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.

Nitrate (NO₃^‒) is the most important source of mineral nitrogen (N) affecting the vegetative growth, the tuber yield and the quality of potato (Solanum tuberosum L.). The screening of 16 potato cultivars for low nitrate content was reported and the effects of genotype and experimental factors on nitrate accumulation were studied. Both genotype and growing season had a highly significant effect on dry weight, number of tubers/plant, yield and nitrate accumulation in potato which varied significantly from one genotype to another. Furthermore, nitrate accumulation varies with the season, being higher in the first season (autumn) than in the second season (spring), for all the genotypes. The cultivars Safrane and Universa followed by Actrice and Alaska produced the highest tuber yield/plant during the first and second season, respectively, accumulating higher quantities of nitrate compared to other cultivars. Ponomera cultivar was of interest from a breeding perspective due to both combining best tuber yield/plant and low nitrate accumulation for both growing season. Expression pattern of nitrate transporter genes (StNRT1.2, StNRT1.5 and StNRT2.1) has been reported. Thus, these genes were differentially expressed which could be explained in part by the difference in nitrate accumulation rate between the studied cultivars. The results showed that high accumulator genotype got significant higher expression level of StNRT1.2, StNRT1.5 or StNRT2.1 which lead to the higher nitrate uptake rate and consequently higher nitrate accumulation than low accumulator genotype.

The goal of this investigation was to evaluate the in vitro and in vivo efficiency of Raphanus raphanistrum extracts against Fusarium and Pythiaceae species associated with apple and peach seedling decline in Tunisian nurseries. A chemical composition of organic extracts was accomplished using liquid chromatography, thin layer chromatography, and gas chromatography analysis. The in vitro test of three aqueous extract doses of R. raphanistrum against some apple and peach decline agents showed its efficacy in reducing mycelia growth. The in vivo assay of fine powder of this plant on peach seedlings revealed that treatment 8-weeks before the inoculation and planting was more efficient than the treatment before one week. This experiment revealed that the root weight of peach seedlings inoculated by F. oxysporum was improved to 207.29%. For apple seedlings, the treatment 8 weeks before the inoculation and plantation was more efficient than the treatment one week before; it reduced the root browning index. The study of R. raphanistrum chemical composition and its efficiency showed that the glucosinolates products: nitrile (4-Hydroxy-3-(4-methylphenylthio) butane nitrile, benzene acetonitrile, 4-fluoro,butane nitrile, 4-hydroxy-3-[(4-methylphenyl) thio] nitrile), and thiocyanate molecules (thiocyanic acid, ethyle) are responsible for the anti-fungal activities.

The purpose of this study was to investigate the impact of marine algal extract as foliar spray on growth, physiological, mineral composition, different osmoprotectant levels, various parts of antioxidant system, and gene expression of greenhouse lettuce (Lactuca sativa L.) plants grown under saline conditions (50mM and 100mM). Through LC/MS analysis, the algal extract's phenolic composition was determined by its abundance in quinic acid, gallic acid, kaempferol and luteolin. The concentration of leaf proline increased while the biomass production, chlorophyll fluorescence, SPAD index and mineral composition all decreased as a result of salt stress. The salt-stress tolerance mechanism in lettuce involved the expression of genes that encode antioxidant enzymes, including LsSOD, LsCAT, and LsAPX, in both stressed and control plants, which demonstrates their important roles. The findings revealed that plants that were treated with marine algal extract had a greater ability to handle salt challenge, as evidenced by a significant (p < 0.05) increase in plant growth, SPAD index, Fv/Fm ratio, a better nutritional status in addinto a better osmoprotection against salt stress. Malondialdehyde level, Hydrogen peroxide and stability index levels were significantly decreased. Furthermore, the antioxidant system saw a significant improvement, as demonstrated by the increased activity of catalase (CAT), superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) under moderate stress conditions (50mM) and more abundant LsCAT transcripts in the stressed plants. Overall, our findings indicate that marine algal extract appears to be an effective biostimulant product for treating lettuce under saline conditions. Keywords: antioxidant enzymes, chlorophyll fluorescence, gene expression, growth performance, Lactuca sativa L., marine algal extract, mineral composition, osmoprotectants.

The current applied research evaluated the impact of magnetic water on agronomic and physiologic responses of tomatoes. The field experiment consisted of the irrigation of a 1000 m² tomato plot with two water treatments (NMW = non-magnetized water; MW = magnetized water) and three tomato varieties (Dorra, Ercole, and Gladys). Biomass accumulation, yield, physicochemical quality traits, osmoticums, antioxidant enzymes, and the transcript level of defense-related genes were analyzed. Results showed that MW treatment showed 32%, 53%, and 57% yield increase in Dorra, Ercole, and Gladys, respectively. Dorra and Gladys were, respectively, the highest and the lowest yielding varieties. MW was effective in enhancing the irrigation water use efficiency (IWUE) and irrigation water productivity (IWP). Plants grown under MW had less catalase (CAT), guaiacol peroxidase (GPOX), super oxide dismutase (SOD), and ascorbate peroxidase (APX) activities, and hydrogen peroxide (H₂O₂) level. The reducedproline and soluble sugar content (SSC) accumulation in MW treatment indicate a reduced osmotic reaction. The upregulation of SlAPX in Gladys and SlSOD in Dorra and Ercole with MW had positive impacts on growth regulation and reduction in oxidative damage. The results clarified the roles of MW and its rule mechanisms in tomato, giving more theoretical foundation for physical water treatment in the agricultural sector.