Regeneration and development of Coffea arabica L. plants through indirect somatic embryogenesis

Abstract

Micropropagation of AS2K clones Arabica coffee (Coffea arabica L.) was attempted through indirect somatic embryogenesis by using ten different parts of the leaf such as shoot, first leaf base, second leaf base, third leaf base, first leaf middle, second leaf middle, third leaf middle, first leaf tip, second leaf tip, and third leaf tip. The influence of the part of leaf explants, combination of plant growth regulator (PGRs) in the induction of embryogenic callus and regeneration of embryo somatic were studied. Furthermore, the various protocols to induce regeneration of somatic embryo into plantlet through different step of subculture and the use of various germination medium were demonstrated. The morphological characteristics and histological analysis of embryogenic callus and embryo development were observed. In this experiment, it was observed that the M5 medium supplemented with 1 mg/L 2,4-D, 1 mg/L BAP and 4 mg/L 2-ip was closely associated with third leaf tip explants for induction of embryogenic callus. The maximum number of globular, heart-shape, torpedo and cotyledones (18, 4, 12, 4, respectively) were achieved on ERM6 medium containing 2 mg/L BAP without activated charcoal on 90th day for regeneration of embryo somatic. The length of roots is the most influence paramater on plantlet regeneration, and the 17th protocol which used B medium, large embryos and twice phase of subculture from liquid medium to solid medium is the best protocol for plantlet regeneration. The protocol developed could be useful highly for large-scale micropropagation in these commercially important Arabica coffee clones. Key words: Indirect somatic embryogenesis; 24-D; BAP; histology; anatomy.