Genetic Dissection Of Excellent Fiber Quality In Upland Cotton(Gossypium Hirsutum L.)Germplasm With Introgression Genetic Elements From Island Cotton(G. Barbadense L.)

Upland cotton, Gossypium hirsutum L. which dominates the world’s cotton fiberproduction, has high lint yield but undesirable fiber quality. However, island cotton (G.barbadense L.), another cultivated allotetraploid cotton species, has superior fiberquality but lower lint yield. Extensive efforts have been put into doing successfulwide-cross between upland cotton and island cotton in order to enhance the fiberquality of upland cotton. Unfortunately, improvement directly through interspecifichybridization has proven to be very difficult due to the excessive segregation ofinterspecific progenies. However, a series of germplasms (introgression lines) withimproved fiber quality containing chromosomal introgressions from island cottonhave been created. But most introgression lines with superior fiber quality also havesome unfavorable alleles affecting lint yield introgressed into the genome. Thisnegative association between lint yield and fiber quality is known as linkage drag andhas proven difficult to break by traditional breeding methods. Molecular markersprovide a useful approach for fine dissection of these exogenous useful genomiccomponents related to fiber quality and selection of economically important traits incotton.Luyuan 343 is an introgression line with excellent quality fiber geneticcomponents from island cotton, while Lumianyan 22 is a Bt cotton varietycharacterized by desired agronomy traits. In this study, genetic linkage map wasconstructed with the polymorphic SSR markers using a mapping populationconstructed by Luyuan 343 and Lumianyan 22. A relatively fine mapping of the locirelated to fiber quality was carried out based on accurate identification ofintrogression fragments in genome.1. Genomic DNA of Lumianyan 22, Luyuan343, F1 and F2 population wasisolated. A total of 7470 pairs of SSR primer were used to screen polymorphismbetween Lumianyan 22, Luyuan343 which resulted in 136 pairs of polymorphic primer, and the polymorphism primer pairs accounted for 1.82 percent of the total.There were 119 co-dominant markers which accounted for 87.5 percent of thepolymorphic markers, and other 17 markers were dominant markers. Based on theprevious work in our lab, a total of 366 of polymorphic markers were applied toanalyze the marker genotypes of all 209 individuals of the F2 population.. Linkagegroup were constructed by JoinMap3.0. Among the total 366 polymorphic markers,334 polymorphic loci could be mapped into 43 linkage groups and covered a totalgenetic distance of 1779.2 cM, approximately 34.23 percent of cotton genome.2. To determine the introgression fragments from Sea Island in luyuan343, all ofthe 334 polymorphic primer pairs in linkage groups were served to compare theirPCR bands among the two parents, TM-1, which is widely used as the standardgenetic line of upland cotton and Ashimouni, which is the donor Sea Island cottonparent of the introgression line, Luyuan343. Total of 144 introgression marker lociwere detected, which were distributed in 24 linkage groups and covered a total geneticdistance of 440cM, approximately 8.46 percent of cotton genome. Most ofintrogression fragments and introgression loci were proved to be distributed inchromosome 16, chromosome 2and chromosome 23.3. Total of 24 QTLs associated with fiber quality were detected with softwareWinQTLCartographer2.5 by Compose Interval Mapping (CIM) method in three datasets, F2, F2:3LQ and F2:3HN. Four QTLs were associated with fiber length, twoQTLs were related to fiber uniformity, and three QTLs were for fiber micronaire andseven were for fiber elongation. The numbers of QTL for lint fiber strengthpercentage and lint percentage were three and five respectively. The QTLs wereanchored in chromosome 2, chromosome 7, chromosome 16, chromosome 17, andchromosome 23, which tended to be clustered in a special chromosomal region.qFS-C7-1, which explains 26.21%, 25.58% and 13.74% of phenotype variation andthe efficiency genotype comes from Luyuan 343, can be detected in three data sets,and qLP-C17-1, whose efficiency genotype comes from Lumianyan 22, explains15.52%, 14.88% and 7.97% of phenotype variation in three data sets respectively.4. Eighteen of QTLs were detected to be associated with introgression fragmentsand introgression loci, accounted for 75 percent of total QTLs in this study, including four QTLs for fiber length, two QTLs for Micronaire value, five QTLs forfiber elongation, three QTLs for fiber strength and four QTLs for lint percentage.Therefore, we were concluded that the majority of genetic components conferredfavorable contributions on excellent fiber quality in the genome of introgression lineof upland cotton were the introgression chromosomal fragments or intrgression locifrom Sea Island cotton. Further identify the introgression genomoic components andconsequently evaluate their genetic effects on fiber quality related traits by molecularmarkers will be great benefit on MAS in upland cotton breeding.