Study the Effect of Some Citrus Peel Extracts Against Plant Pathogenic Fungi

The safest and most effective and preventive method that inhibits the growth of phytotoxic fungi is the biological method using metabolic materials, which are environmentally friendly. The current study focusses on extracting bioactive compounds from some citrus peels, and evaluating antimicrobial activity against some pathogenic plant fungi, also detecting the active compound using GC-MS. The five extracts of peels citrus included, Citrus aurantifolia (key lime), Citrus singensis (orange), Citrus maxima (pomelo), Citrus limon (lemon), and Citrus reticulate (mandarin orange). The extracts were evaluated against seven fungal species, including Alternaria solani, Alternaria alternate, Rhizoctonia solani, Macrophomina phaseolina, Trichothecium roseum, Fusarium solani, and Fusarium equiseti. The results showed that peels extract of pomelo (PPE) is the most effective anti-fungal, which was clear for all types of fungi used in the examination, and which recorded the highest inhibitory diameter against the fungus F. equiseti, followed by peels extract of the orange (OPE) and lemon peels extract (LPE), respectively, while lowest antifungal activities have been recorded in peels extracts of mandarin orange (MOPE) and key lime peels extract (KPE), respectively. The diameters of inhibition that represent the antifungal activity of the other extracts ranged between 0 and 25 mm, which constitute significant differences between them and (PPE). The most active extract (PPE) was analysed using GC-MS, and the result included the detection of 50 different compounds. According to the GC-MS results, furfural (4.91%), auraptenol (1.38%), 2-methoxy-4-vinylphenol (0.92%) and hexadecanoic acid-, methyl ester (0.80%) were the major components in the essential oil obtained from peels extract of pomelo (PPE), in addition of ethyl oleate (0.65%), alpha-terpineol (0.32%), osthole (0.31%), which were known as antifungal compounds.