Photoperiod and vernalization alleles and their combinations greatly affected phenological and agronomic traits in bread wheat under autumn and spring sowing conditions

The responses to temperature (vernalization) and day length (photoperiod) in wheat (Triticum aestivum L.) are entirely defined by allelic differences at the respective VRN-1 and PPD-1 loci. These two physiological factor greatly affect wheat phenology. Using molecular markers, a panel of 61 diverse bread wheat varieties were genotyped for VRN-1 and PPD-1 alleles, and the traits were evaluated under autumn and spring sowing conditions to investigate the impact of the alleles and their combinations on phenological stage, morphological traits, and yield traits. The results revealed that the earlier heading (HD), and flowering (FD) conferred by insensitive alleles for VRN-1 and PPD-1 genes was consistent regardless of the variation under the two sowing conditions. The effects of a single dominant allele of VRN-1 were similar, with an additive effects when combined. The effects of a single PPD-1 insensitive allele differed, with Ppd-D1a stronger than Ppd-B1a, and Ppd-A1a was the least, with an additive effects when combined. Secondly, varieties sown under spring condition recorded a larger flag leaf area when compared to those sown under autumn condition regardless of the single and combined influence at the VRN-1 and PPD-1 loci. When compared to other genes, PPD-D1 had a consistent and significant effect on flag leaf area, spike length, and plant height across both sowing conditions. Furthermore, the sensitive allele Ppd-D1b had larger biomass across both sowing conditions, but this did not translate into increased yield because the Ppd-D1a insensitive allele recorded higher yield. The impact of PPD-D1 gene on grain yield was evident across both sowing conditions. Overall, according to the findings of this study, VRN-1 and PPD-1 genes impact in modulating phenology stages, morphological, spike and yield traits was dependent on the sowing conditions and also on genetic background with the spring and insensitive alleles poised to be favored for selection.