Genetic Analysis Of QTL Mapping For Seeding Traits And Heterosis For Plant Height In Wheat

A set of 168 doubled haploid (DH) lines derivatives of a cross between Huapei 3 and Yumai 57, and an immortalized F₂ (IF₂) population generated by randomly permutated intermating of these DHs were investigated, and QTL of coleoptile length, tiller, root traits, plant height and the HL of plant height were mapped. The work will provide gene resources for molecular marker assisted selection and molecular aggregation breeding by design, and provide inform- ation for marker-assisted selection strategy in hybrid wheat breeding.The results were as the following:1. A set of 168 doubled haploid (DH) lines derivatives of a cross between Huapei 3 and Yumai 57, and an immortalized F₂ (IF₂) population generated by randomly permutated intermating of these DHs were investigated. The immortalized F2 population is favorable for QTL analysis due to its similar proportions of genotypes in the population, and the replicability at multiple locations over several years.2. QTL/HL for PH in DH and IF₂. A total of three additive QTL, two dominance QTL, four pairs of epistatic QTL, and twenty heterotic loci were detected for PH in the three environments. Two QTL, QPh2D and QPh4D, were detected on chromosomes 2D and 4D with minor interaction of additive by environment. In addition, several other heterotic loci for PH were also identified on chromosome 2D in very close regions with similar marker intervals. Among them, QTL QPh2D-2 and QPh2D-7 explained the variance of PH by 29.77% and 55.77%, respectively. Another QTL associated with PH heterosis, QPh7D-2, was mapped in the marker interval between Xwmc273.2 and Xcfd175 on chromosome 7D in the three environments.3. QTL for tiller in DH and IF₂. A total of nine and eighteen significant QTL were detected across environments for tillering in the DH and IF₂ populations, respectively. Four QTL were common between the two populations. A major QTL located on the 5D chromosome with the allele originating from Yumai 57 was detected and increased 1.92 and 3.55 tillers in MTW and MTS. The QTL (QMts6D, QEth6D) having a neighboring marker interval at Xswes679.1 and Xcfa2129 on chromosome 6D were detected in MTS and ETH.4. QTL for root traits in IF₂. A total of seven additive QTL and twelve pairs of epistatic QTL were mapped on chromosomes 1A, 1D, 2A, 2B, 2D, 3A, 3B, 5D, 6D and 7D. Additive, dominant and epistatic effects were observed across these QTL, including the interactions between additive and additive, additive and dominance, dominance and additive, as well as dominance and dominance. The phenotypic variation explained by each QTL ranged from 0.01% to 11.91%. In the interval between Xwmc41 and Xbarc349.2 on chromosome 2D, a QTL for total root length and root dry weight was detected.5. QTL for coleoptile and root in DH. Eight additive QTL were detected for coleoptile length. Among them, QCl2A, QCl4B and QCl4D, located on chromosome 2A, 4B and 4D, were detected both under the normal treat- ment and 20% PEG-6000 treatment, explaining 6.09%¹6.31% of the phenotypic variation. Ten additive QTL were detected for root length, in which, QRl6A, located in the interval between Xgwm82 and Xwmc553 on chromosome 6A, can be detected under the two treatments, explaining 8.26% and 9.74% of the phenotypic variation. Furthermore, eighteen pairs of epistatic QTL for coleoptile length or for root length were detected, and most of their epistatic interactions are between non-additive QTL and non-additive QTL.