Factors Affecting in Vitro Shoot Regeneration in Hypocotyls of Brinjal (Solanum melongena L.) in the Early Steps of Agrobacterium-Mediated Transformation

An attempt was made to assess the effect of size, age and position of the explant, pre-culture and high cytokinin concentration in the pre-culture medium on shoot regeneration in brinjal hypocotyls co-cultivated with Agrobacterium. The study was carried out using hypocotyl explants of brinjal cv. Manjarigota, Agrobacterium strain A208 and shoot regeneration medium (full-strength basal MS medium, 2μM BAP + 0.05μM NAA, 3% sucrose and 0.8% agar) containing Cefotaxime (250-500mg l-1) and Kanamycin (100mg l-1). Hypocotyl explants showed callus initiation and shoot regeneration response after 10-12 and 20-22 days of culture, respectively. Five-day-old explants did not survive Agrobacterium infection, and ten-day-old explants showed higher shoot regeneration (29±1.91%) than older explants. Explants of medium size (1cm long; 32±2.62%) from the apical region (38.57±2.61%) showed better shootregeneration ability than explants of any other size or region. A period of four days of pre-culture (33.33±3.76) was optimal best for best shoot-regeneration in hypocotyl explants. No regeneration was seen in hypocotyl explants at shorter or longer pre-culture period. High cytokinin (10μM) in shoot regeneration medium during pre-culture enhanced shoot regeneration response (47.27±2.98%) in explants co-cultivated with Agrobacterium. Effects of various factors documented in this study will be useful in developing an efficient Agrobacterium-mediated transformation protocol in brinjal cv. Manjarigota.