Germination, seedling growth requirements and antimicrobial properties of Boscia albitrunca — A keystone species in arid southern Africa

• Boscia albitrunca is an ecologically, culturally and medicinally important plant in southern Africa.
• The effect of some abiotic factors on seed germination and seedling growth of B. albitrunca were investigated.
• Warm stratification (30 °C) of intact seeds for 14 days achieved maximum germination.
• Higher antimicrobial activity was recorded for root extracts of some treatments.

Boscia albitrunca (Burch.) Gilg & Gilg-Ben (Capparaceae) is an ecologically, culturally and medicinally important plant in southern Africa. The effect of some abiotic factors on seed germination and seedling growth of B. albitrunca were investigated. Warm stratification (30 °C) of intact seeds (with seed coat) for 14 days achieved maximum germination (100%). Intact seeds without stratification showed very low germination (8%). Smoke–water (1:500 v/v)-treated seeds (without seed coat) showed a significant increase in germination (83%) compared to the control (47%) at 25 °C under a 16 h photoperiod. Increasing watering frequency enhanced most of the growth parameters of four-month-old B. albitrunca seedlings. Similar results were obtained when seedlings were treated with 25% Hoagland's nutrient solution. Deficiency of macronutrients (N, P and K) negatively affected growth of B. albitrunca seedlings. Higher antimicrobial activity of the experimental seedlings was observed in 80% ethanol extracts compared to the water extracts. The best minimum inhibitory concentration (MIC) values of 0.39, 0.78 and 0.78 mg/ml against Bacillus subtilis, Staphylococcus aureus and Escherichia coli respectively, were observed in 80% ethanol root extracts of seedlings supplied with 25% Hoagland's nutrient solution and grown with phosphorus deficiency. Similar results were obtained for antifungal activity with these treatments. Findings of this study will be useful for the propagation of B. albitrunca plants with insight on ways to promote high antimicrobial activities.