Identification and validation of QTLs for 100-seed weight using chromosome segment substitution lines in soybean

The 100-seed weight (100SW) is one of the most important traits that control soybean yield. To identify the quantitative trait loci (QTL) of 100SW, 120 BC₃F₅ chromosome segment substitution lines (CSSLs) were cultivated over three years. The CSSLs were developed from a cross between the cultivated soybean variety 'Jackson' and the wild soybean accession 'JWS156-1', followed by continuous backcrossing using 'Jackson' variety as a recurrent parent. A total of nine QTLs (qSW8.1, qSW9.1, qSW12.1, qSW13.1, qSW14.1, qSW16.1, qSW17.1, qSW17.2, and qSW20.1) were detected on eight chromosomes. Of these, qSW12.1 (LOD = 6.78-12.31) was detected over the three successive years on chromosome 12 as a novel, stable, and major QTL. To validate the effect of qSW12.1, a residual heterozygous line (RHL), RHL564, which showed heterozygous at the qSW12.1 region, was selected from the BC₃F₅ population. Of the two homologous genotypes in the progenies produced by self-pollination of RHL564, a higher seed weight was observed in the 'Jackson' genotype plants than that in the 'JWS156-1' genotype plants. qSW12.1 was delimited in an interval of approximately 1,348 kb between the BARCSOYSSR_12_1282 and BARCSOYSSR_12_1347 markers on chromosome 12.