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  1. Artikel: Impacts of Continued Exposure to a Susceptible Host Genotype on Aggressiveness of

    Jin, Jing / Shew, H David

    Plant disease

    2022  Band 106, Heft 2, Seite(n) 373–381

    Abstract: Pathogen adaptation can threaten the durability of partial resistance. Mixed plantings of susceptible and partially resistant varieties may prolong the effectiveness of partial resistance, but little is known about how continued exposure to a susceptible ...

    Abstract Pathogen adaptation can threaten the durability of partial resistance. Mixed plantings of susceptible and partially resistant varieties may prolong the effectiveness of partial resistance, but little is known about how continued exposure to a susceptible genotype can change the aggressiveness of pathogen isolates adapted to a source of partial resistance. The objective of this study was to examine the effects of continued exposure to a highly susceptible tobacco genotype on isolates of
    Mesh-Begriff(e) Genotype ; Phytophthora/genetics ; Nicotiana/genetics ; Virulence
    Sprache Englisch
    Erscheinungsdatum 2022-02-09
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-09-20-1972-RE
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  2. Artikel: Impacts of Continued Exposure to a Susceptible Host Genotype on Aggressiveness of Phytophthora nicotianae Isolates Adapted to Multiple Sources of Partial Resistance

    Jin, Jing / Shew, H. David

    Plant disease. 2022 Feb. 28, v. 106, no. 2

    2022  

    Abstract: Pathogen adaptation can threaten the durability of partial resistance. Mixed plantings of susceptible and partially resistant varieties may prolong the effectiveness of partial resistance, but little is known about how continued exposure to a susceptible ...

    Abstract Pathogen adaptation can threaten the durability of partial resistance. Mixed plantings of susceptible and partially resistant varieties may prolong the effectiveness of partial resistance, but little is known about how continued exposure to a susceptible genotype can change the aggressiveness of pathogen isolates adapted to a source of partial resistance. The objective of this study was to examine the effects of continued exposure to a highly susceptible tobacco genotype on isolates of Phytophthora nicotianae that had been adapted to partial resistance. Isolates of P. nicotianae previously adapted to two sources of partial resistance were continually exposed to either the original host of adaptation or a susceptible host. After six generations of host exposure, isolates obtained from the partially resistant and the susceptible hosts were compared for their aggressiveness on the resistant host and for differences in expression of genes associated with pathogenicity and aggressiveness. Results suggested that exposure to the susceptible tobacco genotype reduced aggressiveness of isolates adapted to partial resistance in K 326 Wz/– but not of isolates adapted to partial resistance in Fla 301. Quantification of pathogenicity-associated gene expression using qRT-PCR suggested the rapid change in aggressiveness of isolates adapted to Wz-sourced partial resistance may have resulted from modification in gene expression in multiple genes.
    Schlagwörter Phytophthora nicotianae ; durability ; gene expression ; genotype ; pathogenicity ; pathogens ; tobacco
    Sprache Englisch
    Erscheinungsverlauf 2022-0228
    Umfang p. 373-381.
    Erscheinungsort The American Phytopathological Society
    Dokumenttyp Artikel
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-09-20-1972-RE
    Datenquelle NAL Katalog (AGRICOLA)

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  3. Artikel: Components of Aggressiveness in

    Jin, Jing / Shew, H David

    Plant disease

    2021  Band 105, Heft 7, Seite(n) 1960–1966

    Abstract: Black shank is a devastating disease of tobacco caused ... ...

    Abstract Black shank is a devastating disease of tobacco caused by
    Mesh-Begriff(e) Phytophthora/genetics ; Plant Diseases ; Nicotiana
    Sprache Englisch
    Erscheinungsdatum 2021-08-04
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-09-20-1929-RE
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  4. Artikel: Components of Aggressiveness in Phytophthora nicotianae During Adaptation to Multiple Sources of Partial Resistance in Tobacco

    Jin, Jing / Shew, H. David

    Plant disease. 2021 July 19, v. 105, no. 7

    2021  

    Abstract: Black shank is a devastating disease of tobacco caused by Phytophthora nicotianae. Host resistance has been an integral part of black shank management but after the loss of Php single-gene resistance following its widespread deployment in the 1990s, ... ...

