Spikelet number and grain number per spike are two crucial and correlated traits for grain yield in wheat. Photoperiod-1 (Ppd-1) is a key regulator of inflorescence architecture and spikelet formation in wheat. In this study, near-isogenic lines derived from the cross of a synthetic hexaploid wheat and commercial cultivars generated by double top-cross and two-phase selection were evaluated for the number of days to heading and other agronomic traits. The results showed that heading time segregation was conferred by a single incomplete dominant gene PPD-D1, and the 2 kb insertion in the promoter region was responsible for the delay in heading. Meanwhile, slightly delayed heading plants and later heading plants obviously have advantages in grain number and spikelet number of the main spike compared with early heading plants. Utilization of PPD-D1 photoperiod sensitivity phenotype as a potential means to increase wheat yield potential.

Background: The wheat FRIZZY PANICLE (WFZP) gene is a regulatory hub that controls spikelet formation in bread wheat, WFZP-D, as a favorable gene for wheat yield improvement. The sequences of WFZP-D in bread wheat accessions are known to be highly conserved. Methods: In this study, re-sequencing of WFZP homoeologous genes from 98 widely distributed Aegilops tauschii (the donor of the wheat D genome) germplasms was carried out to identify natural variations at both the nucleotide and polypeptide levels. Conclusions: WFZP homeolog exhibited high conservation with no functional variants in the key AP2/ERF domain. Haplotype characterization identified five haplotypes (Hap-D1 to Hap-D5) based on nine single-nucleotide polymorphisms, five of which induced single amino acid residue substitutions downstream of the AP2/ERF domain. Hap-D1 (identical to Triticum aestivum WFZP-D) and Hap-D2 are two most common. Hap-D1 is concentrated in Iran and Azerbaijan, primarily associated with ssp. strangulata, while Hap-D2 displays broad distribution across the range and primarily belongs to ssp. tauschii. The remaining haplotypes (Hap-D3/4/5) are identified in ssp. tauschii accessions. These findings suggest that strategic integration of ssp. tauschii into wheat-breeding programs could enhance genetic diversity. The identified natural variations provide potential haplotype resources for improving wheat yield potential.