Organogenesis from megagametophyte and zygotic embryo explants of the gymnosperm Dioon edule Lindley (Zamiaceae, Cycadales)

Organogenic cultures were induced from zygotic embryo and megagametophyte e xplants of the Central American cycad species, Dioon edule. Plant growth me dium consisted of B5 major salts, Murashige and Skoog minor salts and organ ics, 400 mg l(-1) glutamine, 100 mg l(-1) arginine, 100 mg l(-1) asparagine , 60 g l(-1) sucrose, 8 g l(-1) Difco Bacto agar and was supplemented with kinetin (0 - 13.94 mu M) and 2,4-dichlorophenoxyacetic acid (2,4-D) (0 - 9. 05 mu M) arranged as a 5 x 4 factorial in a randomized block design. Callus initiation occurred on a wide range of medium formulations from megagameto phyte explants; however, shoot formation occurred only on medium supplement ed with 2.26 mu M 2,4-D. In comparison, callus initiation from explanted zy gotic embryos occurred on fewer medium formulations, and adventitious shoot induction occurred from callus on formulations with 9.29-13.94 mu M kineti n + 0.45-9.05 mu M 2,4-D. Rooted shoots, derived from megagametophyte and z ygotic embryo cultures, have been regenerated.