Abstract:

The wild cotton species of G genome in Australia have some outstanding characters such as the delayed gland morphogenesis trait that is available in the utilization of cotton seeds and provides higher resistance to pest and diseases. However, the upland cotton germplasm with the trait has not been obtained due to the distant relationship between the G genome species and upland cotton. Protoplast fusion technique which depends on the success in the somatic culture of two different species can avoid sexual incompatibility in convention hybridization. Fewer papers have been reported on plant regeneration from somatic culture successfully in wild cotton species. In this paper, callus inducing and plant regeneration of the two wild cotton species G genome, Gossypium australe F. Muell. and Gossypium nelsonii Fryx. were studied through the regulation of culture conditions such as plant growth regulators (PGR) and carbon sources with the Gossypium klotzschianum Anderss of D genome as a control. The results indicated that under the same condition, the frequency of somatic embryo germination and the plant regeneration ability of G. klotzschianum were high, and most of the regenerated plants from G. klotzschianum were normal. For G. nelsonii, although many plantlets were regenerated, most of them were monstrous , while that of G. australe was still staying at the stage of somatic embryo, indicating that the plant regeneration of G genome cotton species obtained in our experiment was more difficult than that of D genome species. Furthermore, the callus of G genome species induced in the medium with the hormone combination of 0.1 mg L^-1 KT + 0.1 mg L^-1 2,4-D held good for cell differentiation, and it was better for proliferation of the embryogenic callus in the medium with 0.2 mg L^-1 KT + 0.5 mg L^-1 IBA. It was helpful for initiation of somatic embryos when IBA concentration in the medium was decreased to 0.25 mg L^-1 and KT was increased up to 0.3 mg L^-1, and the medium of MSB5 with 0.15 mg L^-1 KT and 0.5 mg L^-1 NAA was in favor to plant regeneration. In addition, glucose, the sugar source in tissue and cell culture, was good for callus induction from the G genome cotton species, while maltose was even better than glucose for proliferation of embryogenic callus and germination of somatic embryo. This report provides an useful technique for somatic culture of the wild cotton species, and also ensures the protoplast fusion feasibly between these wild cotton species and other cotton species to converge several good traits into a new germpalsm. However, it is needed to study further about the various culture factors and conditions for building a quick and high efficient tissue culture regeneration technique of the two wild cotton species of G genome.

Key words: G. nelsonii, G. australe, Somatic embryogenesis, Plant regeneration