scholarly journals Effect of Partial Resistance on Phytophthora Stem Rot Incidence and Yield of Soybean in Ohio

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 308-312 ◽  
Author(s):  
A. E. Dorrance ◽  
S. A. McClure ◽  
S. K. St. Martin
Keyword(s):  
Partial Resistance ◽  
Phytophthora Sojae ◽  
Stem Rot ◽  
Environment Interaction ◽  
Genetic Traits ◽  
Soybean Cultivars ◽  
Negative Effect ◽  
Effect On Yield ◽  
Rps Gene ◽  
Disease Pressure

Phytophthora root and stem rot of soybean commonly causes losses in both stand and yield in Ohio. Environmental conditions which favor the pathogen typically occur in many areas of the state during late spring and summer. This study examined the performance of 12 soybean cultivars with partial resistance, with or without Rps genes, to different populations of Phytophthora sojae and various levels of disease pressure. The soybean cultivars were evaluated in seven field environments with and without metalaxyl over 4 years. There was a highly significant genotype-environment interaction which was due in part to variable disease pressure. The incidence of Phytophthora stem rot in subplots ranged from 0 to 10 plants in the most susceptible cultivar, Sloan, while significantly less stem rot developed in cultivars with high levels of partial resistance or partial resistance combined with an Rps gene in three of the seven environments. Metalaxyl applied in-furrow had a significant effect on early and final plant populations as well as yield (P < 0.001) in two of the seven environments, and for yield (P = 0.05) in one environment. This indicates that at these two environments, 2001 Lakeview and VanBuren, early season Phytophthora disease was controlled with the in-furrow fungicide treatment. When diverse populations of P. sojae were present, yields from soybean cultivars with high levels of partial resistance were significantly higher than those with low levels of partial resistance. Soybean cultivars with specific resistance genes Rps1k, Rps1k + Rps6, or Rps1k +Rps3a had higher yields than plants with only partial resistance in environments where race determination indicated that the populations of P. sojae present were not capable of causing disease on plants with the Rps1k gene. However, in an environment with very low disease pressure, yields of soybean cultivars with partial resistance were not significantly different from those with single Rps genes or Rps gene combinations. These results demonstrate that genetic traits associated with high levels of partial resistance do not have a negative effect on yield. Soybean cultivars that had the most consistent ranking across environments were those with moderate levels of partial resistance in combination with either Rps1k or Rps3a.

Comparison of Phytophthora sojae populations in Iowa and Nebraska to identify effective Rps genes for Phytophthora stem and root rot management

2021 ◽  
Author(s):  
Rashelle Matthiesen-Anderson ◽  
Clarice Schmidt ◽  
Vinicius C. Garnica ◽  
Loren Giesler ◽  
Alison E Robertson
Keyword(s):  
Root Rot ◽  
Partial Resistance ◽  
Specific Resistance ◽  
Phytophthora Sojae ◽  
Soybean Variety ◽  
Soybean Cultivars ◽  
Soybean Genotypes ◽  
Rps Gene ◽  
High Level ◽  
Almost All

Phytophthora stem and root rot (PSRR) of soybean, caused by the oomycete Phytophthora sojae, is prevalent in Iowa and Nebraska. Reducing losses to PSRR primarily relies on growing cultivars with specific resistance (Rps) genes. Predominant genes used in commercial soybean cultivars include Rps 1a, Rps 1c, Rps 1k, and Rps 3a. Knowing which Rps gene to deploy depends on knowledge of which genes are effective against the pathogen. From 2016 to 2018, 326 isolates of P. sojae from were recovered from fields in Iowa and Nebraska and classified into pathotypes based on their virulence on 15 soybean genotypes. A total of 15 and 10 pathotypes were identified in Iowa and Nebraska, respectively. Almost all isolates were virulent on Rps 1a, while over 70% of isolates were virulent on Rps 1c and Rps 1k. Only 2.3% of isolates from Iowa were virulent on Rps 3a. Among commercial soybean cultivars tested in the Illinois Soybean Variety trials from 2010 to 2020, Rps 1c was always the most frequently reported gene followed by Rps 1k. In contrast, Rps 1a and Rps 3a were present in less than 10% and less than 5 % of the cultivars tested, respectively. Since many of the P. sojae isolates in our study were virulent on Rps 1a, Rps 1c, and Rps 1k, soybean cultivars with these genes are unlikely to provide protection against PSRR unless they have a high level of partial resistance.

