Genetic dissection and validation of a major QTL for grain weight on chromosome 3B in bread wheat (Triticum aestivum L.)

Grain weight is one of the key components of wheat (Triticum aestivum L.) yield. Genetic manipulation of grain weight is an efficient approach for improving yield potential in breeding programs. A recombinant inbred line (RIL) population derived from a cross between W7268 and Chuanyu 12 (CY12) was employed to detect quantitative trait loci (QTLs) for thousand-grain weight (TGW), grain length (GL), grain width (GW), and the ratio of grain length to width (GLW) in six environments. Seven major QTLs, QGl.cib-2D, QGw.cib-2D, QGw.cib-3B, QGw.cib-4B.1, QGlw.cib-2D.1, QTgw.cib-2D.1 and QTgw.cib-3B.1, were consistently identified in at least four environments and the best linear unbiased estimation (BLUE) datasets, and they explained 2.61 to 34.85% of the phenotypic variance. Significant interactions were detected between the two major TGW QTLs and three major GW loci. In addition, QTgw.cib-3B.1 and QGw.cib-3B were co-located, and the improved TGW at this locus was contributed by GW. Unlike other loci, QTgw.cib-3B.1/QGw.cib-3B had no effect on grain number per spike (GNS). They were further validated in advanced lines using Kompetitive Allele Specific PCR (KASP) markers, and a comparison analysis indicated that QTgw.cib-3B.1/QGw.cib-3B is likely a novel locus. Six haplotypes were identified in the region of this QTL and their distribution frequencies varied between the landraces and cultivars. According to gene annotation, spatial expression patterns, ortholog analysis and sequence variation, the candidate gene of QTgw.cib-3B.1/QGw.cib-3B was predicted. Collectively, the major QTLs and KASP markers reported here provide valuable information for elucidating the genetic architecture of grain weight and for molecular marker-assisted breeding in grain yield improvement.