Uapaca kirkiana phenological phases and effect of fruit thinning on fruit traits in Malawi

Uapaca kirkiana is one of the most preferred indigenous fruit trees in many countries of southern Africa, including Malawi, but it has a long juvenile phase. In order to shorten this juvenile period, grafting is widely applied. High fruit load, small fruit size and premature fruit abortion have been observed in mature U. kirkiana. This high fruit load may lead to alternate bearing and/or production of small fruits in the next fruiting season. This study was undertaken at ICRAF-Makoka in Malawi with the objectives of assessing (1) the effect of fruit thinning on U. kirkiana fruit yield and size and (2) establishing leaf and fruit phonological phases of U. kirkiana annual growth cycle. Immature fruits were thinned manually to one fruit per cluster along the tree branch either (1) 5 cm, (2) 10 cm, or (3) 15 cm apart. Leaf, flowering and fruiting phenological phases (onset and end) were established. Fruit thinning significantly (P<0.0001) improved fruit weight and thinning fruit 15 cm apart produced bigger fruits with smaller endocarp (rind) weight. It also reduced seed weight, an indication of improvement in fruit pulp content. No major variations in phenological phases were found in the two years of the study. We conclude that fruit thinning improved U. kirkiana fruit weight and size, especially at longer fruit thinning distance of 15 cm apart.