Abstract
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.