Earliness per se quantitative trait loci and their interaction with Vrn-B1 locus in a spring wheat population

In the spring wheat-growing regions of western Canada, early maturity is an important trait for timely harvest to avoid frost damage, and associated harvest and post-harvest problems. Earliness is genetically regulated by vernalization, photoperiod, earliness per se genes, and complex gene interactions. In this study, we explored the effect of these gene complexes on the expression of 11 agronomic traits in the CDC Teal x CDC Go Canadian western red spring wheat-mapping population. The population of 187 recombinant inbred lines was genotyped with 341 DArT polymorphic markers and a functional Vrn-B1 marker, and phenotyped over 3 years in replicated trials. The dominant allele of Vrn-B1 reduced the number of days to heading, flowering and maturity, and increased leaf color concentration and plant height, but did not affect grain yield in the presence of common genetic backgrounds with dominant Vrn-A1a and Ppd-D1 alleles at two epistatic loci, Vrn-A1 and Ppd-D1. A total of 21 QTLs were identified for all phenotypic traits recorded, except plant height and grain protein content. Two earliness per se QTLs were mapped on chromosomes 1A (QEps.dms-1A) and 4A (QEps.dms-4A) in all three growing seasons, contributing 15-27 and 8-10 %, respectively, to the total genetic variation in days to maturity. The two earliness QTLs and Vrn-B1 exhibited additive interaction. Lines carrying dominant alleles at these three loci headed, flowered and matured 1.7, 1.9 and 4 days earlier, respectively, but yielded 0.43 t ha(-1) less than lines with recessive alleles.