Effect of salicylic acid on phenolic compounds related to date palm resistance to Fusarium oxysporum f.sp. albedinis

Salicylic acid (SA) plays a key role in establishing resistance to pathogens in many plants. To study the possible involvement of SA in the resistance of date palm (Phoenix dactylifera L.) to Fusarium oxysporum f. sp. albedinis (FOA), we investigated levels of phenolic compounds, known as indicators of resistance in the date palm/ Fusarium pathosystem. After treatment with SA the content of root soluble phenolics in F. oxysporum inoculated date palm seedlings was about 4 times higher in cv. Bousthami noir and 6 times higher in cv. Jihel than that in untreated plants showing disease symptoms. The largest increase was at a SA concentration of 50 µM. SA treatment also enhanced the content of cell wall phenolics. In addition, inoculation of SA-treated roots of date palm with FOA (strain ZAG) resulted in a greater number of plants showing only limited hypersensitive reaction-like necrotic lesions. In contrast, SA-untreated plants normally showed spreading necrosis in response to fungus inoculation

AN INNOVATIVE STRATEGY BASED ON UNCERTAINTY PROFILE FOR THE VALIDATION OF MICROBIOLOGICAL METHODS FOR COUNTING ENTEROBACTERIACEAE IN FOODS

Objective: A new and powerful statistical approach known as the uncertainty profile concept has been suggested for both testing the validity and making easy and straightforward interpretation of results obtained during the validation of an analytical method. The main goal of this paper is to confirm the applicability of this new strategy for the validation of a commercial kit, microbiological method, for the enumeration of the Enterobacteriaceae in foods and the estimate of the measurement uncertainty by using the newly provided formula and without referring to any additional experiments.Methods: An innovative formula to assess the uncertainty by using validation data and without recourse to other additional experiments was proposed. The uncertainty was evaluated through the two-sided β-content, γ-confidence tolerance interval, which is computed with three manners: the Mee's approach, the Generalized Pivotal Confidence, and the Modified Large Simple procedureResults: After the use of the three chemometric method of calculation of tolerance intervals, the obtained results with uncertainty profile show without doubt that the enumeration method is valid over the range of target values given that the upper and the lower 66.7 %-content, 90 %-confidence tolerance limits have fallen within the two acceptance limits of±0.25 Log unit. If the β is stretched to 80 %-content, 90 %-confidence, the three computed tolerance intervals lead to different decisions.Conclusion: we have demonstrated the ability of the uncertainty profile to be used for testing the validity of enumeration method which represents the first application of an uncertainty profile to food microbiological methods, and provides good estimations of the uncertainty measurements for each concentration level.Keywords: Validation, Uncertainty profile, β-content-γ-confidence tolerance interval, Uncertainty measurement, Microbiological metho

Effect of Exogenous Application of Jasmonic Acid on Date Palm Defense Reaction against <em>Fusarium oxysporum</em> f.sp. <em>albedinis</em>

The effect of jasmonic acid in the date palm defence reaction against Fusarium oxysporum f. sp. albedinis was investigated taking into account changes in H2O2 and malonyldialdehyde (MDA) levels and peroxidase activity. Treatment of seedlings of two cultivars with jasmonic acid increased levels of H2O2 and enhanced lipid peroxidation as indicated by MDA accumulation and an increase in peroxidase activity. Similar changes occurred with date palm seedlings infected with Foa and showing necrotic hypersensitive-reaction like lesions. In general, both Foa and jasmonic acid increased H2O2 to a level 2 to 7 times that of the control, depending on the treatment and the time of analysis. Peroxidase activity was 2 to 3 times greater and MDA levels were increased 2 to 8 times. In contrast, seedlings presenting disease symptoms did not show any such reactions. It is suggested that oxidative burst (H2O2 generation) and its consequences (lipid peroxidation) and the change in peroxidase activity are used by date palm to resist Foa and that jasmonic acid is a signal for the expression of these defence reactions