A haplotype block associated with thousand-kernel weight on chromosome 5DS in common wheat (Triticum aestivum L.)

Spike number per unit area, number of grains per spike, and thousand-kernel weight(TKW) are important yield components for wheat(Triticum aestivum L.). TKW has the highest heritability among the three components. We validated 27 simple sequence repeat(SSR) loci associated with TKW in an F2:5breeding population grown in four environments. A cfd78265 bpmarker on chromosome 5DS showed the strongest association with TKW and had a significantly positive effect on TKW compared to allele cfd78259 bp, with mean increases of 5.17, 3.63, 4.11, and 5.16 g in the four environments. Markers cfd67 and cfd40 flanking cfd78 also showed significantly positive associations with TKW with increases of 5.11, 3.29, 4.31, and 4.50 g for cfd67205, and4.98, 3.49, 4.06, and 4.84 g for cfd40187 compared with cfd67203 and cfd40190in the four environments, respectively. A major quantitative trait locus for TKW spanning 2.94 c M on chromosome 5DS was detected by association mapping.Strong linkage disequilibrium(LD)(r2 0.2) was detected Resear among the three linked markers, which formed three haplotype blocks in the F2:5breeding population. Mean TKW differences between Hap B-I and Hap B-II were 5.80, 4.41, 4.02,and 5.06 g in the four environments, respectively. Moreover,significant LD was detected only between cfd78 and cfd67 and between cfd67 and cfd40 in a germplasm collection. This study provides a base for cloning genes related to TKW on chromosome 5DS.