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 Races of Phytophthora sojae and Their Virulences on Soybean Cultivars in Heilongjiang, China

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 87-91 ◽  
Author(s):  
Shuzhen Zhang ◽  
Pengfei Xu ◽  
Junjiang Wu ◽  
Allen G. Xue ◽  
Jinxiu Zhang ◽  
...  
Keyword(s):  
Phytophthora Sojae ◽  
Heilongjiang Province ◽  
Plant Mortality ◽  
Pathogen Population ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Soybean Cultivars ◽  
Rps Gene ◽  
First Time ◽  
Important Disease

Phytophthora root and stem rot, caused by Phytophthora sojae, is an economically important disease of soybean (Glycine max) in Heilongjiang Province, China. The objectives of this research were to determine the race profile of P. sojae in Heilongjiang and evaluate soybean cultivars for reactions to the pathogen races. A total of 96 single-zoospore P. sojae isolates were obtained from soil samples collected from 35 soybean fields in 18 counties in Heilongjiang from 2005 to 2007. Eight races of P. sojae, including races 1, 3, 4, 5, 9, 13, 44, and 54, were identified on a set of eight differentials, each containing a single resistance Rps gene, from 80 of the 96 isolates. Races 1 and 3 were predominant races, comprising 58 and 14 isolates, and representing 60 and 7% of the pathogen population, respectively. Races 4, 5, 44, and 54 were identified for the first time in Heilongjiang, and each was represented by two to three isolates only. Sixty-two soybean cultivars commonly grown in Heilongjiang Province were evaluated for their resistance to the eight P. sojae races identified using the hypocotyl inoculation technique. Based on the percentage of plant mortality rated 5 days after inoculation, 44 cultivars were resistant (<30% mortality) to at least one race. These cultivars may be used as sources of resistance in soybean breeding programs.

scholarly journals Pathotype and Genetic Shifts in a Population of Phytophthora sojae Under Soybean Cultivar Rotation

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 614-624 ◽  
Author(s):  
S. Stewart ◽  
N. Abeysekara ◽  
A. E. Robertson
Keyword(s):  
Partial Resistance ◽  
Management Practices ◽  
Gene Diversity ◽  
Genotypic Diversity ◽  
The United States ◽  
Phytophthora Sojae ◽  
Resistant Cultivar ◽  
Stem Rot ◽  
Economic Losses ◽  
Continuous Rotation

Changes in pathotype structure of Phytophthora sojae populations have been attributed to deployment of race-specific resistant Rps genes in soybean that have been incorporated into commercial cultivars to reduce losses due to Phytophthora root and stem rot. To test this hypothesis, a cultivar rotation study was established from 2007 through 2010 in microplots at a site in Iowa with no history of soybean cultivation. All microplots were inoculated with P. sojae isolate PR1, race 1 (vir 7) prior to planting in year 1. Six rotations were tested: (i) continuous planting of a P. sojae-susceptible cultivar, (ii) continuous planting of a cultivar with high partial resistance to the pathogen, (iii) continuous planting of a cultivar with the Rps 1k gene, (iv) annual rotation of a susceptible with a resistant cultivar, (v) annual rotation of a partially resistant cultivar with a cultivar with the Rps 1k gene, and (vi) 4-year rotation of cultivars with Rps 1k, 1c, 3a, and 1k genes in year one, two, three, and four, respectively. The diversity of 121 isolates of P. sojae that were recovered by baiting from soil samples collected from the experiment were assessed using pathotyping and eight microsatellite markers, and compared with PR1. Changes in pathotype and multilocus genotypes (MLGs) were recorded at the second sampling date, indicating that P. sojae has the ability to evolve quickly. In total, 14 pathotypes and 21 MLGs were recovered over the 4-year experiment, and only 49 and 22% of the isolates had the same pathotype and MLG, respectively, as PR1. The number of isolates of P. sojae recovered varied among rotations, with more isolates recovered from rotations that included a cultivar with partial resistance. Gain of virulence was detected on Rps 1a, 1b, 1c, 1d, and 3a and was not dependent on rotation. Using simple-sequence repeat analysis, 10 alleles that were different from those of PR1 were detected throughout the 4-year period. Cultivar rotation affected the genetic structure of the P. sojae population. Recovery of isolates with different MLGs, genotypic diversity (G = 4.7), and gene diversity (UHe = 0.45) were greater under continuous rotation with partial resistance. Phytophthora root and stem rot causes economic losses in the north-central region of the United States annually. An improved understanding of the effect of Rps gene deployment on P. sojae diversity would lead to improved management practices and reduced losses.

scholarly journals Pathogenic Diversity of Phytophthora sojae in Ohio Soybean Fields

