IN-VITRO REGENERATION OF PLANTLETS FROM MATURE EMBRYOS OF PINUS AYACAHUITE

A plantlet regeneration protocol was developed for Pinus ayacahuite va r. ayacahuite (Ehrenb.). Embryos from mature seeds from ten provenance s were cultured in a 16-h photoperiod for 3 days on a medium containin g 30 mM sucrose and 0.7% agar. Cotyledons from these embryos were subc ultured onto MCM medium (Bornman 1983) supplemented with 50 mu M N-6-b enzyladenine and 90 mM sucrose for 2 weeks. Bud development and shoot elongation were maximized by subculturing the explants on half strengt h AE medium (von Arnold and Ericksson 1981), supplemented with 60 mM s ucrose and 0.05% activated charcoal every 30 days. Seed source had a s ignificant effect on the responses of the embryos to the bud induction protocol. For the provenance with the best response to bud induction, about 79% of the cultured cotyledons formed buds, and each cotyledon formed a mean of 9.1 buds, so that about 70 shoots could be induced fr om each seed. The best rooting response (40% rooting) was obtained by treating the shoots for 8 h with 100 mu M naphthalene acetic acid.