Endogenous sugars associated with development of somatic embryos of coffee (coffea arabica l.)

Abstract

Plant tissue culture allows rapid in vitro regeneration of plants. Processes and factors related to development of coffee somatic embryos are not well established, resulting in poor induction or few embryos and hence low regeneration of coffee seedlings. This research identified and quantified endogenous sugars (glucose, fructose and sucrose) associated with somatic embryogenesis in Coffea arabica cultivar Ruiru 11. Third leaf pair of greenhouse-grown mother plants was used as explants in half-strength Murashige and Skoog (MS 1962) media. Both green and brown leaf discs cultures with and without embryos were used to characterise the sugars. Embryos with fresh culture media and leaf explants were used as controls. A complete random design replicated thrice and repeated in two seasons in 2014 was used. Sucrose, fructose and glucose were extracted and analyzed using a Knuer HPLC and identified by comparing retention time with that of sucrose standard. Glucose content was significantly (P<0.05) high in brown leaf discs without embryos in both seasons (40.15 mg/g and 37.75 mg/g FW, respectively). Fructose content was significantly (P<0.05) high in brown leaf discs without embryos in both seasons (48.4mg/g and 42.4 mg/g FW). Sucrose content was significantly (P<0.05) high in fresh leaves in both seasons (18.87 mg/g and 19.57 mg/g, respectively) whereas in season 2, the sucrose content was significantly (P<0.05) high in embryos on green leaf discs (58.43 mg/g). Harmful effects of high accumulation of fructose and glucose which are reducing in nature resulted in no embryo development in the brown leaf discs. High sucrose which resulted in brown and green leaf discs with embryos implied that embryo maturation is associated with storage material accumulation and is accompanied with an increase in sucrose to hexose ratio.