Molecular Tagging And Location Of QTL For Resistance To Disease And High Yeild Breeding Traits In Upland Cotton

As a major source of fibers,cotton is an important economic crop and plays an important role in the global economy.The technology of "short,dense and early"(short plant height,dense populations and earlier maturity) accelerated the development of Xinjiang cotton production.The cotton in Xinjiang covered about 20%of the total cotton area in China and contributes nearly about 33%to the national cotton yeild.Fusarium wilts and Verticillium wilts are the main diseases of cotton in the world.The incidence area of Fusarium wilt reached to 46 thousand hectare in 1995 according to the survey of the plant protection station in Xinjiang.At present,the majority of the varieties from nurtures in Xinjiang were not resistance to Fusarium wilt and Verticillium wilts.How to enhance the resistance of variety to disease has become the important factor for breeder.Selection breeding and planting cultivars of resistance to the disease were the most economical effective solution to the problem.As breeding a new cultivar through the traditional ways needed a long period,which didn't meet the stringent demand of production.Traditional selection breeding is more dependent on the phenotypic of crop.Phenotypic traits marker --plant height,grain color,shoot yellow,ears--have been taken important action in tradition breeding.In this study,the objective of this research is to screen the stable QTL related resistance and agronomic traits basing on different populations under the technology with "short,dense and early" and these QTLs will be used effectively for MAS during the process of breeding in the future.1,Genetic Diversity among Xinjiang Upland Cotton Cultivars Based on EST-SSR MarkersThe genetic diversity among Xinjiang 50 upland cotton cultivars was investigated based on EST-SSR.A total of 91 bands with polymorphism had been detected in these cultivars by screening the 42 EST-SSRs loci.Based on EST-SSR data,the coefficient of similarity among 50 upland cotton cultivars was calculated varying from 0.11 to 0.83.It was indicated that the more genetic diversity among those cultivars was presented,while genetic diversity in same origin in Xinjiang had been narrowed.The 50 cultivars can be divided into two subgroups based on the coefficient of similarity,and most of the tested cultivars were consistent with their pedigree.It was testified that EST-SSR markers derived directly in transcribed:regions of the genome,provide a more-direct estimate of genetic diversity of cotton cultivars.2,QTL Mapping of Genes Resistant to Verticillium Wilt In Xinjiang Upland CottonTwo molecular mapping F₂ populations were derived from the intraspecific cross of the highly tolerant G.hirsutum cv.(Xinluzhong10) and the susceptible G.hirsutum cv. (Junmianland Xinluzhao7).A total of 5400 simple sequence repeat(SSR) primer pairs were screened over resistant and susceptible parents.The first map comprises 62 loci mapped to 15 linkage groups covering 593.6 cM of the genome.The second genetic map comprises 78 loci mapped to 20 linkage groups covering 830.2 cM of the cotton genome. The two mapping F₂ population were used to analyze quantitative disease-related trait loci (QTLs).The two mapping F_2:3 families were phenotyped with a non-defoliating V.dahliae. A total of 8 QTLs across two populations and two disease development periods were detected by Composite Interval Mapping(CIM).Four QTLs of resistance to V.wilt were detected on four linkage groups and explained 59.1%,63.5%,13.6%and 26.9%of the phenotypic variance with LOD＞3 respectively.The other four QTLs were detected on two linkage groups,with LOD peaks ranging from 2.6 to 21 and explained 7.3%,56.9%,32.7%, and 7.18%of the phenotypic variance.This might mean that the resistance of V.wilts was controlled by polygene.Three QTLs located on the position of chromosomes 13,which is nearer the marker NAU1211,had large effect,it might be the same QTLs.In comparison with previously published data,some QTLs related to V.wilt localized on the five chromosomes(Chr.5,Chr.9,Chr.13,Chr.15 and Chr.20) were localized in similar regions or homeologous regions as previously reported QTLs.Those QTLs can be used effectively for MAS during the process of breeding in the future.3,Mapping of Genes Resistant to Fusarium Wilt of Upland Cotton in XinjiangFusarium wilt is a serious disease in most cotton growing areas of the world.The identification of resistance genes is critical for developing sound breeding strategies.In this study a genetic linkage map was constructed using 173 F₂ individuals developed by acrossing two elite lines of Upland