Hierarchical structure of pathogenic variation among Rhynchosporium secalis populations in Idaho and Oregon

1992 ◽  
Vol 70 (4) ◽  
pp. 810-817 ◽  
Author(s):  
Stephen B. Goodwin ◽  
Robert W. Allard ◽  
Shirlee A. Hardy ◽  
Robert K. Webster
Keyword(s):  
Pacific Northwest ◽  
Resistance Genes ◽  
Local Population ◽  
Rhynchosporium Secalis ◽  
Causal Organism ◽  
Pathogenic Variation ◽  
Differential Cultivars ◽  
Electrophoretic Data ◽  
Differential Cultivar ◽  
Major Resistance Genes

Ninety-four isolates of Rhynchosporium secalis, the causal organism of the barley scald disease, from four populations (infected fields) in Idaho and eight in Oregon, were tested for pathogenicity to 14 barley differential cultivars; 60 distinct pathotypes, 33 in Idaho and 28 in Oregon, were found among the 94 isolates. Pathogenicity to most of the differentials was found in each local population sampled. One differential cultivar, CI 5831, was resistant to all isolates tested. Isolates from the same cultivar in different locations usually had different pathogenicities, and most pathotypes were genetically heterogeneous mixtures of many different genotypes based on previous electrophoretic data. The sampled cultivars generally had few or no resistance genes, suggesting that the R. secalis populations in Idaho and Oregon are characterized by large amounts of seemingly unnecessary pathogenicity. When the total pathogenic diversity was partitioned into hierarchical components using the Shannon information statistic, 58% was accounted for by the within-population component, 33% among populations within regions, and only 9% by the between-region component. Because most of the pathogenic variation is within local populations, these populations should adapt rapidly to introduced resistance genes; therefore traditional methods of breeding for resistance to R. secalis using single major resistance genes are not likely to be effective in the Pacific Northwest. Key words: pathogenicity index.

scholarly journals Pathogenic Variation of Colletotrichum lindemuthianum causing Anthracnose of Beans (Phaseolus vulgaris) in Uganda

2017 ◽  
Vol 5 (3) ◽  
pp. 89-98
Author(s):  
Moses J. Kiryowa ◽  
Aston Ebinu ◽  
Vincent Kyaligonza ◽  
Stanley T. Nkalubo ◽  
Pamela Paparu ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Single Gene ◽  
Colletotrichum Lindemuthianum ◽  
Breeding Programs ◽  
Pathogenic Variation ◽  
Broad Spectrum Resistance ◽  
Differential Cultivars ◽  
Differential Cultivar ◽  
Bean Anthracnose ◽  
Pathogenic Variability

Colletotrichum lindemuthianum is a highly variable pathogen of common beans that easily overcomes resistance in cultivars bred with single-gene resistance. To determine pathogenic variability of the pathogen in Uganda, samples of common bean tissues with anthracnose symptoms were collected in eight districts of Uganda, namely Kabarole, Sironko, Mbale, Oyam, Lira, Kapchorwa, Maracha and Kisoro. 51 isolates sporulated successfully on Potato Dextrose Agar and Mathur’s media and were used to inoculate 12 differential cultivars under controlled conditions. Five plants per cultivar were inoculated with each isolate and then evaluated for their reaction using the 1 – 9 severity scale. Races were classified using the binary nomenclature system proposed by Pastor Corrales (1991). Variation due to cultivar and isolate effects was significant (P≤0.001) for severity. The 51 isolates from eight districts grouped into 27 different races. Sironko district had the highest number of races followed by Mbale and Kabarole. Races 2047 and 4095 were the most frequently found, each with 10 isolates grouped under them. Race 4095 was the most virulent since it caused a susceptible (S) reaction on all 12 differential cultivars and the susceptible check. This was followed by races 2479, 2047 and 2045 respectively. Two races, 4094 and 2479, caused a susceptible reaction on the differential cultivar G2333, which nevertheless, showed the most broad spectrum resistance followed by cultivars Cornell 49-242, TU, and AB136 respectively. These cultivars are recommended for use in breeding programs aiming at breeding for broad spectrum resistance to bean anthracnose in Uganda.

