Genetic Map Construction Of Allotetraploid Cotton (Gossypium Hirsutum L.×Gossypium Barbadense L.)

Cotton is the most important natural fiber crop, and is also important oil and protein source crop in the world. Cotton production occupies an important position in the national economic development in China. With the development of science and technology and the improvement of people’s living level, cotton breeding not only needs to increase yield, but also pays attention to the improvement of fiber quality. Conventional genetic breeding methods require a long period, and the breeding efficiency is low. However, the advance of DNA markers provides a rapid and precise approach for the improvement of crop. Using DNA molecular markers to construct the genetic linkage map of cotton, to locate and identify the favourable genes could promote the improvement of cotton fiber yield and fiber quality.Gossypium hirsutum and Gossypium barbadense are two cultivated allotetrapolid cotton species. Gossypium hirsutum is characterized by high yield and wide adaptability, but the fiber quality is poor. Meanwhile Gossypium barbadense is characterized by good fiber quality, has strong resistance to verticillium wilt, however the yield of fiber is lower than Gossypium hirsutum. The construction of saturated interspecific cotton linkage map provides the reference for establishing Chr. omosome single segment substitution lines and identifying the favourable genes, and the research has important implications for the molecular marker assistant selection and genomic studies of cotton.The present study established an intraspecific backcross population with188individuals from G. hirsutum cv. CCRI35and G. barbadense cv. Pima S-7, and contrcuted a SSR genetic linkage map. The main results were summarized as follows:1. Screening polymorphic primersA total of4161SSR primer pairs were used to screen the polymorphic primers between mapping parents CCRI35and Pima S-7, and1139polymorphic primer pairs were obtained, accounting for27.4%of the total primer pairs.2. Genotyping BC1populationThe polymorphic primer pairs (1139pairs) were used to genotype the the188individuals of BC, population [(CCRI35×PimaS-7)×CCRI35], and1286loci were obtained. A total of1286loci were tested by Chi-square, the result showed that144loci distorted from Mendelian segregation ratio1:1(P<0.05), accounting for11.2%of the total loci.3. Construction of Genetic Linkage Map of BC1populationA total of1286loci were used to perform genetic linkage analysis, a genetic linkage map with1241loci and26groups was constructed. This map spanned3445.4cM with an average distance of2.8cM between two adjacent markers, accounting for about77.5%of the whole allotetraploid cotton genome.