EFFECTS OF AUXINS AND CYTOKININS ON CALLUS INDUCTION IN LEAF CULTURES OF COFFEA ARABICA F1 HYBRID
Access to planting materials is one of the main challenges constraining the wide adoption of the disease resistant, high yielding F1 hybrid coffee variety Ruiru 11 in Kenya. Mass propagation of this variety currently depend on a combination of methods, namely, artificial cross pollination, vegetative propagation and direct somatic embryogenesis. Both artificial cross pollination and vegetative propagation are cumbersome, labour intensive and inefficient on return on investment whereas direct embryogenesis is not amenable to temporary immersion systems which are more prolific. Protocols which optimise the use of indirect somatic embryogenesis, with an intervening callus stage, enable the full exploitation of temporary immersion systems for mass propagation of hybrid coffee variety, cultivar Ruiru 11. The objective of the current study was to investigate effects of plant growth regulators on the resultant callus from leaf explants from Ruiru 11 code 93 and Code 71. Plant growth regulators, auxins (2,4-dichlorophenoxy acetic acid [2,4-D] and Indole-3-butyric acid [IBA]) and cytokinin (Kinetin and Benzyl amino purine [BAP]), used singly and in combinations, were supplemented in Murashige and Skoog (MS) Media in different concentration levels – 0.5 mg/L, 1.0 mg/L, 1.5 mg/L, 2.0 mg/L and 2.5 mg/L-. Callus induction was observed in leaf cultures on Murashige and Skoog (MS) media with different concentration of 2,4-D supplied singly and across all auxin (2,4-D and IBA) and cytokinin (Kin and BAP) combination treatments. Maximum callus induction, Code 71 (88%) and Code 93 (100%) was obtained from MS media supplemented with 2,4-D and BAP (2.5+0.5 mg/L) which induced embryogenic white calli. Highest fresh weight was also obtained at 0.973 ± 0.011g (Code 71) and 0.649 ± 0.03g (Code 93) in similar combinations. This study provides a protocol for mass production of the two Coffee arabica varieties to meet the existing demands.