Effects of Genotype and Plant Growth Regulators on Callus Induction in Leaf Cultures of Coffea arabica L. F1 Hybrid

Abstract

Access to planting materials is one of the main challenges constraining the widespread adoption of the disease resistant Coffea arabica L. F1 hybrid variety Ruiru 11 in Kenya. Production of the planting materials for the variety relies on several cost-intensive methods including hand pollination for hybrid seed production and vegetative propagation through cuttings. These seed production methods are inefficient and costly and rely heavily on the weather conditions. Production and supply of planting materials for the commodity is therefore unable to meet the annual demand for the variety. In an attempt to bridge the gap between the supply and demand, tissue culture technique has been deployed at the Coffee Research Institute in Kenya. This however requires empirical tests to optimise in vitro mass propagation protocols for hybrid coffee varieties. The current study investigated the effects of genotype and plant growth regulators, auxins and cytokinins, on induction of embryogenic callus in two composite genotypes of Coffea arabica L. F1 hybrid variety Ruiru 11. Code 71 and Code 93. Leaf explants from the F1 hybrid were cultured on half-strength Murashige and Skoog (MS) media supplemented with varied concentrations of plant growth regulators. Callus formation was evaluated weekly until the 60th day. Genotypic effects were assessed based difference on callus induction rates, biomass fresh weights and callus formation. The genotypes tested showed highest callus induction 88% (Code 71) and 100% (Code 93) with respect to the formation of embryogenic calli. Highest fresh weight was obtained at 0.973 ± 0.011g in Code 71 and 0.649 ± 0.03 g in Code 93 in MS media supplemented with 2,4-D + BAP (2.5+0.5 mg/L). The observed results are useful in formulating the best growth regulator concentration suitable for mass in vitro propagation of genotypes of Arabica coffee hybrid Ruiru 11 through callus induction in vitro of leaf explants.