Plant Disease ◽  
2003 ◽  
Vol 87 (2) ◽  
pp. 139-146 ◽  
Author(s):  
A. E. Dorrance ◽  
S. A. McClure ◽  
A. deSilva
Keyword(s):  
Shannon Index ◽  
Phytophthora Sojae ◽  
Reduced Tillage ◽  
Management Tools ◽  
Tillage Practices ◽  
Soybean Cultivars ◽  
The Mean ◽  
Production Practices ◽  
Rps Gene ◽  
Pathogenic Diversity

Problems with early season soybean stand establishment, and an increase in incidence of Phytophthora root and stem rot caused by Phytophthora sojae, prompted a reassessment of the pathogen population in Ohio. Earlier studies had indicated a potential for pathogen adaptation to commonly deployed Rps genes in soybeans. Fifty-seven fields, part of an earlier study in 1990 and 1991, along with 29 additional fields were sampled in either 1997 or 1999. Two soybean cultivars, Sloan (rps) and Resnik (Rps1k), were used as bait in a seedling bioassay to isolate P. sojae from the soil samples. P. sojae was recovered from 82 of the 86 fields sampled. Of the 429 isolates recovered from these soils, 325 and 104 were baited with soybean cultivars Sloan and Resnik, respectively. The P. sojae population in Ohio increased in the number of pathotypes (races) as well as in complexity since the earlier surveys. There were 72 and 202 pathotypes identified on 8 and 13 Rps gene differentials, respectively, in the current study. When the data were compared by location, 96, 65, 73, 78, 51, and 52% of the locations had at least one isolate with virulences to Rps1a, Rps1b, Rps1c, Rps1k, Rps3a, and Rps6, respectively. The mean complexity, the number of susceptible interactions on 8 differentials, increased from 3.01 to 4.06 between 1991 and 1997/1999. In addition, the pathogenic diversity as measured by the Shannon index increased from 2.71 to 3.28 for isolates recovered from the 57 fields sampled in both surveys. Producers whose fields were sampled were surveyed to determine if changes in the P. sojae population could be linked with production practices. There was a significant association between (P ≤ 0.05) reduced tillage practices and the presence of isolates that had virulence to Rps1k; reduced tillage fields also had isolates with virulence to a greater number of differentials. Due to the percentage of isolates that have virulence to many of the Rps genes, it is questionable how long a single Rps gene or several stacked Rps genes will remain viable disease management tools for P. sojae, unless a novel Rps gene is identified.

Reactions of Canadian short-season soybean cultivars to three races of Phytophthora sojae

2010 ◽  
Vol 90 (2) ◽  
pp. 207-210 ◽  
Author(s):  
S Z Zhang ◽  
A G Xue ◽  
J X Zhang ◽  
E. Cober ◽  
T R Anderson ◽  
...  
Keyword(s):  
Glycine Max ◽  
Key Words ◽  
Phytophthora Sojae ◽  
Stem Rot ◽  
Soybean Cultivars ◽  
Resistant Sources ◽  
Short Season

Of 87 short-season soybean cultivars evaluated for reactions to three races (1, 3, and 5) of Phytophthora sojae Kaufmann and Gerdemann, 29 showed resistance to at least one of the three races. These resistant sources may be used for pyramiding Rps genes and deployment of P. sojae resistant soybean cultivars in Canada. Key words: Soybean, Glycine max, phytophthora root and stem rot, Phytophthora sojae

scholarly journals Virulence Composition of Phytophthora sojae in Michigan

Plant Disease ◽  
2001 ◽  
Vol 85 (10) ◽  
pp. 1103-1106 ◽  
Author(s):  
R. C. Kaitany ◽  
L. P. Hart ◽  
G. R. Safir
Keyword(s):  
Phytophthora Sojae ◽  
Control Measures ◽  
Stem Rot ◽  
Soybean Plant ◽  
Soybean Cultivars ◽  
Plant Samples ◽  
First Time

Knowing the virulence composition of Phytophthora sojae is important for the management of Phytophthora root and stem rot of soybean. Plant samples were collected in Michigan from diseased plants in soybean fields with Phytophthora root and stem rot symptoms. Eighty-seven isolates of P. sojae were evaluated for virulence using 13 differential soybean cultivars. Rps 3b, 3a, 1b, 1k, and 6 were resistant to 81, 77, 74, 69, and 66% of the isolates, respectively, while Rps 1a and 7 were resistant to only 12 to 13% of the isolates. Races 2, 25, 41, and 44 of P. sojae were identified among the isolates and reported for the first time in Michigan. Virulence formulae of 69 isolates did not match those of currently known races of P. sojae. Nine isolates were considered nonpathogenic. Incorporating Rps genes 1b, 1k, 3a, 3b, and 6 in soybean cultivars with good field tolerance, in conjunction with other control measures, should offer improved protection of soybeans from Phytophthora root and stem rot in Michigan.

