IDENTIFICATION OF MOLECULAR MARKERS LINKED TO QUANTITATIVE TRAIT LOCIFOR SOYBEAN RESISTANCE TO CORN-EARWORM

One hundred and thirty nine restriction fragment length polymorphisms (RFLPs) were used to construct a soybean (Glycine max L. Merr.) geneti c linkage map and to identify quantitative trait loci (QTLs) associate d with resistance to corn earworm (Helicoverpa tea Boddie) in a popula tion of 103 F-2-derived lines from a cross of 'Cobb' (susceptible) and PI229358 (resistant). The genetic linkage map consisted of 128 marker s which converged onto 30 linkage groups covering approximately 1325 c M. There were 11 unlinked markers. The F-2-derived lines and the two p arents were grown in the field under a plastic mesh cage near Athens, Ga., in 1995. The plants were artificially infested with corn earworm and evaluated for the amount of defoliation. Using interval-mapping an alysis for linked markers and single-factor analysis of variance (ANOV A), markers were tested for an association with resistance. One major and two minor QTLs for resistance were identified in this population. The PI229358 allele contributed insect resistance at all three QTLs. T he major QTL is linked to the RFLP marker A584 on linkage group (LG) ' M' of the USDA/Iowa State University public soybean genetic map. It ac counts for 37% of the total variation for resistance in this cross. Th e minor QTLs are linked to the RFLP markers R249 (LG 'H') and Bng047 ( LG 'D1'). These markers explain 16% and 10% of variation, respectively . The heritability (h(2)) for resistance was estimated as 64% in this population.