Population Structure and Resistance to Mefenoxam of <i>Phytophthora capsici</i> in New York State

Dunn, Amara R.; Milgroom, Michael G.; Meitz, Julia C.; McLeod, A.; Fry, William E.; McGrath, M. T.; Dillard, H. R.; Smart, Christine D.

doi:10.1094/pdis-03-10-0221

Cited by 72 publications

(81 citation statements)

References 41 publications

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“…As a result, the genus has been the focus of many population biology studies (Bhat and Browne 2007;Bhat et al 2006;Bienapfl and Balci 2014;Cooke et al 2003Cooke et al , 2005Dobrowolski et al 2003;Donahoo and Lamour 2008;Duan et al 2008;Dunn et al 2010;Eggers et al 2012;Gevens et al 2008;Hantula et al 2000;Hulvey et al 2010;Ivors et al 2004;Lamour and Hausbeck 2001;Linde et al 1997Linde et al , 1999. These studies have shown that population structures can vary considerably between different regions and species.…”

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“…These studies have shown that population structures can vary considerably between different regions and species. For example, populations of Phytophthora cactorum in the United States, England, and Finland were shown to have lower genetic diversity (Bhat et al 2006;Hantula et al 2000) than populations of P. citricola, P. capsici, P. nicotianae, and P. infestans from agricultural or nursery systems (Bhat and Browne 2007;Dunn et al 2010;Lamour and Hausbeck 2001;Shattock 1988).…”

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Genotypic Diversity of Phytophthora cinnamomi and P. plurivora in Maryland’s Nurseries and Mid-Atlantic Forests

2017

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Genetic diversity of two Phytophthora spp.-P. cinnamomi (102 isolates), commonly encountered in Maryland nurseries and forests in the MidAtlantic United States, and P. plurivora (186 isolates), a species common in nurseries-was characterized using amplified fragment length polymorphism. Expected heterozygosity and other indices suggested a lower level of diversity among P. cinnamomi than P. plurivora isolates. Hierarchical clustering showed P. cinnamomi isolates separated into four clusters, and two of the largest clusters were closely related, containing 80% of the isolates. In contrast, P. plurivora isolates separated into six clusters, one of which included approximately 40% of the isolates. P. plurivora isolates recovered from the environment (e.g., soil and water) were genotypically more diverse than those found causing lesions. For both species, isolate origin (forest versus nursery or among nurseries) was a significant factor of heterozygosity. Clonal groups existed within P. cinnamomi and P. plurivora and included isolates from both forest and nurseries, suggesting that a pathway from nurseries to forests or vice versa exists.The genus Phytophthora includes numerous species that are among the most significant plant pathogens worldwide. As a result, the genus has been the focus of many population biology studies (Bhat and Browne

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Genotypic Diversity of Phytophthora cinnamomi and P. plurivora in Maryland’s Nurseries and Mid-Atlantic Forests

2017

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“…Repeated use of metalaxyl and mefenoxam has resulted in the selection of resistant isolates of F capsici (9,21,28,(31)(32)(33). Resistance to metalaxylbased products necessitates additional fungicides and novel methods" of fungicide application to improve control of F capsici.…”

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Using Soil-Applied Fungicides to Manage Phytophthora Crown and Root Rot on Summer Squash

