Molecular characterization of vernalization response genes in Canadian spring wheat

Vernalization response (Vrn) genes play a major role in determining the flowering/maturity times of spring-sown wheat. We characterized a representative set of 40 western Canadian adapted spring wheat cultivars/lines for 3 Vrn loci. The 40 genotypes were screened, along with 4 genotypes of known Vrn genes, using previously published genome-specific polymerase chain reaction primers designed for detecting the presence or absence of dominant or recessive alleles of the major Vrn loci: Vrn-A1, Vrn-B1, and Vrn-D1. The dominant promoter duplication allele Vrn-A1a was present in 34 of 40 cultivars/lines, whereas the promoter deletion allele Vrn-A1b was present in only 1 of the western Canadian cultivars (Triticum aestivum L. 'Rescue') and 2 of its derivative chromosomal substitution lines. The intron deletion allele Vrn-A1c was not present in any line tested. Only 4 of the western Canadian spring wheat cultivars tested here carry the recessive vrn-A1 allele. The dominant allele of Vrn-B1 was detected in 20 cultivars/lines. Fourteen cultivars/lines had dominant alleles of Vrn-A1a and Vrn-B1 in combination. All cultivars/lines carried the recessive allele for Vrn-D1. The predominance of the dominant allele Vrn-A1a in Canadian spring wheat appears to be due to the allele's vernalization insensitivity, which confers earliness under nonvernalizing growing conditions. Wheat breeders in western Canada have incorporated the Vrn-A1a allele into spring wheats mainly by selecting for early genotypes for a short growing season, thereby avoiding early and late season frosts. For the development of early maturing cultivars with high yield potential, different combinations of Vrn alleles may be incorporated into spring wheat breeding programs in western Canada.