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NOVEL PROSOPIS JULIFLORA LEAF ETHANOLIC EXTRACT COATING FOR PROTECTION OF APPLE AGAINST PENICILLIUM EXPANSUM AND OTHER POSTHARVEST PATHOGENS
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Date
2026-06
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Amal Mabkhout M H Hadi_OGS Approved Thesis.pdf
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Abstract
Postharvest spoilage remains a major challenge in fruit preservation and long-term storage, particularly for apples (Malus domestica), which are highly susceptible to microbial deterioration. This study evaluated the antifungal and preservative efficacy of Prosopis juliflora water soluble leaf ethanolic extract (PJ-WS-LE) as a natural alternative to synthetic fungicides. The antifungal activity of Prosopis juliflora extract was assessed using both in vitro and fruit assays against Penicillium expansum and other apple-associated pathogens. A total of five fungal isolates (Penicillium expansum, Aspergillus flavus, Aspergillus niger , Alternaria, and Fusarium ), along with 35 yeast and bacterial isolates, were obtained from infected apples, with P. expansum identified as the primary pathogen. In vitro assays demonstrated strong antifungal activity of P. juliflora extract against Penicillium expansum, with inhibition rates of 90%, 87.3%, and 99.7% recorded at concentrations of 5, 10, and 20 mg/mL, respectively, and a minimum inhibitory concentration (MIC) of 3.125 mg/mL. The extract also exhibited a clear dose-dependent inhibition against Alternaria sp. and Aspergillus flavus, where increasing concentrations corresponded to enhanced suppression of fungal growth. Koch’s postulates confirmed the pathogenicity of P. expansum, identifying it as the primary causal pathogen. In contrast, apple inoculation with the yeast and bacterial isolates yielded negative results, as the mixed cultures failed to induce infection after one month of incubation, suggesting that these microorganisms were secondary causal agents of spoilage. Furthermore, Fruit bioassay demonstrated complete prevention of infection in treated apples (0% disease incidence) and a 40% reduction under curative treatment conditions compared to untreated apples (control). Treated apples maintained better storage parameters, including higher firmness (32.6 N vs 21.5 N), reduced microbial loads (log bacteria: 4.06 vs 5.87; log fungi: 1.67 vs 3.82), and preservation of natural color (RAL 1016–1018) after four weeks of storage. In addition, vitamin C content was better preserved in treated samples, reaching approximately 20 mg/L, indicating enhanced nutritional quality. Overall, these findings confirm that Prosopis juliflora leaf extract is a potent, eco-friendly coating, capable of suppressing postharvest pathogens, maintaining fruit quality, and extending the shelf life of apples.