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Title:   Author  item
                                            ABDURAKHMONOV, I - Uzbekistan Academy Of Sciencesitem
                                            BURIEV, Z - Uzbekistan Academy Of Sciencesitem
                                            SHERMATOV, S - Uzbekistan Academy Of Sciencesitem
                                            ABDULLAEV, A - Uzbekistan Academy Of Sciencesitem
                                            URMONOV, K - Uzbekistan Academy Of Sciencesitem
                                            KUSHANOV, F - Uzbekistan Academy Of Sciencesitem
                                            EGAMBERDIEV, S - Uzbekistan Academy Of Sciencesitem
                                            SHAPULATOV, U - Uzbekistan Academy Of Sciencesitem
                                            ABDUKARIMOV, A - Uzbekistan Academy Of Sciencesitem
                                            Saha, Sukumaritem
                                            Jenkins, Johnieitem
                                            Kohel, Russellitem
                                            Yu, Johnitem
                                            PEPPER, A - Texas A&M Universityitem
                                            KUMPATALA, S - Dow Agro Sciencesitem
                                            Ulloa, Mauricio
  Submitted to: Book Chapter
                                    Publication Type: Book / Chapter
                                    Publication Acceptance Date: 9/28/2011
                                    Publication  Date: 3/16/2012
                                    Citation: Abdurakhmonov, I.K., Buriev, Z.T., Shermatov, S.E., Abdullaev, A.A., Urmonov, K., Kushanov, F., Egamberdiev, S.S., Shapulatov, U., Abdukarimov, A., Saha, S., Jenkins, J.N., Kohel, R.J., Yu, J., Pepper, A.E., Kumpatala, S., Ulloa, M. 2012. Genetic diversity in Gossypium genus. In: Caliskan, M., editor. Genetic Diversity in Plants. InTech. p. 313-338.Interpretive Summary: Global cotton germplasm resources are important sanctuaries of important genes and genetic variability that can be used to improve cotton resistance against biotic and abiotic stresses with high productivity and fiber quality.  The overall objective of this book chapter is to present a detail review on the diversity of cotton gene pools present in the collection in eight major countries such as: Uzbekistan (18971 accessions), India (10469 accessions), USA (10318 accessions), China (8837 accessions), Russia (6276 accessions), Brazil(4296), CIRAD France (3070 accessions) and Australia (1711 accessions). We observed that Uzbekistan (2680 accessions), India (2283 accessions) and USA (1923 accessions) collections have significant number of accessions for Asian diploid cottons, G. herbaceum and G. arboreum belonging to the secondary gene pool. Considering only G. hirsutum accessions, exotic and cultivar germplasm represent a wide range of genetic diversity in yield and fiber quality parameters. For example, in the analyses of ~1000 G. hirsutum exotic and cultivated accessions in the two different environments, Mexico and Uzbekistan, we observed a wide range of useful agronomic diversities present in the collections. In one or two environments, the cotton boll mass varies in a range of 1-9 grams per boll, 1000 seed mass varies in a range of 50-170 grams, the lint percentage varies in a range of 0-45%, Micronaire varies in a range of 3-7 mic, the fiber length varies in a range of 1-1.28 inch, and fiber strength varies in a range of 26-36 g/tex. The paper presented the detailed reports on the genetic diversity present in the collections based on morphological phenotypes. The paper also presented detailed analysis on genetic variation in different species and gene pools of cotton based on molecular results. Analysis of a large number of G. hirsutum accessions from exotic germplasm and diverse ecotypes/breeding programs with SSR markers confirmed the narrow genetic base of Upland cotton cultivar germplasm pool (with the genetic distance range of 0.005-0.26 suggesting the occurrence of a genetic ‘bottleneck’ during domestication events of the Upland cultivars at the molecular level. Results also revealed a narrow genetic base within G. barbadense accessions with genetic distance of 7-11%. The use of SSR markers revealed that the genetic distance between G. hirsutum and G. barbadense was in a range of 42-54%. Molecular diversity using SSR markers was higher within G. arboreum accessions (an average 25%) compared to G. herbaceum accessions (an average 4%), suggesting differences in genetic diversity between these two closely related A-genome species in germplasm collections. Previous studies suggested that the low genetic diversity in cultivar germplasm was a timely caution to accelerate efforts on broadening the genetic base of Upland cotton germplasm resource using gene pools from wild, primitive, pre-domesticated primary, secondary and tertiary gene pools.
                                Technical Abstract: The overall objectives of this paper are to report on cotton germplasm resources, morphobiological and agronomic diversity of Gossypium genus and review efforts on molecular genetic diversity of cotton gene pools as well as on the challenges and perspectives of exploiting genetic diversity in cotton. The collection of germplasm in eight major countries can be reported as follows: Uzbekistan (18971 accessions), India (10469 accessions), USA (10318 accessions), China (8837 accessions), Russia (6276 accessions), Brazil(4296), CIRAD France (3070 accessions) and Australia (1711 accessions). In that, the primary content of these collections consists of accessions for two cultivated cotton species, G. hirsutum and G. barbadense. Uzbekistan (2680 accessions), India (2283 accessions) and USA (1923 accessions) collections are the richest ones to maintain a great number of accessions for Asian diploid cottons, G. herbaceum and G. arboreum belonging to the secondary gene pool. Considering only G. hirsutum accessions, exotic and cultivar germplasm represent a wide range of genetic diversity in yield and fiber quality parameters. For example, in the analyses of ~1000 G. hirsutum exotic and cultivated accessions in the two different environments, Mexico and Uzbekistan, we observed a wide range of useful agronomic diversities. In one or two environments, the cotton boll mass varies in a range of 1-9 grams per boll, 1000 seed mass varies in a range of 50-170 grams, the lint percentage varies in a range of 0-45%, micronaire varies in a range of 3-7 mic, the fiber length varies in a range of 1-1.28 inch, and fiber strength varies in a range of 26-36 g/tex. There was also a wide range of variation on photoperiodic flowering (day neutral, weak to strong photoperiodic dependency) and maturity. The introduction of genetic diversity into elite cotton germplasm from exotic lines is difficult due to genetic drag and genomic incompatibility between the groups.  Analysis of a large number of G. hirsutum accessions from exotic germplasm and diverse ecotypes/breeding programs with SSR markers confirmed the narrow genetic base of Upland cotton cultivar germplasm pool (with the genetic distance range of 0.005-0.26).  Results suggested an additional evidence for the occurrence of a genetic ‘bottleneck’ during domestication events of the Upland cultivars at the molecular level. A previous study using SSR markers  showed that the genetic distance between G. hirsutum and G. barbadense was in a range of 42-54%. In spite of wide spectra of genetic diversity in Gossypium genus and extensive cotton genomics efforts, cotton lags behind other major crops for marker-assisted breeding due to limited polymorphism in the cultivated germplasm. This underlies broadening of cultivar germplasm genetic base through mobilization of useful gene variants from other gene pools into cultivated germplasm. There is a need for application of modern innovative genomics tools such as association mapping to identify genetic causatives of natural variations preserved in cotton germplasm resources and their use in plant breeding.


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