The Evaluation And Identifying QTL Of Fiber Yield And Quality Traits Of Chromosome Segment Substitution Lines (Bc₅F₃、BC₅F_3:4、BC₅F_3:5) In Upland Cotton

Upland cotton （Gossypium hirsutum） with high fiber yield and wide adaptability has the weaknessof narrow genetic basis and weak fiber quality. It is very important for enlarging the genetic germplasmand cotton genetic improvement to introgress the excellent traits and genes resistant to verticillium to G.hirsutum from G. barbadense. In the study, CSSLs （Chromosome Segment Substitution Lines） werederived from combination of early-maturing variety CCRI36（Chinese Cotton Research Institute36,Gossypium hirsutum） as the recurrent parent and hai1（Gossypium barbadense） as the donor parent.BC₅F₃individuals were selected to evaluate the phenotypic traits related to yield and fiber quality inBC₅F₃:4and BC₅F_3:5line populations. Total of408BC₅F₃individuals were detected by SSR markers foridentifying the donor chromosome fragments and QTL for fiber yield and quality related traits, whichlayed the foundation for further QTL fine mapping and molecular-assisted breeding.1. A great deal of materials superior to the recurrent parent CCRI36were acquired throughphenotypic analysis of fiber yield and quality traits in the BC₅F₃individuals in2009, BC₅F₃:4linesin2010and BC₅F_3:5lines in three environments （Anyang in Henan province, Shihezi in Xinjiangprovince and Liaoyang in Liaoning province） in2011. The transgressive rate over the recurrent parentCCRI36for fiber length were34.96%,54.86%,47.57%,68.87%,62.75%, and58.09%respectively inall populations(BC₅F₃individuals, the selected BC₅F₃individuals, BC₅F₃:4lines and BC₅F_3:5lines inthree environments); the highest fiber length for BC₅F_3:5lines reached to33.96mm in Liaoyang. Thetransgressive rate over the CCRI36for fiber strength in the all populations were22.76%,48.48%,40.27%,45.58%,47.59%, and46.08%respectively; the highest fiber strength for BC₅F_3:5lines reachedto34.00cN/tex in Liaoyang. The transgressive rate for micronaire with the data from3.7to the recurrentparent CCRI36in BC₅F₃:4lines and BC₅F_3:5lines were from48.63%to72.55%. The transgressive ratesover the CCRI36for boll weight and lint percentage in all populations were from14.93%to50.50%and from12.25%to71.78%, respectively.2.210pairs of SSR markers selected from12linkage groups were used to detect the genotype of the408selected BC₅F₃individuals. The results showed that the genetic background of the BC₅F₃individuals was almost returned to the background of CCRI36in detected ranges. The chromosomesubstitution rate of the recurrent parent CCRI36was from83.8%to100%in the BC₅F₃individuals, theaverage rate was97.5%; the average length from the donor parent hai1chromosome fragments was51.4cM in BC₅F₃individuals, which covered2.5%of the tested length; the average length forhomozygous hai1chromosome fragments was18.5cM, which covered0.9%of the tested length; theaverage length for heterozygous hai1chromosome fragments was32.8cM, which covered1.6%of thetested length. In detected ranges,46（11.27%） plants had no hai1chromosome introgression fragment,76（18.63%） plants had one introgression fragment, and57（13.97%） plants had two introgressionfragments, and229（56.13%） plants had three or more introgression fragments.3. QTL for fiber yield and quality related traits were detected in BC₅F₃individuals, BC₅F₃:4lines,BC₅F_3:5lines in three environments by the software of QTL IciMapping V3.2（LOD=2） with CSL function. Total of41QTL controlled fiber quality traits were detected, and a single QTL could explainfrom2.50%to7.31%of phenotypic variance. Total of50QTL controlled fiber yield-related traits weredetected, and a single QTL could explain from2.50%to6.15%of phenotypic variance. A total of27QTL could be detected in two or more populations or environments. The13QTL （one for fiber length,fiber uniformity, micronaire, boll weight, lint percent and bolls per plant, respectively; two for fiberelongation and plant height, respectively; three for seed index） could be detected in two populations orenvironments, eight QTL （one for fiber length, lint percent and seed index, respectively; two for bollweight; three for fiber elongation） could be detected in three populations or environments, six QTL （onefor fiber length and seed index, respectively; two for boll weight and lint percent, respectively） could bedetected in four populations or environments. These QTL detected in different populations andenvironments could be used for molecular assistant breeding.4. Total of15plants （lines） which contained1-14hai1chromosome fragments, showed stability inthree generations for fiber quality, most of them with fiber length and fiber strength over30mm and30cN/tex. These CSSLs with excellent trait genes from G. barbadense could be used for selecting singlesegment substitution lines （SSSLs）, QTL fine mapping and pyramid breeding.