QTL mapping of antibiosis resistance to common cutworm (Spodoptera litura Fabricius) in soybean

The common cutworm (CCW; Spodoptera litura Fabricius; Lepidoptera: Noctuidae) is a major pest of soybean [Glycine max (L.) Merr.] in Japan. Previously, we analyzed a soybean cultivar named Himeshirazu and found that it exhibits a heritable antibiosis resistance to CCW. In this study, we performed quantitative trait locus (QTL) analysis using composite interval mapping (CIM) method to locate the source of the antibiosis resistance of Himeshirazu. We used a previously reported F-2 segregating population of susceptible 'Fukuyutaka' X resistant Himeshirazu. We constructed a linkage map spanning 2270.4 cM with 146 simple sequence repeat (SSR) markers and a phenotype marker (pubescence color). Two QTLs for antibiosis resistance were detected in linkage group (LG) M. One was located between SSR markers Satt220 and Satt175, with a maximum logarithm of odds (LOD) score of 12.7 and r(2) = 0.283. The other was located between Satt567 and Satt463, with a maximum LOD score of 6.8 and r(2) = 0.159. The resistant allele of both QTLs was derived from Himeshirazu. One-way ANOVA of the F-2 family classified by genotypes of SSR loci linked to each QTL suggested that a significant antibiosis effect was exhibited when both QTLs were homozygous for the resistant allele.