Quantitative trait loci analysis of stem strength and related traits in soybean

Stem strength is one of the major influencing factors of lodging in soybean Glycine max (L.) Merr.] as well as other crops. To identify quantitative trait loci (QTL) associated with stem strength and related traits in soybean, a recombinant inbred line (RIL) population consisting of 165 lines derived from Zhongdou No. 29 × Zhongdou No. 32 was used in 3 years. Significant positive correlations were found among the four traits (stem strength, stem diameter, number of nodes, root dry weight). A linkage map spanning 1,240.7 cM was constructed using 245 SSR (simple sequence repeat) markers and a phenotypic marker (leaflet shape). By composite interval mapping and two-round strategy of QTL meta-analysis, 32 consensus QTL and 19 unique QTL were identified, respectively. Of eight pleiotropic unique QTL, two QTL (uq.A2-2 and uq.A2-3) located at the intervals of 23.2–26.8 and 38.5–42.4 cM on linkage group A2, respectively, were associated with all the four traits. Additive × environment (ae) interaction effects, epistasis (aa) and epistasis × environment (aae) interaction effects of QTL were detected as well. The results provide useful information for further genetic studies on stem strength of soybean.