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.

Common Phytophthora sojae pathotypes occurring in South Dakota

2021 ◽  
Author(s):  
Rawnaq Chowdhury ◽  
Connie Tande ◽  
Emmanuel Z Byamukama
Keyword(s):  
Glycine Max ◽  
South Dakota ◽  
Resistance Genes ◽  
Phytophthora Sojae ◽  
Stem Rot ◽  
Inoculation Technique ◽  
Glycine Max L ◽  
Rps Gene ◽  
Important Disease

Phytophthora root and stem rot, caused by Phytophthora sojae, is an important disease of soybean (Glycine max L.) in South Dakota. Because P. sojae populations are highly diverse and resistance genes deployed in commercial soybean varieties often fail to manage the disease, this study was initiated to determine P. sojae pathotype distribution in South Dakota. A total of 216 P. sojae isolates were baited from soil collected from 422 soybean fields in South Dakota in 2013-2015 and 2017. The pathotype of each isolate was determined by inoculating 10 seedlings of 13 standard soybean P. sojae differential lines using the hypocotyl inoculation technique. Of the 216 pathotyped isolates, 48 unique pathotypes were identified. The virulence complexity of isolates ranged from virulence on one Rps gene (Rps7) to virulence on 13 Rps genes and mean complexity was 5.2. Harosoy (Rps7), Harlon (Rps1a), Williams 79 (Rps 1c), William 82 (Rps1k), Harosoy 13XX (Rps1b), were susceptible to 98, 80, 78, 73, 72% of the isolates, respectively. These results highlight the highly diverse P. sojae pathotypes in South Dakota and the likely Rps genes to fail in commercial soybean varieties

scholarly journals Population Structure Among and Within Iowa, Missouri, Ohio, and South Dakota Populations of Phytophthora sojae

Plant Disease ◽  
2016 ◽  
Vol 100 (2) ◽  
pp. 367-379 ◽  
Author(s):  
S. Stewart ◽  
A. E. Robertson ◽  
D. Wickramasinghe ◽  
M. A. Draper ◽  
A. Michel ◽  
...  
Keyword(s):  
Gene Flow ◽  
South Dakota ◽  
Genotypic Diversity ◽  
Phytophthora Sojae ◽  
Field Variation ◽  
Limited Gene Flow ◽  
Rps Gene ◽  
Pathogen Populations ◽  
High Level ◽  
Important Disease

Phytophthora root and stem rot, caused by Phytophthora sojae, is an economically important disease of soybean throughout the Midwestern United States. This disease has been successfully managed with resistance (Rps) genes; however, pathogen populations throughout the Midwest have developed virulence to many Rps genes, including those that have not been deployed. To gain a better understanding of the processes that influence P. sojae evolution, the population genetic structure was compared among populations using one isolate collected from 17, 33, and 20 fields in Iowa, Ohio, and South Dakota, respectively, as well as multiple isolates from individual fields in Iowa, Ohio, and Missouri. Genotypic diversity was measured using 21 polymorphic microsatellite (simple-sequence repeat) markers. and pathotype diversity using 15 soybean differentials. For all but three of the populations with low sample size, there was a high level of pathotype diversity and a low to moderate level of genotypic diversity among the populations for both comparisons between states and within-field variation. None of the Rps-gene differentials were resistant to all of the isolates. There were 103 unique multilocus genotypes identified in this study and only 2 were identified from the same field. Although no clones were identified in more than one field, pairwise FST indicated that some gene flow within neighboring fields does occur but not across the region, including fields from neighboring states. These results suggest that there is a strong probability that each state may have their own or several regional populations, as well as provide further evidence of high diversity within this homothallic pathogen which may be due, in part, to limited gene flow, mutation, or outcrossing, and this likely affects the success of deployment of resistance.

