Acacia tortilis (Forsk) Hayne subsp raddiana (Savi) in a North African pseudo-savanna: Morphological variability and seed characteristics

Abstract

Acacia tortilis (Forsk) Hayne subsp. raddiana (Savi) Brenan (Family Fabaceae; subfamily Mimosoideae) is a pioneer tree of dry areas and it is a drought-resistant species. In spite of its several uses, there are no published studies which deal with relation between its adaptive features and fruit production for the Tunisian Arboretum. For this reason, a study was carried out in Bouhedma National Park to investigate morphology and seed production of A. tortilis pseudo-savanna for three successive years: 2006, 2007 and 2008. Two hundred and fifty trees from five plots in the three integral protection zones from five altitudes were studied to assess their genetic variation based on morphological parameters and fruit characteristics. The averages of the main descriptive morphological values of A. tortilis trees are 3.52 m of the height, 13.83 cm of the diameter at the base, 7.47 cm for the diameter at 1.30 m, 4.46 m for the diameter of crown North-South and 4.15 m for the diameter of crown East-West. The means of the main descriptive morphological values of pods are for the number of seeds before maturity 189.36, for number of seeds after maturity 50.625, for loss in pods 85.06%, for total number of seeds 406.11, for total weight of seeds 14.12 g and for the percentage of seeds infested 32.72%. Most of the measured parameters showed significant differences that indicate a high genetic diversity. Bruchidus has been recorded as a serious pest of A. tortilis seeds. The infested of seeds is directly related to number and loss in pods, number and weight of seeds (Pr <0.0001). Key words: Acacia tortilis, altitude, morphological diversity, pods, production, seeds.