Antifungal activities of aqueous extracts of moroccan medicinal plants against Monilinia spp. agent of brown rot disease

Apple fruit is one of the worldwide most industrially valuable horticulture crops. However, the fruit is vulnerable to post-harvest brown rot degradation caused by Monilinia laxa and Monilinia fructigena, which is a prominent pre-and post-harvest disease of tree fruit. Numerous non-chemical post-harvest treatments have been investigated so far to control these pathogens to provide an alternative option to the synthetic fungicides that are commonly used and may have negative effects on human health and the environment. Therefore, this study aimed to assess the in vitro and in vivo efficacy at different concentrations of nine plants' aqueous extracts from Mentha pulegium, Citrus aurantium, Thymus vulgaris, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Rosmarinus officinalis, Citrus sinensis and Eucalyptus radiate against the development of brown rot. The results demonstrated significant antifungal activities of all tested aqueous extracts on both fungi compared to the thiophanate-methyl fungicide (1 ppm) (100% inhibition). At the concentration of 1.5 mg/ml, S. aromaticum and O. compactum extracts were the most effective, showing significant inhibition values against M. laxa (91.06%) and against M. fructigena (90.02%). Interestingly, at higher concentration, spore germination of both Monilinia strains was significantly reduced with inhibition rate of 98.64% for M. laxa and 93.04% for M. fructigena. Also, high flavonoids and polyphenols contents were shown. Aqueous extracts of O. compactum, S. aromaticum, and T. vulgaris reduced the brown rot severity and incidence in vivo. The application of these plants' aqueous extracts on fruits seems to have a significant effect on fruit quality persistence, as indicated by weight loss, fruit firmness, total soluble solids, titrable acidity, and maturity index during 15 days of storage at 4 °C. The spectra analyzed from all tested plants revealed typical peaks and a large variety of functional groups such as C–H bonds, O–H groups, and C–C stretching. The plant’s aqueous extracts studied can be used as bio-fungicides against brown rot diseases.