Orange (Citrus sinensis) is an important horticultural crop of India which is prone to post-harvest damage during storage, transport, and distribution due to fungal pathogens. These phytopathogenic fungi are conventionally controlled through synthetic fungicides. However, with increasing concern for health hazards and environmental pollution due to rampant usage of synthetic fungicides has forced us to devise alternative natural and eco-friendly strategies for their effective control. Natural plant-derived extracts and compounds have evoked immense interest toward their antibacterial and antifungal activities. The present investigation envisages the isolation and characterization of predominant fungal pathogens from C. sinensis obtained from 56 samples collected from the distribution chain of Delhi NCR. The isolated fungi included Aspergillus niger, Alternaria citri, and Penicillium digitatum. In vitro assays were conducted to assess the fungicidal/fungistatic potential of 11 bioactive plant extracts on these isolates by determination of minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC). Out of 11 bioactive extracts tested 10 had fungistatic, 4 had fungicidal, and 1 had no activity on these isolates. n-Hex fraction of Nepeta longibracteata and Actinocarya tibetica and MeOH extract of Zingiber officinale and Glycyrrhiza glabra was found to be most active against A. niger with MIC and MFC values of 125 μg/mL. MeOH extract of G. glabra was most active against A. citri and n-Hex fraction of N. longibracteata and A. tibetica and MeOH extract of Z. officinale and G. glabra was most active against P. digitatum. The results obtained from the present study indicated that these extracts demonstrate antifungal effects against post-harvest phytopathogen of C. sinensis and can offer effective bioactive control. However, more advanced experimental studies are required to identify and pinpoint the exact bioactive compound/molecule responsible for the antifungal activities observed and further work is required to develop appropriate formulations which can be effectively integrated and applied commercially.
Key words: Citrus sinensis, Phytopathogenic fungi, Aspergillus niger, Alternaria citrii, Penicillium digitatum, Minimum Inhibitory concentrations (MIC) and Minimum fungicidal concentrations (MFC).
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