Identification of Quantitative Trait Loci Controlling Agronomic Traits Indicates Breeding Potential of Tibetan Semiwild Wheat (Triticum aestivum ssp tibetanum)

Tibetan semiwild wheat (Triticum aestivum ssp. tibetanum Shao) is a primitive hexaploid wheat resource found in Tibet. It is characterized by tolerance to nutrition deficiency and strong seed dormancy and has potential to be useful in wheat breeding programs. To tap the advantages of Tibetan semiwild wheat in wheat breeding, we investigated nine agronomic traits including heading date (HD), anthesis date (AD), plant height (PHT), tiller number (TN), spike length (SL), spikelet number per spike (SNS), spikelet density (DS), grain weight per spike (GWS), and 1000-grain weight (TGW) in 186 recombinant inbred lines from a cross between Tibetan semiwild wheat 'Q1028' and common wheat 'Zhengmai 9023' (ZM 9023) across three growing seasons. Forty-five qualitative trait loci (QTLs) on 12 chromosomes were detected. The phenotypic variation explained by each of these QTL ranged from 4.7 to 29.7%. Positive alleles for 28 of these QTLs were derived from Q1028. Of these QTLs, 25 (56%) were detected in at least two growing seasons. Fifteen stable QTLs that were significant across all three growing seasons were identified. Novel QTLs derived from Q1028 were identified, such as QSd. sau7A for spikelet density, QTgw. sau-2B for TGW and QSns. sau-3D for SNS. Eleven QTL clusters were detected, including one on chromosome 5A flanked by the markers wPt-9094 and wPt-9513. This cluster consists of QTLs controlling HD, AN, PHT, SL, and spikelet density and explained 6.6 to 12.6% of the phenotypic variation in these traits. The QTLs and molecular markers identified here could be useful in fine mapping and breeding programs.