Allelic Variation Analysis at the Vernalization Response and Photoperiod Genes in Russian Wheat Varieties Identified Two Novel Alleles of Vrn-B3

Heading time is an important agronomic trait affecting the adaptability and productivity of common wheat. In this study, 95 common wheat varieties from Russia and the late-maturing breeding line ‘Velut’ were tested for allelic diversity of genes having the strongest effect on heading. In this research, allelic variation at the Ppd-D1, Vrn-A1, Vrn-B1, Vrn-D1, and Vrn-B3 loci was tested. The Vrn-B1 and Vrn-B3 loci provided the largest contribution to genetic diversity. We found two novel allelic variants of the Vrn-B3 gene in the studied varieties. Ten varieties carried a 160 bp insertion in the promoter region, and the breeding line ‘Velut’ carried a 1617 bp insertion. These alleles were designated Vrn-B3e and Vrn-B3d, respectively. The analysis of the sequences showed the recent insertion of a retrotransposon homologous to the LTR retrotransposon (RLX_Hvul_Dacia_ RND-1) in the Vrn-B3d allele. Plants with the Vrn-B3e and the ‘Velut’ line with the Vrn-B3d allele headed later than the plants with the wild-type allele; among these plants, ‘Velut’ is the latest maturing wheat variety. Analysis of the gene expression of two groups of lines differing by the Vrn-B3 alleles (Vrn-B3d or vrn-B3) from the F₂ population with ‘Velut’ as a parental line did not reveal a significant difference in the expression level between the groups. Additional research is required to study the reasons for the late maturation of the ‘Velut’ line. However, the studied wheat varieties could be used as a potential source of natural variation in genes controlling heading times.