Construction Of Molecular Linkage Map And QTL Mapping Of Cultivated Allotetraploid Cotton(Gossypium Hirsutum L.x Gossypium Barbadense L.)

Intraspecific narrow genetic base has become a main problem for genetic improvementof Gossypium hirsutum L. Transmission of valuable genes extensively and efficiently betweenG.hirsutum L. and G.barbadense L. is essential for their breeding improvements, which islimited mainly by linkage drag. High density genetic map provides a firm framework not onlyfor gene loci tagging, marker-assisted selection to reduce linkage drag and map-based cloningof important genes, but also for investigation of genomic structure and evolution of cotton.Based on a BC1 population from cross between G. hirsutum L.× G. barbadense L., a combinedSSR-SRAP genetic map of tetraploid cotton was constructed and QTL mapping wasperformed. The main results were summarized as follows: 1.A BC1 mapping population of 140 individuals between G. hirsutum L. cv TM-1 × G.barbadense L. cv Hai7124 was developed by backcrossing TM-1 to an individual plant of(TM-1×Hai7124)F1. The distribution of the TM-1 genotype frequency of 774 polymorphicloci indicated the BC1 mapping population was normal on the whole and suitable for mapconstruction. 2. A total of 542 of 1386 SSR primer combinations analyzed identified polymorphismbetween TM-1 and Hai7124. Due to backcrossing, 21 dominant loci from TM-1 were notcapable of being used in our BC1 mapping population. The rest 521 polymorphic primer pairsamplified 634 marker loci. 66 SRAP primer combinations that amplified clear and stablepolymorphism between the two parents were used in population analysis and generated 140marker loci. A total of 774 marker loci were used to construct genetic linkage groups usingMapmaker/EXP version 3.0b software with LOD value of 8.0 and maximum distance of 30.0cM. The resulted BC1 map comprised of 694 marker loci mapped into 37 linkage groups withan average distance between adjacent markers of 8.7cM (Kosambi, K) and covered 6032.3cM.A single linkage group of this map comprised of 2 to 40 marker loci and covered 2.1 to III364.3cM, with an average distance between markers from 1.05 to 12.44 cM. 3. A set of monosomic and telodisomic lines for 20 of the 26 gametic (1-3, 5-7, 9-12,14-18, 20, 22, 23, 25 and 26) chromosomes of tetraploid cotton were used to assign linkagegroups to chromosomes. Among the 37 linkage groups, 27 were assigned to 20 chromosomes.Eight of the rest linkage groups were associated to A or D sub-genome by analysis the markerloci in the representative A and D diploid species, G. herbaceum L and G.raimondii, and 2small linkage groups unassigned. The yellow pollen gene locus (P1) and the petal spot genelocus (R2) from Hai7124 were mapped to chromosome 7 and chromosome 5, respectively.Distribution analysis of duplicated marker loci among chromosomes bridged 12 of 13 pairs ofhomoeologous chromosomes of tetraploid cotton. 4. Among the 774 polymorphic marker loci, 77 loci showed distorted segregation, ofwhich 49 marker loci were mapped onto the linkage map. Deviated markers distributedunevenly across chromosomes or linkage groups and sub-genomes. More distorted markerloci were mapped into A sub-genome (78%) than D sub-genome (22%). Obvious clusters ofdeviated marker loci, which accounting for 65.4% of mapped deviated loci, were investigatedon chromosome 2, 3 and 7 and linkage group A01. These chromosomal regions might containsegregation distortion regions (SDR). 5. Based on the newly constructed genetic map of tetraploid cotton, QTL mapping andanalyzing of fiber quality traits, leaf morphology traits and leaf chlorophyll content wereperformed with composite interval mapping (CIM) method using phenotypic data from BC1and BC1S1 progenies. Twenty three QTLs for fiber quality traits were detected on 13chromosomes or linkage groups. Twenty nine QTLs for leaf morphology were detected on 15chromosomes or linkage groups and QTLs for leaf chlorophyll content were mapped onchromosome 28 and chromosome 20. Closely linked makers to objective tra...