QTL Mapping For Yield And Fiber Quality Traits From The Chromosome Segment Substitution Lines Of Gossypium Tomentosum

Cotton is an excellent economical crop.Gossypium hirsutum L.is widely planted in the world because of its high yield and strong adaptability,however,the fiber quality of upland cotton could be improved.Gossypium tomentosum is a wild specie with a few favorable traits such as high-density trichome,insect resistance,drought resistance and elite fiber quality.Therefore,introducing favorable alleles from G.tomentosum into G.hirsutum will be beneficial to cotton breeding.In the present study,the high yield upland cotton cultivar CCRI35 was used as the recurrent parent,and the G.tomentosum P0601211 was used as the donor parent to develope chromosome segment substitution lines（CSSL）.A total of 358 SSR markers were used to detect the genotypes of 559 individuals in the BC₃F₂ population.Combining with the phenotypic data of BC₃F₂ individuals,BC₃F_2:3 and BC₃F_2:4 lines,QTL mapping were identified for yield and fiber quality.The main results are as follows:1.Genotype analysis of CSSL individualsThe genetic background recovery rate of CSSL ranged from 76.3%to 97.3%,and the average recovery rate was 89.7%.The total length of introgression segments ranged from 67.9cM to 919.3cM,the average length of that was 377.5cM,accounting for 9.5%of whole genome.Among them,the average length of the homozygous segments is95.3cM,accounting for 2.4%of whole genome;the average length of the heterozygous segment is 282.2cM,accounting for 7.1%of whole genome.The number of introgression segments in individuals ranged from 5 to 74,with an average of 27.2 per individual.2.Genotype analysis of CSSL chromosomesAmong the 26 chromosomes,the genetic background recovery rate of each chromosome ranged from 77.1%to 96.4%,and the average recovery rate was 89.9%.The average length of introgression segment was 14.4cM,accounting for 9.2%of whole genome.Among them,the length of homozygous segment was between 0.9cM and9.8cM,with an average length of 3.6cM,accounting for 2.3%of whole genome;the length of heterozygous segment was between 3.2 cM and 28.2 cM,with an average length of 10.8 cM,accounting for 6.9%of whole genome.The length of Chr21 was the longest（38.0 cM）,and the length of Chr4 was the shortest（4.2 cM）.3.QTL mapping of yield and fiber quality traitsA total of 177 QTLs were detected,including 85 yield related QTLs（21 for lint percentage,40 for seed index,24 boll weight）,and 92 fiber quality related QTLs（28 for fiber length,16 for fiber uniformity,14 for fiber strength,20 for fiber micronaire,14 for fiber elongation）.The explaining phenotypic variation of these QTLs ranged from 1.7%to 12.6%.A total of 101 QTLs were detected in A subgenome and 76 QTLs were detected in D subgenome.Forty-two QTLs were detected in two environments（two for lint percentage,19 for seed index,one for boll weight,10 for fiber length,one for fiber uniformity,two for fiber strength,three for fiber micronaire,four for fiber elongation）,and 11 QTLs were detected in three environments（one for lint percentage,seven for seed index,two for fiber length,one for fiber micronaire）.The favorable allels of 80QTLs were contributed by G.tomentosum and the others were provided by CCRI35.