Evaluation And QTL Mapping For Yield Traits, Fiber Quality And The Resistance To Verticillium Wilt In Upland Cotton In Different Environments

Cotton has made a significant contribution to the textile industry in China as the most important natural fiber crop. People also plant this cash crop all over the country and totally there are five cotton-growing regions such as the Yellow river valley cotton-growing area, the Yangtze valley cotton-growing area, the northwest interior cotton-growing area, the northern cotton-growing area and south-china cotton-growing area according to the climate, geographical conditions and the main producing areas. In our study, we use a recombined inbred line population with its female parent Acala1517and its male parent Dezhou047to plant in five different areas according to the five cotton-growing regions for two years. We collect the yield component traits and cotton fiber quality traits phenotypic value to find out the QTL which stability appeared in different environment and to find out the interaction effect between genotype and environment.1. We choose Liaoyang, Anyang, Quzhou, Ezhou, Kashi and Hainan for our testing site according to the main five cotton-growing regions. The cotton output is very different from each other in those places, the Yangtze valley cotton-growing area has a highest cotton output with plentiful rainfall and a higher accumulated temperature, the second highest cotton output is in the northern cotton-growing area where has the highest accumulated temperature but not enough precipitation, the next is in the Yellow river valley cotton-growing area, the northwest interior cotton-growing area has a lowest output with insufficient accumulated temperature. Precipitation and accumulated temperature are the two main factors that affect the cotton production.2. Most of the yield traits and fiber quality traits in different environments obey normal distribution and minor-polygene controls their expression. Data analysis turns out that there is a significant positive correlation among plant height, node of first fruiting branch, branch number and boll number. Seed index and ginning out turn, seed index and seed cotton yield have a significant negative correlation in under different experimental conditions. For fiber quality traits, between fiber length and fiber uniformity, fiber length and fiber strength show a significant positive correlation and there is a significant negative correlation between fiber length and micronaire, fiber length and elongation, fiber uniformity and elongation, micronaire and fiber strength, elongation and fiber strength in different environments. For seed cotton yield, boll number and boll weight play a decisive role in every environment. The relationships between them are very complex because of linkage and other reasons.3. In this study totally17358SSR primers were used to screen polymorphism among two parents and finally237SSR primers pass muster and shows254polymorphism loci in RIL population. We use Joinmap3.0(LOD=3.0) to get a genetic linkage map and113loci were divided into29linkage groups and covered934.22cM, approximately20.99%of the whole cotton genome. Each group has2to10markers and the average level is3.9with an average distance8.27cM.4. We use WinQtlCart2.5(LOD=2.5) to analysis field and fiber quality data to find out QTL in every environments,49QTL control the expression of cotton yield traits and each of the single QTL could explain5.8%-28.4%of phenotypic variance,15QTL control the expression of fiber quality traits and each of the single QTL could explain7.2%-12.7%of phenotypic variance,1QTL control the expression of verticillium wilt resistant with explaining13.9%phenotypic variance.2QTL (1for fiber length,1for ginning out turn) can be detected in3different environments, and5QTL (1for node of first fruiting branch,1for boll number,1for ginning out turn,1for seed index,1for fiber strength) can be detected in2different environments. Those stability QTL can be used in MAS.5. Mixed linear model composite interval mapping was used to find out the interaction between genotype and environments with QTLNetwork2.0(LOD=2.5).14QTL show interaction effect and specifically expressed in different environment. Those QTL control the expression of plant height, branch number, boll number, seed index, boll weight, seed cotton yield, fiber length, fiber uniformity and micronaire. Those genes expressed with the effect of environment.