cotton(Zhongmiansuo35 and Junmian1) as parents.The maps with 75 loci were covered 743.1cM length of the cotton genome.Phenotype of F₂ population to disease-related trait was evaluated by Phenotype of F_2:3 families.In the assessment of individual phenotype of disease resistance as dominant marker,the gene of resistance to Fusarium wilt were located on Chr.17 groups by linkage map analysis using bridge markers.In 2004 a new genetic linkage map was constructed by acrossing the same two elite lines of Upland cotton.The result still suggested that one major QTL with the resistance to Fusarium wilt were tightly linked to JESPR304.Another genetic linkage map was constructed using 160 F₂ individuals developed by acrossing two elite cultivars of Upland cotton,"Changrong",highly sensitive to wilt and "Sumian10",highly resistant to wilt.One major gene detected with resistance to Fusarium wilt was tightly linked to JESPR304 with 0.80cM genetic interval distance and explained the phenotypic variance of 19.9%.In order to detect the degree of linkage between the resistance gene and JESPR304, 40 susceptible Upland cotton cultivars and 86 resistant Upland cotton cultivars were screened using JESPR304.The results showed there is intensely linkage between the resistance gene and JESPR304.Using composite Interval Mapping method a total of five QTLs resistant to Fusarium wilt were detected on four linkage groups(Chr.7,Chr.15,Chr.23,Chr.17) in Zhongmiansuo35 and Junmian1 population.One major QTL with resistance to Fusarium wilt showed to be tightly linked to JESPR304 with 0.06 to 0.2cM genetic interval distance,and it explained over 50%of the phenotypic variance.The gene /QTL will be of great significance in breeding and molecular marker-assisted selection.4,QTL Mapping of Yield Components for Main Cultivars Planted of Upland Cotton in XinJiangWe used three above-mentioned molecular linkage maps for characterizing quantitative trait loci(QTLs) determining yields related traits of cotton which can provide DNA molecular markers to be used in cotton improvement.The three molecular linkage maps shared same 22 pairs of SSR primers,covered all of the cotton genome except chromosome 2 and chromosome 26.Under Xinjiang "short,dense and early" planted condition,16 possible QTLs of yield related traits(Lint yield,Lint percentage,Boll size, Seed index) were suggested with LOD＞2.0.Five seed index QTLs were located on chromosome1,5 and 7;Five lint percentage QTLs were located on chromosome7,13 and LG6;Five boll size QTLs were located on chromosome7,17;One lint yield QTL were located on chromosome17.As nine correlated QTLs of boll size,seed index and lint percentage were located on chromosome7,it was clearly that these QTLs were distributed on same or neighbor position and would play important significances on breeding.All of unlinkaged markers of the three maps were surveyed using single marker analysis method and 8 marker related to yield traits were suggested with LOD＞2.0.In comparison with previously published data,the seed index QTL were assigned to the chromosomes Chr.1 andCh r.5in this paper were the same as previously published reports.The rest QTL on the level chromosomes(Chr.7,Chr.13) were different from previously published reports.5,QTL Mapping of some Plant Morphological Traits for Main Cultivars of Upland Cotton Planted in XinJiangWe used the above-mentioned molecular linkage maps for characterizing quantitative trait loci(QTLs) determining cotton morphological traits.Under Xinjiang "short,dense and early" experiment condition,four morphological traits—plant height,the first Fruit nodes, main-lobe length(L1),second-lobe length(L2)—were studied,15 possible QTLs/loci which had LOD＞2.5 were suggested.Two first Fruit nodes QTLs were identified on Chr.5 and Chr.7.Three plato height QTLs were located on Chr.13,Chr.25 and Chr.17,and two of its alleles were originated from the male parent.Ten QTLs of main-lobe length(L1) and second-lobe length(L2) were located on Chr.7,Chr.15,Chr.19,Chr.21,Chr.23,LG6, LG17 and Chr.17.All of unlinked markers of the three maping population were surveyed using single marker analysis method and 9 markers related to morphological traits were detected with LOD＞2.0.Three markers were related to yield traits and 6 markers to main-lobe length(L1) and second-lobe length(L2) explained about 5.2-8.0%of the phenotypic variance.In comparison with previously published data,the QTLs assigned to specific chromosomes(Chr.15,Chr.21,Chr.23,Chr.25) in this paper were the same as previously published reports.In addition,we also found the rest QTLs were different from previously published reports on the chromosomes level(Chr.7,Chr.17,Chr.19).