Screening And Identification For Thermotolerance Of Cotton Germplasm Resources

Cotton(Gossypium spp)originated in the subtropical region,has become one of the important economic crops and fiber crops,cultivated all over the country.The main cultivars in our country is upland cotton(Gossypium hirsutum),which heat tolerance is differential.Some are heat resistant varieties,while some varieties are sensitive to high temperature.In recent years,periodic heat damage happened frequently in July and August in cotton planting areas of China,especially in Yangtze River valleys,resulting in boll abscission at the peak time of cotton flowering and boll loading.It not only reduces the number of summer boll and early autumn boll,but also seriously affected the lint yield and fiber quality of cotton.The high temperature stress has become an important limiting factor for cotton yield and fiber quality of cotton.Carrying out the research of cotton heat resistance,screening of heat resistant germplasm and breeding of heat resistant varieties has become the most important task at present in order to adapt to the current cotton planting environment,the emergence of more extreme high temperature at future,stabilize the lint yield,improve the heat resistance and ensure the fiber quality of cotton.In this study,more than 260 cotton varieties were selected as materials which characters of heat resistant were unknown.Screening germplasm resources which may have heat resistant by field observation,investigation,statistics and analysis.Using what were screened as materials by investigating of boll weights,infertility seed rate,boll numbers,pollen vitality,pollen morphology,maximum pollen tube length and the pollen germination percentage of different cotton germplasm resources cultured in different temperature in vitro to determine the heat resistant identification index,and then the rapid cotton heat resistant evaluation system was constructed,and lay the foundation for the cotton heat resistance research in the future.The main results were as following:1.Under the condition of high temperature in the field of natural planting,boll weights of different germplasm,maximum pollen tube length and the pollen germination percentage in vitro at 30℃,45 and ℃ 50 ℃ cannot be used as cotton field appraisal index.2.The boll numbers,infertility seed rate,Pollen vitality,pollen morphology,can be used as reference indexes in heat resistant identification of cotton as well as the pollen germination percentage in vitro at 35 and 40℃ ℃.3.Through principal component analysis,the 31 germplasm resources could be classified as four categories: high temperature resistance type,moderately high temperature resistancetype,moderately high temperature sensitive type and high temperature sensitive type.W181,GA141,W9704 and D180 belong to high temperature resistance type varieties.