Phenotypic variation among five provenances of Pterocarpus angolensis in Zimbabwe and Zambia

Abstract

The feasibility of utilising morphological markers for determining existing provenance variation in the African savanna tree Pterocarpus angolensis was assessed. Five provenances were used: Mtao, Gokwe, Nyazura, Chesa (Zimbabwe) and Kapirimposhi (Zambia). Two weeks after germination, seedlings were inoculated with mycorrhizal inoculum and raised in a glasshouse. Height and collar diameter were measured at one, three and five months of age (before stem dieback), and at 14 months (after stem dieback). At the time of dieback, percentage of seedlings losing leaves, stem dieback and mortality were recorded; numbers of new shoots produced in the recovery period were also determined. To further assess growth, leaf, stem and root dry biomass were measured after stem dieback at 14 months. At one month, Chesa seedlings were the tallest and Kapirimposhi seedlings were significantly shorter (p < 0.05) than the rest of the provenances. However, at three and five months of height growth no significant differences were observed. At one month, diameter growth was significantly different with the Kapirimposhi provenance having the smallest diameter (p < 0.05). At three and five months of seedling growth only the Gokwe provenance was significantly different from the rest of the provenances. By seven months of age, stem dieback was observed and foliage loss was over 60% in each of the five provenances. At 14 months of seedling growth after stem dieback the Nyazura and Kapirimposhi provenances were significantly shorter, whereas there were no significant differences in diameter growth and dry biomass from root, stem, leaf or root:shoot dry biomass ratio. Fourteen months after germination new shoots emerged from various axillary bud positions depending on the extent of dieback.

Keywords: diameter, dieback, height, morphological markers, Pterocarpus angolensis