QTL Maping For Yield And Fiber Quality Traits From(G.hirsutum Cultivar × G.hirsutum Race Palmeri) RIL Population

Cotton is an important economic crop in China,and plays a pivotal role in national economy in our country.At present,the germplasm resources in G.hirsutum are scarce and the genetic basis is relatively narrow.There is a certain negative correlation between cotton fiber yield and quality,and it is difficult to simultaneously improve yield and quality.The use of distant hybridization,crossing the cultivated varieties of G.hirsutum with wild lines,and selecting and breeding offspring,can transfer the beneficial traits of wild species and wild lines to cultivated Gossypium hirsutum,thereby cultivating new cotton varieties.In this study,Gossypium hirsutum cultivar CCRI35 with high-yield and wide adaptability was crossed with G.hirsutum race palmeri accession TX-832,which has the characteristics of resistance to Verticillium wilt,cold tolerance,drought tolerance,etc.,and a recombinant inbred line population including 182 lines was developed.The SNP identified by SALF-seq and SSR markers were used to construct a high-density genetic map for the RIL population,and the yield and fiber quality traits collected from six Environment were applied to detect QTL.The main findings are as follows:1.Genetic map constructionThe 15765 SNP markers obtained by SLAF-seq sequencing and the 153 SSR markers with polymorphisms between the parents,a total of 15918 markers,were used to construct a genetic map with mapping software,and the co-separation markers were integrated.A genetic map containing 3311 polymorphic loci,which covered 4690.73c M（A-subgroup 2603.84 c M,and D-subgroup 2086.90 c M）and occupied approximately 95.97%of G.hirsutum genome,was constructed with an average distance between adjacent marker of 1.46c M.There are totally 3158 SNP lociand153SSR loci.Among them,1758 loci（1679 SNP loci,79 SSR loci）located on the A subgenome and 1553 loci（1479 SNP loci,74 SSR loci）located on the D subgenome.2.Performance of yield and fiber quality traitsThe F_2:6 recombinant inbred lines had a wide range of variation in yield related traits and fiber quality traits,and these traits showed continuously and normally distribution.At the same time,the population showed obvious super-parental segregation in the traits including boll weight,seed index,lint percentage,lint index,fiber length,fiber uniformity and fiber strength.Correlation analysis showed that a significant or extremely significant positive pairwise correlation exists among seed index,lint index,boll weight,fiber length,fiber strength,fiber uniformity,and fiber elongation in at least one Environmentironment.Specially,fiber micronaire,lint percentage and lint index showed a very significant positive pairwise correlation in all the six Environment.3.QTL mapping for yield and fiber qualityUsing the constructed high-density genetic map,a total of 248 QTL,including180QTL for five fiber quality traits and 68 QTL for four yield traits,were identified on 26chromosomes.Sixty-eight QTL for yield traits included 30 boll weight QTL,10 lint index QTL,15 lint precentage QTL,and 13 seed index QTL.The LOD values ranged from 2.5 to 10.57,explaining 6.2%-23.5%of the phenotypic variation.One hundred and eighty QTL for fiber quality include 55 QTL for fiber length,45 QTL for uniformity,51 QTL for fiber strength,9 QTL for fiber micronaire,and 20 QTL for fiber elongation.The LOD value ranges from 2.5 to 15.31,explaining 6.1%-33.8%phenotypic variation.Fifty-seven QTL detected in three or more environment,q LPA07.1 existed stably in all six environment,explaining the phenotypic variation of 6.4%-11.8%,and the favorable allele came from CCRI35;q FMD03.1 was detected in four environment,explaining10.5%-33.8%of the phenotypic variation,and the favorable allele came from CCRI35.One hundred and fifty-four QTL distributed in 42 QTL-clusters on 23 chromosomes except for A06,D02,and D06.These stable QTL and QTL clusters lay the foundation for research on candidate gene cloning and functional analysis.