Miller, Daniela MichelleFlowering time in wheat is regulated mainly by response to seasonal environmental cues and controlled by the photoperiod and vernalization pathways. Allelic diversity in genes controlling these pathways is used by breeders to adapt wheat for optimal yield in a broad range of environments. This study characterized genetic loci influencing heading date in a soft red winter wheat doubled haploid population. Two photoperiod insensitivity alleles, Ppd-A1a and Ppd-D1a, were found to have major effects in eight field locations. The Ppd-A1 locus explained up to 16.8% of variation in heading date, whereas the Ppd-D1 locus explained up to 39.7%. In reduced vernalization greenhouse experiments, a QTL in the same region as the VRN-A1 gene explained up to 42.4% of variation in heading date, suggesting that the population differed in this region. Assays for previously-described allelic diversity in the VRN-A1 gene, however, did not detect any polymorphism between parents of the population.enThesisPlant sciencesAgricultureGeneticsdoubled haploidflowering timephotoperiodsoft red winter wheatvernalizationwheat