    Abstract Black shank is a devastating disease of tobacco caused by Phytophthora nicotianae. Host resistance has been an integral part of black shank management but after the loss of Php single-gene resistance following its widespread deployment in the 1990s, growers have relied on varieties with varying levels of partial resistance. Partial resistance is effective in suppressing disease, but continued exposure can result in an increase in pathogen aggressiveness that threatens durability of the resistance to P. nicotianae. Aggressiveness components in P. nicotianae were characterized following adaptation on two sources of partial resistance, Fla 301 and the Wz genomic region from Nicotiana rustica. An aggressive isolate of the two major races of P. nicotianae, race 0 and race 1, was adapted for either one/two or five/six generations on the two resistance sources, giving four sets of isolates based on race, number of generations of adaptation, and source of resistance. Across the four sets of isolates, adapted isolates infected higher proportions of tobacco root tips, produced more sporangia per infected root tip, and caused larger lesions than their respective nonadapted isolates of the same race and from the same resistance source. Adapted isolates also produced more aggressive zoospore progeny than the nonadapted isolates. Adaptation to partial resistance involves multiple aggressiveness components and results in the increased aggressiveness observed for P. nicotianae. These results improve our knowledge on the nature of P. nicotianae adaptation to partial resistance in tobacco and indicate that different resistance sources are likely to select for similar aggressiveness components in the pathogen.
    Schlagwörter Nicotiana rustica ; Phytophthora nicotianae ; durability ; genomics ; pathogens ; progeny ; root tips ; sporangia ; tobacco ; zoospores
    Sprache Englisch
    Erscheinungsverlauf 2021-0719
    Umfang p. 1960-1966.
    Erscheinungsort The American Phytopathological Society
    Dokumenttyp Artikel
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-09-20-1929-RE
    Datenquelle NAL Katalog (AGRICOLA)

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  5. Artikel: The Origin of The Problem: Characterization of Paraguayan

    Sanabria-Velazquez, Andres / Enciso-Maldonado, Guillermo A / Thiessen, Lindsey / Shew, H David

    Plant disease

    2024  

    Abstract: Septoria leaf spot is a significant disease affecting cultivated stevia, potentially reducing yields by > 50%. The disease is caused by Septoria steviae, first identified in 1978 in Japan as a new pathogen of stevia. Understanding the origin of S. ... ...

    Abstract Septoria leaf spot is a significant disease affecting cultivated stevia, potentially reducing yields by > 50%. The disease is caused by Septoria steviae, first identified in 1978 in Japan as a new pathogen of stevia. Understanding the origin of S. steviae could clarify how it spread to new production areas. To investigate this, twelve isolates of Septoria sp. were obtained from stevia's native range in the Amambay forests and field plantings in Paraguay from 2018 to 2020. These isolates underwent colony morphology and molecular characterization of Actin, β-Tubulin, Calmodulin, ITS, LSU, RPB2, and TEF1α loci. GenBank sequences from S. steviae isolates collected in France, Japan, and the United States (USA) were included. Multi-locus sequence phylogenetic analysis generated a maximum likelihood (ML) tree. The morphological characteristics of Paraguayan isolates were similar to previously reported S. steviae type cultures from Japan. The ML analysis showed that Paraguayan isolates formed a monophyletic group with S. steviae isolates from France, Japan, and the USA. During blotter tests, pycnidia and cirri of S. steviae were observed on multiple stevia seed surfaces from different sources. Further characterization confirmed viable pathogenic conidia of S. steviae. This observation suggests that S. steviae could be associated with stevia seed, possibly spreading from the center of origin to other countries. This research is the first to genetically characterize S. steviae from Paraguay and propose its potential spread mechanism from the center of origin to the rest of the world.
    Sprache Englisch
    Erscheinungsdatum 2024-05-19
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-11-23-2362-RE
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  6. Artikel ; Online: Seasonal dynamics and fungicide sensitivity of organisms causing brown patch of tall fescue in North Carolina.

    Koehler, Alyssa M / Shew, H David

    Mycologia

    2017  Band 109, Heft 4, Seite(n) 667–675

    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 ... ...

