| Upland cotton(Gossypium hirsutum L.) exhibits the most widely cultivated at95%of overall cotton production. Upland cotton is characterized by high fiber yield and wide adaptability, but has the narrow genetic base, medium fiber quality with the single type. Sea Island cotton (Gossypium barbadense L.) has the excellent fiber, high resistance to verticillium wilt. It is very important to create the new Upland materials with high-quality, high yield, and resistance to verticillium wilt for enlarging the genetic germplasm and cotton genetic improvement by introgressing the genes of excellent fiber and resistant to verticillium wilt from Sea Island cotton to Upland cotton.Chromosome segment substitution lines (CSSL) also known as introgression lines (ILs), is created by introgressing the donor chromosome segments to the same genetic background with the marker-assisted selection (MAS), CSSLs include one or a few homozygous chromosome segments are derived from the donor parent, but the rest of the genome is the same as the recipient parent. Therefore, it is an ideal material for genome research, especially QTL fine mapping and map-based cloning. Sub16has the background of genetic standard line of G hirsutum ace. TM-1with the16th chromosome of G. barbadense ace.3-79. In the study, a set of G. barbadense ace.3-79chromosome16segment substitution lines (CSSL16) were developed via created BC2F2:3、BC2F2:4groups with molecular marker-assisted selection (MAS), and with TM-1as a recipient parent and Sub16as a donor. Based on the results, further, we mapped the QTLs related to agronomic traits. The main results are as follows:1.Development of the CSSLsThe F1was developed by a cross using TM-1as the recipient parent and Sub16as the donor parent, and then F1was backcrossed two times with TM-1as recurrent parent. After that, the obtained individuals were successively selfed from BC2F1, BC2F2, BC2F2:3to BC2F2:4with molecular marker-assisted selection (MAS) by using the marker information on the constructed high-density interspecific genetic map of chromosome16in our lab. Thus, we obtained the CSSL16with22lines.We named the CSSL16lines from CSSL16-1to CSSL16-22. The developed CSSL16groups consisted of22lines and45introgressed segments in total. Of them,9were introgressed with single segment, accounting for41%of the total lines;8were introgressed with two segments, accounting for36%,5were introgressed with three and more segments, accounting for23%. The total length of introgression segments was257.81cM, which is1.98times of the genetic length of the chromosome16, covered92%of the genome of chromosome16. The substituted segment length varied in each line, ranging from the shortest of0.15cM to the longest of35.95cM, with an average length of5.7cM.2. QTL mapping related to agronomic traits by using CSSL16groupsAgronomic traits were investigated using TM-1, Sub16and22substitution lines, and carried out QTL tagging by joint positioning analysis. The agronomic traits are growth period, yield, fiber quality and seed traits. Twenty seven QTL with additive effect were identified. Among the27QTL,4QTL were related to growth period:one budding stage, two flowering stage, one boll opening stage;6QTL were related to yield:two seed index, two lint percentage, two boll number; one micronaire QTL related to fiber quality;16QTL were related to seed traits:one protein contain,13kinds of amino acids in each one, C18-1and C18-2each one. Further,109epistatic effect QTL were identified. The results will lay a foundation for the fine mapping and cloning of target QTL, important traits molecular design breeding in cotton. |
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