Identification, mapping, and confirmation of a soybean gene for bud blight resistance

Bud blight, caused by Tobacco ringspot virus (TRSV; Genus: Nepovirus; Family: Comoviridae), can significantly reduce the seed yield and seed quality of soybean [Glycine mar (L.) Merr.]. The identification of resistance genes and the development of resistant cultivars constitute an effective strategy for preventing yield loss. The objectives of this study were to identify and map quantitative trait loci (QTLs) conditioning resistance to bud blight and validate their genomic location with two populations derived from the cross of 'Young' (resistant) X PI 416937 (susceptible). One population consisted of 116 F-4:7 lines and was used to map restriction fragment length polymorphism (RFLP) markers associated with resistance to bud blight. The lines were grown in one-row plots in a randomized complete block design with two replications. The plots were naturally infected with TRSV. At maturity, soybean plots were visually scored according to the number of plants that exhibited terminal bud death. A major QTL was identified and mapped on linkage group (LG) F by the RFLP marker K644_1. It accounted for 82% of the variation in bud blight score. To verify the genomic location of the major bud blight QTL, a second population of Young X PI 416937 that consisted of 180 F-2:3 lines was evaluated. In this population, simple sequence repeat (SSR) markers on LG F near the putative genomic location of the bud blight QTL were utilized. The major QTL conditioning bud blight resistance was confirmed and found to be closely linked to the Satt510 marker.