Optimization of in vitro direct regeneration of multiple shoots in upland cotton (Gossypium hirsutum L.) cv. Iranian varieties

A direct shoot regeneration protocol was optimized for upland cotton (Gossypium hirsutum L.). Three cultivars of cotton namely Bakhtegan, Zeta-2 and their hybrid (Bakhtegan×Zeta-2) were used to study the effects of zeatin, kinetin, benzylaminopurine and indole-3-acetic acid on shoot regeneration from shoot tip explants excited from 7-10 day-old seedlings culture in vitro. Apical meristems in Hybrid variety produced maximum number shoot (7.66 shoots/ explant) when cultured on MS medium supplemented with 0.1 mgl-1 zeatin and activated charcoal (2 gl-1). Cultures of each cultivar continued for five subcultures and morphological characteristic each subculture was evaluated. Maximum length of regeneration shoots (2.75 cm) was achieved on medium containing zeatin in the cultivar Zeta-2. The highest number of nodes (4.5) and leaves (3.5) were observed in the fifth subculture of the cultivars Zeta-2 and Bakhtegan while the highest values for the same characters were observed in the last subculture of Hybrid genotype. Explants of all three genotypes formed organogenic masses that differentiated to secondary shoots on repeated subcultures.