REPRODUCTIVE PHENOLOGY AND PROPAGATION OF Pycnanthus angolensis (WELW.) WARB. IN SOUTHWESTERN NIGERIA

Abstract

Pycnanthus angolensis is one of the overexploited indigenous tree species used in phytomedicine. Various parts of the tree are harvested from wild populations for ethnobotanical purposes, thus threatening the sustainable utilisation of the species. However, information on phenology and propagation techniques pre-requisite for ex-situ conservation of this species is limited. Therefore, flowering and fruiting patterns, germplasm characteristics and in vitro propagation protocols of Pycnanthus angolensis were investigated.

Matured trees of Pycnanthus angolensis (20.0±5.0years) were purposively selected from Osun (Gbongan, Ajaba), Ekiti (Otun, Ayetoro) and Oyo (Idito, Adewumi) States, based on availability. Population frequency, onset and duration of flowering and fruiting (months) and period of fruit colour change (days) were monitored for 24 months. Fruit and seed morphology were determined by measuring weight (g), width (cm) and length (cm) of 100 samples per location. One hundred seeds per location were sown in the nursery to determine germination speed (day-1), total germination and seedling survival. In a completely randomised design experiment, 10 uniformly growing seedlings were selected from each location and used to assess seedling height (cm), nodulation and Number of Leaves (NL) for four months. Four growth hormones: Naphthalene Acetic Acid (NAA), 6-Benzyl Amino Purine (BAP), Kinetin and Indole Butyric Acid (IBA), were used for in vitro propagation of embryo and nodes of seedlings following standard procedures. Shoot height (cm), Number of Nodes (NN), NL, plantlet survival, Shoot Formation (SF, %) and callus induction were assessed for four months. Data were analysed using descriptive statistics and ANOVA at α0.05.

Population frequency was highest in Gbongan (10.5%) and least in Idito (1.8%). Flowering onset and duration were September-November and 5-8 months, respectively. Fruiting onset and duration were January-June and 8-10 months, respectively. Four stages of colour change: brown (30-150), green (30-105), greenish yellow (30-89) and yellow (90-202) were observed. Highest fruit weight (19.9±0.2), width (5.3±0.0) and length (4.2±0.0) were obtained from Ajaba, Otun and Gbongan, respectively. Ayetoro had the least weight (12.5±0.2), while Idito had the least width (3.9±0.0) and length (2.7±0.1). Seed weight varied from 2.1±0.1 (Ayetoro) to 4.4±0.1 (Ajaba), while width increased from 1.4±0.1 (Ajaba) to 2.4±0.1 (Gbongan). Otun had highest seed length (3.4±0.0), while Idito had the least (2.9±0.0). Germination speed, total germination and seedling survival ranged from 27-49, 13-81% and 11-56%, respectively. Highest seedling height (22.9±1.4), nodulation (15.0±0.8) and NL (12.9±0.7) were from Gbongan; while the least (8.0±1.4, 5.0±0.8 and 2.6±0.7) were from Ayetoro. For in vitro propagation of embryos, highest Shoot height (2.1±1.0), NN (3.2±1.0), NL (2.4±0.8) were from Ayetoro, Ajaba and Gbongan, respectively. Idito had the least shoot height (1.6±1.0) while Adewumi had the least NN (2.3±1.0) and NL (1.4±0.8). Plantlet survival varied from 4-25%. Shoot formation (20%) were obtained for nodes exposed to 1.0-3.0 mg/L NAA+10mg/L IBA and 30% callus induction was observed for nodes treated with MS+1.0 mg/L NAA+10 mg/L IBA. Pycnanthus angolensis exhibited extensive flowering and fruiting period. Germplasm characteristics influenced seedling growth. Embryo and nodal culture for in vitro propagation were feasible using MS+1.0mg/L NAA and MS+1.0mg/L NAA+10mg/L IBA, respectively.