Sustainable use and conservation of Vitex doniana Sweet: unlocking the propagation ability using stem cuttings

Abstract

One of the major constraints for domesticating widely used wild tree resources by local communities is the lack of adequate propagation techniques. In the case of Vitex doniana, seed propagation has usually been reported difficult and vegetative regeneration is rarely explored. To understand how stem cutting size or hormone application affect the sprouting and early growth ability in that species we used two categories of cutting diameter (1cm<D1<2cm and 2cm<D2<4 cm) and three categories of cutting length (L1 = 30 cm, L2 = 50 cm, L3 = 70 cm) and hormone application as fixed factors in a split-split-plot design. A cohort of ten cuttings were used as experimental unit to measure cutting sprouting rates, the sprouting time, the number of new buds, the twig length and the number of leaves. Generalized models with poisson or binomial error distribution were used to test for deviance. To account for pseudoreplication due to repeated measures, we used generalized mixed effect models fit by maximum likelihood. Allometric analyses were performed to understand how the main factors affect the relationships between the twig length and the number of leaves. The results reveal that hormone effect on cutting sprouting was not obvious. However, cutting diameter and length significantly affect sprouting rates, the sprouting time, the number of new buds, the twig length, and the number of leaves produced. Stem cutting of 30 cm height and 2 to 4 cm diameter performed well (100% sprouting) compared to others. The relationships between the twig length and the number of leaves also changes with different cutting diameter and length. These findings offer new insights into the agroforestry promotion of Vitex doniana to reduce the pressure on wild tree population in Benin.