes sampled from nature.
Collapse
Affiliation(s)
- Eric van der Walt
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
| | - Edward P. Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Arvind Varsani
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
- Electron Microscope Unit, University of Cape Town, Cape Town, South Africa
| | - J. E. Polston
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
| | - Rosalind Billharz
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Lara Donaldson
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
| | - Adérito L. Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
| | - Darren P. Martin
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| |
Collapse
|
12
|
van der Walt E, Martin DP, Varsani A, Polston JE, Rybicki EP. Experimental observations of rapid Maize streak virus evolution reveal a strand-specific nucleotide substitution bias. Virol J 2008; 5:104. [PMID: 18816368 PMCID: PMC2572610 DOI: 10.1186/1743-422x-5-104] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 09/24/2008] [Indexed: 12/18/2022] Open
Abstract
Background Recent reports have indicated that single-stranded DNA (ssDNA) viruses in the taxonomic families Geminiviridae, Parvoviridae and Anellovirus may be evolving at rates of ~10-4 substitutions per site per year (subs/site/year). These evolution rates are similar to those of RNA viruses and are surprisingly high given that ssDNA virus replication involves host DNA polymerases with fidelities approximately 10 000 times greater than those of error-prone viral RNA polymerases. Although high ssDNA virus evolution rates were first suggested in evolution experiments involving the geminivirus maize streak virus (MSV), the evolution rate of this virus has never been accurately measured. Also, questions regarding both the mechanistic basis and adaptive value of high geminivirus mutation rates remain unanswered. Results We determined the short-term evolution rate of MSV using full genome analysis of virus populations initiated from cloned genomes. Three wild type viruses and three defective artificial chimaeric viruses were maintained in planta for up to five years and displayed evolution rates of between 7.4 × 10-4 and 7.9 × 10-4 subs/site/year. Conclusion These MSV evolution rates are within the ranges observed for other ssDNA viruses and RNA viruses. Although no obvious evidence of positive selection was detected, the uneven distribution of mutations within the defective virus genomes suggests that some of the changes may have been adaptive. We also observed inter-strand nucleotide substitution imbalances that are consistent with a recent proposal that high mutation rates in geminiviruses (and possibly ssDNA viruses in general) may be due to mutagenic processes acting specifically on ssDNA molecules.
Collapse
Affiliation(s)
- Eric van der Walt
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa.
| | | | | | | | | |
Collapse
|
13
|
Varsani A, Shepherd DN, Monjane AL, Owor BE, Erdmann JB, Rybicki EP, Peterschmitt M, Briddon RW, Markham PG, Oluwafemi S, Windram OP, Lefeuvre P, Lett JM, Martin DP. Recombination, decreased host specificity and increased mobility may have driven the emergence of maize streak virus as an agricultural pathogen. J Gen Virol 2008; 89:2063-2074. [PMID: 18753214 PMCID: PMC2886952 DOI: 10.1099/vir.0.2008/003590-0] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 06/17/2008] [Indexed: 01/20/2023] Open
Abstract
Maize streak virus (MSV; family Geminiviridae, genus Mastrevirus), the causal agent of maize streak disease, ranks amongst the most serious biological threats to food security in subSaharan Africa. Although five distinct MSV strains have been currently described, only one of these - MSV-A - causes severe disease in maize. Due primarily to their not being an obvious threat to agriculture, very little is known about the 'grass-adapted' MSV strains, MSV-B, -C, -D and -E. Since comparing the genetic diversities, geographical distributions and natural host ranges of MSV-A with the other MSV strains could provide valuable information on the epidemiology, evolution and emergence of MSV-A, we carried out a phylogeographical analysis of MSVs found in uncultivated indigenous African grasses. Amongst the 83 new MSV genomes presented here, we report the discovery of six new MSV strains (MSV-F to -K). The non-random recombination breakpoint distributions detectable with these and other available mastrevirus sequences partially mirror those seen in begomoviruses, implying that the forces shaping these breakpoint patterns have been largely conserved since the earliest geminivirus ancestors. We present evidence that the ancestor of all MSV-A variants was the recombinant progeny of ancestral MSV-B and MSV-G/-F variants. While it remains unknown whether recombination influenced the emergence of MSV-A in maize, our discovery that MSV-A variants may both move between and become established in different regions of Africa with greater ease, and infect more grass species than other MSV strains, goes some way towards explaining why MSV-A is such a successful maize pathogen.
