REGENERATION OF TOMATO (LYCOPERSICON-ESCULENTUM MILL) - SOMATIC EMBRYOGENESIS AND SHOOT ORGANOGENESIS FROM HYPOCOTYL EXPLANTS INDUCED WITH 6-BENZYLADENINE

In vitro regeneration of plants was achieved in four cultivars of toma to (Lycopersicon esculentum Mill.). The explants were 10-mm hypocotyl sections, excised from 2-wk-old seedlings grown on Murashige and Skoog (MS) medium supplemented with or without 6-benzyladenine (BA). The hy pocotyl explants were subcultured on MS medium without growth regulato rs or on MS media supplemented with 5, 10, 20, or 40 mu M BA Regenerat ion through somatic embryogenesis and shoot organogenesis occurred in explants of all treatments, even on hypocotyls from seedlings grown on basal medium and subcultured to medium without growth regulators. Exp lants from seedlings grown on BA-supplemented medium produced the high est frequency of regenerants when subcultured to media containing BA. In contrast, BA had an inhibitory effect on explants obtained from see dlings grown on media lacking BA. Light microscopic observations confi rmed that regeneration occurred via both somatic embryogenesis and sho ot organogenesis from the subepidermal cortical tissue. Developing som atic embryos were encased in a distinct protoderm, had a suspensor-lik e structure, and were loosely attached to the hypocotyl tissue. Somati c embryos and shoots developed into complete plants on a medium lackin g growth regulators.