ADDITION OF BENZYLADENINE TO COCONUT EXPLANTS CULTURED In vitro IMPROVES THE FORMATION OF SOMATIC EMBRYOS AND THEIR GERMINATION LA ADICIÓN DE BENCILADENINA A EXPLANTES DE COCOTERO CULTIVADOS In vitro MEJORA LA FORMACIÓN DE EMBRIONES SOMÁTICOS Y SU GERMINACIÓN

Coconut (Cocos nucifera L.) production has been declining in Mexico and other countries due to deadly diseases; therefore, massive production of palms resistant to diseases is needed for replanting. Production of somatic embryos and micropropagation could be a very useful technique to produce free disease coconut population. Explants (embryogenic-structures) of Pacific Tall 2 ecotype were cultured in an induction medium defined as I (semisolid Y3 medium containing 0.65 mM 2,4-dichlorophenoxyacetic acid) and treated with the cytokinin benzyladenine (BA) at 0, 25, 100 or 200 M to evaluate its effect on embryogenic callus formation. The BA treatments did not affect the percentage of embryogenic callus formation. In order to evaluate the effect of the BA treatments on the late formation and germination of somatic embryos, the embryogenic calluses obtained in medium I were transferred to medium II (semisolid Y3 medium, containing 6 M 2,4-dichlorophenoxyacetic acid and 300 M BA). The best treatment was obtained from callus treated with 100 M BA; 72 % of them produced 27 embryos per responding callus at 150 d while with 25 M BA and the control (0 M BA) only 4 embryos were formed. The highest percentage (50 %) of calluses with germinating embryos occurred with 100 M BA at 150 d; other treatments produced only 20 %. In this BA concentration, the number of germinating embryos per callus was 10, while with the other treatments only 2-3 embryos were formed at 150 d. The total yield of embryos and germinating embryos from 100 explants were 73.6 and 19.0, with 0 M BA, and 753.2 and 249.0 with 100 M BA. Pre treatment of coconut explants with BA (100 M) and further treatment with 6 M 2,4-D