Resistance and partial resistance to Phytophthora sojae in early maturity group soybean plant introductions

Abstract

Phytophthora sojae, an important yield limiting pathogen of soybean, causes seed, seedling, root, and stem rots. Losses caused by P. sojae can be controlled by both major gene and partial resistance. Early maturity group (MG) soybeans are an increasingly important crop in northwestern Minnesota and eastern North Dakota. Early MG plant introductions (PIs) from the USDA Soybean Germplasm Collection and early MG public and private cultivars were evaluated for resistance and partial resistance to P. sojae. Of the 113 PIs, PI438445, and PI438454 exhibited resistance to P. sojae races 4, 7, 17, and 28 indicating they may possess either Rps1c, Rps1k, previously unidentified or multiple resistance gene to Phytophthora sojae (Rps) genes. Because they exhibited partial resistance equal to or greater than the standard check cultivar Conrad, three early MG soybean cultivars (MN0902, MN0302, and 91B53) were selected as standard checks to evaluate early MG PIs for partial resistance. Sixty-nine PIs were evaluated for partial resistance to P. sojae races 7 and 25 using the inoculum layer method. Of this group of PIs, 22 had the same level of partial resistance as Conrad to P. sojae race 7 while 19 had the same degree of partial resistance to race 25. Twelve PIs had same level of partial resistance as Conrad to both P. sojae races 7 and 25. The PIs and cultivars identified in this study will be of great value in developing early MG soybean cultivars suitable for planting in Canada and the northern United States.

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

“…However, partial resistance to P. sojae is reportedly expressed in the roots of cultivars with high levels of resistance (i.e., limited root rot and the absence of stem rot) ( Dorrance et al, 2007 ; Mideros et al, 2007 ; Schmitthenner, 1985 ; Tooley and Grau, 1984 ). The partial resistance expression site in the current study might be inconsistent with that of several other studies that assessed root damage ( Abeysekara et al, 2016 ; Burnham et al, 2003 ; Jia and Kurle, 2008 ; Lee et al, 2013a , 2013b ; McBlain et al, 1991 ; Schneider et al, 2016 ; Stewart and Robertson, 2012 ; Tucker et al, 2010 ; Wu et al, 2011 ). This discrepancy was likely because our evaluation was based on the damping-off elicited by the severe infection around the lower hypocotyl and not root damage.…”

“…Unlike Rps -mediated resistance, this incomplete resistance leads to different levels of susceptibility/resistance among cultivars and can be evaluated based on decreased infection or colonization efficiency, the development of smaller lesions, and the production of fewer oospores in infected plant tissue ( Dorrance, 2018 ; Mideros et al, 2007 ). In the US, soybean germplasm exhibiting various levels of partial resistance has been identified by screening the plant introduction series of the soybean germplasm collection belonging to the US Department of Agriculture ( Dorrance and Schmitthenner, 2000 ; Jia and Kurle, 2008 ; Schneider et al, 2016 ). Several quantitative trait loci have been detected ( Abeysekara et al, 2016 ; Burnham et al, 2003 ; Lee et al, 2013a , 2013b ; Schneider et al, 2016 ; Tucker et al, 2010 ; Wu et al, 2011 ).…”

Identification of quantitative trait loci for partial resistance to Phytophthora sojae in soybean

“…ÔWilliamsÕ) with known partial resistance characteristics were included as controls for comparison. ÔConradÕ was considered to have a high level of partial resistance to P. sojae, whereas ÔWilliamsÕ was a moderately susceptible cultivar (low level of partial resistance) (Burnham et al 2003, Jia andJames 2007). The level of partial resistance of ÔConradÕ, ÔWilliamsÕ, Su88-M21 (high level of partial resistance), Xinyixiaoheidou (low level of partial resistance) and RIL lines was determined according to the average lesion lengths measured from the slant board assays as described below, respectively.…”

A survey of soybean germplasm for resistance to Phytophthora sojae

“…Jia and Kurle (2007) reported that 3-, 5-, 7-, and 10-day-old P. sojae grown on V8 juice agar medium were used to inoculate soybean lines at the same growth stage, and no significant difference was found in plant reaction when equal amounts of the inoculum slurry were used. In this study, we used mycelium of 7-day-old cultures grown on LBA instead of oospores to inoculate hypocotyls and roots of seedlings.…”