    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 EC
    Mesh-Begriff(e) Basidiomycota/classification ; Basidiomycota/drug effects ; Basidiomycota/isolation & purification ; DNA, Fungal/genetics ; DNA, Ribosomal Spacer/genetics ; Festuca/microbiology ; Fungicides, Industrial/pharmacology ; Microbial Sensitivity Tests ; North Carolina ; Plant Diseases/microbiology ; Rhizoctonia/classification ; Rhizoctonia/drug effects ; Rhizoctonia/genetics ; Rhizoctonia/isolation & purification ; Seasons
    Chemische Substanzen DNA, Fungal ; DNA, Ribosomal Spacer ; Fungicides, Industrial
    Sprache Englisch
    Erscheinungsdatum 2017-10-11
    Erscheinungsland England
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 281335-x
    ISSN 1557-2536 ; 0027-5514
    ISSN (online) 1557-2536
    ISSN 0027-5514
    DOI 10.1080/00275514.2017.1377587
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  7. Artikel: Validation of Standard Area Diagrams to Estimate the Severity of Septoria Leaf Spot on Stevia in Paraguay, Mexico, and the United States.

    Sanabria-Velazquez, Andres D / Enciso-Maldonado, Guillermo A / Maidana-Ojeda, Marco / Diaz-Najera, Jose F / Thiessen, Lindsey D / Shew, H David

    Plant disease

    2023  Band 107, Heft 6, Seite(n) 1829–1838

    Abstract: Septoria leaf spot (SLS) affects stevia leaves, reducing their quality. Estimates of SLS severity on different genotypes are made to identify resistance and as a basis to compare management approaches. The use of standard area diagrams (SADs) can improve ...

    Abstract Septoria leaf spot (SLS) affects stevia leaves, reducing their quality. Estimates of SLS severity on different genotypes are made to identify resistance and as a basis to compare management approaches. The use of standard area diagrams (SADs) can improve the accuracy and reliability of severity estimates. In this study, we developed new SADs with six illustrations (0.5, 1, 10, 25, 40, and 75% severity). The SADs were validated by raters with and without experience in estimating SLS. Raters evaluated 40 leaf photos with SLS severities ranging from 0 to 100% without and with the SADs. Agreement (ρ
    Mesh-Begriff(e) United States ; Stevia ; Mexico ; Reproducibility of Results ; Paraguay ; Ascomycota/genetics
    Sprache Englisch
    Erscheinungsdatum 2023-06-13
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-07-22-1609-RE
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  8. Artikel: Adaptation of Phytophthora nicotianae to Multiple Sources of Partial Resistance in Tobacco

    Jin, Jing / McCorkle, Kestrel L. / Cornish, Vicki / Carbone, Ignazio / Lewis, Ramsey S. / Shew, H. David

    Plant disease. 2022 Mar. 28, v. 106, no. 3

    2022  

    Abstract: Host resistance is an important tool in the management of black shank disease of tobacco. Race development leads to rapid loss of single-gene resistance, but the adaptation by Phytophthora nicotianae to sources of partial resistance from Beinhart 1000, ... ...

    Abstract Host resistance is an important tool in the management of black shank disease of tobacco. Race development leads to rapid loss of single-gene resistance, but the adaptation by Phytophthora nicotianae to sources of partial resistance from Beinhart 1000, Florida 301, and the Wz gene region introgressed from Nicotiana rustica is poorly characterized. In greenhouse environments, host genotypes with quantitative trait loci (QTLs) conferring resistance from multiple sources were initially inoculated with an aggressive isolate of race 0 or race 1 of P. nicotianae. The most aggressive isolate was selected after each of six host generations to inoculate the next generation of plants. The race 0 isolate demonstrated a continuous gradual increase in disease severity and percentage root rot on all sources of resistance except the genotype K 326 Wz/–, where a large increase in both was observed between generations 2 and 3. Adaptation by the race 0 isolate on Beinhart 1000 represents the first report of adaptation to this genotype by P. nicotianae. The race 1 isolate did not exhibit significant increases in aggressiveness over generations but exhibited a large increase in aggressiveness on K 326 Wz/– between generations 3 and 4. Molecular characterization of isolates recovered during selection was completed via double digest restriction-site associated DNA sequencing, but no polymorphisms were associated with the observed changes in aggressiveness. The rapid adaptation to Wz resistance and the gradual adaptation to other QTLs highlights the need to study the nature of Wz resistance and to conduct field studies on the efficacy of resistance gene rotation for disease management.
    Schlagwörter DNA ; Nicotiana rustica ; Phytophthora nicotianae ; black shank disease ; disease control ; disease severity ; genotype ; greenhouses ; quantitative traits ; resistance genes ; root rot ; tobacco
    Sprache Englisch
    Erscheinungsverlauf 2022-0328
    Umfang p. 906-917.
    Erscheinungsort The American Phytopathological Society
    Dokumenttyp Artikel
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-06-21-1241-RE
    Datenquelle NAL Katalog (AGRICOLA)