Meyer

Hausbeck

2013

Plant Disease

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Meyer, M. D., and Hausbeck, M. K. 2013. Using soil-applied fungicides to manage Phytophthora crown and root rot on summer sauash Plant Dis 97:107-112.Phytophthora crown and root rot (Phytophthora capsici) of summer squash is especially difficult to manage because all commercial cultivars are highly susceptible to P. capsici. Producers have traditionally relied on foliar fungicide applications to control Phytophthora crown and root rot despite their limited efficacy. Soil fungicide applications, including via subsurface drip chemigation, have recently gained interest as a method of improving control of P. capsici infections. In this study, soil drenches and foliar applications of 11 fungicides were compared for control of Phytophthora crown and root rot of summer squash in replicated field and greenhouse trials. Fungicides were applied at 7-day intervals. Incidence (%) of plant death was assessed from 7 to 42 days post inoculation (dpi) in field trials. Crown rot severity was rated on a scale of 1 (no wilting) to 5 (plant death) from 5 to 21 dpi in greenhouse trials. Results of field and greenhouse trials were similar. Plant death of 'Cougar' following inoculation with P. capsici isolate 12889 occurred at all growth stages from first true-leaf to full maturity in field trials. Plant death 42 dpi differed significantly (P < 0.0001) among fungicides and application methods. The fungicideapplication method interaction also was significant. Some fungicides were ineffective regardless of application method. In general, soil drenches were more effective than foliar applications at limiting plant death but no treatment completely controlled disease symptoms. Mean plant death 42 dpi was 41% for soil drenches and 92% for foliar sprays. Drenches of fluopicolide, mandipropamid, or dimethomorph limited plant death to <10% and prevented yield loss associated with root and crown rot. Foliar applications generally did not reduce plant death compared with the untreated, inoculated control, and were unable to prevent yield loss in field trials. In greenhouse trials, crown rot severity differed significantly (P < 0.0001) among fungicides, application methods, and cultivars when plants were inoculated with P. capsici isolate 12889 or SP98. Crown rot was less severe and disease progress was slower following soil drenches than foliar applications. Some fungicide treatments were more effective on 'Leopard,' which was less susceptible to P. capsici than 'Cougar.' Soil application methods, including soil drench and drip chemigation, should be evaluated when fungicides are registered for soilborne disease control, because these methods provide better control of Phytophthora crown and root rot than foliar application.

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“…It is interesting that until the year 2012 no natural recombinants of P. ramorum have been observed (Grünwald et al 2012). In contrast, among P. capsici populations from the USA and South Africa the occurrence of sexual reproduction and high levels of genetic diversity have been described (Dunn et al 2010;Gobena et al 2012;Meitz et al 2010). Although in populations of P. capsici from Peru and in most provinces of China asexual clonal lineages dominate (Hu et al 2013;Hurtado-Gonzales et al 2008).…”

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Evaluation of PCR markers for Phytophthora infestans mating type determination

et al. 2018

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Late blight is a devastating potato disease caused by Phytophthora infestans. This organism can reproduce asexually and sexually between the strains of two mating types named A1 and A2. Mating type is an important strain characteristic affecting the pathogen's population structure. We validate different PCR markers for P. infestans mating type determination by comparison of the results obtained with the markers (W16, S1, PHYB) with the pairing test results for 26 isolates collected worldwide and for a group of 146 Polish isolates. This study identifies an interesting feature of the isolates of genotype US-1. For all these A1 mating type isolates, the product specific for A2 isolates is amplified using the marker W16. Analysis of sequences of W16 PCR products indicates high similarity of the US-1 isolates with modern A2 mating type isolates. When US-1 isolates are excluded from analysis, 95 and 96% of isolates are correctly assigned by markers W16 and S1, respectively, when compared with the pairing test results. Marker PHYB produces 14% of discrepant results with the pairing test. Our results show that molecular markers can be useful tools for P. infestans mating type determination, but their application should be preceded by validation in each local population since their efficiency may vary depending on a pathogen's genotype.

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Population Structure and Resistance to Mefenoxam of Phytophthora capsici in New York State

Cited by 72 publications

References 41 publications

Genotypic Diversity of Phytophthora cinnamomi and P. plurivora in Maryland’s Nurseries and Mid-Atlantic Forests

Genotypic Diversity of Phytophthora cinnamomi and P. plurivora in Maryland’s Nurseries and Mid-Atlantic Forests

Using Soil-Applied Fungicides to Manage Phytophthora Crown and Root Rot on Summer Squash

Evaluation of PCR markers for Phytophthora infestans mating type determination

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