Project Summaries

INTROGRESSION OF GOSSYPIUM GERMPLASM TO INCREASE GENETIC DIVERSITY FOR COTTON IMPROVEMENT

J. M. Stewart and Bill Hendrix, University of Arkansas

Three germplasm lines were publicly released. These were derived from a trispecies interspecific hybrid of G. herbaceum x G. armourianum x G. hirsutum. This is a valuable source of genetic diversity for public and private cotton breeders. 

DNA was extracted from three representatives each of approximately 60 accessions of G. hirsutum comprising accessions from the littoral area of each of the major Caribbean Islands, the Yucatan Peninsula and 9 accessions from south Florida. AFLP reactions are currently being performed and electrophoresis gels analyzed for polymorphisms. Preliminary results indicate that the Florida cottons form a distinct clade that includes only two accessions from the Caribbean area. The Florida cottons also appear to be the most closely related accessions to the wild G. hirsutum of the northern coast of the Yucatan Peninsula.

Many of the diploid species do not yield good quality DNA when standard procedures used for isolation of DNA from the cultivated cotton are used. A procedure was developed that yields DNA from all species tested that is sufficiently clean that PCR, endonuclease restriction, and AFLP ligation were not inhibited by unwanted contaminants. Major modifications appear to be in the addition of more reducing agent and the addition of an ammonium salt to the cleaning solution.

A research project was begun to obtain a measure of the molecular diversity of the Australian arid zone species and to determine if natural hybridization has occurred among the species. Field observations suggest that G. australe has invaded the range of G. nelsonii and G. bickii, and that natural hybridization has occurred. G. australe is distributed across the continent, but the other two have more restricted distributions. The project comprises approximately 70 accessions of G. australe that represent the diversity across the entire continent of Australia; 25 G. nelsonii accessions; 18 G. bickii accessions; and recently approximately 20 G. sturtianum accessions where these were sympatric with one or more of the other three species. These accessions should provide evidence of any natural hybridization. Where number of seed and seedling viability permitted, we are growing at least three representatives of each accession in the greenhouse to establish that molecular differences are specific to an accession and not within an accession. Seed were obtained from most of the accessions to assure that the germplasm is maintained. DNA has been extracted from each plant and analyses are in progress.