Gene-Based Allele Specific Marker for Resistance to Phytophthora sojae in Soybean (Glycine max L.)

Phytophthora sojae is a soil-borne oomycete that causes both pre- and post-emergence damping-off disease in soybean that are present in poorly drained soils. Phytophthora root and stem rot of soybean has become an emerging threat to soybean production in South Korea as soybean cultivation in paddy fields has increased recently. The cultivar Daewon was identified as a genetic source for resistance to P. sojae isolate 2457; moreover, a 573 kb resistance locus was previously mapped on chromosome 3 via linkage analysis using Daepung × Daewon recombinant inbred line (RIL) population. This study aimed to develop a gene-based molecular marker associated with P. sojae resistance using single nucleotide polymorphisms (SNPs) at this locus. Three sets of single nucleotide amplified polymorphism (SNAP) markers were initially designed based on genic SNPs in the identified genomic region. Of these, the marker SNAP-Set2 successfully worked for allele-specific amplification for the respective Daepung and Daewon, as well as 20 RILs derived from crosses of the two cultivars. To validate this marker, 11 soybean germplasms were randomly selected and genotyped, which resulted in reliable allele-specific amplification that agreed with the 180 K Axiom® SoyaSNP array data. Phenotypic evaluation of the 20 RILs and the 11 germplasms subsequently demonstrated that Daepung-type and Daewon-type for the SNAP-Set2 are both associated with susceptibility and resistance to P. sojae isolate 2457. The availability of a molecular marker linked to this resistance locus would expedite the use of this valuable resistance allele in soybean breeding programs for increased resistance to P. sojae.