Somatic embryogenesis and plantlet regeneration from embryogenic suspension culture in muskmelon

A rapidly and maintainable embryogenic suspension culture of Cucumis melo was accomplished by transferring embryogenic callus, obtained from mature cotyledon and hypocotyl explants in liquid medium. The cultures obtained were flooded with clumps of globular embryos with very little non-embryogenic tissues. The number and size of somatic embryos/clump was measured to quantify growth of embryogenic tissues under given conditions. The suspensions were sub-cultured every 15 days by adding 10 ml of the old suspension to 40 ml of fresh medium. Initiation and proliferation of such embryogenic suspension cultures depend upon the genotype and various exogenous plant growth regulators fortified to the culture medium at different levels. Culture medium MS2D (MS + 2.0 mg I-1 2,4-D) proved superior for callus induction from cultured mature cotyledon and hypocotyl segments. For the establishment of suspension cultures, the liquid MS medium fortified with 2.0 mg I-1 2,4-D and 0.5 mg I-1 BAP was found to be the most effective. For subsequent subcuturing, reduced level of 2,4-D at 1.0 mg I-1 in combination with 0.5 mg I-1 BAP promoted faster development of somatic embryos. Frequent and efficient plantlet regeneration occurred on MS medium with 0.5 mg I-1 each of NAA, BAP and kinetin. Among the four genotypes tested Pusa Madhuras followed by Local cultivar responded better as compared to other genotypes. Regenerated plants were found to be phenotypically normal and true-to-the-type.