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ABSTRACT. This study aims to evaluate the effect of seed priming for two pepper varieties by extracts of two algae thalli on the performance of growth at vegetative stage.The seeds were soaked in thalli aqueous extracts (at 20, 40, 60, 80 and 100 g/L), for 24 h at 28±2°C, rinsed thoroughly with distilled water and then dried to their initial weight as a first batch (SD), a second batch of seeds was considered, corresponding to seeds placed in Petri dishes to germinate directly after washing (SND). Untreated seeds were the control. The results showed than the priming has improved seedlings growth for both varieties. Seed priming with algae aqueous extracts has improved roots and shoots length. The best stimulations were 220% and 70%, respectively, recorded for seedlings of Baklouti and Chargui varieties, following the priming with the extract of Padina pavonica at 40 g/L concentration.These improvements appear to be related to a better photosynthetic intensity, an increase in the number of leaves and the water content, which were noted in plants from pretreated seeds. Finally, the results indicate that, generally, the plantlets from SND were more vigorous. The results of this work show that algae could be an inexhaustible resource of substances, that can be used as an alternative to chemicals used in the pretreatment of seeds, reducing the risk of pollution and preserving the biological material.

This study was conducted to evaluate the effect of seed bio-priming on the salinity tolerance of pepper (Capsicum annuum L. var Chargui). The pretreatment was carried out by the aqueous extracts of Padina pavonica (at 60 g/L) and Jania rubens (at 80 g/L). The tests were carried out at 0, 3 and 12 g/L of salt for germination and 0 and 3 g/L for the growth which was conducted in hydroponics. Seeds were soaked in these extracts, and two batches were considered (treated and untreated (control)). The results showed that the effect of salt was harmful on the integrity of the membrane, respiration, and mineral (Potasium and Posphorus) compositions of pepper. Nevertheless, it increased proline, total soluble sugars, sodium and secondary metabolites accumulation. the pretreatment showed that the best tolerance to salt stress in pepper was due to a better oxidative status demonstrated by the reduction of oxidative damage (reduction of leakage of electrolytes and MDA content), accumulation of secondary metabolites, at better hydration resulting from more efficient osmotic adjustment due to the accumulation of osmotica (proline, total soluble sugar, potassium and phosphorus) and an increase in metabolic activity by the improving breathing. This technique of biological pretreatment may submit with agriculture an interesting tool to increase plant tolerance to salt stress and to find an alternative to any chemical use.

The present study was undertaken to assess the in vitro antifungal activity of petroleum ether, chloroform, methanol and aqueous extracts of Datura metel L. leaves and flowers, against two Trichoderma species (Trichoderma harzianum and Trichoderma viride) and three formae speciales of Fusarium oxysporum, that is, Fusarium oxysporum f. sp. melonis, Fusarium oxysporum f. sp. lycopersici and Fusarium oxysporum f. sp. tuberosi. Radial growth of the pathogen on PDA plates was recorded after 3 to 7 days of incubation at 25°C. Results revealed an important antifungal activity of D. metel leaf and flower aqueous extracts at all concentrations tested (1, 2, 3 and 4%) against pathogenic fungus. However, the extent of response to extracts was species specific. In fact, the highest inhibition (69%) of T. viride mycelial growth was observed with flower aqueous extracts. Indeed, F. oxysporum f. sp. melonis was found to be more susceptible than the other fungal species to organic extract; radial growth inhibition varied from 24 to 76% and from 31 to 76% in the presence of leaf and flower organic extracts, respectively. In addition, the radial growth of F. oxysporum f. sp. Lycopersici was reduced by all organic extracts. The fungicidal activity of leaf extracts was more effective against F. oxysporum f. sp. tuberosi as compared to flower extracts. Both Trichoderma species were less sensitive to D. metel organic extracts than Fusarium species. Our findings showed that D. metel extracts can be used as potential source of fungicides to control the phytopathogenic fungi tested.

In the present research work, Nicotiana glauca Graham was used as a potential source of biologically active compounds. The antifungal activity of leaf and flower aqueous and organic extracts (petroleum ether, chloroforme and methanol) was assessed in vitro against three phytopathogenic fungi and two antagonistic agents. These target fungi were subjected to the different types of extracts already incorporated into the Potato Dextrose Agar (PDA) medium at various concentrations. Results revealed an important antifungal activity of N. glauca leaf and flower aqueous extracts at all concentrations tested (1, 2, 3 and 4%). However, a relative difference in the extent of the response of the same fungal agent to the extracts tested was observed. In fact, Trichoderma viride was found to be more sensitive than the other target species, where the radial growth inhibition noted varied from 37.4 to 63.14% depending on aqueous extracts concentrations and the maximum inhibition was obtained with leaf aqueous extracts applied at 1 and 2% concentrations. Moreover, T. viride and Fusarium oxysporum f. sp. melonis were found to be the most sensitive to leaf and flower organic extracts as compared to the other agents. Growth of T. viride was inhibited by 33.7% in the presence of chloroforme leaf extract and petroleum ether flower extracts tested at 3000 and 9000 ppm, respectively. Furthermore, the radial growth of F. oxysporum f. sp. melonis was reduced by more than 31 and 20% with leaf petroleum ether and flower chloroform extracts, respectively, applied at 9000 ppm. T. harzianum, F. oxysporum f. sp. tuberosi and F. oxysporum f. sp. lycopersici were found to be less sensitive to N. glauca organic extracts as compared to aqueous extracts.