Phytophthora root and stem rot of soybean.

Genome-wide association mapping of partial resistance to Phytophthora sojae in soybean plant introductions from the Republic of Korea

“…Phytophthora root and stem rot was the second most yield-limiting disease of soybean [ Glycine max (L.) Merr] between 1996 and 2009 [ 1 , 2 ]. This disease, caused by the soil-borne oomycete pathogen Phytophthora sojae [ 3 ], is prevalent when soil conditions become saturated [ 4 ], allowing the asexual, motile zoospores to chemotactically travel to soybean roots [ 5 , 6 ]. Upon infection, P. sojae will produce haustoria and acquire nutrients in a hemi-biotrophic manner [ 7 ].…”

“…Upon infection, P. sojae will produce haustoria and acquire nutrients in a hemi-biotrophic manner [ 7 ]. Susceptible plants will develop lesions, experience wilting and chlorosis, and, in severe cases, plant death [ 4 ].…”

Variation in the Resistance of Japanese Soybean Cultivars to Phytophthora Root and Stem Rot during the Early Plant Growth Stages and the Effects of a Fungicide Seed Treatment

“…Phytophthora sojae , which is a homothallic oomycete classified in the kingdom Stramenopiles ( Dorrance, 2018 ; Förster et al, 1990 ; Harper et al, 2005 ; Tyler, 2007 ), grows saprophytically and readily produces sexual oospores in soil and infected plant tissue. The oospores can survive in soil and diseased plant debris for extended periods ( Dorrance et al, 2007 ; Tyler, 2007 ), suggesting that soybean plants grown in fields previously infected with Phytophthora root and stem rot are continuously at risk of developing the disease. The mycelia grown in soil and infected plant tissue produce asexual spores called sporangia, in which motile zoospores are generated.…”

“…Host resistance to P. sojae , which is one of the most economical and environmentally friendly disease control measures, has been well-studied, especially for major resistance (R) gene-mediated resistance involving the race-specific interactions between soybean and P. sojae ( Dorrance, 2018 ; Dorrance et al, 2007 ; Grau et al, 2004 ; Sugimoto et al, 2012 ). Previous studies identified 20 or more R genes or alleles ( Rps : resistance to P. sojae ), some of which have been commercially deployed to manage the disease in soybean fields ( Dorrance, 2018 ; Jiang et al, 2017 ).…”

“…Partial resistance against Phytophthora root and stem rot is not expressed in the soybean seed, but is effective during the growth stage in which the first trifoliate leaf is formed as well as in the subsequent stages ( Schmitthenner and Dorrance, 2015 ). The resulting primary symptom is decreased root colonization ( Dorrance et al, 2007 ). Additionally, ‘Hark’ plants (i.e., susceptible cultivar) inoculated at 16 days after seeding are more resistant to Phytophthora root and stem rot than younger plants ( Jimenez and Lockwood, 1980 ).…”