Abstract

Leaf, fruit, wood, and gum of fifty-five plants collected in Sudan were evaluated by Dish pack method for their allelopathic activity through volatile chemicals using lettuce (Lactuca sativa) as a receptor plant. Several potential plants with high allelopathic activity, such as Terminalia brownie, Euphorbia hirta, Diospyros mespiliformis, Corchorus olitorius, Adansonia digitata, Hibiscus sabdariffa, were determined. Baobab (A. digitata) leaves demonstrated relatively higher inhibition (23.9 and 21.5% of hypocotyl and radicle, respectively) than most of the screened plant species. Identification of the volatile compounds using headspace gas chromatography-mass spectrometry revealed 1-decyne as the main volatile compound naturally released from dried baobab leaves. EC50 (50% growth inhibition) of radicle and hypocotyl growth of lettuce seedlings by authentic 1-decyne was determined in the headspace air using by GC-MS with Cotton Swab method at the concentration of 0.5 ng/ml. The obtained results could fully explain the plant growth inhibitory activity of baobab volatiles by the presence of 1-decyne. Thus, in this study, we first identified 1-decyne as a new volatile allelochemical from baobab leaves. 1-decyne might be an important allelochemical for the survival of baobab in Africa and our findings may also offer a potential for future development of new volatile plant growth modulator.

Key words: Adansonia digitata, baobab, 1-decyne, allelopathy, volatile, GC-MS, Sudan.