Genetic and Molecular Characterization of Vernalization Genes Vrn-A1, Vrn-B1, and Vrn-D1 in Spring Wheat Germplasm from the Pacific Northwest Region of the USA

The objective of this study was to determine the Vrn-1 allelic composition of spring wheat germplasm from the Pacific Northwest region of the USA. Individual plants from 56 spring wheat lines were crossed to near-isogenic tester lines carrying the dominant allele Vrn-A1, Vrn-B1 or Vrn-D1. F-2 progeny were evaluated for growth habit in the field and Vrn-1 allelic composition was determined through chi-square analysis. Lines also were analysed with DNA sequence-based Vrn-1 allele-specific markers. A majority of the germplasm carried the dominant allele Vrn-A1a alone or in combination with Vrn-B1, Vrn-D1 or Vrn-B3 alleles. Vrn-B1 and Vrn-D1 were almost always associated with other dominant Vrn-1 allele(s). Based on DNA sequence analysis, a novel Vrn-B1 allele referred to as Vrn-B1b, which carried a single nucleotide polymorphism (SNP) and a 36 bp deletion, was identified in cultivar 'Alpowa'. These results will be useful to wheat breeders for choosing parents with different Vrn-1 alleles for crossing to maximize diversity at the Vrn-1 loci with an expectation of identifying superior Vrn-1 allelic combinations for cultivar improvement.