Abstract :
Callus induction in immature embryo, hypocotyl and root explants of 5 Iranian cottons spp. (Sahel, Sepid, No.200, Khordad and Barbadense-5595) were studied on MS nutrient medium supplemented with some hormonal combinations of 2,4-D and BAP. The study was carried out at the Cotton Research Institute of Iran (CRII) in Gorgan. Analysis of results showed that percent of callus formation was significant at 1% level for cultivar, explant type, hormonal combinations of nutrient medium and explant * hormonal combinations of medium interaction. The callus formation frequency was varied between different cultivars and explants. The highest callus formation (81%) was related to immature embryo explant of cv. No.200, whereas, the root explant of Sepid cultivar with 25.8% showed the lowest callus formation percent. In general, immature embryo explants possessed higher callus formation potential than hypocotyl and root segments on all nutrient media. Immature embryos on the MS medium containing 0.5 mg/l 2,4-D and 2 mg/l BAP expressed the greatest callus formation frequency (85.6%). However, MS medium containing 0.5 mg/l 2,4-D without cytokinin was the best nutrient medium for hypocotyls and roots (51.6 and 38.3%, respectively). The suitable medium for callus induction in hypocotyls and roots was probably when used in greater concentration of auxin by reducing cytokinin, but for immature embryo, it was probably having positive effects on callus formation of cotton cultivars when used in greater concentrations of auxin and cytokinin. Therefore, plant growth regulators are essential for callus induction, however, high concentration of cytokinins reduce callus induction in hypocotyls and roots and increase callus induction in immature embryos, but high concentration of auxins play positive role in this respect and increase callus induction frequency in all explants.
