--K. V. Rao, P. Suprasanna and G. M. Reddy

Most of the cereal tissues cultured in vitro regenerate plants through somatic embryogenesis (Vasil, 1987). In maize, embryogenesis has been reported from inbreds and hybrids. Previously we have reported on callus induction, somatic embryogenesis and plant regeneration from glume calli (MNL 1983, 1986). The present report deals with the screening of local germplasm and the effect of certain amino acids on embryogenesis in immature embryo cultures. Immature embryos of inbreds CM117, CM119, CM120, CM400, CM111 and a hybrid (DHM-1) (obtained from Maize Research Station, Amberpet, Hyderabad), and sweet corn were tested for efficient callusing and embryogenesis. Of these, DHM-1 exhibited a high frequency of somatic embryogenesis (52%) compared to other genotypes (10-38%), on MS medium supplemented with 2mg/l 2,4-D + 3% sucrose. Amino acids like L-proline, glutamic acid, asparagine and tryptophan were also used to see their effect on the frequency of embryogenesis at concentrations of 5-25mM in MS + 2,4-D medium. L-proline (10-15mM) was found to be effective in enhancing the frequency of embryogenesis by about 15% over that of controls without proline. Higher concentrations (20 and 25mM), however, decreased the embryogenic potentiality of the calli. Asparagine and glutamic acid did not have any effect, whereas tryptophan was found to be inhibitory. Plants were regenerated from the embryogenic cultures of sweet corn and DHM-1 and were transferred to vermiculite pots, surviving only for about a week, in mist chamber. Different methods of acclimatization are being used for further growth of these plants.

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