Barley grass as a source of pathogenic variation in Rhynchosporium secalis

1981 ◽  
Vol 32 (1) ◽  
pp. 21 ◽  
Author(s):  
SM Ali
Keyword(s):  
Resistance Genes ◽  
Genetic Basis ◽  
Rhynchosporium Secalis ◽  
Pathogenic Variation ◽  
Pathogenic Variability ◽  
F2 Progeny

The pathogenic variability of 150 isolates of Rhynchospovium secalis collected in southern Australia was examined on 20 biotypes of barley grass (Hordeum lepovinum). The isolates were differentiated into 20 pathotypes on the basis of the reactions of the barley grass. The genetic basis of resistance and susceptibility of barley grass to R. secalis was determined from F2 progeny of crosses among three resistant and two susceptible biotypes of barley grass. The resistance genes identified were all dominant.

scholarly journals A Comprehensive Review of the Major Genes Conditioning Resistance to Anthracnose in Common Bean

HortScience ◽  
2004 ◽  
Vol 39 (6) ◽  
pp. 1196-1207 ◽  
Author(s):  
James D. Kelly ◽  
Veronica A. Vallejo
Keyword(s):  
Common Bean ◽  
Resistance Genes ◽  
Durable Resistance ◽  
Gene Pyramiding ◽  
Resistance Breeding ◽  
Gene Clusters ◽  
Allelic Series ◽  
Multiple Alleles ◽  
Differential Cultivars ◽  
Major Resistance Genes

Resistance to anthracnose in common bean is conditioned primarily by nine major independent genes, Co-1 to Co-10 as the Co-3/Co-9 genes are allelic. With the exception of the recessive co-8 gene, all other nine are dominant genes and multiple alleles exist at the Co-1, Co-3 and Co-4 loci. A reverse of dominance at the Co-1 locus suggests that an order of dominance exists among individual alleles at this locus. The nine resistance genes Co-2 to Co-10 are Middle American in origin and Co-1 is the only locus from the Andean gene pool. Seven resistance loci have been mapped to the integrated bean linkage map and Co-1 resides on linkage group B1; Co-2 on B11, Co-3 on B4; Co-4 on B8; Co-6 on B7; and Co-9 and Co-10 are located on B4 but do not appear to be linked. Three Co-genes map to linkage groups B1, B4 and B11 where clusters with genes for rust resistance are located. In addition, there is co-localization with major resistance genes and QTL that condition partial resistance to anthracnose. Other QTL for resistance may provide putative map locations for the major resistance loci still to be mapped. Molecular markers linked to the majority of major Co-genes have been reported and these provide the opportunity to enhance disease resistance through marker-assisted selection and gene pyramiding. The 10 Co-genes are represented in the anthracnose differential cultivars, but are present as part of a multi-allelic series or in combination with other Co-genes, making the characterization of more complex races difficult. Although the Co-genes behave as major Mendelian factors, they most likely exist as resistance gene clusters as has been demonstrated on the molecular level at the Co-2 locus. Since the genes differ in their effectiveness in controlling the highly variable races of the anthracnose pathogen, the authors discuss the value of individual genes and alleles in resistance breeding and suggest the most effective gene pyramids to ensure long-term durable resistance to anthracnose in common bean.

scholarly journals Distribution of Pathotypes of Rhynchosporium secalis and Cultivar Reaction on Barley in Alberta

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 391-396 ◽  
Author(s):  
K. Xi ◽  
T. K. Turkington ◽  
J. H. Helm ◽  
K. G. Briggs ◽  
J. P. Tewari ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Environmental Conditions ◽  
Rhynchosporium Secalis ◽  
Pathogen Virulence ◽  
Commercial Cultivars ◽  
Major Resistance Genes ◽  
Different Levels

