Adaptation of Phytophthora sojae to Rps Resistance Genes over the Past Two Decades in North Dakota

Phytophthora root rot, caused by Phytophthora sojae, is a major disease of soybean in North Dakota, especially in the Red River Valley (RRV). Planting resistant cultivars is the primary management. The resistance genes Rps 1c, 1k, 3a, and 6 are the most common genes deployed in this region. To determine the efficacy of these genes and document the pathotype changes in the population of P. sojae over several decades, a survey of pathotypes was conducted in 2015 in three counties in the southern RRV and compared with similar surveys conducted in 1991 to 1994 and 2002 to 2004 in the same area. The results showed that from 1991 to 1994 when 6% of the pathotypes could defeat the Rps1c gene, by 2004 it was 57% of the pathotypes, and that percentage remained the same in 2015. However, in 1994 no pathotype could defeat Rps 1k, but by 2004 it was 12% and in 2015 it was 41%. Pathotypes that defeat Rps 3a and 6 have been few over the years. Pathotypes that defeat both 1c and 1k increased from none to 31% between 1994 and 2015. With the increasing complexity of P. sojae pathotypes, new strategies for managing this pathogen in the future will be needed.

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Pathotypes, Distribution, and Metalaxyl Sensitivity of Phytophthora sojae from North Dakota

Plant Disease ◽

10.1094/pdis-92-7-1062 ◽

2008 ◽

Vol 92 (7) ◽

pp. 1062-1066 ◽

Cited By ~ 19

Author(s):

B. D. Nelson ◽

I. Mallik ◽

D. McEwen ◽

T. Christianson

Keyword(s):

North Dakota ◽

Resistance Genes ◽

Phytophthora Sojae ◽

Limited Growth ◽

Phytophthora Root Rot ◽

The Past ◽

Virulence Phenotype ◽

Metalaxyl Sensitivity ◽

Race 4 ◽

Important Disease

Phytophthora root rot, caused by Phytophthora sojae, is the most important disease of soybean (Glycine max) in North Dakota. Because of the expansion of soybean hectares and appearance of disease on cultivars with resistance genes, we investigated the pathotypes, distribution, and metalaxyl sensitivity of P. sojae in North Dakota. Soil from 347 soybean fields in 20 counties in eastern North Dakota was collected between 2002 and 2004, and P. sojae was baited from the soil with the susceptible cultivar McCall. The virulence phenotype of each isolate was determined on eight differentials, and all isolates were tested for sensitivity to metalaxyl incorporated into V8 agar. The pathogen was recovered from 80 fields located in five counties. Sixteen pathotypes, which included 14 known races and two previously reported pathotypes that had not been assigned a race, were identified out of 157 isolates. A single pathotype was recovered from 61 fields, 2 pathotypes from 14 fields, 3 pathotypes from 4 fields, and 4 pathotypes from 1 field. Pathotypes with virulence phenotypes 1a,1c,7 (race 4; 39%) and 1a,7 (race 3; 28%) were the most common, representing 67% of the total isolates. One or both of these pathotypes was found in 79% of the fields where P. sojae was recovered. Seven of the 157 isolates showed limited growth on metalaxyl after 14 days of incubation. In the past 10 years, the number of pathotypes of P. sojae in North Dakota has increased from 4 to 16, and pathotypes have developed that can attack the three most common resistance genes found in soybean cultivars for the region.

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Performance of Selected Carrot Cultivars in North Dakota

HortScience ◽

10.21273/hortsci.30.4.883f ◽

1995 ◽

Vol 30 (4) ◽

pp. 883F-883

Author(s):

Damon C. Johnson ◽

Richard G. Greenland ◽

Rudy Radke ◽

Chiwon W. Lee

Keyword(s):

North Dakota ◽

Temperature Fluctuations ◽

Growing Season ◽

Red River ◽

Fresh Market ◽

Red River Valley ◽

The Past ◽

Yield And Quality ◽

Surrounding Areas

The Red River valley and surrounding areas of North Dakota are ideal sites for growing high-quality carrots for fresh-market, processing, and dehydrated products. The results of cultivar trials performed for the past 3 years indicate that from 20 to 50 ton/acre of fresh carrots can be produced with or without irrigation in this region. The average sizes of individual carrots are big (260 to 310 g/root) due to high daytime temperatures and large diurnal temperature fluctuations during the growing season. In 1994, the highest yielding carrot cultivars were `Toudo', `Danvers 126', `Delmar', `Babbette', and `Beta III' when evaluated near Absaraka, N.D. Cultivars with highest sugar contents were `Sweetness', `Apache', `Presto', `Comanche', and `Navajo'. A summary of 2-year data on the yield and quality of carrots grown in North Dakota is presented.

