Biological Study on Alternaria alternata isolated from infected Vegetables in Sana’a, Yemen
Alternaria alternata, the causal agent of early blight, is one of the most destructive pathogens affecting tomato and potato crops in Yemen, with documented yield losses of up to 80%. The traditional reliance on synthetic fungicides has led to environmental degradation and the emergence of resistant strains, necessitating the development of sustainable, eco-friendly alternatives. This study aimed to isolate and identify A. alternata from infected crops in the Sana’a Governorate and evaluate the in vitro antifungal efficacy of essential oils (EOs) derived from Cupressus macrocarpa leaves. Of the 41 initial isolates, 19 were identified as A. alternata based on morphological and microscopic characterization. Pathogenicity assays revealed significant variability in virulence, with isolate 1T1 (from tomato) exhibiting the highest disease severity (56%). Gas Chromatography-Mass Spectrometry (GC-MS) analysis identified the major chemical constituents, including monoterpenes (4-terpineol, γ-terpinene, and α-terpinene) and fatty acid esters. In vitro assays demonstrated potent fungicidal activity; at concentrations of 0.2%, 0.4%, and 0.6%, the EO achieved up to 97% mycelial growth inhibition at the highest concentration. This efficacy was comparable to that of the synthetic fungicide difenoconazole (0.1%). These findings suggest that C. macrocarpa essential oil is a promising biofungicide candidate for sustainable management of Alternaria blight.
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