QTL Analysis Of Fiber Quality And Resistance To Verticillium Wilt Using G. Hirsutum×G. Barbadense Backcross Populations

In order to Introgress elite QTL alleles of G. barbadense L. for fiber quality and resistance to verticillium wilt into G. hirsutum L. and enlarge the narrow genetic base of G hirsutum and provid more new gerplasm resource for the variety development, the elite G. hirsutum variety 'Zhongmiansuo36' and G barbadense 'Hail' were respectively used as recurrent and donor parent to produce backcross populations, including the 1st (BC₁F₁ and BC₁S₁) and 2nd(BC₂F₁) backcross generations. QTL analysis of fiber quality, yield-related trait and verticillium wilt resistance trait on three phenotypic data sets were proceeded by Composite Interval Mapping.Most of fiber quality traits, yield-related traits and verticillium wilt traits fit the normal distribution in the Kolmogorov-Smirnov test. Fiber length had significantly positive correlation with fiber strength and negative correlation with micronaire, seed index had significantly positive correlation with boll weight and negative correlation with lint percentage, lint percentage had negative correlation with fiber length and strength. These correlations could be genetically explained by QTLs co-location in this experiment.A total of 1123 SSR primer pairs were used to screen polymorphism among two parents Zhongmiansuo36 , Hail and their F₁ progeny, which resulted in 357 polymorphic primer pairs, and 226 of them were used to screen the BC₁F₁ population. Linkage test indicated 220 of 239 locus derived from 226 primer pairs could be mapped to 32 linkage groups and covered a total genetic distance of 2408cM, approximately 40% of cotton genome.The average distance of markers were 10.9cM. 26 of all linkage groups were assigned to corresponding chromosome.38 QTLs for fiber quality traits were mapped in three generations. QTL numbers for fiber length, strength, micronaire, uniformity and elongation ratio were 11, 7, 6, 8, 6, respectively. Each QTL could explain 6.8 % 18.5 % of phenotypic variance. Three fiber length QTLs and one micronaire QTL could be detected in two of three generations.19 QTLs for yield-related traits were mapped in three generations using CIM. QTL numbers for lint percentage, boll weight and seed index were 11,2 and 6, respectively. Each QTL could explain 7%²3.7% of phenotypic variance, one QTL for lint percentage could be detected on the same position of LG24 in the three generation and other 3 QTLs for lint percentage on the different linkage group in two of the three generations, which indicate that these QTLs should have stable genetic effect under different genetic backgrounds and could be used for marker assisted selection.23 QTLs for verticillium wilt were mapped in BC₂F₁ and BC₁S₁ generations. QTL numbers for disease index and ratio of susceptivity were 17 and 6, respectively. Each QTL could explain 6.4% 24.5% of phenotypic variance. One QTL for disease index on the linkage LG17 with 0.03cM away from the nearest loci could be detected in BC₂F₁ from verticillium wilt nursery evaluation and 2 generations of BC₂F₁ and BC_S1 from the field condition, which could explain 24.5% of phenotypic variance at most, which showed the stable genetic effects for resistance to verticillium wilt. This resistance allele was derived from the sea island cotton parent and could be used for marker assisted breeding.