INTERACTIVE EFFECT OF GA3 AND POLYAMINES ON IN VITRO SOMATIC EMBRYOGENESIS FROM IMMATURE EMBRYOS IN MAIZE (ZEA MAYS L.)

In vitro somatic embryogenesis was studied in composite maize cultivar, Gaurav by culturing immature embryos. To obtain efficient callus, immature embryos were inoculated in MS medium supplemented with 5 mgl(-1) 2,4-D and 2 mgl(-1) NAA + 1 mgl(-1) BAP under 16 hr photoperiod and 150 mu molm(-2)s(-1) light intensity at 28 +/- 2 degrees C. Higher percentage of callus formation was reported in media containing 2,4-D. Longer duration of subculturing resulted in browning of calli and degradation of embryoids. The overall frequency of embryogenesis ranged from 65-78% and frequency of green shoot formation ranged from 35-48%. In order to analyze the interactive effect of polyamines and GA(3) on somatic embryogenesis, the proliferated calli were inoculated in MS medium supplemented with twenty seven combinations of polyamines (Putrescine, Spermine and Spermidine) and GA(3). Higher concentration (150 mu M) of Putrescine with GA(3) (50-150 mu M) was found to be most effective for inducing somatic embryogenesis. Though, spermine at lower concentration (50 mu M) with GA(3) showed the drastic increase but putrescine at higher concentration was found comparatively more effective. Spermidine at varying concentrations (50-150 mu M) gave poor results only in combination with lower concentration (50 mu M) of GA(3). It can be concluded that spermine at lower concentration (50 mu M), while putrescine only at higher concentration (150 mu M) exhibited positive interaction with GA(3) in terms of somatic embryogenesis. Present findings may be used as an effective tool for advancing genetic purity of hybrids and composite maize cultivars production in future and also for studying the physiological and molecular aspects of genetic transformation.