Novel chromosome segment substitution lines derived from <i>japonica</i> cultivar ‘Yukihikari’ in the genetic background of ‘Joiku462’ cultivar and identification of quantitative trait loci for heading date and grain quality

In this study, we mapped quantitative trait loci (QTLs) associated with heading date and grain quality traits in a novel set of 44 chromosome segment substitution lines (CSSLs) derived from closely related rice (<i>Oryza sativa</i> L. ssp. <i>japonica</i>) cultivars 'Yukihikari' (good grain quality) and 'Joiku462' (superior eating and high grain appearance qualities). Days to heading (DTH), apparent amylose content (AAC), protein content (PC), thousand brown-grain weight (TBGW), brown grain length (BGL), brown grain width (BGWI), brown grain thickness (BGT), and the contents of 12 mineral elements (S, P, Mg, Ca, K, Mo, Cu, Zn, Mn, Fe, Sr, and Si) in polished rice were evaluated in 44 CSSLs grown in two different environments. We identified 78 QTLs, including 8, 7, 8, 8, 19, 10, and 10 for DTH, AAC, PC, TBGW, BGL, BGWI, and BGT, respectively, and 2, 1, 3, and 2 for S, Mo, Cu, and Zn contents, respectively. Several QTLs were observed in the same region, forming 17 clusters on chromosomes 1-10. These QTLs can facilitate gene isolation and breeding to develop rice cultivars with optimum heading time and improved grain quality.