Pathotype Complexity and Genetic Characterization of Phytophthora sojae Populations in Illinois, Indiana, Kentucky, and Ohio

2021 ◽  
Author(s):  
Linda Weber Hebb ◽  
Carl A. Bradley ◽  
Santiago Xavier Mideros ◽  
Darcy E. P. Telenko ◽  
Kiersten Wise ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Resistance Genes ◽  
Genetic Characterization ◽  
Specific Resistance ◽  
Agricultural Practices ◽  
Phytophthora Sojae ◽  
Simple Sequence Repeat Markers ◽  
Rps Gene ◽  
Simple Sequence

Phytophthora sojae, the causal agent of Phytophthora root and stem rot of soybean, has been managed with single Rps genes since the 1960’s, but has subsequently adapted to many of these resistance genes, rendering them ineffective. The objective of this study was to examine the pathotype and genetic diversity of P. sojae from soil samples across Illinois, Indiana, Kentucky, and Ohio by assessing which Rps gene(s) were still effective and identifying possible population clusters. There were 218 pathotypes identified from 473 P. sojae isolates with an average of 6.7 out of 15 differential soybean lines exhibiting a susceptible response for each isolate. Genetic characterization of 103 P. sojae isolates from across Illinois, Indiana, Kentucky, and Ohio with 19 simple sequence repeat markers identified 92 multilocus genotypes. There was a moderate level of population differentiation among these four states, with pairwise FST values ranging from 0.026 to 0.246. There was also moderate to high levels of differentiation between fields, with pairwise FST values ranging from 0.071 to 0.537. Additionally, cluster analysis detected the presence of P. sojae population structure across neighboring states. The level of pathotype and genetic diversity, in addition to the identification of population clusters, supports the hypothesis of occasional outcrossing events that allow for an increase in diversity and the potential to select for a loss in avirulence to specific resistance genes within regions. The trend of suspected gene flow among neighboring fields is expected to be an ongoing issue with current agricultural practices.

Disease resistance and pathogen population genetic

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. 245-248
Author(s):  
B.A. McDonald ◽  
C. Linde
Keyword(s):  
Resistance Gene ◽  
Resistance Genes ◽  
Durable Resistance ◽  
Genetic Resistance ◽  
Pathogen Population ◽  
Evolutionary Forces ◽  
Boom And Bust ◽  
Major Resistance Genes ◽  
Pathogen Populations ◽  
Plant Pathosystems

Plant pathologists have seen many boom-and-bust cycles following the deployment of resistant varieties. These cycles result when pathogen populations adapt to the presence of a major resistance gene by evolving a new population that can overcome this resistance gene. The breakdown of genetic resistance is due to the evolution of the local pathogen population because of selection for mutants, recombinants, or immigrants that are better adapted to the resistant cultivar. To understand the process that leads to breakdown of a resistance gene, we need to understand the processes that govern pathogen evolution. Population geneticists have identified five evolutionary forces that interact to affect the evolution of organisms. We ranked these risks and developed a quantitative framework to predict the risk that a pathogen will evolve to overcome major resistance genes. Our hypothesis is that much of the durability of resistance genes is due to the nature of the pathogen population rather than to the nature of the resistance gene. The framework we developed can be used as a hypothesis to test against a large number of plant pathosystems. The underlying principles of the framework can be tested individually or in combination according to the available knowledge of the population genetics for any pathogen. We propose that this framework can be used to design breeding strategies to break the boom-and-bust cycle and lead to durable resistance.

scholarly journals Traits of Soybean-Infecting Phytophthora Populations from Illinois Agricultural Fields

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1139-1145 ◽  
Author(s):  
D. K. Malvick ◽  
E. Grunden
Keyword(s):  
Poor Performance ◽  
Phytophthora Sojae ◽  
Technical Grade ◽  
Pathogen Virulence ◽  
Phytophthora Spp ◽  
History Of ◽  
Restricted Region ◽  
Phytophthora Rot ◽  
Rps Gene

