Evaluation On Genetic Diversity Of Phenotypic Characters And Study On Method For Core Collection Constriction In Sea Island Cotton

In this study, we used 211 Sea Island cotton varieties(strains) as test materials, analyzed the main distribution regularities of quantitative characters,and made correlation analysis and principal component analysis of the quantitative traits; had a clustering analysis of 211 varieties by using the SPSS. On the basis, we analyzed the core germplasm construction methods of Sea Island,selected out a suitable core germplasm building method for Sea Island andanalyzed the core germplasm through molecular markers and genetic diversity, the main results were as follows:1.This study analyzed diversity of 15 phenotypic traits among the 211 sea island,there was a big difference between the variation coefficients of different characters, the biggest character variation coefficient is lint yield,and the smallest is maturity. The diversity index variation range of different characters is 1.55-2.08. The study also found that the diversity index does not match with the variation coefficient of one trait.2.According to different sources, the 211 materials were differentially analyzed the agronomic traits, yield traits and quality traits using variance analysis. 14 traits were reached significant difference on the three types of characters except the beginning pitch number. And selected representative materials for further breeding work according to attention traits and different source, which provide reference for future breeding work.mean time, 211 materials were analyzed by variance in different years,the study show that the average of 15 characters reached significan level in three years.3.Through analysis the generalized heritability of the 15 characters, the generalized heritabilityorderof agronomic and yield characters is: plant height > beginning section height>beginning section number >ginning outturn> single boll weight > effective boll number > lint yield.The heritabilityorderof quality traits is: spinning consistency > specific strength>uniformity>micronaire value>upper average length>elongation rate>maturity>short-staple rate.The lint yield,maturity and short-staple ratehave lower heritability; therefore, these characters were suitable to choose in mid-late generations in configuration hybrid combinations.4.The size orderof comprehensive genetic variation coefficient of agronomic traits and yield traits is: beginning section height>plant height >beginning section number> effective boll number> lint yield >ginning outturn> single boll weight.The genetic variation coefficient order of quality traits is: strength>spinning consistency> micronaire vaule> elongation >upper average length> maturity > short-staple rate.The genetic variation coefficient of plant height, lint yield, specific strength, micronaire value and upper average length, which are the biggest concerns charactersin cotton breeding,was greater than 20%, the results showed that the group has more abundant hereditary variability.5. When the choice is 1% and 5%, there have high value of relative genetic progress in plant height, starting high and strength, micronaire, genetic potential and genetic advance are better.6.Through analyzed the correlation between different traits we found that various characters have extensive connections instead of independent with each other. 59 traits were extremely significant correlation, of which 37 traits were extremely significant positive correlation, 22 traits were extremely significantly negative correlation. 9 traits were significant correlation, including 4 significant positive correlation characters and 5 significantlynegativecorrelation traits.7.Principal component analysis of Sea Island cotton results showed that the cumulative contribution rate of the first 5 factors reached 82.02%, which is quality factor, output factor, cotton boll characteristic factor, the maturity factor and the beginning section characteristic factors.8.By cluster analysis of sea island phenotypes, the 211 varieties of sea island can be divided into five types, the first category includes 83 materials,the second category contains 45 materials, the third class contains 57 materials, the fourth class contains 1 materials, the fifth class contains 25 materials. Materials of different groups have different phenotypic characteristic, the fiber quality of the fifth class is the best.9.From four levels to discuss the optimal core germplasm building strategy of sea island, the genetic distance(chi-square distance and Euclidean distance), clustering methods(class average method, the longest distance method, the shortest distance method and the sum of squared residuals method), sampling methods(completely random sampling method, random sampling after cluster, and preferred sampling method)and the overall sampling rate(5%, 10%, 15%, 20%, 25%, 30%,35%, 40% and 45%). Using the mean difference percentage, variance difference percentage, terrible coincidence rate and change rate of variation coefficient to test the advantages and disadvantages of each strategies, the results showed that, under the 20% overall sampling rate, combining the euclidean distance with the shortest distance method to system clustering and the random sampling in group was the best policy for structure core germplasm of sea island.10.Taking cluster sampling variation degree method for many times, using the shortest distance clustering methods and the euclidean distance, under the 20% overall sampling rate, preliminary built 43 sea island core germplasm. The qualitative character, diversity index average,quantitative trait variance percentage difference and variation coefficient change rate were higher than the original germplasm, 97% coincidence rate; From the scatter diagram of principal component analysis we can see core germplasm keep the seed quality genetic structure maximum. The building core germplasm can well represent the original germplasm genetic diversity.11.43 core germplasm were analyzed through genetic diversity, the similarity coefficient is between 0.40 and 0.95, the average similarity coefficient is 0.735, which showed that core germplasm genetic variation of 43 varieties is widespread, all varieties can be completely separated when the similarity coefficient is 0.95, further verified the construction of core germplasm has a good representative in sea island.