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Submitted to: Intech
Publication Type: Book / Chapter Publication Acceptance Date: 2/18/2014 Publication Date: 7/2/2014 Citation: Ulloa, M. 2014. The diploid D genome cottons (Gossypium spp.) of the new world. In: Abdurakhmonov, I.Y., editor. World Cotton Germplasm Resources. Volume 8. Rijeka, Croatia:Intech. p. 201-229. Interpretive Summary: Cottons of the New World or the America continents are part of a great reservoir of important genes for improving fiber quality, pest and disease resistance, and drought and salt tolerance in the modern cultivated Upland/Acala and Pima (also known as Sea Island or Egyptian) varieties. This wide genetic diversity (genetic makeup among individuals) is desirable for long-term cotton improvement and in the reduction of crop vulnerability to diseases. In this chapter, the most recent classification of the New World Gossypium species, information about the most recent collections and unclassified taxa, and information about their distribution and dissemination in their natural habitat are presented. Also, a review of molecular studies and future research is presented as an alternative solution of resolving poorly defined morphological differences between two species as well as the future molecular utilization of these species. The efficacy of transgenic technology is entirely dependent on gene discovery. Additional studies using the next generation sequencing (NGS) technology will provide additional information on these unique important genes for cotton improvement. The functional genes identified with NGS would be important resources to improve the cotton crop through transgenic technology. In addition, this new information could be used to improve existing tools such as marker assisted selection for molecular breeding or to develop new tools to locate and characterize germplasm and cultivars or gene- sequences of DNA encoding proteins that controlled the expression of these important traits. Technical Abstract: The diploid D genome cottons (Gossypium spp.) of the New World are part of a great reservoir of important genes for improving fiber quality, pest and disease resistance, and drought and salt tolerance in the modern cultivated Upland/Acala (G. hirsutum) and Pima [also known as Sea Island or Egyptian (G. barbadense)] cottons. The allotetraploid Upland (AD1) and Pima (AD2) cottons provide the natural fibers for the textile industry. The Dt subgenome species-progenitors (D genomes) do not produce commercial fibers. Eleven of the 13 formerly reported species of the New World from the D genome reside in the country of Mexico. The other two D species have disjointed distributions; one is G. raimondii, which is endemic to Peru, and the other is G. klotzschianum, which is found in the Galápagos Islands. Some D species display arborescent growth habits and express unique flowering and fruiting habits (following defoliation in the dry season). Molecular analyses performed on Gossypium species using marker-DNA-genes and microsatellites or simple sequence repeats (SSR) clustered all species into distinct phylogenetic groups, which were consistent with geographical distribution, dissemination, genetic relatedness, and population structure of these D species. Recently, the genome sequence of the best model, closest living ancestor relative of the allotetraploid cottons - Dt subgenome (G. raimondii) was published. This new information compiled with the ongoing next generation sequencing projects around the world will provide additional insights into the evolution, population structure, genetic diversity, and utilization of this genetic resource. In situ conservation of some of these species is threatened. New roads and population growth continue to increase. In this chapter, we present the most recent classification of the D Gossypium species, updated information about the most recent collections and unclassified taxa, and information about their distribution and dissemination in their natural habitat. Also, a review of molecular studies and future research is presented as an alternative solution of resolving poorly defined morphological differences between two species as well as the future molecular utilization of these species. |