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  9. Artikel ; Online: Validation of Standard Area Diagrams to Estimate the Severity of Septoria Leaf Spot on Stevia in Paraguay, Mexico, and the United States

    Sanabria-Velazquez, Andres D. / Enciso-Maldonado, Guillermo A. / Maidana-Ojeda, Marco / Diaz-Najera, Jose F. / Thiessen, Lindsey D. / Shew, H. David

    Plant Disease. 2023 June 01, v. 107, no. 6 p.1829-1838

    2023  

    Abstract: Septoria leaf spot (SLS) affects stevia leaves, reducing their quality. Estimates of SLS severity on different genotypes are made to identify resistance and as a basis to compare management approaches. The use of standard area diagrams (SADs) can improve ...

    Abstract Septoria leaf spot (SLS) affects stevia leaves, reducing their quality. Estimates of SLS severity on different genotypes are made to identify resistance and as a basis to compare management approaches. The use of standard area diagrams (SADs) can improve the accuracy and reliability of severity estimates. In this study, we developed new SADs with six illustrations (0.5, 1, 10, 25, 40, and 75% severity). The SADs were validated by raters with and without experience in estimating SLS. Raters evaluated 40 leaf photos with SLS severities ranging from 0 to 100% without and with the SADs. Agreement (ρc), bias (Cb), precision (r), and intracluster correlation (ρ) coefficients were significantly closer to “true” severity values when the SADs was used by inexperienced (ρc = 0.89; Cb = 0.97; r = 0.90, ρ = 0.81) and experienced (ρc = 0.94; Cb = 0.99; r = 0.95, ρ = 0.91) raters. The SADs were tested under field conditions in Paraguay, Mexico, and the United States, with inexperienced raters assigned to two groups, one SADs trained and the other not trained, that estimated SLS severity three times: first, all raters without SADs and no time limit for the estimates; second, only the SADs-trained group used SADs and no time limit; and third, only the SADs-trained group used SADs, with a time limit of 10 s imposed per specimen assessment. Agreement and reliability of SLS severity estimates significantly improved when raters used the SADs without a time limit. The use of the new SADs improved the accuracy, precision, and reliability of SLS severity estimates, enhancing the uniformity in assessment across different stevia programs.
    Schlagwörter Septoria ; Stevia ; leaf spot ; leaves ; Mexico ; Paraguay ; disease severity ; phytopathometry ; Septoria steviae ; Stevia rebaudiana
    Sprache Englisch
    Erscheinungsverlauf 2023-0601
    Umfang p. 1829-1838.
    Erscheinungsort The American Phytopathological Society
    Dokumenttyp Artikel ; Online
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-07-22-1609-RE
    Datenquelle NAL Katalog (AGRICOLA)

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  10. Artikel: Adaptation of

    Jin, Jing / McCorkle, Kestrel L / Cornish, Vicki / Carbone, Ignazio / Lewis, Ramsey S / Shew, H David

    Plant disease

    2022  Band 106, Heft 3, Seite(n) 906–917

    Abstract: Host resistance is an important tool in the management of black shank disease of tobacco. Race development leads to rapid loss of single-gene resistance, but the adaptation ... ...

    Abstract Host resistance is an important tool in the management of black shank disease of tobacco. Race development leads to rapid loss of single-gene resistance, but the adaptation by
    Mesh-Begriff(e) Genotype ; Phytophthora/genetics ; Plant Diseases/genetics ; Quantitative Trait Loci/genetics ; Nicotiana/genetics
    Sprache Englisch
    Erscheinungsdatum 2022-03-10
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 754182-x
    ISSN 0191-2917
    ISSN 0191-2917
    DOI 10.1094/PDIS-06-21-1241-RE
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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