This study reports the nitrate level of 22 vegetables species collected from 40 farms in several locations of an intensive agricultural area in two regions of Tunisia (Sousse and Monastir). Nitrate levels ranged between 57 and 2970 mg kg -1 . The highest and the lowest levels were found in turnip and tomato, respectively. Only five species (potato, field bean, cauliflower, pea and artichoke) had exceeded the norms established by the World Health Organization. Factors influencing nitrate accumulation in some vegetables were analyzed and discussed. It was observed that nitrate contents in vegetables varied depending on the type of vegetables, genetic factor, level of nitrogen fertilization and soil nitrogen content.

Knowledge on phenotypic and chemical diversity among fennel (Foeniculum vulgare Mill.) cultivars is a milestone in the improvement of this specie which is considered as one of the most important medicinal plants. For this purpose, the present study was conducted in order to compare for the first time fennel cultivars regarding their agro-morphological traits as well as their essential oil yield and composition. Ten fennel cutivars were cultivated in a randomized completely block design whereas the seeds essential oil was analysed by GC-MS analysis. All phenotypic traits showed variation among the cultivars examined. Correlations between traits showed a significant positive relation between yield and height, number of leaves, number of branches, number of umbels , number of umbellate and peduncle length. Significant genotypic variations were also observed in essential oil content and composition in which trans-anethole, estragole, fenchone and limonene were the main constituents. Clustering method classified the ten fennel cultivars into 3 major groups. Moreover, PCA analysis showed great dispersion of these cultivars. The diversity identified in this study, especially from the three varietal types, showed that some cultivars are featured with several agro-morphological and chemical characteristics and could be further exploited as promising material for the creation of new varieties.

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