Evaluation of Carbon Sources and Plant Growth Regulators for Successful Callus Induction of two Cotton Cultivars (Worer 50 and Sisikuk 02) from Cotyledon and Hypocotyl Explants

Abstract

Cotton (Gossypium hirsutum L) is one of the most important fiber crops, which play a key role in the world economy, and it is commercially grown in the tropical and sub-tropical region of more than 90 countries. However, the production of cotton is adversely affected by biotic and abiotic stress. To overcome such kind of problem the application of tissue culture techniques is very essential. Therefore, the objective of this study was to optimized carbon, growth regulator and explant sources for successful callus induction of two commercially grown cotton (Gossypium hirsutum L) cultivars (‘Worer 50’ and ‘Sisikuk 02’). For this experiment cotyledon and hypocotyl with the size of 2-3mm 2 and 3-5mm respectively from seven days old, aseptically seeding cultured on MSB5 medium supplemented with three carbon sources (maltose, glucose and sucrose) at different concentrations to investigate their effect on callus initiation and phenol reduction. For callus induction, cotyledon and hypocotyl cultured on MSB5 medium containing different concentrations and combinations of KIN (kinetin), TDZ (thidiazuron), NAA (naphthalene acetic acid) and 2,4-D (2,4- dichloro phenoxy acetic acid), used. The results revealed that maltose (30 g/l and 40 g/l) and glucose 30 g/l showed callogenesis at hypocotyl explant within a week and both glucose and maltose at all concentration level was effective to control phenolic compound. Whereas sucrose with all concentration showed phenolic compound and relatively showed less callus response. Maximum percentage of callus with compact feature was recorded on MSB5 culture medium fortified with 0.5 mg/l KIN + 0.1 mg/l 2,4-D for Sisikuk 02 88 % and 72 % for Werer 50 . Friable callus with maximum percentage were recorded on MSB5 medium fortified with 0.1 mg/l TDZ in combination with 0.1 mg/l NAA. Hypocotyl explant showed 16 to 88% callus response whereas cotyledon explant gave from 4 to 76%. The results of this study provide useful information to go for the next stages of regeneration and of course better carbon sources, explant and hormone combination were identified for the cotton cultivars grown in Ethiopia.