Biochemical Genetic Mechanism And QTLs Of Early Maturing Without Decrepitude In Shorted-season Upland Cotton (G. Hirsutum L.)

Face to the premature senescence of Short Season Cotton(SSC), Six cultivars from two types of SSC were selected , three SSC without premature senescence and 3 SSC with premature senescence. The 6×6 diallel crossing design was selected. Yield, earliness, fiber and biochemical characters of the SSC were studied to explain the mechanism of the biochemical inheritance. The next is results.Seed yield , lint yield , lint percentage, boll weight and bolls existed significant dominant effects and dominantxEnvironment effects. The additive X additive epistasis and AdditionxEnvironment effects also existed significant. The lint percentage before frost existed significant AdditionxEnvironment effects. The epistasis xEnvironment effects and Addition effects also existed significant. Date of first square and The situation of first fruit branch existed significant dominant effects and dominantxEnvironment effects. The additive X additive epistasis effects also existed. Date of first flower, Date of first boll opening existed significant additive effects and dominant effects, the epistasis xEnvironment effects also existed. It were relative with the fiber quality traits that existed significant dominant effects and dominantxEnvironment effects. We also studied the genotypic and phenotypic correlations between yield, earliness and fiber quality.The content of chlorophyll, CAT, POD, SOD activities in SSC without premature senescence were higher than in the SSC with premature senescence. The F₁ in the SSC without premature senescence had higher heterosis than their parents. But the F₂ heterosis was low. The content of MDA in SSC with premature senescence is higher than in the SSC without premature senescence. The MDA content of the F₁ in the SSC without premature senescence was lower than in the SSC with premature senescence.It was the first that the biochemical index was considered character for genetic study. Chlorophyll existed significant the additive × additive epistasis , additive xEnvironment effects and dominantxEnvironment effects. CAT and POD existed significant dominant effects and dominantxEnvironment effects. SOD existed significant the epistasisxEnvironment effects, dominantxEnvironment effects. The additive effects also existed significant. MDA existed significant the epistasisxEnvironment effects, dominant effects, dominantxEnvironment effects, the mother effect ,the father effects ,the mother xEnvironment and the father xEnvironment were the first detected.The genetic relatives were studied between the main agronomy traits and biochemical characters. The results were supplied for the base of assistant breeding.The first molecular genetic map of the SSC(G hirsutum L) was constructed. The biochemical characters at the different stage were located the different linkage groups. Using SSR, SRAP, TRAP primer combinations analyzed identified polymorphism between Zhongmiansuo 10 and Liao 4086. The F₂ mapping population of 279 individuals by crossing the SSC without prematuresenescence cultivar Liao 4086 and the premature senescence cultivar Zhong miansuo 10. The 89 polymorphism primer pairs amplified 124 marker loci. The 32 polymorphism primer pairs amplified Co- dominant bands. A total of 94 marker loci were used to construct 21 genetic linkage groups(LOD>3.0). Each linkage groups included 2 and 17 molecular markers .the length of each linkage group was from 0.4 to 83cM. The shortest distance was 0.1 cM and the biggest distance was 34.2cM between two molecular markers. The total length was 648.4cM and covered 13.0% of the whole cotton genome. Four linkage groups were assigned to 4 chromosomes.16 QTLs for the content of chlorophyll, CAT, POD, SOD activities and the content of MDA were the first detected. Two QTLs for CAT activities could be explained 11.7% and 73.2% phenotype variance. Two QTLs for SOD activities could be explained 5.0% and 5.2% phenotype variance. Four QTLs for chlorophyll could be explained 6.2% and 7.2% phenotype variance. 8 QTLs were assigned to the 18 chromosome (LG3). One QTLs for POD activities could be explained 79.9% phenotype variance. Two QTLs for MDA could be explained 85.0% and 87.0% phenotype variance. These QTLs would be used to assist the SSC breeding in the future.