Identification And Genetic Diversity Analysis On Waterlogging Tolerance In Cotton

Cotton is one of the most important economic and oil crop in the world, well as the main raw material of the textile industry. Since the founding of the people’s republic of China, cotton production has obtained efficient development, but further improving the yield has met a bottleneck. One of the largest restrictions factor is the, frequent natural disasters (abiotic) adversity stress such as flood and draught stress in recent years. Waterlogging severly affects the growth of the plants, reduce the stablitiy of yield and profit of cotton, which is becoming one of the challenges confronted by the steady development of cotton industry in Yangtze River area in the contemporary. As a result, it is is very important to breed cotton varities which shows better response to waterlogging.The aim of this study is to assess the resistance variety to waterlongging, among of different varieties including land cotton, island cotton covering Xingjiang province, Yellow River district, and Yangtze River area. Based on the comparison of the resistance to waterlongging of different varieties, idea about germplasm can be discovered. A total of 263 varieties from different area were assessed in the Yangtze University Agronomy test site shedding in the year of 2012 and 2013. The assessing figures included fully expanded leaf number, new red leaves, aerial root, leaf wilting in the condition of treated with waterlogging and 3-4 days after removing the waterlogging. After that, some varieties with strong resistance and sensitivity to waterlogging obtained.Cotton varieties with resistance to waterlogging can be chose and identified by comparing the morphological traits of land cottons treated with waterlogging. The plant height, root shoot ratio, stem diameter, leaf number, chlorophyll content, fresh weight and dry weight of above ground and underground part of cotton were measured for 34 land cotton varieties. After that, the principle components and cluster analysis were conducted to the resistance to waterlogging.The main intention of the evaluation of discriminated cotton germplasm resource was to select, the specific variety which shows satable resistance to waterlogging, which can provide resistant materials and scientific fundamental stratigies for the research of the genetic basis and gene mapping of waterlogging resistance. Because of the complexity of the mechanism of waterlogging resistance, the level of resistance to waterlogging could be assessed only if several techonology includes morphological, physiological and chemical measurements were combined together. In order to improve the efficiency of breed and assessing, it is indispensable to find an easy index the level of resistance.(1)The root and shoot ratio is the most sensitive index to assess the sensitivity to waterlogging in the cotton seedling stage. So it is reliable to evaluate the growth condition of cotton by this value. Aerial parts of the plant, total leaf area, fresh weight and dry weight of above ground, dry leaf number after processing, underground part is representative, which can be chose prior to other traits. The rank of resistance and fuzzy Cluster result according to the resistance value is consistence with the real observation, which indicates that this can be used as the computing method to assess the level of cotton resistance to waterlogging.(2) In order to elucidate the genetic variation of wet-tolerance related cotton germplasm, we set up 145 SSR markers which spanning the whole genome. After screening we choose 44 simple sequence repeat (SSR) makers which were explored to analyzed 48 upland cotton varieties. The results indicated that a total of 170 alleles, with an average of 3.86 alleles per locus detected by the polymorphic 44 SSR primers. For the waterlog tolerant accessions, mean polymorphism information content (PIC), the average effective numbers of alleles (Ne) and the average genotype diversity index (H’) were 0.632,1.7104 and 0.3937 and 0.628, respectively. For waterlogging sensitive accessions, the PIC, Ne, and the H’were 0.628,1.7216 and 0.3994, respectively. The mean value of similarity coefficients were similar between wet-tolerance germplasms and waterlog sensitive germplasms varies from 0.462 to 0.925 and from 0.462 to 0.925, respectively. Relatively, the waterlogging tolerant germplasms exhibited relatively larger variation range. Using the method of unweighted pair group method with arithmetic mean cluster analysis (UPGMA), the 48 upland cotton varieties were categorized into two major groups. The first cluster consists of 39 accessions, and the second cluster contains 9 accessions. The high genetic similarity coefficients was observed in most of the germplasms analyzed in the study, which indicated the waterlog-related cotton accessions own narrow genetic base. The current study should be helpful for assessing cotton pedigrees in breeding elite varieties with high waterlogging tolerance, and studying the mechanism of waterlogging tolerance in upland cotton.In this study, a total of 263 core parent materials of cotton were assessed to waterlogging using double set of basins, which can simulate the real situation of flood. At the same time, the characterization of cotton germplasm resource in different ecological area was compared. Eventually,5 varieties with strong resistance to waterlogging and eight varieties with sensitivity to waterlogging were selected. The resistance to waterlogging of cotton is a complex problem which is affected by several factors. In order to provide reference and research basis for selecting accurate varieties with resistance, understand the genetic mechanism and resistance mechanism, it is needed to reveal the morphological, physiological and chemical mechanism of the varieties with resistance to waterlogging.