| Quality improvement is one of the major breeding objectives for wheat in China. Hybrid vigor, variation, heritability and correlations were computed in P1, P2, F1, F2 and F2:3 from Zhongyou 9507 with good bread making quality as female parent crossing with five male parents (Annong 91168, Gaoyou 503, Ji 5099, Lumai 5 and Jinmai 45). QTL mapping was performed in 71 doubled-haploid lines derived from the cross Zhongyou9507/CA9632. Traits included SDS sedimentation value, mixograph parameters, grain protein content, grain hardness, flour colour, grain yellow pigment and grain PPO activity. Molecular assisted selection was also tested using molecular markers of storage protein. Major results are described below:1. Genetic analysis of gluten strength1.1 The F1 hybrid vigor of grain protein content and SDS sedimentation were not significant in all five crosses. It was nearby middle-parents velue.1.2 Selection of parents mainly determined the range, coefficient of variation and selection potentiality. Good quality plants can be selected easily in the crosses with strong gluten strength X strong gluten strength and medium-strong gluten strength.1.3 Significantly correlation coefficients between F3SDS sedimentation and mixograph parameter were presented in most crosses, but it was not significant in Zhongyou 9507/Lumai 5.1.4 Heritabilities of grain protein content and SDS sedimentation were different in crosses. The narrow heritability (h2N%) were estimated using correlation regression coefficient (r) and regression coefficient (b). The h2N% of protein content were 22.5-58.9% (r) and 20.0-38.3% (b). The h2N% of SDS sedimentation were 62.9-89.5% (r) and 43.7-75.6% (b). The broad heritabilities (h2B%) of protein content and SDS sedimentation were 38.1-79.1% and 60.5-87.7%, respectively. The realized heritabilities (h2R%) and genetic advance of SDS sedimentation were also significantly higher than protein content, so it can be selected efficiently in F2 generation.2. QTL mapping of gluten strength2.1 Glu-Dl and 1BS had a great influence on gluten strength. However, 1BS or 1RS had a slight effect on index of width, and Glu-Dl with small contribution to SDS sedimentation and peak time of mixograph. Glu-A3 contributed slightly to gluten strength. Glu-A3d had a slight positive influence on SDS sedimentation and a high positive effect on grain protein content. Subunits 5+10 can compensate the negative effects of dough strength associated with 1BL/1RS translocation.2.2 173 markers including 143 SSR, 26 AFLP and 4 STS of storage protein were mapped on 21 chromosomes. Length of linkage map was 2881 cM, with an average distance of markers was 16.6 cM. 18 wmc markers that were not mapped previously were placed onto the genetic linkage map.2.3 Three methods including composite interval mapping (CIM), interval mapping (IM) and simple linear regression (SLR), and method of BSA were used to detect QTL of gluten strength. The results indicated that Glu-Dl and Glu-B3/GH-B1 were major QTLs.2.4 Six QTL located on 1BL, 2DL, 5A, 5D, 6A and 7D, were associated with grain protein content. Two QTL on 5D and 2DL played a significant role in this trait with LOD scores 2.6 and 2.7, and accounting for 13.4% and 15.5% of the phenotypic variance, respectively.2.5 Five QTL located on 2DL, 1A, 2B, 4D and 5D, were associated with grain hardness. The marker Xgwml90 on 5DS was major QTL, with score 8.1 and accounting for 32.3% of the phenotypic variance.3. QTL mapping of flour colour traits3.1 Three major QTL located on 4D, 4A and 5D, were associated with flour brightness L, with LOD scores 4.7-7.6, 2.6-5.1 and 3.5-5.1, and accounting for 14.8-23.4%, 13.6-16.3% and 10.0-16.6% of the variation in three sites, respectively. The QTL on 5D is close to the major QTL of grain hardness.3.2 Two major QTL located on 7AL and 4D were associated with flour yellowness b, with LOD score 5.5-9.1 and 7.4-8.1, and accounting for 12.9-37.6% and 18.7-21.1% of the phenotypic variance in three locations, respectively. O...
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