Validation and genetic characterisation of a seed weight quantitative trait locus, qSW17.1, in progenies of cultivated and wild soybean

Context: Seed weight is an important agronomic trait for determining yield and appearance quality of soybean (Glycine max (L.) Merr.). Understanding the genetic basis of seed weight might lead to improvement of these traits in soybean by optimising different genes or alleles controlling seed weight. Aims: A major quantitative trait locus (QTL) for seed weight, qSW17.1, was identified previously. In this study, we used progenies of cultivated soybean and wild soybean (Glycine soja Sieb. and Zucc.) for further validation and characterisation of qSW17.1. Methods: A BC4F2 population, a heterogeneous inbred family (HIF) population, and a pair of qSW17.1 near-isogenic lines (NILs) developed from progenies of a cross between cultivated soybean variety Jackson and wild soybean accession JWS156-1 were cultivated under field conditions. QTL analysis and candidate gene mining were conducted. Key results: A QTL corresponding to qSW17.1, which explained 19.84% and 31.71% of the total phenotypic variance in BC4F2 and HIF populations, respectively, was detected. The NIL with the cultivated soybean allele showed higher shoot biomass than the NIL with the wild soybean allele under hydroponic growth conditions, suggesting that the large-seed-size allele of qSW17.1 might be beneficial in soybean seedling establishment. qSW17.1 was delimited to a physical interval of 2515 kb on chromosome 17. Glyma.17G108500 showed a large (similar to 3.27-fold) difference in expression between the two NILs, and was considered a candidate gene underlying qSW17.1.