Construction Of Chromosome Segment Substitution Lines And QTL Mapping Of Lint Percentage In A Sub-genome Of Gossypium Barbadense

Cotton,the world's important natural fiber crops,is an indispensable raw materials on cotton textile industry.With the rapid development of Chinese economy,it is urgent necessary to improve cotton production and fiber quality.There are four cultivated species of cotton,of which upland cotton(Gossypium.hirsutum)and island cotton(Gossypium.barbadense)account for more than 97% of the world's total cotton production.Upland cotton is characterized by high fiber yield and moderate fiber quality.However,island cotton is characterized by low fiber yield and good fiber quality.It is essential for improving fiber quality in upland cotton that transmission of favorable alleles from G.barbadense into G.hirsutum.In this study,CCRI35 was used as the recipient parent,and Pima_S7 used as the donor parent.we developed a set of CSSLs through molecular assisted-selection in BC3F2 generations.QTLs of lint percentage were mapped by BC3F2 individuals and BC3F2:3 families.The main results were summarized as follows:1.Analysis of substitution fragment of BC3F2According to the genetic map constructed in the laboratory,the genotypes of 591BC3F2 individuals were detected by 183 SSR markers distributed on the A sub-genome.The results showed that the chromosome background response rate of recurrent parent in the BC3F2 individuals ranged from 67.9% to 100%,with an average of 92.3%.The lowest number of substituted segment is 1,the laegest number is 12,with an average number of 4.2.Among them,9 individuals were detected without G.barbadense chromosome introgression fragment,37 plants with one introgression fragment,and 66 plants with 2 introgression fragments.The total length of the replacement fragment was mainly distributed between 100 cM and 300 cM,accounting for 67.0% of the population.The average length of subsitituted segments is 148.4cM.2.Analysis of substitution fragment of A sub-genomeThe recovery rate of each chromosome recurrent parent is higher,with an average of 91.7%;the chromosome 7(chr.7)is the largest and reaches 94%;the chr.4 is the lowest and reaches 89.4%.The average length of the homozygous fragments on each chromosome is between 1.5cM and 10.6cM,with an average of 3.1cM.The average length of the hybrid fragments is between 3.3cM and 13.6c M,with an average of 8.0c M.The average length of the total fragment on each chromosome is between 7cM and21.3cM,the mean is 11.1cM.Chr.7,Chr.8,Chr.10,Chr.12 and Chr.13 coverage ratereached 100%.Chr.1,Chr.2,Chr.3,Chr.5,Chr.9 and Chr.11 of deletion rate is0.5%-4.4%.The deletion rates of Chr.4 and Chr.6 were 8.4% and 7.1%.3.QTL mapping of lint percentageBase on the update genetic map and the phenotypic data of lint percentage in two environments(2015 and 2016).7 QTLs for lint percentage were detected.These QTL located on Chr.1,Chr.5,Chr.6,Chr.7,Chr.11,Chr.12 and Chr.13.They explained phenotypic variation from 2.1% to 3.9%.Six favorable alleles of QTL derived from CCRI35,and one favorable allele derived from Pima_S7.