Testing different grafting methods for vegetative propagation of baobab (Adansonia digitata L.) in Kenya to assist its domestication and promote cultivation

Abstract

Baobab (Adansonia digitata L.) is an indigenous fruit tree species of drylands in sub-Saharan Africa. Its leaves, fruits and seeds are important for income generation and food and nutrition security of local communities. Its fruit pulp is rich in vitamin C and calcium, among other nutrients. Domestication of baobab, using mother trees with desired traits for vegetative mass propagation and planting, could meet the increasing demand for baobab pulp and the decreasing abundance of the trees in natural habitats. Two grafting methods were tested in the ICRAF nursery site (Nairobi, Kenya) to identify a suitable propagation technique. Two mother trees were selected (Trees 1 and 2) for harvesting scions. ‘Top cleft’ and ‘side veneer’ grafting were performed on a total of 38 rootstocks for each mother tree (20 of 1-year and 18 of 2-year age), resulting in a total of 76 grafted trees. The grafted trees were then followed during eight months. The experiment was conducted to evaluate grafting success and shoot growth. Statistical analyses included Binomial Logistic Regression for survival rates and three-factorial ANOVA for shoot length. The overall grafting survival rate was 63%. Top cleft grafting showed slightly more survival success than side veneer (71% vs. 55%, p = 0.114). Using 2-year old rootstock was significantly more successful than 1-year old ones (75% vs. 53%; p = 0.029). Using scions from mother Tree 1 was significantly more successful than from Tree 2 (82% vs. 45%; p = 0.001). Length of new shoots growing from the scions of the successful grafts did not significantly differ among the treatments. Our results showed that both grafting methods and rootstock ages were successful and can contribute to the development of baobab domestication programmes for improving food security and livelihoods in African drylands.