INFLUENCE OF EXPLANT AND CULTURE MEDIUM ON SOMATIC EMBRYOGENESIS OF COFFEE LEAVES

Abstract

Somatic embryogenesis induction in coffee (Coffea spp.) is affected by explant type and culture medium. This work was done in order to obtain the optimal type of foliar explant and culture medium for somatic embryogenesis induction in 13 selected genotypes of Coffea spp. Explants of immature (Hi), young (Hy) and mature leaves (Hm) were compared in each genotype. Later, only Hy and Hi explants were evaluated in three culture media: the control MT medium with BAP (1.12 mg L^-1); the MS1 medium with BAP (1.12 mg L^-1) and 2,4-D (0.05 mg L^-1); and MS2 medium with BAP (2.21 mg L^-1), 2,4-D (0.05 mg L^-1), AIB (1 mg L^-1) and Benomyl (1 g L^-1). The percentages of oxidation, contamination, growth of tissue border, callogenesis, embryogenic callus and number of globular embryos were evaluated. Hm did not present morphogenic response. Hy exhibited 18 % to 100 % of callogenesis in four genotypes and 45 % to 63 % in two genotypes; on the other hand, Hy formed 9 % to 100 % of callus in 12 genotypes and 18 % to 72 % in nine genotypes. Callus presence in Hi and Hy explants depended on the genotype and culture medium. The induced callus by different components of the evaluated medium was not always embryogenic. The number of globular embryos depended on the genotype and oscillated between 58 to 424 embryos in 0.83 g of callus, i.e. 70 to 510 embryos g^-1. The somatic embryogenesis was induced in young and immature foliar explants, in at least one treatment; and the explant type and culture medium with the best morphogenetic response for each genotype was identified.