TAXONOMY AND GERMPLASM RESOURCES

Authors: Percival Jr, Albert; WENDEL, JONATHAN - IOWA STATE UNIVERSITY; STEWART, JAMES - UNIV OF AR, FAYETTEVILLE

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 12/31/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cotton includes 4 domesticated species: New World Upland and Sea Island; and Old World Gossypium arboreum and G. herbaceum. Diversity is evident in that 49 species make up both domesticated and wild cottons with a geographic range that encompasses most tropical and subtropical regions of the world. Wild species represent a large genetic source for potential exploitation by the cotton breeders of the world. Primary, secondary, and tertiary genetic source pools provide a convenient way to classify the various types of cottons in terms of their relative genetic accessibility and utility. The degree of genetic accessibility of different plant materials contained within the cotton germplasm collection is related to the classification of these cottons. The cotton gene pools are categorized by their chromosome number and diversity, with the primary pool comprising the cultivated and wild tetraploid species; the secondary pool comprising the A, B, F and D groups; the tertiary pool comprising the C, E, G, and K groups. Germplasm is useful in cotton improvement to the extent that it is available. Curatorial activities are focused on acquisition, maintenance, and distribution in order to preserve the broadest possible natural variability of cotton as a resource for continued efforts to modify and improve cotton lines. The cotton collection currently maintains over 6,700 seed accessions and represents 101 countries or political jurisdictions. The transfer of desirable characters from exotic sources is documented and shows that the introduction of desirable characteristics into commercially acceptable cotton varieties is an ongoing enterprise. Sources of specific pest resistances have been found from a variety of domestic and feral sources and exploited by diverse cotton improvement programs.

Technical Abstract: The genus Gossypium includes 4 different domesticated species: New World allopolyploids G. hirsutum and G. barbadense (2n=52); Old World diploids G. arboreum and G. herbaceum (2n = 26). The diversity is dwarfed by the entire genus, whose 49 species have a range encompassing most tropical and subtropical regions of the world. The wild species of cotton represent an ample genetic repository for potential exploitation by cotton breeders of the world. Primary, secondary, and tertiary germplasm pools provide a convenient way to classify germplasm in terms of its relative genetic accessibility and utility. Genetic accessibility of plant materials contained within the cotton germplasm collection is related to the classification of the genus. Germplasm pools are categorized by genome with the primary pool comprising the cultivated and wild tetraploid species; the secondary pool comprising the A, B, F and D genomes; and the tertiary pool comprising the C, E, G, and K genomes. Germplasm is useful in cotton improvement to the extent that it is available. Curatorial activities are focused on acquisition, maintenance, and distribution to preserve the broadest possible natural variability of Gossypium as a resource for efforts to modify and improve cotton cultivars. The collection maintains over 6,700 seed accessions of Gossypium species and represents genetic capital from 101 countries or jurisdictions. Transfer of desirable characters from exotic intraspecific and interspecific sources is documented and shows that introduction of desirable germplasm into agronomically acceptable cotton cultivars is an ongoing and dynamic enterprise. Sources of specific resistances have been found from a variety of germplasm sources and exploited by diverse cotton improvement programs.