EFFECT OF EXPERIMENTAL CONDITIONS AND GENOTYPIC VARIABILITY ON SOMATIC EMBRYOGENESIS IN COFFEA-ARABICA

The somatic embryogenic potential of leaf explants from greenhouse-grown plants of eight Coffea arabica genotypes was investigated on three different gelose-gelled culture media (Dublin, Pierson, and Yasuda). Four of these genotypes were reactive. Optimal somatic embryogenesis was obtained when the explants were taken from microcutting and cultured on gelrite-gelled Yasuda's medium. Under these culture conditions, somatic embryos and plantlets were obtained in two previously recalcitrant genotypes. The histocytological callus development was found to be identical in responsive or recalcitrant genotypes. Embryogenic cells formed at two successive points during callogenesis and their subsequent development varied according to culture conditions. Cells initiated in 10- to 15-day-old calli either degenerated or developed directly into embryos. Cells initiated in 60-day-old calli became isolated and developed into embryos or their development was arrested. Embryos obtained in these conditions were able to develop into plantlets.