Abstract

L.tN. Gitonga, S. T. Gichuki, K. Ngamau, AWT Muigai, EM Kahangi, LA Wasilwa, S Wepukhulu and N Njogu

Macadamia, (Macadamia spp.) is conventionally propagated by grafting scions from selected superior cultivars onto rootstocks raised from seed, a process that takes about two years in addition to high inputs thus ending up with costly seedlings. A study was conducted to investigate the possibilities of applying tissue culture techniques in mass production of clean planting materials. Different types of explants sourced from either grafted seedlings or from intact or cut-back field grown trees were evaluated in view of their regenerative potential. The effects of age and genotype of the explant were also investigated. Results indicated the significant effect of explant type in mass production. Only nodal segments gave satisfactory results producing two to three shoots within four to six weeks. Nodal segments at the 1st, 2nd and 3rd bud position performed better than those obtained at the 4th, 5th and 6th bud position. Explants from mature field-grown trees displayed similar properties to those from grafted green-house seedlings and were better than those obtained from cut-back trees. Explants from cultivars of Macadamia integrifolia performed better than (M. integroifolia × Macadamia tetraphylla) hybrids. These results suggest that optimization of these factors can help in development of a commercially viable tissue culture system for Macadamia.