Evaluation of Soybean Cultivars with the Rps1k Gene for Partial Resistance or Field Tolerance to Phytophthora sojae

Crop Science ◽  
2006 ◽  
Vol 46 (6) ◽  
pp. 2427-2436 ◽  
Author(s):  
C. R. Ferro ◽  
C. B. Hill ◽  
M. R. Miles ◽  
G. L. Hartman
Keyword(s):  
Partial Resistance ◽  
Phytophthora Sojae ◽  
Soybean Cultivars

scholarly journals Pathotype Diversity of Phytophthora sojae in Eleven States in the United States

Plant Disease ◽  
2016 ◽  
Vol 100 (7) ◽  
pp. 1429-1437 ◽  
Author(s):  
A. E. Dorrance ◽  
J. Kurle ◽  
A. E. Robertson ◽  
C. A. Bradley ◽  
L. Giesler ◽  
...  
Keyword(s):  
United States ◽  
Partial Resistance ◽  
The United States ◽  
Phytophthora Sojae ◽  
Soil Samples ◽  
The State ◽  
Soybean Seedling ◽  
Northern Regions ◽  
Rps Gene

Pathotype diversity of Phytophthora sojae was assessed in 11 states in the United States during 2012 and 2013. Isolates of P. sojae were recovered from 202 fields, either from soil samples using a soybean seedling bioassay or by isolation from symptomatic plants. Each isolate was inoculated directly onto 12 soybean differentials; no Rps gene or Rps 1a, 1b, 1c, 1k, 3a, 3b, 3c, 4, 6, 7, or 8. There were 213 unique virulence pathotypes identified among the 873 isolates collected. None of the Rps genes were effective against all the isolates collected but Rps6 and Rps8 were effective against the majority of isolates collected in the northern regions of the sampled area. Virulence toward Rps1a, 1b, 1c, and 1k ranged from 36 to 100% of isolates collected in each state, while virulence to Rps6 and Rps8 was less than 36 and 10%, respectively. Depending on the state, the effectiveness of Rps3a ranged from totally effective to susceptible to more than 40% of the isolates. Pathotype complexity has increased in populations of P. sojae in the United States, emphasizing the increasing importance of stacked Rps genes in combination with high partial resistance as a means of limiting losses to P. sojae.

scholarly journals Genetic Analysis of Soybean Plant Introductions with Resistance to Phytophthora sojae

2007 ◽  
Vol 97 (1) ◽  
pp. 106-112 ◽  
Author(s):  
S. G. Gordon ◽  
S. A. Berry ◽  
S. K. St. Martin ◽  
A. E. Dorrance
Keyword(s):  
Single Gene ◽  
Phytophthora Sojae ◽  
Stem Rot ◽  
Soybean Plant ◽  
Phenotypic Analysis ◽  
Plant Introductions ◽  
Two Generations ◽  
Rps Gene ◽  
Serious Disease ◽  
The Individual

Phytophthora sojae, which causes Phytophthora root and stem rot of soybean, is a serious disease worldwide and is managed primarily by deploying cultivars with resistance. Thirty-two soybean plant introductions (PIs), all but three of which were from South Korea, were proposed as new sources of single-gene resistance to P. sojae. The objective of this study was to characterize the inheritance of resistance to P. sojae in these PIs. Twenty-two soybean populations from crosses of these PIs and the susceptible cv. Williams were inoculated with P. sojae OH17 (vir 1b, 1d, 2, 3a, 3b, 3c, 4, 5, 6, 7), and OH25 (vir 1a, 1b, 1c, 1k, 7). These isolates were selected because they are virulent on soybeans with all known Rps genes and many Rps gene combinations. Thirteen of the twenty-two populations had consistent segregation responses following inoculations between the two generations. In two PIs, resistance was conferred by two genes to OH17 and three genes to OH25. Resistance to both isolates was conferred by a single gene in PI 398440 although the individual families were not resistant to the same isolates. The data suggest that six of the populations have three-Rps gene combinations as previously proposed, while another four may have either a novel Rps gene or a four-Rps gene combination. Based on this phenotypic analysis, novel and uncharacterized Rps genes may be present in this material. More importantly, these PIs may serve as sources of novel Rps genes that can be used to more effectively manage Phytophthora root and stem rot.

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