Identification and validation of novel plant compactness QTL in common wheat

Plant compactness (PC) is a crucial agronomic trait that affects plant density in wheat, which in turn influences biomass and grain yield potential. The canopy of high-yielding wheat varieties should exhibit appropriate aboveground plant architecture. In this study, three recombinant inbred line (RIL) populations were generated to identify and validate quantitative trait loci (QTL) related to plant compactness. The erect and compact tillering genotype SN05525 was used as a common parent. A total of 193 F₈ RILs from the cross SN05525/SN22 were genotyped using the high-density Illumina iSelect 90 K single nucleotide polymorphism (SNP) assay.

A linkage map with 7180 SNP loci was constructed, revealing six QTL on chromosomes 3B (Qpc.sdau-3B.1, Qpc.sdau-3B.2),5B (Qpc.sdau-5B), 5D (Qpc.sdau-5D), 2 A (Qpc.sdau-2 A), and 7 A (Qpc.sdau-7 A) that control compact tillers. Qpc.sdau-3B.1, Qpc.sdau-5D, and Qpc.sdau-5B accounted for up to 16.70%, 16.89%, and 14.56% of the phenotypic variance, respectively. Kompetitive allele-specific PCR (KASP) markers were developed for these QTL, and their effects were validated in two additional RIL populations, SN05525/Luyuan 502 and SN05525/Xinong 511. Significant effects of Qpc.sdau-3B.1 and Qpc.sdau-5D on compactness were observed in the validation populations.

Three major QTL loci closely related to plant compactness in wheat were successfully identified, and their effects were validated in two additional RIL populations across multi environments. Plant architecture plays a crucial role in enhancing yield and economic value in wheat. In the process of molecular marker-assisted selection breeding, the closely linked KASP markers could potentially be utilized in molecular marker-assisted selection for adjusting plant compactness and for further characterization of the underlying gene(s).