Improving exploitation of Pterocarpus angolensis : seed germination, micropropagation and genetic diversity
Studies of seed dormancy breakage, micropropagation and genetic diversity were conducted on seed from Zambia and Zimbabwe. In seed dormancy breakage, nicking part of the seed coat and gibberellic acid treatments GA3 and GA4/7 were investigated. In Study 1) nicking had significantly higher germination, with a rate of 99% within five days of sowing, whereas GA3 treatment and the control had 65 and 69% germination respectively after four weeks. In study 2) 36, 36, 55 and > 91% germination were obtained with GA4/7, GA3, the control and nicking respectively after six weeks. In micropropagation experiments designed to investigate the optimum conditions for plantlet production, 6-benzylaminopurine (BAP), isopentenyl-adenine (2-iP) and thidiazuron (TDZ) were tested for shoot induction of cuttings from four weeks old P. angolensis seedlings. BAP at 5 mg.l-1 had significantly higher shoot multiplication compared to 0 - 2 mg.l-1 BAP concentrations. Sprouted axillary buds in 0.1 to 2 mg.l-1 TDZ treated cuttings did not elongate to usable sizes compared with BAP treated shoots. 2-iP at 0.5 - 5 mg.l-1 produced roots instead of shoots. Indole-3-butyric acid (IBA), indole-3-acetic acid (IAA) and the control were tested for ability to root cuttings. IAA at 1 mg.l-1 and IBA at 1- 4 mg.1-1 had a significantly higher number of roots. The control was efficient in root production. Using RAPD markers, within population genetic variation was revealed. Moderately high population differentiation of PHIst = 0.165 and 0.192 were found in two studies. This revealed significant gene flow between populations. These studies can be used to guide sustainable management, utilisation and domestication of P. angolensis in the future.