PROPAGATION VÉGÉTATIVE DE VITEX DONIANA SWEET À PARTIR DE SECTIONS DE RACINE

Vitex doniana Sweet is a common multipur- pose species in tropical Africa, which has considerable socio-economic importance. Unfortunately, it is extracted from the wild and there has been little or no focused ef- fort to domesticate and cultivate the spe- cies. Mastering its propagation through root segment cuttings (RSC) is a real alternative to the difficult process of regeneration from seeds. The aim of our study was to assess two of the key factors (rooting  medium  and root diameter) that influence its root- ing ability. The root system of 23 trees was partially excavated to a depth of 20 cm. Root segment cuttings 15 cm in length were carefully cut and arranged horizontally in a polypropagator, on five different substrates. The experimental setup involved a split-plot design with three replications. The main treatment was applied to all five substrates: black soil (Bs), fine sand (S), sawdust (Sd), 50% Bs/50%  Sc (Bs-Sc)  and 50% Bs:50%    S (Bs-S). The secondary treatment covered two diameter size classes (0.5-1cm; 1.1-2.5 cm). The  latency  time  before  emergence  was  8 weeks for the aerial shoots and 12 weeks for the roots. After 28 weeks, the percentage of leafy shoots formed  varied  from  28.3% in the black soil substrate (Bs) to 55.0% in the sand (S). Aerial shoots developed mainly (82%) on the distal  pole. The RSC diame-  ter had a significant influence  (P  <  0.01) on the development of leafy shoots. The budding rate of the RSC was 21 ± 1.8% for 0.5-1 cm RSC and 86 ± 7.8% for 1.1-2.5 cm RSC. The diameter also had a significant impact (P < 0.001) on RSC rooting. The rooting rate was 12 ± 2.3% for 0.5-1 cm RSC and 59.3 ± 4.7% for 1.1-2.5 cm RSC. These results show that  vegetative propagation by RSC could improve the economic value o f V.    doniana  in Cameroon’s  savannah uplands.