Antibacterial and Antibiofilm Activities From Insect-pathogenic Fungal Extracts Against Xanthomonas oryzae pv. oryzae (Xoo) Causing Blight Disease of Rice

Insect-pathogenic fungi (IPF) are valuable sources for producing a wide variety of secondary metabolites with biological activities that have a broad range of uses in medicine, agriculture, and other fields of science. The purpose of this study was to evaluate the antibacterial and antibiofilm activities of fungal extracts against Xanthomonas oryzae pv. oryzae (Xoo), the plant pathogenic bacteria responsible for causing leaf blight disease in rice. A total of 166 specimens were selected from three entomopathogenic genera, including Ascopolyporus, Beauveria, and Metarhizium. They were screened for their activities using disc and broth microdilution techniques. Based on the results of screening against Xoo, the maximum zone of inhibition was obtained from the fungus Metarhzium ellipsoideum (P-MY04008) with diameters of clear zone 17.33±1.15 mm, followed by Beauveria cf. asiatica (Y-NHJ06455BE, 15.33±1.15) and Metarhizium ovoidosporum (P-MY02604BE, 15.00±1.00). Approximately 69% of the isolates demonstrated antibiofilm activity against Xoo at a concentration of 1024 micrograms per milliliter. Among these isolates, 7.38% exhibited effective biofilm inhibition, 63.62% showed less than 50% prevention, and 31.58% yielded unsatisfactory results due to increased biofilm formation. The findings indicated that insect-pathogenic fungi (IPF) have the potential to serve as abundant sources for producing bioactive agents with antibacterial properties.