Genetic mapping of the Rcs2 locus in soybean cultivar Kent for resistance to frogeye leaf spot

Abstract

The fungal disease frogeye leaf spot (FLS) can reduce yield up to 30% in susceptible soybean [Glycine max (L) Merr] cultivars. The Rcs2 locus in the cultivar Kent provides resistance to all the named Cercospora sojina races currently found in the United States; however, this locus for resistance to FLS has not been molecularly mapped yet. F2:3 and recombinant inbred line (RIL) populations derived from a cross of Forrest × Kent were phenotyped in greenhouse assays with isolate S23 of C. sojina, and reactions were determined using a visual estimate of disease severity. A bulked segregant analysis and linkage mapping with Kompetitive allele‐specific PCR (KASP) markers in the F2:3 population located the Rcs2 locus on chromosome 11. The locus was mapped in the RIL population derived from the same pedigree and refined to a 336 kb interval by evaluating recombination break points in the RILs. This region contains 31 gene models, and Kent has polymorphisms in 11 of these genes and/or promoter regions of the Williams82.a2.v1 genome. The Rcs2 locus and linked markers reported will be useful in marker‐assisted selection for FLS resistance. This research will also guide future efforts to understand the landscape of FLS resistance in United States soybean germplasm and to discover the causal genes for Rcs2 resistance.