QTL Mapping For Agronomic Traits From The Chromosome Segment Substitution Lines Population Of G.mustelinum A Sub-genome In G.hirsutum Background

Cotton is the most important natural fiber crop,and also an oil and protein crop.The most widely cultivated Gossypium hirsutum exhibits high fiber yield,but the genetical basis of G.hirsutum is relatively narrow,which hinders the progress of genetic improvement of cotton.G.mustelinum is one of the five wild tetraploid cotton species,and has the advantages of resistance to Verticillium wilt,insect resistance and potential alleles with good fiber quality.It is of great importance to introgress the excellent traits genes from G.mustelinum to G.hirsutum for broadening the genetic basis of G.hirsutum,and improving yield traits and fiber quality traits in G.hirsutum.In this study,a BC₃F₂ chromosome segment substitution lines?CSSLs?population were obtained by backcrossing with G.mustelinum as donor parent and G.hirsutum?CCRI35?as recurrent parent.The SSR markers on A sub-genome in a linkage map constructed by our lab were selected to genotype the BC₃F₂ population,and the phenotypic data of BC₃F₂ and BC₃F_2:3:3 population were used to identify QTL for fiber yield and quality traits.The results provide a basis for excavating and locating the allelic traits of G.mustelinum and further improving the genetic basis of G.hirsutum.The main findings are as follows:1.G.mustelinum substitution segment of CSSL individualA total of 191 SSR markers,which evenly distribute on A sub-genome of the G.hirsutum and G.mustelinum genetic map,were employed to genotype 564 BC₃F₂individuals.The results showed that the chromosome substitution rate of the recurrent parent among the BC₃F₂ individuals was from 76.1%to 99.1%,and the average rate was 89.9%.One individual plant had no G.mustelinum chromosome substitution segment,the other plants contained the chromosome substitution segment number from 1 to 28,and the average substitution segment is 12.4;the total length of the donor substitution segment in BC₃F₂ individuals was ranged from 17.9cM to 476.4cM,which covered 0.9%²3.9%of A sub-genome,the average total length was 188.3cM and the average substitution rate was 9.4%.2?Substitution segment of G.mustelinum A sub-genomeThe chromosome substitution segments percentage of recurrent parent in the 13chromosomes of A sub-genome of the chromosome segment substitution line was from82.3%to 93.4%.Chr05 has the longest length was 230.0cM,and Chr04 has the shortest length was 54.0cM.The percentage of homozygous G.mustelinum chromosome substitution segments in the 13 chromosomes of A sub-genome of the chromosome segment substitution line was from 1.3%to 4.1%,Chr01 has the longest length of homozygous G.mustelinum chromosome substitution segment was 6.0cM,Chr04 has the shortest length of homozygous G.mustelinum chromosome substitution segment was 1.9cM;the percentage of heterozygous G.mustelinum chromosome substitution segments in the 13 chromosomes of A sub-genome of the chromosome segment substitution line was from 4.8%to 12.6%,Chr01 and Chr10 has the longest length of heterozygous G.mustelinum chromosome substitution segment was 18.4cM,Chr04 has the shortest length of heterozygous G.mustelinum chromosome substitution segment was 4.9cM;the percentage of total G.mustelinum chromosome substitution segments in the 13 chromosomes of A sub-genome of the chromosome segment substitution line was from 6.1%to 17.2%,Chr01 has the longest length of total G.mustelinum chromosome substitution segment was 25.1cM,Chr04 has the shortest length of total G.mustelinum chromosome substitution segment was 8.6cM.3.QTL mapping of fiber yield and quality traitA total of 34 QTL of fiber yield and quality trait were identified in BC₃F₂ and BC₃F_2:3:3 population,distributed on 12 chromosomes?A01-A12?,among which 17 QTL for yield traits?4 for boll weight,6 for lint percentage and 7 for seed index?,17 QTL for fiber quality?7 for fiber length,3 for fiber uniformity,3 for fiber strength,3 for fiber micronaire and 1 for fiber elongation?,LOD value ranged from 2.03 to 8.01,the additive effect was from-2.37 to 2.01,and account for phenotypic variance from 1.8%to 6.7%;In addition,5 QTL?qLP-A07.1,qLP-A08.1,qSI-A01.2,qFL-A03.1,qFM-A08.1?were proved to be stable in two populations.