Evaluation of food preservatives, low toxicity chemicals, liquid fractions of plant extracts and their combinations as alternative options for controlling citrus post-harvest green and blue moulds in vitro

摘要

The post-harvest moulds Penicillium digitatum and Penicillium italicum are important plant pathogens and spoilage-causing molds especially against citrus fruits. If not treated, post-harvest moulds can cause enormous economic losses during storage and marketing. Therefore, more investigations are needed to examine new antifungal agents against such fungi. In this work, we aimed to evaluate the antifungal activity of some plant extracts (namely, Harmal seeds (Peganum harmala L.), cinnamon bark (Cinnamomum cassia L.) and sticky fleabane leaves (Inula viscosa L.), food preservatives (namely, sodium benzoate, sodium molybdate, ammonium heptamolybdate tetrahydrate, potassium carbonate and sodium bicarbonate) and their mixtures, i.e., plant extracts and food preservatives against P. digitatum and P. italicum. Both disc agar diffusion method and broth dilution methods was used to evaluate the antifungal activity of the plant extracts and food preservatives. Results revealed that methanolic fractions of cinnamons' bark and sticky fleabane leaves showed the highest efficacy. MIC values of 150 and 37.5 μg mL~(-1) were obtained with cinnamons' fraction against P. italicum and P. digitatum, respectively. Sodium benzoate was the most effective against tested fungal species. The obtained MIC values against P. digitatum and P. italicum were 37.5 and 75 μg mL~(-1), respectively. Mixtures of tested chemicals showed synergistic effects against both fungal species. Mixtures of sodium benzoate and fractions of either cinnamon or sticky fleabane reflected synergistic effects against P. italicum and antagonistic effects against P. digitatum. Inhibition zones against P. italicum ranged between 38-57 mm.