Identification Of Favorable Alleles Of QTL For Yield And Fiber Quality Traits Of Gossypium Barbadense

Cotton is an important economic crop and also a major natural fiber crop in China,which is widely distributed.Driven by the continuous improvement of living standards and textile technology,higher requirements have been placed on the output and quality of cotton fibers.Gossypium hirsutum,known as upland cotton,has the characteristics of high yield and strong adaptability.It is currently the most widely cultivated cultivar in the world,accounting for about 95%of the world's cotton fiber.Gossypium barbadense?island cotton?possesses excellent fiber quality,of which the length,fineness and strength are more prominent than G.hirsutum.However,the yield of G.barbadense is lower than G.hirsutum.By introgressing favorable genes from island cotton to upland cotton,thus broadening the genetic background and improving the agronomic traits such as fiber quality and yield of upland cotton.In this study,cultivar C084-220 of G.barbadense and cultivar CCRI35 of G.hirsutum were used as parent materials to construct CSSLs population,which composed523 individuals.The SSR markers were selected on the D sub-genome of the genetic map constructed in the early stage of the lab to detect the genotype of each individual,and investigating phenotypic of yield and quality traits from the BC3F2,BC3F2:3,BC3F2:4and BC3F2:5 population.Combining the genotype data of A sub-genome in the lab with the genotype data of D sub-genome in this study,as well as the phenotypic data of four groups,the QTLs for the yield and fiber quality traits were identified.The main findings are as follows:1.Genotype analysis of individual in CSSLsAccording to the genotype detection result of BC3F2 population,the substitution segments of each individual were analyzed using GGT software.The result showed that the average recovery rate was 86.08%,the genetic background recovery rate of 523individuals was from 54.60%to 97.80%,and 83.2%individuals background recovery rate reached more than 80%.The total length of substitution segments range from10.95cM to 826.91cM,the average total length was 246.45cM,and the average substitution rate was 13.50%.All 523 individuals contained C084-220 chromosome segments.The number of substitution segments with each individual was from 2 to 41,and the average number of substitution segments was 19.64.2.Genotype analysis of chromosomes in CSSLsThe average genetic background recovery rate of each chromosome was 86.2%,and the average background recovery rate was from 81.2%to 90.9%.The length of upland cotton segments in Chr19 was up to 179.0cM,and the length of upland cotton segments in Chr18 was the least 79.8cM.The homozygous segments of island cotton in chromosomes were from 2.8cM to 9.9cM,of which Chr21 contains the longest homozygous segments,Chr22 contains the shortest homozygous segments,and the percentage of homozygous segments of island cotton is from 2.1%to 4.9%,the average substitution rate is 3.5%.The heterozygous segments of island cotton in chromosomes were from 9.5cM to 26.7cM,of which Chr21 contains the longest heterozygous segments,Chr26 contains the shortest heterozygous segments,and the percentage of heterozygous segments of island cotton is from 6.8%to 13.2%,the average substitution rate is 10.0%.The total substitution segments of island cotton in chromosomes were from 12.8cM to 36.6cM,of which Chr21 contains the longest total substitution segments,Chr26 contains the shortest total substitution segments,and the percentage of heterozygous segments of island cotton is from 9.2%to 18.1%,the average substitution rate is 13.4%.3.QTL mapping for yield and fiber qualityA total of 126 QTL for yield and fiber quality trait were detected in the BC₃F₂,BC₃F_2:3,BC₃F_2:4:4 and BC₃F_2:5:5 population,which contain 49 QTL for yield traits?32 QTL for lint percentage and 17 QTL for seed index?,and 77 QTL for fiber quality?20 QTL for fiber length,10 QTL for fiber uniformity,16 QTL for fiber strength,12 QTL for micronaire and 19 QTL for fiber elongation?,LOD values ranged from 2.0 to 25.9,and the explaining phenotypic variation was from 1.8%to 21.2%.A total of 24 QTL were detected in multiple environments.The favorable alleles of 50 QTL derived from C084-220,and 76 QTL derived from CCRI35.4.QTL clustersIn this study,14 QTL clusters were identified on 10 chromosomes,5 and 9 of them were distributed in the A and D sub-genomes,respectively.Three QTL clusters were detected on Chr08,two QTL clusters were detected on Chr14 and Chr21,and one QTL cluster was detected on each of the remaining chromosomes.These QTL clusters contain a total of 48 QTL,of which 12 QTL were stable in multiple environments.