Forty-four barley accessions and commercial cultivars with different levels of resistance to scald caused by Rhynchosporium secalis were evaluated for scald reaction from 1997 to 1999 at various sites in Alberta. The accessions Hudson, Atlas, Atlas 46, Atlas 68, Abyssinian, and Kitchin that have the major resistance genes were resistant to pathotypes of R. secalis at all sites. Although scald levels were low for these accessions, they were significantly different among years. Pathotypes of R. secalis and environmental conditions affected diseases levels on 32 commercial cultivars, resulting in significantly different scald reactions among sites and seasons. Resistance in commercial cultivars, AC Stacy, Kasota, and Seebe, held up at most sites with the majority of cultivars being intermediate to moderately susceptible. Cultivars that were previously considered resistant were intermediate in reaction and became increasingly susceptible at some sites from 1997 to 1999. Pathogen virulence was more diverse at the sites where the cultivars became increasingly susceptible compared with sites where the same cultivars were resistant. Scald reactions of the commercial cultivars depended on location, which reflected the presence of different pathotypes, as well as variation in environmental conditions. Consequently, scald management via cultivar choice will be dependent on location.

scholarly journals Pathogenic Variation in Rhynchosporium secalis on Barley in Ethiopia

2000 ◽  
Vol 5 (2) ◽  
pp. 75
Author(s):  
K. Meles ◽  
M. Hulluka ◽  
M.L. Deadman
Keyword(s):  
Resistance Genes ◽  
Geographical Location ◽  
Effective Resistance ◽  
Rhynchosporium Secalis ◽  
Malting Barley ◽  
Differential Host ◽  
Barley Cultivars ◽  
Pathogenic Variation ◽  
Pathogenic Variability

This paper presents the first detailed study on pathogenic variability in Rhynchosporium secalis in Ethiopia. Twenty four isolates of R. secalis, collected from Arsi, Bale and Shoa, major barley growing locations in Ethiopia, were tested on ten differential host cultivars, with known genes for resistance to the disease. The most frequent pathotypes were those inducing susceptible reactions on cvs Steudelli and Kitchen and the least complex pathotype identified was able to induce a susceptible reaction on these two cultivars only. Pathotypes 16 and 7 were the most complex and were able to induce susceptible reactions on 10 and 9 of the differential host cultivars respectively. These pathotypes were collected from research stations and were isolated from improved barley cultivars belonging to the malting barley type. The most frequent pathotype was pathotype 6 which was represented by four isolates from different locations in Arsi, Bale and Shoa. Pathogenic variation was detected amongst spores collected from the same field and from the same geographical location. The most effective resistance genes were those possessed by Turk, La-Mesita, Bey, Nigrinudum, Jet and Forrajera.   

scholarly journals Development of Bacterial Spot on Near-Isogenic Lines of Bell Pepper Carrying Gene Pyramids Composed of Defeated Major Resistance Genes

1999 ◽  
Vol 89 (11) ◽  
pp. 1066-1072 ◽  
Author(s):  
C. S. Kousik ◽  
D. F. Ritchie
Keyword(s):  
Disease Severity ◽  
Resistance Genes ◽  
Field Studies ◽  
Residual Effects ◽  
Specific Gene ◽  
Near Isogenic Lines ◽  
Bacterial Spot ◽  
Isogenic Lines ◽  
Major Resistance Genes ◽  
Race 4

