Email: scott.boden@adelaide.edu.au

Photoperiod insensitivity has been selected by breeders to adapt crops to diverse environments and farming practices. In wheat, photoperiod insensitivity is contributed by constitutive alleles of Photoperiod-1 (Ppd-1) that relieve the requirement of long daylengths to flower; however, these alleles also limit yield by reducing the number and fertility of grain-producing florets through processes that are poorly understood.

Here, we investigated the influence of Ppd-1 on genes that control flowering time and inflorescence development using near-isogenic lines (NILs) that contain either photoperiod insensitive (Ppd-D1a) or null (ppd-1) alleles of Ppd-1.

By analysing the influence of Ppd-1 in field-grown plants at stages when spikelet number is determined and floret development initiates, we found that Ppd-1 regulates flowering and inflorescence development by determining the seasonal progression of gene expression. We report that Ppd-1 influences the stage-specific expression of genes with roles in auxin signalling, meristem identity, and protein turnover, and analysis of differentially expressed transcripts discovered bZIP and ALOG transcription factors that regulate flowering time and spikelet architecture.

Intriguingly, the ALOG transcription factor shares a conserved role in barley, indicating it plays a central role in the formation of unbranched spike inflorescences of the Triticeae. These findings enhance our understanding of genes and that regulate inflorescence development in wheat and introduce new targets for improving yield potential and flowering time.