Endogenous Chlorogenic Acid and Caffeine Associated with in Vitro Somatic Embryogenesis of Coffee (Coffea Arabica L.)

Abstract

Coffee plays a central role in Kenyan economy through foreign exchange and income earnings. However, its production has been constrained by factors like high production cost, inappropriate technology and inadequate seedlings. Coffee somatic embryogenesis is another vegetative propagation method, besides cuttings and grafting. Its main use is for F1 hybrid propagation to avoid manual hybrid seed production. Developmental processes and factors related to coffee somatic embryogenesis are not well established, resulting in poor induction or few embryos and low subsequent seedling regeneration. This study identified and quantified endogenous chlorogenic acid (CGA) and caffeine phenols and alkaloids associated with Coffea arabica ‘Ruiru 11’ somatic embryogenesis. Third leaf pairs of greenhouse-grown mother plants were cultured in half-strength Murashige and Skoog, 1962 media. Both green and brown leaf discs with and without embryos constituted treatments, and embryos with fresh culture media and leaf explants constituted controls. A completely random design replicated thrice and repeated once in 2014 was used. Chlorogenic acid and caffeine were extracted and analyzed using a Knuer HPLC system and identified by comparing their retention time with that of standards. Fresh leaves had high 6.51 mg/g FW CGA and 1.14 mg/g FW caffeine. Chlorogenic acid amounting 5.34 mg/g FW was significantly (P<0.05) high in embryos on green leaf discs. Embryos on brown leaf discs had significantly (P<0.05) high 0.5778 mg/g FW caffeine. Green leaf discs with embryos had 0.004 mg/g FW highest endogenous CGA. Culture media with embryos on green leaf discs had 0.6935 mg/g FW highest caffeine. Generally, higher CGA was in non-embryogenic brown and green leaf discs, compared to embryogenic brown and green leaf discs. Embryogenic capacity seemed to be associated with a balance of phenolics. High caffeine in embryos formed on brown leaf discs was a result of accumulation during embryogenesis. The inference that high caffeine in culture media allowed development of somatic embryos when embryos avoided caffeine auto-toxicity through space and time separation will be presented and discussed.