An efficient system of micropropagation via somatic embryogenesis from root-derived callus was established in

Arabica coffee (Coffea arabica L.). Twenty-six callus lines were induced on MS (Murashige and Skoog, 1962)

medium supplemented with combinations of NAA (0, 0.1, 0.5, 1 and 2 mg/L) plus BA (0, 1 and 2 mg/L), or 2,4-D

(0, 0.1, 0.5, 1 and 2 mg/L) plus TDZ (0, 1 and 2 mg/L). Subsequently, two types of somatic embryos were obtained

from callus cultures and named S-type and I-type embryos. The S-type embryos were obtained from an 18-monthold

callus line which was induced and maintained at 2 mg/L TDZ and 0.1 mg/L 2,4-D near the end of each period

of the subculture. These embryos have a developmental barrier, which did not pass through the torpedo stage

and could be overcome by a supplement of 2 or 5 mg/L BA. The I-type embryos were induced from 3-month-old

callus when transferred onto induction media, i.e., MS supplemented with TDZ (2 and 5 mg/L) plus 2,4-D (0 and

0.1 mg/L). The significantly highest response, i.e., 13.3 embryos per callus clump was obtained at 2 mg/L TDZ.

In this study, the results reveal that TDZ has a crucial effect on embryogenic callus induction, proliferation and

subsequent somatic embryogenesis.