Comparative Analysis of Selected Factors Affecting Fruit Phenotype and Yield of Sclerocarya birrea in Tanzania

Abstract

Knowledge of fruit physical properties and yield is imperative for trees with commercial domestication
prospects like Sclerocarya birrea. This study assessed individual fruit weight and diameter as well as yield per tree for the three subspecies of Sclerocarya from two types of land use (farmland and wild). Ten female trees were randomly selected from on-farm and wild sites for each subspecies. From each tree, diameter and weight of 50 randomly selected fruits were measured during a peak fruiting while all fruits per tree were counted and recorded throughout the entire fruiting season for two consecutive years. Results showed that subspecies multifoliolata had significantly heavier fruits and more yield than subspecies birrea and caffra (p < 0.001) Fruits from subspecies birrea were significantly larger than those from the other two subspecies (p < 0.001).Trees from the wild population yielded more fruits that were also heavier that those from on-farm but the difference was only significant for subspecies multifoliolata (p < 0.001) Fruits from on-farm population of subspecies birrea were significantly the largest in diameter (p < 0.001). There was a strong relationship between fruit properties with crown diameter &dbh; and between yield and crown diameter while a decline in rainfall reduced fruit yield across the species and land use. Our results indicate that fruit physical properties and yield have allometric relationship with tree size structure and they vary with rainfall, type of subspecies and probably pollination intensity but not with farmers’ selection pressure and intervention.

Key Words: Sclerocarya, Yield, Land-use, Tanzania