Disease severity caused by races 1 through 6 of Xanthomonas campestris pv. vesicatoria on eight near-isogenic lines (isolines) of Early Calwonder (ECW) with three major resistance genes (Bs1, Bs2, and Bs3) in different combinations was evaluated in the greenhouse and field. Strains representing races 1, 3, 4, and 6 caused similar high levels of disease severity, followed by races 2 and 5 on susceptible ECW. Race 3 caused severe disease on all isolines lacking resistance gene Bs2. Race 4, which defeats Bs1 and Bs2, caused less disease on isoline ECW-12R (carries Bs1 + Bs2), than on isolines ECW, ECW-10R (carries Bs1), and ECW-20R (carries Bs2). Similar results were obtained with race 4 strains in field studies conducted during 1997 and 1998. In greenhouse studies, race 6, which defeats all three major genes, caused less disease on isoline ECW-13R (carries Bs1 + Bs3) and ECW-123R (carries Bs1 + Bs2 + Bs3) than on isolines ECW, ECW-10R, ECW-20R, and ECW-30R (carries Bs3), but not on ECW-23R (carries Bs2 + Bs3). In greenhouse studies with commercial hybrids, strains of races 4 and 6 caused less disease on Boynton Bell (carries Bs1 + Bs2) than on Camelot (carries no known resistance genes), King Arthur (carries Bs1), and X3R Camelot (carries Bs2). Race 6 caused less disease on hybrid R6015 (carries Bs1 + Bs2 + Bs3) and Sentinel (carries Bs1 + Bs3) than on Camelot. Residual effects were not as evident in field studies with race 6 strains. Defeated major resistance genes deployed in specific gene combinations (i.e., gene pyramids) were associated with less area under the disease progress curve than when genes were deployed individually in isolines of ECW or commercial hybrids. Successful management of bacterial spot of pepper is achieved incrementally by integrating multiple tactics. Although there is evidence of residual effects from defeated genes, these effects alone likely will not provide acceptable bacterial spot control in commercial production fields. However, when combined with sanitation practices and a judicious spray program, pyramids of defeated resistance genes may aid in reducing the risk of major losses due to bacterial spot.

scholarly journals Pathogenic Variation of Phakopsora pachyrhizi Isolates on Soybean in the United States from 2006 to 2009

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 75-81 ◽  
Author(s):  
M. Twizeyimana ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
Resistance Genes ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Soybean Genotype ◽  
Pathogenic Variation ◽  
Differential Set ◽  
Soybean Genotypes ◽  
Soybean Leaves

The introduction of Phakopsora pachyrhizi, the cause of soybean rust, into the United States is a classic case of a pathogen introduction that became established in a new geographical region overwintering on a perennial host (kudzu, Pueraria lobata). The objective of our study was to classify the pathogenic variation of P. pachyrhizi isolates collected in the United States, and to determine the spatial and temporal associations. In total, 72 isolates of P. pachyrhizi collected from infected kudzu and soybean leaves in the United States were purified, then established and increased on detached soybean leaves. These isolates were tested for virulence and aggressiveness on a differential set of soybean genotypes that included six genotypes with known resistance genes (Rpp), one resistant genotype without any known characterized resistance gene, and a susceptible genotype. Three pathotypes were identified among the 72 U.S. P. pachyrhizi isolates based on the virulence of these isolates on the genotypes in the differential set. Six aggressiveness groups were established based on sporulating-uredinia production recorded for each isolate on each soybean genotype. All three pathotypes and all six aggressiveness groups were found in isolates collected from the southern region and from both hosts (kudzu or soybean) in 2008. Shannon's index based on the number of pathotypes indicated that isolates from the South region were more diverse (H = 0.83) compared with the isolates collected in other regions. This study establishes a baseline of pathogenic variation of P. pachyrhizi in the United States that can be further compared with variation reported in other regions of the world and in future studies that monitor P. pachyrhizi virulence in association to deployment of rust resistance genes.

scholarly journals Identification of Phaeoisariopsis griseola pathotypes from five States in Brazil

2002 ◽  
Vol 27 (1) ◽  
pp. 78-81 ◽  
Author(s):  
ALOISIO SARTORATO
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Resistance Genes ◽  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Phaeoisariopsis Griseola ◽  
Moist Chamber ◽  
Differential Cultivars ◽  
Pathogenic Variability ◽  
Resistant Genotypes

Due to the increased importance of angular leaf spot of common bean (Phaseolus vulgaris) in Brazil, monitoring the pathogenic variability of its causal agent (Phaeoisariopsis griseola) is the best strategy for a breeding program aimed at developing resistant genotypes. Fifty one isolates of P. griseola collected in five Brazilian States were tested on a set of 12 international differential cultivars in the greenhouse. When inoculated plants showed symptoms but no sporulation was observed, they were transferred to a moist chamber for approximately 20-24 h. After this period of time, if no sporulation was observed, the plants were considered resistant; otherwise, they were considered susceptible. From the fifty-one tested isolates, seven different pathotypes were identified. No Andean pathotypes were identified; consequently, all isolates were classified as Middle American pathotypes. Pathotype 63-31 was the most widespread. Pathotype 63-63 overcame resistance genes present in all differential cultivars and also the resistance gene(s) present in the cultivar AND 277. This fact has important implications for breeding angular leaf spot resistance in beans, and suggests that searching for new resistance genes to angular leaf spot must be pursued.

