Mapping loci and genes controlling heading and maturity time in common wheat under long-day conditions and assessing their effects on yield-related traits

The duration of the vegetation period significantly impacts yield formation and is one of the important characteristics of spring common wheat (Triticum aestivum L.) varieties. The primary developmental phases influencing the vegetation period include the time from seedling emergence to heading and from heading to maturity. To identify genes and loci associated with these traits under long-day conditions typical of Western Siberia and to assess their impact on yield components, we conducted QTL mapping followed by an evaluation of yield-related traits in lines carrying different alleles of key heading time genes. For mapping, we used an F2 population derived from a cross between the varieties Obskaya 2 and Tulun 15, which contrast in their heading and maturity times. QTL analysis identified a novel locus on the long arm of chromosome 7B associated with maturity time, as well as two loci on chromosome 2D and the short arm of chromosome 7B associated with heading time. Gene analysis within these loci revealed candidate genes for the "seedling-maturity" trait, with expression patterns corresponding to the known maturity time regulator NAM-1. The localization of loci for the "seedling-to-heading" trait suggested their correspondence to the well-known genes Ppd-D1 and Vrn-B3. Analysis of progeny carrying the Ppd-D1a and Vrn-B3a allele combination demonstrated that Ppd-D1a had a stronger effect on heading time than Vrn-B3a, and their combined presence resulted in the earliest heading - on average, five days earlier than in lines with the Ppd-D1b and vrn-B3 alleles. Evaluation of yield-related traits (number and weight of grains per main spike and per plant, and 1,000-grain weight) indicated that Ppd-D1 was significantly associated with all traits, with the Ppd-D1a allele generally exerting a negative effect on yield. In contrast, Vrn-B3 had a comparatively smaller effect on yield traits than Ppd-D1.