QTL Analysis For Dough Alveogram Characters And Content Of Grain Starch Components In Wheat

Common wheat (Triticum aestivum L.) is one of the most important staple crops world-wide. The grain yield and other important agronomic traits and quality traits of wheat are generally controlled by multiple genes, and inherited as QTL. QTLs are useful for finding gene location that controlled quality of wheat, and QTLs have become an important and essential component element in wheat quality improvement. In recent years, more QTLs that superior to traditional QTL were detected by conditional QTL through the different environment as well as the period, the work will not only prepare gene resources for molecular marker assisted selection and molecular polymerize breeding by design, but also lay a foundation for fine mapping and clone some important genes.In this study, using a doubled haploid (DH) population lines derived from a cross between two elite Chinese wheat cultivars Huapei 3/Yumai 57 (Triticum aestivum L.), and a previous genetic linkage map containing 323 sites for QTL. On the one hand, QTLs for five alveogram characters were evaluated in the three different environments in order to obtain main effect QTL sites. On the other hand, dynamic accumulation of starch components (grain starch, amylose, amylopectin) were evaluated in the six different environments under two years, the results was used to identify the dynamic quantitative trait loci (QTL) for starch components (grain starch, amylose, amylopectin) in wheat (Triticum aestivum L.). Genes/QTLs of starch components synthesis were expressed on the molecular aspects to clarify molecular genetic mechanism of wheat starch accumulation. The results were as follows:1. Quantitative Trait Loci for Dough Alveogram Characters in Cultivated WheatQTLs for dough tenacity, dough extensibility, dough strength, swelling index and elasticity index of alveogram characters were evaluated in the three different environments by using the software of QTLNetwork 2.0 based on the mixed linear model approach.?Seventeen additive QTLs and seven pairs of epistatic QTLs were detected in three different environments, which were distributed on chromosomes 1B, 2B, 3B, 4B, 1D, 7D and 5A, a QTL could account for phenotypic variance from 1.64% to 28.28%, respectively. QTLs (QDten4B, QDext4B and QSin4B) were detected for dough tenacity, dough extensibility and swelling index on the Xwmc48-Xbarc1096 interval of chromosome 4B, which had the opposite direction of additive effects. The Xwmc93-GluD1 interval on chromosome 1D had the same direction of additive effects on swelling index, dough strength and elasticity index with high contribution of 3.19%, 17.74%, 28.28%, the sites were QSin1D, QDstren1D and QEin1D respectively, and the favorable alleles were contributed by Yumai 57. For the seven epistatic QTLs, the epistatic effects were not significant and without epistatic×environment interactions.2. Phenotypic analysis for contens of grain starch and components in wheatThe date analysis for amylose, amylopectin and wheat starch from a population of 168 DH lines was produced by the cross between two Chinese common wheat varieties Huapei 3 (female parent)×Yumai 57 (male parent), sugessing that the main component of starch is indicated significant transgressive segregation in the descendant of the group. Segregation continuously among the DH population suggests that the trait approximately followed normal distributions, most values of skewness and kurtosis were less than 1.0, indicating typical inheritance of quantitative traits and suitability of the data for QTL analysis.3. Dynamic QTL analyses of grain starch and components in wheatThe number of QTLs in grain starch, amylose and amylopectin that was detected by unconditional mapping were seven, four, three respectively. The number of grain starch, amylose and amylopectin that was detected by conditional mapping were four, six, four. Among them, QGsc4A and QAms4A were detected continuously at five stages under unconditional mapping. QGsc4A was detected by the conditional method at the periods of 12d after flowering, 17d after flowering and 32d after flowering. QAms4A was detected by the conditional method at the periods of 12d after flowering, 17d after flowering and 22d after flowering. These indicating that the accumulated effects of QTL/genes for grain starch and amylose were expressed differently.QGsc6A, QAms2A, QAmp1B were detected by the conditional method and undetected by the unconditional method during 22d, 32d and 22d after flowing, respectively. Indicating that the expression of gene is dynamic, and the unconditional mapping method combined with the conditional mapping method could detect more QTLs.4. Epistatic QTL analyses of grain starch and components in wheat.Under six environments, eight pairs of epistatic QTLs were detected by unconditional mapping, the contribution of phenotype ranged from 1.62% to 5.60%. In contrast nine pairs of epistatic QTLs were detected by conditional mapping, the contribution of phenotype ranged from 1.62% to 6.21%. Amone them, the number of epistatic QTLs in grain starch, amylose and amylopectin that were detected by unconditional mapping were three, four, and one respectively. The number of epistatic QTLs in grain starch, amylose and amylopectin that were detected by conditional mapping was four, four, and one respectively. Epistatic QTLs for starch, amylose and amylopectin with micro effect as the same as the main effect QTL play an important role in accumulation.