Phytophthora rot caused by Phytophthora sojae is a common and significant disease of soybean (Glycine max) in Illinois and throughout the Midwestern United States. The pathogenic characteristics of P. sojae populations in several Midwestern states have been reported recently, but pathogenicity and fungicide sensitivity traits of populations in Illinois were poorly understood. Isolates (n = 121) of soybean-infecting Phytophthora spp. were baited using susceptible cv. Sloan seedlings from soybean field soils with a history of seedling diseases in 24 counties across Illinois. The pathotype and race of isolates of P. sojae were characterized using 11 differential soybean cultivars in greenhouse tests using a hypocotyl inoculation method. Sensitivity to the fungicidal compounds metalaxyl and mefenoxam was tested with 63 isolates in vitro. Most (96%) of the Phytophthora isolates sampled from Illinois soybean fields were P. sojae, but 4% were an unidentified Phytophthora sp. as determined by phenotypic and genotypic traits. We present a preliminary description of another Phytophthora sp. from soybean fields in a restricted region of Illinois that is pathogenic and capable of killing soybean. Based on eight Rps gene differentials (Rps1a, 1b, 1c, 1d, 1k, 3a, 6, and 7 ), 22 virulence pathotypes of P. sojae were identified and 88% of all isolates were characterized to a defined race. The four most common races, which were 58% of all isolates, were races 1 (21%), 4 (15%), 33 (12%), and 28 (10%). Based on 11 differentials, (those noted above and Rps 2, 4, and 5), 31 virulence pathotypes were identified. The mean virulence complexities, which are the number of susceptible interactions on the sets of 8 and 11 Rps gene differentials, were 3.3 and 3.7, respectively. All isolates tested were sensitive to Apron XL, Allegiance, technical grade mefenoxam, and technical grade metalaxyl at 1.0 μg a.i./ml. The population of P. sojae is diverse and composed of multiple pathotypes and races in Illinois, and the results suggest that pathogen virulence partially explains poor performance of Phytophthora-resistant cultivars in many Illinois soybean fields.

scholarly journals Beneficial Effects of Fungicide Seed Treatments for Soybean Cultivars with Partial Resistance to Phytophthora sojae

Plant Disease ◽  
2001 ◽  
Vol 85 (10) ◽  
pp. 1063-1068 ◽  
Author(s):  
A. E. Dorrance ◽  
S. A. McClure
Keyword(s):  
Partial Resistance ◽  
Seed Treatment ◽  
Phytophthora Sojae ◽  
Soybean Seeds ◽  
Damping Off ◽  
Seed Treatments ◽  
Beneficial Effects ◽  
Rps Gene ◽  
Greenhouse Assay ◽  
Zoospore Suspension

Phytophthora sojae is a yield-limiting soybean pathogen in areas where soils remain saturated for long periods of time. P. sojae has been successfully managed with single dominant resistance genes (Rps genes). The proportion of fields with populations of P. sojae capable of causing susceptible interactions with many of the Rps genes has increased in number. The fungicides metalaxyl and mefenoxam have been used both as in-furrow and seed treatments to provide protection against damping-off caused by P. sojae. To determine the plant age when partial resistance and Rps genes are effective against P. sojae, we evaluated a greenhouse assay in which soybean seeds were planted and inoculated with a zoospore suspension to compare the disease reaction of soybean seeds and seedlings. Efficacy of different fungicide rates also was evaluated using the cultivar with partial resistance with this inoculation technique. Seeds and seedlings of a cultivar with high levels of partial resistance were susceptible to infection by P. sojae while those of a cultivar with an Rps gene were resistant. For the cultivar with partial resistance, reductions in percent emergence and the number of damped-off seedlings were significantly higher for plants inoculated at the day of planting compared to inoculations of plants with unifoliates present (5 days after planting). Results also indicate that fungicide seed treatment on cultivars with partial resistance may be beneficial when the environmental conditions that favor P. sojae infections occur prior to soybean emergence. This greenhouse assay appears to be useful in examining overall fungicide efficacy; however, it did not detect consistent and quantifiable differences in rates of seed treatment fungicides.

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.

