Rooting ability of Vitex fischeri (Meru oak) cuttings under different rooting media and IBA concentrations

Abstract

Demand for Vitex fischeri (Syn. Vitex keniensis), has made it a priority species for commercial planting and improvement programmes. Kenya Forestry Research Institute (KEFRI) has embarked on an improvement program for V fischeri and has selected over 70 trees with superior phenotypes for propagation. However, no vegetative propagation technique has been developed for mass propagation of this species. The objective of this study was therefore to develop vegetative propagation methods for raising V fischeri seedlings through stem cuttings. The cuttings were obtained from crowns of mature trees and l8-month-old seedlings. Five different rooting media (sub soil, forest soil, coconut peat, sand-coconut peat mixture and sand alone) and four Indole Butyric Acid (IBA) hormone concentrations (0, 0.5, 1 and 2%) were used. The experiments were set up in a split-plot design and incubated in a non-mist propagator. Rooting was assessed at the end of 7th week for seedling stem cuttings and 15th week for mature tree cuttings. Rooting percentage, number of roots and root length were analyzed using analysis of variance, linear mixed and generalized linear regression model, respectively. Rooting from seedling stem cuttings ranged from 23 - 93% in various combinations of rooting media and IBA concentrations. Mature tree cuttings and cuttings incubated under sub soil did not root. The highest rooting percentage was recorded under sand (93.3%) followed by coconut peat (83.3 %) at 0.5% IBA concentration. Cuttings in forest soil and sand-peat mixture rooted best at 1 and 2% IBA concentrations. This study recommends use of seedling stem cuttings of V fischeri for vegetative propagation incubated either in sand or forest soil at 0.5 and 1% IBA concentrations, respectively.