PLANT-REGENERATION FROM THE CALLUS DERIVED FROM ROOT EXPLANTS OF CUCUMIS-MELO L CV PUSA-SHARBATI

Studies were undertaken to evaluate the regenerative capacity of root explants of Cucumis melo L. cv. Pusa sharbati, as influenced by the age of the donor seedlings, position of the explant and growth regulators. Root segments were excised from aseptically raised seedlings of different ages (5, 7, 14, 21, 28 and 35 days) and from different regions of the main root (i.e., basal, sub-basal, sub-apical and apical) and cultured on Murashige and Skoog's medium (MS medium) variously supplemented with growth regulators. Regeneration occurred via organogenesis. Shoots regenerated with high frequency indirectly from the callus and later rooted on the rooting medium. Induction of shoot buds from the explant occurred in 2 steps: (i) callus initiation and nodule formation, and (ii) shoot differentiation from the nodule. On MS medium c 3 x 10(-6) M benzylamino purine (BAP)+ 3 x 10(-6) M isopentenylamino purine (2iP), referred to as the nodule induction medium (NI medium), root segments excised from 21-day-old seedlings responded best for callus growth (100%) and nodule formation (83%). The basal root segment showed maximum nodule formation (91.3%) on NI-medium. Regeneration frequency declined from the basal to the apical segment. On MS + BAP (1 x 10(-6) M) 75% of cultures showed shoot differentiation from nodules. Shoots (2 cm long) were rooted on MS + 1 x 10(-6) M indole-3-butyric acid (IBA).