Genetic dissection and validation of a stable QTL for grain roundness on chromosome 5A in bread wheat (Triticum aestivum L.)

• A stable QTL for grain roundness, QGr.cib-5A , was consistently detected across all environments. • The effect of QGr.cib-5A on grain roundness was stable in various genetic backgrounds. • Rounder grain shape has been relatively widely selected during wheat breeding. Wheat grain morphology is an important breeding target considering its impact on yield and end-use properties. However, the genetic basis of grain roundness, a major determinant of grain morphology, remains largely unexplored. In this study, an F 2 and a recombinant inbred line (RIL) populations from Zhongkemai 138 (ZKM138)×Chinese Spring (CS) cross were employed to analyze the genetic basis of grain shape variation. Kompetitive Allele Specific PCR (KASP) markers were developed according to single nucleotide polymorphism (SNP) from bulked segregant exome sequencing (BSE-Seq) of F 2 and Wheat 55K SNP array data online, and then were used to construct two genetic maps of F 2 and RIL populations, spanning 148.89 cM (30 KASP markers) and 129.82 cM (25 KASP markers), respectively. By the traditional QTL mapping method based on these two maps, a stable quantitative trait locus (QTL) for grain roundness (GR), QGr . cib-5A , could be repeatedly highlighted in the interval of 444.8-455.5 Mb on chromosome 5A. Further conditional QTL mapping analysis revealed that grain width was the major contributor to GR at this locus. Besides, the utilization of two tightly linked markers 5A4-15 and 55k-31 showed a 96.27% transmissibility of ZKM138-derived alleles in 134 ZKM138 derivatives alongside a 7.38% increase in GR, and a 65.19% distribution of worldwide varieties. Finally, TraesCS5A02G236400 , possibly encoding a hydroxyproline-rich glycoprotein family protein, was deduced to be the candidate gene. Collectively, these results provided the possibility of facilitating wheat grain shape improvement and enhancing wheat market value.