Effects of five allelic variants of the wheat vernalization gene VRN-B1 on heading date and vernalization requirements.

Winter wheat must undergo vernalization to flower, while spring wheat does not require vernalization. The requirement for vernalization in wheat is primarily controlled by vernalization genes. VRN-1 are the most important vernalization genes. The recessive vrn-1 alleles have a strict vernalization requirement, while dominant mutations in Vrn-1 eliminate or reduce this requirement. In this study, the near-isogenic lines for several VRN-B1 allelic variants (Vrn-B1a, Vrn-B1b, Vrn-B1c, Vrn-B1 d and vrn-B1) were generated in two winter wheat backgrounds. Under field conditions, the four dominant Vrn-B1 allelic variants (Vrn-B1a, Vrn-B1b, Vrn-B1c, and Vrn-B1 d) resulted in an advancement in the heading date by 3-5 days. Using an artificially controlled gradient vernalization treatment (4-5 ℃, ranging from 0 to 45 days with 5-day intervals), the vernalization requirements of VRN-B1 allelic variants were analyzed. The relative effects on vernalization requirements were found to be vrn-B1 > Vrn-B1a = Vrn-B1 d > Vrn-B1b = Vrn-B1c (opposite to the heading date). Gene expression analysis indicates that the earlier heading associated with the dominant Vrn-B1 allelic variants is linked to their open expression under non-vernalization conditions. There may be an expression threshold at the VRN-B1 locus that eliminates the vernalization requirement, and this threshold should be lower than the vrn-B1 levels observed under saturated vernalization conditions. Furthermore, once this hypothesized threshold is reached, there appears to be no dosage effect on VRN-B1 expression. These results deepen our understanding of wheat vernalization genes and provide a theoretical basis for utilizing these genes in breeding programs aimed at improving wheat adaptability.

Supplementary information: The online version contains supplementary material available at 10.1007/s11032-025-01565-1.