| A RIL population(Shannong 01-35×Gaocheng 9411 F8:9), included 173 lines was analyzed using DAr T and SNP(90K) gene microarray technology, and a high density genetic map of Wheat(Triticum aestivum L.) was constructed. QTL mapping was conducted for wheat grain characters, dough rheological properties, pasting properties, steamed bread and bread processing quality under 5 environments in 4 years. According to the major and stable QTL, molecular markers for grain weight were explored. The main results were as follows:1. Construction of high density wheat genetic map: A genetic map covered 21 wheat chrosomes was constructed with 6244 polymorphism markers, including 6001 SNP, 216 DAr T and 27 SSR. The total length of chromsomes was 4895.29 c M, with an average marker interval of 0.77 c M. This genetic map was one of the most precise genetic map including many different types of markers using RIL population and which has the important significance for reference map.2. QTL mapping for quality traits using the high density gemetic map2.1 QTL mapping for kernel characters: Total 7 QTLs controlling thousand grain weight were located on 1B, 4B, 5B and 6A. Among them, QGW4B-17 was detected under several environments with net additive effect of 2.19-3.06 g. All the positive effects came from big kernel parent Shannong 01-35 that was cultivated in our institute.Three QTLs for kernel length were located on 1B and 4B chromosome. Seven QTLs controlling grain width were detected, with the maximum net effective value of 0.11 mm.Total 13 conditional and unconditional QTLs controlling grain hardness were located on 3B,4A, 4B, 5A, 5B, and 6D, of them QKH4 B.4-17, QKH5 B.5-489, QKH4 B.4-2, QKH5 B.5-492 and QKH6D.2-4 were detected under multiple environments. Above mentioned QTLs mainly affected kernel width and grain thickness, but were independent with grain length.One important major QTL was QGW4 B.4-17, which controlling both grain width, grain length and grain weight, but also which was detected to control protein content, wet gluten content, dry gluten content, flour water absorption and texture properties of steamed bread(hardness, the maximum compressive resistance, compression integral area), furthermore,which was related to starch pasting peak viscosity closely.2.2 QTL mapping for protein content, sedimentation value, wet gluten content and gluten index: Seven additive QTLs of protein content were detected on chromosomes 2A, 3A,3B, 4B and 7B. Ten QTLs of sedimentation value were detected on chromosome 1B, 1D, 3A,4B and 7A, and the PVE% was 4.9-16.48%, with the net additive effect values of 1.16-2.64 ml.The synergistic gene loci derived from Gaocheng 9411. Six QTLs of wet gluten were detected on chromosomes 3B, 4B, 6B and 7B with the PVE% of 4.1-11.7%. The synergistic gene loci of Glu-D1, QWG4 B.4-13 and QWG3 B.3-55 were from female parent Shannong 01-35; the PVE% of Glu-D1 for gluten index was 16.1%.2.3 QTL mapping for dough rheological properties:2.3.1 Position on chromsome of QTLs for dough rheological properties: Six unconditional and six conditional QTLs controlling stablity time were located on 1A, 1D, 3B, 5B, 7A and 1A,1B, 3A, 3B, 6A seperatedly. Six epistatic QTLs of stability were detected. Of them, the PVE%of QST5 B.5-481-QST5 B.10-69 reached 13.9% with net effect value of 1.23 min. Total 9 QTLs were detected controlling midline peak height, located on chromosomes 1B, 2B, 4A and 6B,and the synergistic gene loci were mainly from Gaocheng 9411.Nine unconditional QTLs of midline peak time were detected with net effective value of0.13-0.35 min, and with PVE% of 2.4-36.7%. Nine QTLs of midline peak height were located on chromosome 1B, 2B, 3A and 7B with net effective value of 0.64-2.17, and with PVE% of3.7-30.0%. Six conditional and unconditional QTLs of dough resistance were located on chromosomes 1A, 1D, 4A and 5A; fourteen QTLs controlling dough extensibility were located on chromosomes 1B, 2B, 4A and 6B. Six QTLs of elasticity index(Ie) were located on chromosome 1B and 2B. Three gene clusters and 4 QTLs controlling dough strength(W) were located on chromosomes 1A, 1B, 1D, 4B, 5A, 7B and 7D. Eight QTLs of dough force were located on 1A, 1B, 1D, 3A, 5A and 6B. The PVE% of QF3 A.3-17 was 10.76%, higher than that of Glu-A1, which could increase force with 6.68 g. One QTL of dough extensibility was loctated on 5B chromosome with PVE% of 3.2%, and net effective value of 0.95 mm. Five QTLs of integral area of the extension curve were located on 1A, 1B, 3A and 7A.2.3.2 Evaluation of the importance of Glu-1 for dough rheological properties on the level of QTL/gene and its relationship with other QTLs of quality traits: Through QTL mapping for various of dough rheological properties, Glu-D1 was detected controlling farinograph parameters(development time, stability time, tolerance index, farinograph quality number, with maximum PVE% of 24.1%, 24.1% 13.2%, 22.5%, 24.6%, respectively), Mixing properties(midline peak time, value at 8 minutes, midline peak width, peak width at 8 minutes, right slope of peak, with the maximum PVE% of 36.7%, 11.5%, 11.2%, 14.2%,16.5% and 15.5% separately), avelograph parameters(resistance, dough strength, with the maximum PVE% of 17.3% and 23.9%) and extensibily properties(tensile resistance,extensibility, with the maximum PVE% of 9.4% and 22.4%). Glu-D1 is the most important gene