High frequency induction of somatic embryos in cultured leaf expiants of Coffea arabica L.

Abstract

Summary High frequency somatic embryo induction (HFSE) and subsequent plantlet development are reported for the first time in cultures of Coffea arabica leaf tissue expiants. The highest number of replicates of the various treatments with HFSE was observed in experiments where primary cultures were grown on a «conditioning medium» containing basal medium (BM), 3% sucrose, and varying concentrations of 2,4-D and kinetin for 7 weeks; subcultured on conditioning medium of the same formulation with a reduction in the concentration of BM salts (x/2) for 4 weeks. Thereafter, tissues were subcultured on «induction medium» consisting of x/2 inorganic salts and an increased concentration of KNO 3 (2x), BM organics, and kinetin and NAA at a concentration ratio of 2.3/0.27 μM. Micromolar concentration ratios of kinetin and 2,4-D at 18.4/4.5, 18.4/18.0 and 36.8/ 4.5 μM in the «conditioning medium» used for tissues during primary and secondary culture result in the production of optimal HFSE when such tissues are subcultured onto «induction medium». Between 50–60% of the replicate cultures contained tissues with HFSE. Low frequency somatic embryo development (LFSE) was observed in tissues cultured on «induction medium» derived from cultures initially grown on a «conditioning medium» containing NAA and kinetin or NAA and kinetin supplemented with undefined growth factors (liquid endosperm of coconut, casein hydrolysate, yeast extract, and leaf extracts of tabacco and Kalanchoe spp.).