Somatic embryogenesis and plant regeneration from different wild diploid cotton (Gossypium) species

Calli were successfully induced from hypocotyls of eight wild diploid cotton species (Gossypium) on MSB (MS salts and B₅ vitamins) medium supplemented with 0.09 μM 2,4-D (2,4-dichlorophenoxyacetic acid) and 2.32 μM KT (kinetin). Plant growth regulator (PGR) combinations, adding GA₃ (Gibberellic acid), high inorganic salt stress, and PGR-free media were used to induce embryogenic calli from nonembryogenic calli. Embryogenic cultures were induced from G. aridum S. (D₄ genome), G. davidsonii K. (D₃-d genome), G. klotzschianum A. (D₃-k genome), G. raimondii U. (D₅ genome), and G. stocksii M. (E₁ genome). We then observed somatic embryogenesis in the five species while calli of G. africanum V. (A₁-2 genome), G. anomalum W. (B₁ genome), and G. bickii P. (G genome) remained nonembryogenic. Somatic embryogenesis was adjusted by changing sugar sources, regulating combinations of PGRs, and using cell suspension culture. Embryos at various developmental stages produced mature and germinating embryos when cultured on filter paper placed on the media containing different sugar sources. The utility of different sugar sources promoted globular embryos developing into cotyledonary stage and increased the frequency of cotyledonary embryos developing into normal plants. Normal plantlets were regenerated from G. davidsonii, G. klotzschianum, G. raimondii, and G. stocksii. Only abnormal plantlets were obtained in G. aridum. This work will contribute to broadening the number of regenerable cotton species and provide foundations for somatic hybridization in cotton to create new germplasm.