| As an important economic crop,cotton not only provides natural fiber for the textile industry,but also provides raw materials for the oil industry.There are four cultivars of cotton: G.hirsutum,G.barbadense,G.herbaceum and G.arboreum.G.hirsutum.,also named upland cotton,accounts for 98% of total cotton production in China.In our country,upland cotton has some problems of single length,low strength,fineness,poor disease resistance and so on.Because the genetical basis of upland cotton is relatively narrow,it is very difficult to improve the traits by intraspecific hybridization.Wild cottons live in the harsh environment for a long time,through continuous evolution got a lot of excellent traits of resistance,wide,high quality etc.Therefore,introgression of excellent allele from the wild cotton by distant hybridization is possible to improve the fiber quality and resistance of upland cotton.There are few reports on Gossypium mustelinum.G.mustelinum has the most distant relationship with G.hirsutum,it is likely that there are some new genetic loci,can be used for genetic improvement of upland cotton.In this study,we used CCRI35 and Gossypium mustelinum as parents to obtain F1 generation and then backcrossed to obtain BC1 population.SSR molecular markers were used to construct the genetic linkage map between G.hirsutum and G.mustelinum.The results are of important theoretical and practical significance on the further construction of wild cotton chromosome fragment substitution lines.The results are also useful to explore the origin and evolution of tetraploid cotton and to improve the genetic basis of cotton cultivar.The following are the main results of this study.1.Primer polymorphismA total of 3952 of genome SSR markers were used to screen the polymorphic primers between upland cotton cultivar CCRI35 and Gossypium mustelinum.Then 1097 polymorphic primer pairs were obtained,accounting for 27.8% of total primers.The best primers were SWU,the proportion of polymorphism was 46.3%,the primer with relatively low polymorphism was CCRI,and the proportion of polymorphism was 20.6%.2.Genotyping BC1 populationThe polymorphic primer pairs were used to genotype [(CCRI 35 ×Gossypium mustelinum)× CCRI 35] BC1 population and 1200 loci were obtained.The 1163 loci were conducted on ?2 testing.The result showed that 235 loci deviated from the 1:1 Mendelian segregation ratio(P<0.05),accounting for 20.2% of the whole loci.3.Construction of high density genetic mapGenetic linkage analysis is applied to the 1163 loci,and a linkage map with 26 groups was constructed.The length of map covered 3901.8 c M and the average distance between markers were 3.3 c M.A total of 579 loci were mapped on A gonome which covered 1950.1 c M,whereas 584 loci were mapped D genome which covered 1951.7 c M.4.Collinearity Analysis between genetic map and physical mapThe vast majority of loci on the genetic map were in accordance with their locations on the A or D genome sequence of G.hirsutum.In the A genome,1950.1 c M corresponded to 1.09 GB,which spaned 93.1%.In the D genome,1951.7 c M corresponded to 715.69 MB,which spaned 92.4%. |
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