Identification of Stable QTLs and Candidate Genes for Heading Date in Wheat Using a 55K SNP-Genotyped Doubled Haploid Population

Heading date (HD) is a key adaptive trait determining wheat regional suitability, yield stability, and resilience to environmental stresses. We dissected the genetic architecture of heading date (HD) by phenotyping a doubled haploid (DH) population (178 lines, CASL7AS × ZNL12) across five environments and constructing a high-density genetic map with the wheat 55K SNP array. A total of 38 QTLs associated with HD were identified on 12 chromosomes, among which 10 were consistently detected across multiple environments. Two major stable loci, QHD.ZAFU.2B and QHD.ZAFU.4A, explained substantial phenotypic variation and were considered key regulators of heading time. Candidate gene analysis revealed Ppd-B1 (TraesCSU02G196100) as the causal gene for QHD.ZAFU.2B. Within QHD.ZAFU.4A, a zinc finger RNA-binding protein gene (TraesCS4A02G394400) exhibiting strong flag-leaf expression at the heading stage was identified as the most promising candidate. Notably, most favorable alleles were derived from ZNL12, highlighting its potential for breeding applications aimed at manipulating heading time. These results provide valuable genomic resources and molecular targets for marker-assisted selection aimed at optimizing flowering time and improving wheat adaptation.