locus controlling gluten strength.Glu-A1 controlled farinograph parameters(development time, stability time, with the maximum PVE% of 13.3% and 10.7% respectively), Mixing properties(midline peak time,curve tail value, curve value at 8 minutes, right slope of the peak, with the maximum PVE%of 15.7%, 7.0%, 8.29% and 9.47% respectively); avelopgraph parameters(resistance, dough strength, with the maximum PVE% of 8.1% and 7.9% respectively) and dough extension properties(tensile resistance, with maximum PVE% of 6.5%).According to conditional and unconditional QTL analysis, Glu-A1 and Glu-D1 affected sedimentation value and gluten index to regulate of dough rheological properties, while no relationship with protein content and wet gluten content. This study further confirmed the contribution of Glu-A1 and Glu-D1 for quality on the level of QTL/ gene. We further analysized the basic properties of its influence on wheat quality. Two intresting loci unrelated to 7 + 8 HWM-GS were located on chromosome 1B. The first one was 1B.1-24, which mainly controlled dough stability time, sedimentation value, extension, dough strength, midline peak value and width. The second was 1B.1-3 loci, which mainly controlled midline peak value and width, midlie peak time, extensibility, swelling index and dough tenacity/dough extensibility(P/L). The synergistic gene loci were all from Gaocheng 9411.2.4 QTL mapping for pasting properties: Six QTLs of peak viscosity were located on the chromosome 1A, 4A, 4B, 6A and 7A with the PVE% of 2.35-32.64%. Of them QPV4 B.4-17 was detected in multiple environments with the PVE% of 17.82-32.26%. One epistatic QTL(1A.4-1-4B.4-17) controlling peak viscosity, trough viscosity, setback and peak time. Three QTLs(1A.4-1, 4A.2-16, 4B.4-17) related papain digestion loci that controlled peak viscosity.Five new QTLs of breakdown were located on chromosome 1A, 3B, 4A and 5A respectively with papain treated flour, with the PVE% of 2.79-12.54%.2.5 QTL mapping for food processing quality and its correlations with other quality parameters: Combined taste and texture properties analyzer(TPA) determination, QTL mapping for steaming quality and baking quality using the same RIL population was conducted for the first time. Twenty-seven QTLs of steamed bread and bread quality was detected. QH5 B.5-488 and QVol5 B.5-408 was detected to control bread volume and height of steamed bread seperately. QVol5 B.5-408 controlled dough stability time was co-located with QST5 B.5-410 of stability and QGI5 B.5-406 of gluten index, which were important loci controlling gluten strength.Correlation analysis of 37 wheat quality parameters with steamed bread, bread volume,and taste score was carried out. The results showed that: Avelograph parameters and extension properties related to bread quality notabley; Maximum resistance(Force) of extension properties, curve integral area and integral area before peak were correlated significantly with bread volume, the correlation coefficient were 0.52**, 0.58** and 0.52**respectively; Dough strength(W) and elasticity index(Ie) were correlated notably with bread total score with correlation coefficient of 0.51** and 0.44** respectively.2.6 Two interested and important QTLs controllilng simultaneous yield components(thousand grain weight) and quality: The first was 4B.4-17, which controlled grain weight,grain width, grain length, and also which was closely related with protein content, wet gluten content, dry gluten content, flour water absorption, TPA parameters of steamed bread(steamed bread hardness, the maximum compressive resistance 1, compressive integral area)and peak viscosity. This QTL was an important QTL controlled yield components and quality of dough and steamed bread.Another important chromosome region was 5B.5-488, which controlled grain width,grain weight, kernel length, and simutanously which controlled the stability time of dough,breakdown time, evaluation value and height of steamed bread. This gene loci also controlled kernel weight, kernel width and kernel diameter. The synergistic allele for kernel characters derived from Shannong 01-35, while the synergistic alleles related to processing quality were from Gaocheng 9411. These two new located QTLs were of great valuable for improvment of yield and quality in coordiation.3. Exploration of molecular markers: Four CAPS markers were explored according to the major QGW4 B.4-17 and QGW6 A.2-232 and so on. The effectiveness was proved using varities, backcross populations and high generation materials of breeding. For example,average grain weight, grain length, grain width of varieties(lines) with QGW6A-164-G haplotype were higher than that of varietes(lines) with QGW6A-164-A. The difference of them reached significant level. That proved the explored markers could be used for marker assistant selection or gene polymeration breeding.Construction of high density genetic map and detection of important loci controlling grain characteristics and processing quality parameters laid the foundation for fine mapping and gene exploration. Futhermore, which also provided important theoretical and practical significance for improvement of high yield and good qualtiy of wheat varities in coordination through the method of marker assisted selection and gene polymeration breeding. |
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