Phasic development of wheat is largely determined by the interaction of the VRN1 and PPD1 genes with vernalising temperature and photoperiod. VRN1 and PPD1 are regulatory genes, known to influence freezing tolerance, plant morphology and grain yield as well as phasic development. Forty-seven doubled-haploid lines were characterised for Ppd-B1, Ppd-D1, Vrn-A1, Vrn-B1 and Vrn-D1 to determine the effect of allelic combinations of these genes on timing of anthesis and crop growth rate. The lines were grown in replicated field experiments at two locations in Australia. The VRN1 and PPD1 genes accounted for 75% of the genetic variation for time from sowing to anthesis. Vrn-A1 and Vrn-B1 similarly affected time to anthesis, but only Vrn-B1 affected crop growth rate, with the spring Vrn-B1a allele resulting in faster crop growth rates than the winter Vrn-B1v allele. This suggests that the effect of Vrn-B1 on crop growth rate is not a direct consequence of its effect on development per se, but rather due to its influence on other physiological processes.

The faster growth associated with Vrn-B1a may explain the high grain yield of cultivars with this allele in some environments, as shown in a previous study.