Mapping QTL For Yield And Fiber Quality Traits In Gossypium Barbadense Chromosome Segment Substitution Lines With Gossypium Hirsutum Background

Cotton plays an important role in the national economy and the people's livelihood.China is the world's largest cotton producer and consumer.With the rapid improvement of people's living standards,the rapid development of industry and agriculture,and the reform of market policies,the demand for cotton is increasing.The requirements for high-quality cotton fiber are also more and more urgent.Gossypium hirsutum and Gossypium barbadense are two of the tetraploid cultivars.Among them,the yield of G.hirsutum is high,accounting for 97%of the total cotton fiber in the world,but the fiber quality is weak.G.barbadense with weak fiber yield and high fiber quality,which is the textile raw material of high-count yarn.It is the common goal of breeders to introgress the excellent genes of island cotton into the upland cotton and cultivate new cotton varieties with high yield and high quality.In this study,island cotton line C084-220 was used as the recurrent parent,and the high yield upland cotton cultivar CCRI 35 as the recipient parent.A chromosome segments substitution lines?CSSLs?containing 523 individuals was developed,and a total of 164 SSR markers were used to genotype the CSSLs population.QTL for yield and fiber quality traits were identified in BC₃F₂ individuals,BC₃F_2:3:3 and BC₃F_2:4 lines population.The main results are as follows:1.Genotype of CSSLs individualThe genetic background recovery rate of the CSSLs was between 53.2%and99.4%,and the average recovery rate was 87%.The number of introgression segments was between 2 and 40,with an average number of 17.4.The total length of the introgression segments was between 11.1 cM and 868.4 cM,with the average of 235.5cM,and the average introgression rate was 12.7%.2.Genotype of CSSLs chromosomeThe background recovery rate of each chromosome of the CSSLs was between82.8%and 90.4%,with an average of 86.6%.Chr11 has the largest background recovery rate,and the Chr4 was the smallest.The average length of the homozygous introgression segments of the island cotton C084-220 contained in each chromosome of the CSSLs was between 3.5 cM and 7.8 cM with the average introgression rate of 4.8%.The homozygous introgression segments of the Chr8 was the shortest,and the Chr5 has the longest homozygous introgression segments.The average length of the hybrid introgression segments in each chromosome was ranged from 8.5 cM to 25.1 cM,and the average introgression rate was 9.4%.Chr8 has the shortest hybrid introgression segments,and the Chr5 was the longest.The average length of the total introgression segments in the 13 chromosomes of the CSSLs is between 11.9cM and 33.0 cM,where in the Chr8 contains the shortest total introgression segments,and the Chr5 contains the longest total introgression segments.3.QTL mapping of yield and fiber quality traitsA total of 41 QTL were detected in the BC₃F₂ individuals in 2016,BC₃F_2:3population in 2017 and BC₃F_2:4 population in 2018,including 7 seed index QTL,12 lint percentage QTL,7 fiber length QTL,5 fiber strength QTL,1 fiber uniformity QTL,3micronaire QTL and 6 fiber elongation QTL.The 41 QTL were distributed on 11Chromosomes of A sub-group,explaining the phenotypic variation of 1.9%-7.6%,and the LOD is between 2.01 to 5.57.Of the 41 QTL,4 QTL existed in two environments,and these QTL included 1 lint percentage QTL,1 fiber length QTL,1 fiber strength QTL and 1 micronaire QTL.Two lint percentage QTL existed in three environments.Twenty-eight QTL favorable alleles origined from CCRI 35,and the favorable alleles origined from C084-220.