Soybean quantitative trait loci for resistance to insects

Resistance to insects was found in a recombinant inbred (RI) population of soybean derived from nonresistant parents, 'Minsoy' and 'Noir 1' (MN) (240 RI). The objectives of this study were to determine quantitative trait loci (QTLs) associated with this resistance by linkage to either restriction fragment length polymorphism (RFLP) or simple sequence repeat (SSR) markers and to confirm these loci in a new population derived from Minsoy crossed with the elite cultivar Archer (MA) (233 RI). Corn earworm (Helicoverpa zea Boddie) larvae were reared on individual lines of the MN and MA RI and several larval traits were measured. Of the 20 linkage groups (LG) of the composite genetic soybean map, QTLs were found on five LGs in the MN and four in the MA population. The QTL on LG U2 is associated with major effects on larval development in both the MN (r² > 0.12) and the MA population (r² > 0.28). All other QTLs had lesser effects (r² < 0.10). The U2 QTL associated with resistance to insects is of major importance in that: (i) it has been identified in different genetic backgrounds; (ii) it is associated with several larval growth parameters; and (iii) it explains a large proportion of the phenotypic variation. All other QTLs were observed to segregate in only one population. Most of the resistance alleles were associated with the Minsoy parent. Consistent with this observation, Archer and Noir 1 were better corn earworm larval host plants than Minsoy.