29 Tomato ( Lycopersicon esculentum, Mill . ) plant regeneration in absence of exogenous growth regulators Plana, D . , Alvarez, M . , Florido, M . , Lara, R . M . , Moya, C . INCA, Genetic and Plant Breeding Dept . , San José de Las Lajas, La Habana, Cuba . Email: dagmara@inca . edu . cu Development of an in vitro regeneration system without exogenous growth regulators is important for genetic manipulations of particular plant species (Herrera - Estrella, 1999) . The objective of   the present work was to obtain tomato regenerated plants independently of exogenous growth regulators in the culture medium . Dried mature seeds of tomato ( Lycopersicon esculentum, Mill . ) from five cultivars were used as the source of explants . After sterilization, the seeds were sown on filter paper that had been wetted with sterilized water and precultured for zero to three days in the light at 25 o C . Precultured seeds were cut into two parts (Ezura 1993); the portion consisting of the proximal part of the hypocotyls of the embryo was cultured on Murashigue and Skoog (MS) medium (1962), with 30 g . L - 1 commercial sugar, 2g . L - 1 gel rite, mio - inositol 100 mg . L - 1 , thiamine 4 mg . L - 1 and pH adjusted to 5,7 before sterilizing by autoclave at 121 0 C . The number of regenerated adventitious shoots were counted for three weeks (Table 1) . The elongated shoots were excised individually from the explants and subcultured on MS medium for rooting . The plantlets were transplanted into pots with a mixture of litonite and soil (1:1) for growing under greenhouse conditions .   All experiments were repeated twice . The percentage of explants with adventitious shoots ranged from 15 to 69% at the third week (Table 1) . At the same time the adventitious shoots were excised for rooting and the calluses   subcultivated on fresh medium to obtain more adventitious shoots . The Amalia cv . shoots scored for up to 2 . 8 two weeks after the first subculture . Morphological characteristics of regenerated and nonregenerated plants and fruits were similar; on the other hand, forty regenerated plants showed no variations in chromosome number . The advantages of this regeneration method are: it does not employ exogenous growth regulators, it has feasible handling, and also regenerated plants are obtained in a short time . Literature cited: Ezura, H . ; Nishimiya, S . ; Kasumi, M . (1993) . Efficient regeneration of plant independent of exogeneous growth regulators in bell pepper ( Capsicum annumm, L . ) . Plant Cell Reports 12:676 - 680 . Herrera - Estrella, L . (1999) . Plant genetic transformation: technology and applications . In: Métodos en Biología Molécular Vegetal . First International INIA - Carrillanca Workshop and Course on Plant Biothecnology . 58 - 65p . Murashige, T . and Skoog, F . (1962) . A revised medium for rapid growth and biassays with the tobacco tissues cultures . Physiol . Plantarum . 15: 473 - 497 . Table 1, next page