Abstract

Callus induction and somatic embryogenesis from hypocotyl explants of some Iranian cottons spp. (Hashem abad, Kerman, Termez and Sepid) were compared with Coker 312 through induction and formation of embryogenic calli on medium of Murashige and Skoog (MS) with Gamborg vitamins (B₅) supplemented with the following compositions: MSB₁ (0.5 mg/l zeatin), MSB₂ (1 mg/l zeatin), MSB₃ (0.5 mg/l 2,4-dichlorophenoxyacetic acid, 0.1 mg/l kinetin), MSB₄ (1 mg/l 2,4-D, 0.5 mg/l kinetin, 0.5 mg/l zeatin) and MSB₅ (2 mg/l α-naphtalene-3-acetic acid, 1 mg/l kinetin, 0.75 mg/l MgCl₂). The optimum medium for the proliferation of embryogenic calli was MS medium containing B₅ vitamins, 1 mg/l 2,4-D, 0.5 mg/l kinetin and 0.5 mg/l zeatin and the optimum medium for the development of somatic embryos was MS medium (NH₄NO₃ was removed and KNO₃ amount doubled) containing B₅vitamins, 40 g/l sucrose and without hormone. Media MSB₁, MSB₂ and MSB₄ gave the highest percentage (100%) of calli induction in Coker 312 but the lowest induction (46.66%) was observed when Hashem abad explants were cultured in the MSB₃ medium. Embryogenesis percentage of Termez (2.22 to 24.40%), Hashem abad (1.85 to 9.73%) and Sepid (9.06 to 22.28%) genotypes were significantly lower than that of Coker 312 (66.66 to 94.33%). The Kerman genotype did not show embryogenesis. In the histological studies, the different development stages of the embryos (globular, heart, torpedo and cotyledonary) together with callus cells were showed. 

Key words: Hypocotyl explants, somatic embryo, in vitro regeneration, germination, somatic embryogenesis histology.

Abbreviation

Zt, Zeatin; Kt, kinetin; MS, Murashige and Skoog medium (1962);B₅, Gamborg et al., medium (1968); GA₃, giberellic acid; NAA, α-naphtalene-3-acetic acid; 2,4-D, 2,4-dichlorophenoxyacetic acid