Phytophthora sojae pathotype distribution and fungicide sensitivity in Michigan

Plant Disease ◽  
2021 ◽  
Author(s):  
Austin Glenn McCoy ◽  
Zachary Albert Noel ◽  
Janette L Jacobs ◽  
Kayla M Clouse ◽  
Martin I Chilvers
Keyword(s):  
Resistance Genes ◽  
Phytophthora Sojae ◽  
Significant Shift ◽  
Seed Treatments ◽  
Fungicide Sensitivity ◽  
History Of ◽  
Plant Stand ◽  
Rps Gene ◽  
Major Resistance Genes ◽  
Pathogen Populations

Identifying the pathotype structure of a Phytophthora sojae population is crucial for the effective management of Phytophthora stem and root rot of soybean (PRR). P. sojae has been successfully managed with major resistance genes, partial resistance, and fungicide seed treatments. However, prolonged use of resistance genes or fungicides can cause pathogen populations to adapt over time, rendering resistance genes or fungicides ineffective. A statewide survey was conducted to characterize the current pathotype structure and fungicide sensitivity of P. sojae within Michigan. Soil samples were collected from 69 fields with a history of PRR and fields having consistent plant stand establishment issues. Eighty-three isolates of P. sojae were obtained, and hypocotyl inoculations were performed on 14 differential soybean cultivars, all of which carry a single Rps gene or no resistance gene. The survey identified a loss of effectiveness of Rps genes 1b, 1k, 3b and 6, compared to a previous survey conducted in Michigan from 1993-1997. Three effective resistance genes were identified for P. sojae management in Michigan; Rps 3a, 3c, and 4. Additionally, the effective concentration of common seed treatment fungicides to inhibit mycelial growth by 50% (EC50) was determined. No P. sojae isolates were insensitive to the tested chemistries with mean EC50 values of 2.60x10-2 µg/ml for ethaboxam, 3.03x10-2 µg/ml for mefenoxam, 2.88x10-4 µg/ml for oxathiapiprolin, and 5.08x10-2 µg/ml for pyraclostrobin. Results suggest that while there has been a significant shift in Rps gene effectiveness, seed treatments are still effective for early season management of this disease.

scholarly journals Characterization of Colletotrichum lindemuthianum isolates using differential cultivars of common bean in Santa Catarina State, Brazil

2008 ◽  
Vol 51 (5) ◽  
pp. 883-888 ◽  
Author(s):  
Maria Celeste Gonçalves-Vidigal ◽  
Claudia Thomazella ◽  
Pedro Soares Vidigal Filho ◽  
Marcus Vinícius Kvitschal ◽  
Haroldo Tavares Elias
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Colletotrichum Lindemuthianum ◽  
Phaseolus Vulgaris L ◽  
Santa Catarina ◽  
First Report ◽  
Differential Cultivars ◽  
Differential Cultivar ◽  
Santa Catarina State

In 2003 and 2004, 32 isolates of Colletotrichum lindemuthianum obtained from the infected plants of field-grown common bean (Phaseolus vulgaris L.) in Santa Catarina state, Brazil were analyzed based on the virulence to 12 differential cultivars of Phaseolus vulgaris L.. Thirteen distinct races were identified, six of which had not been reported previously in Santa Catarina. This is the first report of the occurrence of 67, 83,101,103,105, and 581 races of C. lindemuthianum. Race 65 was most common (34%). All the isolates were compatible to the cultivars Michelite and Mexico 222. Some isolates infected not only differential cultivar of Mesoamerican origin, but also the ones of Andean origin.

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