In Vitro Antagonistic Activity for Selected Fungal Species Against Wilt Causing Phytopathogens

The present study was carried out with the aim to assist screening of various fungal species for antimicrobial natural products. During this study five different fungi, including Alternaria alternata, Acremonium sp., Alternaria brassicicola, Pythium sp. and Aspergillus flavus were screened against Wilt causing pathogens using the dual culture assay. Among them, Aspergillus flavus was found active fungus against the selected vascular Wilt causing fungus and bacteria, i.e. Fusarium oxysporum (87.50 ± 0.11% inhibition), Xanthomonas campestris (67.00 ± 0.46% inhibition) and Clavibacter michiganensis (72.00 ± 1.02% inhibition). The A. flavus was grown on two different media, i.e. Potato Dextrose Broth (PDB) and Glucose Nutrient Broth (GNB) media for active secondary metabolites. Ethyl acetate (EtOAc) extract of PDB medium gave significant results against selected phytopathogens compared to GNB medium and selected for further study. Crude (1 μg.mL^-1 ) obtained from PDB medium showed 2.50 ± 0.64 mm and 1.97 ± 0.21 mm inhibition zone against X. campestris and C. michiganensis respectively compared to positive reference (streptomycin) and negative refrence (EtOAc) using disc diffusion method. However, the same concentration of crude (1 μg.mL^-1) showed 62.20 ± 2.51% growth inhibitions against Fusarium oxysporum using agar well diffusion method. Further investigation, including various chromatographic and spectroscopic analyses on the separation and isolation of potent metabolites is suggested to get a useful lead structure for development of novel antibiotics to combat resistant pathogens.