Collapse
Affiliation(s)
- Arvind Varsani
- Electron Microscope Unit, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Dionne N. Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Adérito L. Monjane
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Betty E. Owor
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
| | - Julia B. Erdmann
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
- Institute of Biology, Department of Molecular Biology and Plant Virology, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Edward P. Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa
| | - Michel Peterschmitt
- CIRAD, UMR BGPI, TA A54/K, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France
| | - Rob W. Briddon
- National Institute for Biotechnology and Genetic Engineering, Jhang Road, PO Box 577, Faisalabad, Pakistan
| | - Peter G. Markham
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Sunday Oluwafemi
- Department of Crop, Soil and Environmental Management, Bowen University, PMB 284, Iwo, Osun State, Nigeria
| | - Oliver P. Windram
- Warwick HRI Biology Centre, University of Warwick, Wellesbourne CV35 9EF, UK
| | - Pierre Lefeuvre
- CIRAD, UMR 53 PVBMT CIRAD-Université de la Réunion, Pôle de Protection des Plantes, Ligne Paradis, 97410 Saint Pierre, La Réunion, France
| | - Jean-Michel Lett
- CIRAD, UMR 53 PVBMT CIRAD-Université de la Réunion, Pôle de Protection des Plantes, Ligne Paradis, 97410 Saint Pierre, La Réunion, France
| | - Darren P. Martin
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa
| |
Collapse
|
14
|
Shepherd DN, Martin DP, Lefeuvre P, Monjane AL, Owor BE, Rybicki EP, Varsani A. A protocol for the rapid isolation of full geminivirus genomes from dried plant tissue. J Virol Methods 2008; 149:97-102. [PMID: 18280590 DOI: 10.1016/j.jviromet.2007.12.014] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 12/04/2007] [Accepted: 12/20/2007] [Indexed: 11/30/2022]
Abstract
A high-throughput method of isolating and cloning geminivirus genomes from dried plant material, by combining an Extract-n-Amp-based DNA isolation technique with rolling circle amplification (RCA) of viral DNA, is presented. Using this method an attempt was made to isolate and clone full geminivirus genomes/genome components from 102 plant samples, including dried leaves stored at room temperature for between 6 months and 10 years, with an average hands-on-time to RCA-ready DNA of 15 min per 20 samples. While storage of dried leaves for up to 6 months did not appreciably decrease cloning success rates relative to those achieved with fresh samples, efficiency of the method decreased with increasing storage time. However, it was still possible to clone virus genomes from 47% of 10-year-old samples. To illustrate the utility of this simple method for high-throughput geminivirus diversity studies, six Maize streak virus genomes, an Abutilon mosaic virus DNA-B component and the DNA-A component of a previously unidentified New Word begomovirus species were fully sequenced. Genomic clones of the 69 other viruses were verified as such by end sequencing. This method should be extremely useful for the study of any circular DNA plant viruses with genome component lengths smaller than the maximum size amplifiable by RCA.
Collapse
Affiliation(s)
- Dionne N Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
| | | | | | | | | | | | | |
Collapse
|
15
|
Schubert J, Habekuss A, Kazmaier K, Jeske H. Surveying cereal-infecting geminiviruses in Germany--diagnostics and direct sequencing using rolling circle amplification. Virus Res 2007; 127:61-70. [PMID: 17449126 DOI: 10.1016/j.virusres.2007.03.018] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 03/20/2007] [Accepted: 03/20/2007] [Indexed: 11/18/2022]
Abstract
Geminiviruses have spread in German cereal crops during the last few years. In order to identify and classify them, we have compared conventional techniques (enzyme-linked immunosorbent assays, polymerase chain reaction, bacterial cloning, and sequencing) with a newly developed method which uses rolling circle amplification (RCA), restriction fragment length polymorphism (RFLP), and direct sequencing without a bacterial cloning step. Whereas immunological methods utilising polyclonal antibodies were reliable for detection of geminiviruses, they did not discriminate between different German mastrevirus species, in contrast to RCA/RFLP. Direct sequencing gave high fidelity results with the same quality as conventional cloning and sequencing but with significantly reduced effort and costs. Based on a survey of field-derived cereal samples and on DNA sequences of distinct virus isolates we propose two new mastrevirus species, to be named Barley dwarf virus (BDV), and Oat dwarf virus (ODV) according to sequence differences and host range studies. The results show the applicability of RCA-based techniques for field studies and the possibility of sequencing a geminiviral genome without cloning. This approach will accelerate genomics studies of all viruses with small circular DNA genomes. In addition, RCA proves to be a reliable technique allowing for the detection of new geminivirus species as it does not depend on the knowledge of specific primers.
