Diversity of selected macadamia accessions in Kenya and prospects for enhanced breeding

Abstract

Macadamia germplasm in Kenya originated from six seeds of Macadamia tetraphylla introduced in to Kenya in 1946 from Australia . A study was done to determine diversity among 39 accessions of Kenyan Macadamia germplasm using leaf, fruit and flower morphological traits. Analysis of variance indicated significant differences in leaf length, petiole length, number of spines per leaf, fruit length and width, cluster length, number of fruits per cluster, raceme length and number of flowers per raceme. UPGMA cluster analysis and principle component analysis (PCA) revealed inter- and intra-specific variation among species. Three major clusters were formed corresponding to the two cultivated species; Macadamia integrifolia and M. tetraphylla, and their natural hybrids. Leaf traits were the most effective in distributing the accessions in to respective clusters. PC1 accounting for 56.2% of leaf variability was effective in separating the two species on opposite sides. These results showed the relationships among the accessions and can, therefore, guide in cross breeding decision-making. However, molecular characterisation is required to confirm genetic identity and genetic distances.