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Multi-Year Evaluation of Commercial Soybean Cultivars for Resistance to Phytophthora sojae

Plant Disease ◽

10.1094/pdis-94-3-0368 ◽

2010 ◽

Vol 94 (3) ◽

pp. 368-371 ◽

Cited By ~ 22

Author(s):

T. L. Slaminko ◽

C. R. Bowen ◽

G. L. Hartman

Keyword(s):

Resistance Genes ◽

Root Rot ◽

Rapid Development ◽

Soybean Seed ◽

Phytophthora Sojae ◽

Primary Methods ◽

Phytophthora Root Rot ◽

Soybean Cultivars ◽

Information Program ◽

Poorly Drained Soils

Phytophthora sojae causes damping-off, root rot, and stem rot of soybean, particularly in poorly drained soils. Soybean cultivar resistance is one of the primary methods to control this disease, with Rps1c, Rps1k, and Rps1a being the most commonly used genes. The Varietal Information Program for Soybeans (VIPS) at the University of Illinois evaluates soybean cultivars for resistance to a number of diseases including Phytophthora root rot (PRR). The objectives of this research were to evaluate PRR resistance among commercial cultivars or advanced lines, and to compare these results with the information on PRR resistance provided by the company that entered the cultivar in VIPS. Each year from 2004 to 2008, between 600 and 900 cultivars were evaluated for resistance to either race 17 or 26 of P. sojae using the hypocotyl inoculation method. P. sojae single resistance genes were reported in 1,808 or 51% of the entries based on company information. Of these, the most commonly reported resistance genes were Rps1c (50%), Rps1k (40%), and Rps1a (10%). To a much smaller degree, companies reported using Rps3a (0.3%), Rps1b (0.2%), and Rps7 (0.2%). For the duration of the 5-year testing period, almost half of the cultivars (46%) were entered in VIPS with no reported resistance genes, and only nine out of a total of 3,533 entries (less than 0.3%) reported a stacked combination of resistance genes. Agreement between company-reported genes and any resistance found in the VIPS PRR evaluation was highest for those cultivars claiming to have Rps1c (90%) and Rps1k (83%), followed by Rps1a (70%). On average, 54% of the cultivars submitted to VIPS each year were new, reflecting the rapid development and turnover of soybean cultivars provided by the soybean seed companies.

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Observations on the use of potato vine killers in the red river valley of North Dakota

American Potato Journal ◽

10.1007/bf02892274 ◽

1947 ◽

Vol 24 (4) ◽

pp. 110-116 ◽

Cited By ~ 18

Author(s):

Wm. G. Hoyman

Keyword(s):

North Dakota ◽

River Valley ◽

Red River ◽

Potato Vine ◽

Red River Valley

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West Nile Virus Epizootiology, Central Red River Valley, North Dakota and Minnesota, 2002–2005

Emerging Infectious Diseases ◽

10.3201/eid1208.060129 ◽

2006 ◽

Vol 12 (8) ◽

pp. 1245-1247 ◽

Cited By ~ 54

Author(s):

Jeffrey A. Bell ◽

Christina M. Brewer ◽

Nathan J. Mickelson ◽

Gabriel W. Garman ◽

Jefferson A. Vaughan

Keyword(s):

West Nile Virus ◽

North Dakota ◽

River Valley ◽

Red River ◽

West Nile ◽

Red River Valley

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Development of a Simple Hydroponic Assay to Study Vertical and Horizontal Resistance of Soybean and Pathotypes of Phytophthora sojae

Plant Disease ◽

10.1094/pdis-04-17-0586-re ◽

2018 ◽

Vol 102 (1) ◽

pp. 114-123 ◽

Cited By ~ 9

Author(s):

A. Lebreton ◽

C. Labbé ◽

M. De Ronne ◽

A. G. Xue ◽

G. Marchand ◽

...

Keyword(s):

Virulence Factors ◽

Root Rot ◽

Dry Weight ◽

Phytophthora Sojae ◽

Horizontal Resistance ◽

Phytophthora Root Rot ◽

Hydroponic System ◽

Long Term Stability ◽

Vertical Resistance

Phytophthora root rot, caused by Phytophthora sojae, is one of the most damaging diseases of soybean and the introgression of Rps (Resistance to P. sojae) genes into elite soybean lines is arguably the best way to manage this disease. Current bioassays to phenotype the gene-for-gene relationship are hampered with respect to reproducibility and long-term stability of isolates, and do not accurately predict horizontal resistance individually. The aim of our study was to investigate a new way of phenotyping P. sojae isolates and vertical and horizontal resistance in soybean that relies on zoospores inoculated directly into a hydroponic system. Inoculation of P. sojae isolates against a set of eight differentials accurately and reproducibly identified pathotypes over a period of two years. When applied to test vertical resistance of soybean lines with known and unknown Rps genes, the bioassay relied on plant dry weight to correctly identify all genes. In addition, simultaneous inoculations of three P. sojae isolates, collectively carrying eight major virulence factors against 64 soybean lines with known and unknown levels of horizontal resistance, separated the plants into five distinct groups of root rot, allowing the discrimination of lines with various degrees of partial resistance. Based on those results, this bioassay offers several advantages in facilitating efforts in breeding soybean for P. sojae resistance and in identifying virulence factors in P. sojae.

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