Traditional agricultural systems are receiving increasing attention at the international level due to their multifunctional role. The Globally Important Agricultural Heritage Systems (GIAHS) programme of the Food and Agriculture Organization (FAO) aims to identify agricultural systems of global importance, preserve landscape, agrobiodiversity and traditional knowledge and apply the principles of dynamic conservation to promote sustainable development. Biodiversity associated to traditional agricultural practices is particularly important, especially in difficult environments, like traditional oases, for ensuring food and nutrition to local communities. We documented landscape and biological diversity associated with traditional agricultural practices in three traditional oases in Tunisia, through a landscape analysis based on land-use survey, and an assessment of cultivated species. Results show that the landscape structure is dominated by agricultural land uses and characterized by a high level of diversification. Agrobiodiversity is high: we identified 20 varieties of date palm, 21 species of fruit trees, 21 vegetable species and two fodder crops. Results highlighted that traditional oases, as other agroforestry and agricultural heritage systems, continue to play a crucial role in maintaining genetic resources and agrobiodiversity. Farmers who, all over the world, still cultivate applying traditional practices are the main actors that practice a real conservation of genetic resources and diversity by maintaining traditional cultivars and a diversified landscape structure. Our methodology, based on the combined assessment of land uses and agrobiodiversity, can be replicated in other agricultural heritage systems to evaluate and measure possible transformations and identify the best strategies for their preservation.
Tunisia is one of the world’s largest producers of olive oil, and it preserves pools of olive genetic diversity that are still unexplored. A recent prospection and collection program of the National Gene Bank of Tunisia (NGBT) focused on the vast oasis of Degache, in the south west part of Tunisia, where 47 samples were collected and genetically characterized through simple sequence repeat (SSR) markers. Identification and authentication of genotypes were obtained through comparison with reference cultivars belonging to the Olive National Collection of Tunisia (IOC) and with cultivars from Algeria, Italia, Syria and Lebanon. Degache olive genotypes showed large genetic variability, a significant diversity from the reference germplasm, and a clear differentiation from modern varieties. The population structure analysis identified four gene pools characterizing genotypes from different area of origin. Two gene pools appear to be more represented in germplasm from southern Tunisia, where environmental conditions at critical plant development phases, are harsher. This suggests that this germplasm might present traits of adaptation useful for breeding to improve resilience to abiotic stresses. Our results will support ex situ and in situ conservation activities of Tunisian olive germplasm pursued by the National Gene Bank of Tunisia.
SummaryA total of seventeen olive ecotypes were identified in the oasis region of Degache (Tozeur, Tunisia). The following physicochemical parameters of their oils were studied: acidity, refraction index, polyphenol, chlorophyll and carotene contents, oleic, palmitic and linoleic acid levels and the UV absorbance (K232 and K270). The acidity, K232 and K270 parameter values were used to classify most of the olive oils considered as ‘extra virgin’. The highest carotene, chlorophyll and polyphenol contents of the olive oils examined were found to be 13.60 ppm, 9.10 ppm and 796 ppm, respectively. The oleic acid level of the olive oils considered ranged between 47% and 73%, whereas the palimtic acid level ranged between 11.8% and 23%, and the linoleic acid level ranged between 8.8% and 22.5%. Therefore, the fatty acid composition of the most olive oils considered was in keeping with the IOC norms. The Pearson correlation coefficients obtained were found to be negatively significant for the oleic, palmitic and linoleic acid levels recorded. The cluster and principal component analyses performed revealed the importance of fatty acids and polyphenol contents in the clustering of olive ecotypes. The selection of olive ecotypes according to oil quality is possible, requiring further studies focusing especially on their agronomic characters.
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