Confirmation of Additional Quantitative Trait Loci That Underlie Resistance to Soybean Sudden Death Syndrome Using NILs and SNPs.

Soybean (Glycine max (L.) Merr.) cultivars vary in their partial resistance or susceptibility to sudden death syndrome (SDS), caused by Fusarium virguliforme (Aoki). Breeding for improved response has been challenging. There are 42 resistance loci reported. Two quantitative trait loci (QTL) for resistance to SDS (cqRfs4 and cqRfs5) were reported to be clustered within 20 cM of one another on linkage group C2 (Chr. 6). The aims here were to compare the inheritance of those loci for resistance to SDS in a near isogenic line (NIL) population. That NIL population was fixed for resistance to SCN but segregated at two additional loci (cqRfs1 and cqRfs). Used were; a NIL population derived from residual heterozygosity in an F₅:₉ recombinant inbred line EF77 (lines 1-40); SDS response data (2) from each of two locations in different years; four segregating microsatellite and 1,500 polymorphic SNP markers. Polymorphic regions were found from 18,033 Kbp to 18,447 Kbp and 45,768 Kbp to 48,582 Kbp on chromosome (Chr. 6), and 35,776 Kbp to 38,239 Kbp on Chr. 19 that were significantly (P<0.001) associated with resistance to SDS. Rfs4, qRfs8, and qRfs12 were previously reported in these regions, one novel QTL was identified. Rfs5 was not segregating. This study indicates that using the SoySNP6k chip, QTL that underlie SDS resistance could be mapped with much greater accuracy.