Within-field Pathogenic Diversity of Phytophthora sojae in Commercial Soybean Fields in Iowa

2009 ◽  
Vol 10 (1) ◽  
pp. 8 ◽  
Author(s):  
Alison E. Robertson ◽  
Silvia R. Cianzio ◽  
Sarah M. Cerra ◽  
Richard O. Pope
Keyword(s):  
The United States ◽  
Phytophthora Sojae ◽  
Soil Samples ◽  
Soybean Plant ◽  
North Central Region ◽  
North Central ◽  
The North ◽  
History Of ◽  
The Many ◽  
Pathogenic Diversity

Phytophthora root and stem rot (PRR), caused by the oomycete Phytophthora sojae, is an economically important soybean disease in the north central region of the United States, including Iowa. Previous surveys of the pathogenic diversity of P. sojae in Iowa did not investigate whether multiple pathotypes of the pathogen existed in individual fields. Considering the many pathotypes of P. sojae that have been reported in Iowa, we hypothesized multiple pathotypes could exist within single fields. In the research reported herein, several soil samples were collected systematically from each of two commercial fields with a history of PRR in Iowa, and each soil sample was baited separately for isolates of P. sojae. Numerous pathotypes of P. sojae were detected from both fields. As many as four pathotypes were detected in some soil samples (each consisting of six to eight soil cores), which suggests that a single soybean plant could be subjected to infection by more than one pathotype. This possibility presents important implications in breeding resistant cultivars and in the management of PRR. Accepted for publication 14 July 2009. Published 8 September 2009.

scholarly journals Studije tehnologije i studije materijalne kulture: mogućnosti bliže saradnje na primeru koštanih artefakata

2017 ◽  
Vol 12 (3) ◽  
pp. 703
Author(s):  
Selena Vitezović ◽  
Ivan Vranić
Keyword(s):  
Material Culture ◽  
Research Strategy ◽  
Raw Material ◽  
Significant Shift ◽  
Faunal Remains ◽  
Technology Studies ◽  
Archaeological Material ◽  
Theoretical Perspectives ◽  
History Of ◽  
State Of Affairs

Bone artefacts are among the less thoroughly studied classes of archaeological material, especially in the case of particular periods and regions. The reasons behind this are not uniform. The most obvious and general are linked to the research practices of culture-historical archaeology, often neglecting bone artefacts, considering them not sufficiently attractive or informative. The most significant shift towards recognition of a set of potential information gained from bone objects was achieved in the framework of studies of prehistoric technology during the second half of 20th century, especially in the French archaeological school.  This research strategy raised a number of questions concerning the acquisition of raw material, modes of production and usage of objects, whose interpretative potential gained in power, leading to the increased attention paid to faunal remains in archaeological investigations. Yet this source of information on the actual details of relations between people and material culture, opened by technology studies, has not been sufficiently explored.  It may be suggested that the reasons are the narrow specialization of researchers and insufficient inclusion of the gathered information into the wider interpretive framework, various traditions and lack of cooperation among the national archaeological “schools”, language barriers etc. However, the main reason behind this state of affairs may be sought for in non-integrated theoretical perspectives and the lack of clearly articulated interpretive position of researchers seeking to apply the knowledge gained from technology studies, considering this strategy as an “objective, scientific method”, providing concrete answers clearly complying to the expectations of the dominant archaeological paradigm.The paper offers a critical review of a number of examples of application of technology studies in archaeology and possible directions of a more integrated and theoretically informed approach. One of the obvious solutions may be sought in the direction of another research strategy – material culture studies. The aim of the paper is thus to link these two approaches, whose theoretical foundations are not uniform today, but the history of the ideas and the mode of articulation of the basic theoretical assumptions indicate similar theoretical roots.

Malaya Sadovaya in the History of Leningrad Unofficial Culture

2021 ◽  
Author(s):  
Ainsley Morse
Keyword(s):  
Creative Writing ◽  
Significant Shift ◽  
Writing Groups ◽  
Oral Culture ◽  
History Of

Malaya Sadovaya, a short street in Leningrad/St. Petersburg, is similarly the name for a loosely organized social and cultural scene encompassing, among other frequent visitors, a number of young poets. In the history of Leningrad unofficial culture, the Malaya Sadovaya poets represent a significant shift from a primarily “oral” culture of informal public and semipublic readings to a new orientation toward printed works: in 1965, several of the MS poets published a samizdat “almanac” of their work, Fioretti. Along the same lines, Malaya Sadovaya can be seen as marking a path from officially sponsored creative-writing groups to a self-consciously unofficial culture, implicitly (and sometimes explicitly) opposed to the mainstream Soviet aesthetic.

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