Epistatic interaction between vernalization genes Vrn-Am1 and Vrn-Am2 in diploid wheat.

Genes Vrn-A(m)1 and Vrn-A(m)2 control the vernalization requirement in diploid wheat (Triticum monococcum). The epistatic interaction between these two genes on flowering date was studied here using a factorial analysis of variance. One hundred and two F2 plants were classified according to their genotypes for molecular markers tightly linked to Vrn-A(m)1 and Vrn-A(m)2. Mean comparisons showed that the VrnA(m)2 allele for winter growth habit was dominant to the vrn-A(m)2 allele for spring growth habit and that the Vrn-A(m)1 allele for spring growth habit was dominant to the vrn-A(m)1 allele for winter growth habit. A significant interaction was found between these two genes, suggesting that they work in the same developmental pathway. Plants homozygous for the recessive vrn-A(m)2 allele for spring growth habit flowered earlier than plants from the Vrn-A(m)2 class independently of the alleles present at Vrn-A(m)1. However, differences in heading date between plants with the Vrn-A(m)1 allele and those with the vrn-A(m)1 allele were significant only when the dominant Vrn-A(m)2 allele was present. A genetic model for the action of these two vernalization genes is proposed in which the role of Vrn-A(m)1 is to counteract the Vrn-A(m)2-mediated delay of flowering.