Validating a novel allele of viviparous-1 (Vp-1Bf) associated with high seed dormancy of Chinese wheat landrace, Wanxianbaimaizi

Pre-harvest sprouting (PHS) can easily lead to yield losses of wheat and downgrading of grain quality in wheat-growing areas where long periods of wet weather occur frequently during harvest. As a main component of PHS, seed dormancy is often evaluated by germination index (GI). Previous researches have proved allelic variations of Vp-1B to have a close relationship with dormancy of white-grained wheat. In the present study, a mapping population covering 157 recombinant inbred lines was developed from a cross of two white-grained varieties, Wanxianbaimaizi and Jing411. Wanxianbaimaizi is a strongly dormant landrace carrying a novel allele, Vp-1Bf; whereas, Jing411 is a non-dormant variety with wild allele, Vp-1Ba. Our objective was to validate the association between the novel allele and seed dormancy using the population. The results of sequences alignment indicated an insertion of 193 bp and a deletion of 109 bp were both identified in the novel allele, respectively, compared with wild allele in Jing411. Here, the deletion was first detected. As for lines possessing Vp-1Ba, the average GI value was 0.584, significantly higher than that of lines holding Vp-1Bf. Among three genotypes, Vp-1Bf allele was generally corresponded to the lowest average of GI value (0.195), and the highest dormancy; in addition, lines with heterozygous genotype often showed intermediate GI value (0.356). Of 92 RILs with Vp-1Ba, over 70 lines showed higher GI value (> 0.40), and only about 7 lines had lower GI value (< 0.20). On the other hand, among 60 RILs with Vp-1Bf, over 50 lines showed lower GI value (< 0.40), and only about 7 lines had higher GI value (> 0.60). The result of composite interval mapping revealed that a major QTL for seed dormancy was flanked by Xwmc446 and Vp1 on 3BL, which was proximal to Vp1 (7.6-8.4 cM). The locus could explain 24.6-40.7% of total phenotypic variation across three crop seasons. The above results could confirm that the novel allele had a striking association with high seed dormancy, and may be useful for improving PHS tolerance of white-grained wheat.