Somatic embryogenesis of a coffee (Coffea arabica L.) hybrid using leaf explants

Abstract

SummaryCoffea arabica is one of the most traded agricultural commodities in the World, and the major export commodity of Ethiopia. Improvement of this crop requires the development of hybrid varieties that possess desirable traits. The production and distribution of hybrid coffee is difficult due to the high costs required for manual crossing and maintenance. The use of somatic embryogenesis is an effective means of propagation. A protocol for somatic embryogenesis of hybrid C. arabica from leaf explants is described here. Leaf explants collected from healthy 1-year-old seedlings were used. The highest percentage of callus induction was observed from explants cultured on MS medium containing 1.0 mg l–1 2,4-dichlorophenoxyacetic acid (2,4-D) in combination with 2.0 mg l–1 6-benzylaminopurine (BAP). Embryogenic calli were obtained from leaf explants cultured on MS medium supplemented with 0.05 mg l–1 kinetin in combination with 0.1 mg l–1 indole-3-butyric acid (IBA). The highest number of embryos that germinated per explant (14.0 ± 1.7) was obtained on MS medium supplemented with 2.0 mg l–1 BAP in combination with 0.5 mg l–1 gibberellic acid (GA3). The maximum number of roots per plantlet (3.0 ± 1.0) was obtained on half-strength MS medium containing 0.5 mg l–1 indole-3-butyric acid (IBA). Acclimatisation of plantlets was achieved with a survival rate of 96.9%. This is an important achievement as acclimatising embryo-derived plantlets had been the most challenging feature of coffee tissue culture in Ethiopia. This protocol will enable us to multiply and supply large numbers of high quality hybrid coffee seedlings to farmers engaged in coffee production.