Identification and selection of superior phenotypes of Uapaca Kirkiana Muell Arg. (Euphorbiaceae), a priority indengenous fruit tree of Zimbambwe.

Abstract

The International Centre for Research in Agroforestry (ICRAF now known as the World Agroforestry Centre) initiated research and development work on at least 20 priority indigenous fruit trees in 5 countries in Southern Africa including Zimbabwe. The long term objective of this work was to improve food security and income generating capacities of local communities through domestication, marketing and commercialisation of indigenous fruit trees. Country specific priority species were identified based on consultations with a wide range of users. For Zimbabwe, Uapaca kirkiana emerged as a priority species with economic potential and has since become the focus of intensive research. A study aimed at identifying and selecting superior phenotypes of U. kirkiana was initiated in six districts of Murehwa (Natural Region I), Goromonzi (Natural Region II), Rusape (Natural Region II), Bindura (Natural Region II), Masvingo (Natural Region III) and Gokwe (Natural Region IV). Participatory Rural Appraisal (PRA) techniques in the form of group discussions amongst researchers, extensionists, school children, vendors and processors led to the identification of 48 trees of superior phenotypes. Tree location and altitude were recorded using the Geographical Positioning System (GPS). Fruit size, colour, shape were recorded. Total Soluble Solutes (TSS %) was measured using a hand refractometer. The largest fruits (42.3 g/fruit) were collected from Gokwe (ICR03GokZW41) whilst the smallest fruits (9.1 g/fruit) were collected from Rusape (ICR03RusZW53). Fresh fruit weight was strongly correlated to the seed weight (r = 0.813). Fruits with higher pulp content had a lower seed weight (r = −0.452). Fruits from Gokwe and Masvingo had higher TSS percentage. Basing on stakeholders’ selection criteria and laboratory analysis, 23 trees above the mean fruit weight (20.63 g/fruit) were classified as large, whilst 24 trees with pulp content above the mean of 45.18% were classed as pulpy and 22 trees with TSS above 19.53% were classed as sweet. Similarity of the phenotypes was determined through complete linkage in hierarchical cluster analysis. Clustering confirmed the characterisation by farmers using taste as a key method of selecting suitable phenotypes. In-situ conservation and establishment of clones from the selected trees is recommended for purposes of commercialising these superior phenotypes.