Collapse
Affiliation(s)
- Jörg Schubert
- Institute of Resistance Research and Pathogen Diagnostics, Federal Centre for Breeding Research on Cultivated Plants, Erwin-Baur-Str. 27, 06484 Quedlinburg, Germany
| | | | | | | |
Collapse
|
16
|
Willment JA, Martin DP, Palmer KE, Schnippenkoetter WH, Shepherd DN, Rybicki EP. Identification of long intergenic region sequences involved in maize streak virus replication. J Gen Virol 2007; 88:1831-1841. [PMID: 17485545 DOI: 10.1099/vir.0.82513-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The main cis-acting control regions for replication of the single-stranded DNA genome of maize streak virus (MSV) are believed to reside within an approximately 310 nt long intergenic region (LIR). However, neither the minimum LIR sequence required nor the sequence determinants of replication specificity have been determined experimentally. There are iterated sequences, or iterons, both within the conserved inverted-repeat sequences with the potential to form a stem-loop structure at the origin of virion-strand replication, and upstream of the rep gene TATA box (the rep-proximal iteron or RPI). Based on experimental analyses of similar iterons in viruses from other geminivirus genera and their proximity to known Rep-binding sites in the distantly related mastrevirus wheat dwarf virus, it has been hypothesized that the iterons may be Rep-binding and/or -recognition sequences. Here, a series of LIR deletion mutants was used to define the upper bounds of the LIR sequence required for replication. After identifying MSV strains and distinct mastreviruses with incompatible replication-specificity determinants (RSDs), LIR chimaeras were used to map the primary MSV RSD to a 67 nt sequence containing the RPI. Although the results generally support the prevailing hypothesis that MSV iterons are functional analogues of those found in other geminivirus genera, it is demonstrated that neither the inverted-repeat nor RPI sequences are absolute determinants of replication specificity. Moreover, widely divergent mastreviruses can trans-replicate one another. These results also suggest that sequences in the 67 nt region surrounding the RPI interact in a sequence-specific manner with those of the inverted repeat.
Collapse
Affiliation(s)
- Janet A Willment
- Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory 7925, South Africa
| | - Darrin P Martin
- Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory 7925, South Africa
| | - Kenneth E Palmer
- Department of Pharmacology and Toxicology, University of Louisville, 570 South Preston Street, Louisville, KY 40202, USA
- James Graham Brown Cancer Center, University of Louisville, 529 South Jackson Street, Louisville, KY 40202, USA
| | | | - Dionne N Shepherd
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch, Cape Town 7701, South Africa
| | - Edward P Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch, Cape Town 7701, South Africa
- Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory 7925, South Africa
| |
Collapse
|
17
|
Kong P, Hong CX, Tooley PW, Ivors K, Garbelotto M, Richardson PA. Rapid identification of Phytophthora ramorum using PCR-SSCP analysis of ribosomal DNA ITS-1. Lett Appl Microbiol 2004; 38:433-9. [PMID: 15059217 DOI: 10.1111/j.1472-765x.2004.01510.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS The primary objectives of this study were to determine if a single-strand conformation polymorphism (SSCP) analysis can be used for rapid identification of Phytophthora ramorum, an important quarantine plant pathogen worldwide, and to further assess the potential of the SSCP technique as a taxonomic tool for the genus Phytophthora. METHODS AND RESULTS SSCP of ribosomal DNA internal transcribed spacer 1 was characterized for 12 isolates of P. ramorum, using a recently reported protocol. The SSCP patterns of this species then were compared with those of 18 closely related Phytophthora species. Phytophthora ramorum had a unique pattern and was easily distinguished from genetically, morphologically and ecologically close relatives. CONCLUSION An immediate benefit of this study is provision of a highly effective and efficient identification tool for P. ramorum in the quarantine process. SIGNIFICANCE AND IMPACT OF THE STUDY This study also provides additional evidence demonstrating that the SSCP is an ideal DNA marker for species differentiation within the genus Phytophthora.
Collapse
Affiliation(s)
- P Kong
- Department of Plant Pathology, Hampton Roads Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Virginia Beach, VA 23455, USA
| | | | | | | | | | | |
Collapse
|