Analysis On Genetic Diversity Of Gossypium Barbadense Cultivars And Construction Of Genetic Map Of Two Wild Cotton Species In D₃ Genome

Cotton is one of the main crops in the World,and its fiber can be used in textile industry and its seed can be an important oil source.The branches of cotton can be used as livestock feed and industrial raw materials.Cotton has great significance in the economic development.With the rapid development of economy,people pay more and more attention to the quality of cotton.The quality requirements of cotton are also gradually improved.This requires the quality of germplasm to provide basis,using rich germplasm resources and excellent cultivars.The most outstanding characteristic of sea island cotton is good fiber quality,the best one among all cultivated cotton speicies.Sea island cotton can meet the requirements of high quality.It also has such resistance traits as tolerance to cold,drought,disease and insects.We can use these characters of sea island cotton to compensate the shortcomings of high yield of upland cotton?G.hirsutum?.The genetic diversity of sea island cotton is important to the improvement of cultivated cotton.In the genus Gossypium,tetraploid cotton species including G.barbadense are to be originated from the D and A genomes,G.davidsonii and kloczhianum(their genomes were nominated as D_3-d and D_3-k,respectively)are the important species in the D genome and they exist the hybid lethality to the tetraploid cotton including G.barbadense.The two wild speciese may have potentials likely in G.barbadense with better fiber and telorances to bio-and abio stresses.So construction of the genetic map between them may lay a basis to understand evolution of their important traits related to tetraploid cottons and even to utilyze their useful genes.The genetic diversity analysis of sea island cultivars from different countries and regions based on SSR markers and the construction of genetic map of the diploid species were studied in these theses.The main results are as follows:1.Genetic diversity of Gossypium BarbadenseThe genetic relationship and genetic diversity of 299 accessions of sea-island cotton?Gossypium barbadense?were analyzed using 60 pairs of SSR markers.Among the accsessions,121 came from China,86 from Argentina,24 from Egypt,16 from USA,38 from USSR,7 from Vietnam,4 from Syria,2 from Albania and 1 from Sudan.The 60 pairs of polymorphic SSR primers produced 209 alleles in total,and 185were polymorphic,which accounted for 88.5%.2 to 5 alleles could be obtained from each pair of the primers with an average of 3.08.The effective number of alleles?Ne?varied from 1.020 to 3.940 with an average of2.220.The gene diversity?H??was 0.056 to 1.385 with an average of 1.109.The value of allelic polymorphism information content?PIC?ranged from 0.020 to 0.746 with an average of 0.505.Among these different countries and regions from which the accessions came,the order of genetic diversity index from smallest to largest is USA,former Soviet Union,Middle-north Africa,Southeast Asia and Argentina.The genetic diversity of the sea-island cotton germpalsms from Argentina was extraordinary diversified among the different areas.A UPGMA cluster analysis was performed on the genetic distance matrix using NYSTS-pc 2.20 software.Similarity coefficients among the 294 G.barbadense accessions ranged from0.206 to 1?average=0.756?,with the accessions clustering into two groups at a genetic distance of 0.69,the group I were divided into six subgroups,and other 5 accessions formed a class because of their further genetic distances.The result of UPGMA cluster showed that these cultivars could be clustered corresponding to the same source places and similar genetic background information.Besides,the genetic similarity coefficient of sea-island cotton accessions ranged widely.The genetic diversity of the sea-island cotton cultivars from Argentina was extraordinary diversified among these different countries.These results suggested an overview of the genetic diversity of the sea-island cotton accessions,and provide a reference to understand the sea-island cotton domesticatiom and contribution in the world.2.A genetic linkage map of an interspecific cross of G.davidsonii×G.klotzschianumWild cotton accessions used in this study,the sgenome D,has potentials of important agronomic traits which includes resistance to diseases and abundant genetic diversity and also the parent species to tetraploid cotton species including G.barbadense.A linkage map of the two wild diploid D genome species was constructed from their F₂ population.JoinMap 4.0 computer software was used for the construction of genetic map.A total of 494 polymorphic simple sequence repeat markers were used and the map was based entirely on genome-wide simple sequence repeat?SSR?markers.The total length of the map was 1529.6cM and covered 13 linkage groups.The average distance between markers was 3.1cM.The average distance of each linkage group spanned 117.7cM.The average number of markers was 38 for each of the 13 chromosomes.The length of each linkage group ranged from 18 to 82 markers which were from 69.3cM to 182.9cM.There were 125 segregation distortion SSR loci in this map,which accounted for 25.3%.