PHENOLOGY AND GERMPLASM VARIATION OF Tetrapleura tetraptera (SCHUM. AND THONN.) TAUB.

Abstract

Tetrapleura tetraptera is a tree species of great ethnobotanical importance that is highly utilised and as such its natural population is threatened. For sustainable utilisation of the species, there is need for development of protocols for its domestication. However, critical information on species phenology, germplasm characteristics and macro-propagation, which are required for the domestication process are limited. Therefore, the flowering and fruiting patterns; germplasm variation and macro-propagation techniques for Tetrapleura tetraptera were investigated. Tetrapleura tetraptera trees were purposively selected from Forestry Research Institute of Nigeria (FRIN) and National Horticultural Research Institute (NIHORT) in Ibadan for phenological studies, based on availability. Onset and duration (days) of flowering and fruiting, number of flowers/inflorescence and synchrony (Z), were monitored on the trees for 20 months. Visiting insects, frequency of visits, pollen load and fruiting efficiency were assessed. For germplasm variation, 150 fruits each were purposively collected from Ibadan, Mamu, Iwo and Aponmu within the rainforest zone, based on access. Variation in fruit- length (cm), width (mm); number of seeds (NS) and seed weight (g) were determined for each location. In a completely randomised design experiment, height (cm), diameter (mm), and number of leaves of 50 uniformly growing seedlings were measured for six months. Stem cuttings (top, middle and base) obtained from seedlings from all locations were macro-propagated. Cuttings survival, number of roots/cutting (NR) and root length (RL, cm) were assessed using standard procedures. Flowering frequency (FF) was correlated with temperature, relative humidity and rainfall. Data were analysed using descriptive statistics, correlation analysis and ANOVA at α0.05. Flowering occurred twice a year (January-July; October-December), while fruiting occurred between February-August and November-December in both sites. Flowering duration was 104.3±7.6, 48.7±10.6 and 93.8±12.3, 62.3±4.4 at FRIN and NIHORT, respectively. Fruiting duration was similar in both sites (70-131 and 18-38). Number of flowers/inflorescence varied from 294.2±40.3 to 296.6±37.3. The highest Z (FRIN: 0.67±0.1, NIHORT: 0.88±0.1) occurred in the first flowering cycle and least in second (FRIN: 0.34±0.27, NIHORT: 0.43±0.29). Eight and 13 insect species were encountered at FRIN and NIHORT, respectively. Monomorium minimum was most frequent (FRIN: 27.9%; NIHORT: 22.9%). Bombus sp. had highest pollen load (25%), while fruiting efficiency ranged from 0.25-0.99% in both sites. Fruit- length (16.7±1.48-20.9±2.5), width (37.2±5.1-52.4±5.9) and NS (10.8±3.9-15.6±2.4) were significantly different. Aponmu had highest seed weight (16.2±0.1), while Mamu had least (10.9±0.3). Seedling height (53±17.8-61.8±12.6) and number of leaves (14.1±2.9-16.3±2.9) were significantly different. Cuttings survival (56.3%), NR (2.19±2.3) and RL (2.8±2.6) were highest at base and least at top (1.8%, 0.07±0.9 and 0.04±0.3). Mamu had highest survival (38.2%), NR (1.5±2.3), RL (1.56±2.2) while Ibadan had least (12.4%, 0.4±1.2, 0.6±1.9, respectively). Flowering frequency was positively correlated with temperature (r=0.53 (FRIN); 0.52 (NIHORT), but negatively correlated with relative humidity [r=-0.60 (FRIN); -0.22 (NIHORT)]. Tetrapleura tetraptera exhibited extended and synchronised phenological patterns. Fruit and seed source affected early growth and development. Stem cuttings from the base had better rooting ability and are most suitable for macro-propagation.