DEVELOPMENT OF BIO CONTROL USING LACTOBACILLUS SPP. ISOLATED FROM PROBIOTIC FOR ASPERGILLOSIS IN ONIONS CAUSED BY ASPERGILLUS NIGER

Aim: To develop bio control method using Lactobacillus spp. isolated from probiotic for controlling aspergillosis in onions caused by Aspergillus niger. Study Design: Isolation of strains of Lactobacillus spp. from a commercial probiotic named ‘ViBact’ using DMRS agar – Growth in MRS broth- Isolation of Aspergillus niger on Sabouroud’s agar from infected onion- Centrifugation of broth cultures of Lactobacillus spp. –Test using cell free broth of Lactobacillus spp. for inhibitory action on Aspergillus niger using agar gel diffusion technique- Application of cell free broth of Lactobacillus to infected onion and study of progression of symptoms. Place and Duration of Study: Department of Microbiology, H.P.T. Arts and R.Y.K. Science College, Nashik, Maharashtra, India. Duration: June 2021- October 2021 Methodology: Aspergillosis is a common post- harvest fungal disease of onions. Chemical preservatives used to prevent fungal diseases are hazardous to human health. Hence, an alternative method of preservation called ‘biocontrol’ using Lactic Acid Bacteria (LAB) was developed in this study. Aspergillus niger was isolated from infected onion on Sabouroud’s agar. 10 strains of Lactobacillus spp. were isolated from a commercial probiotic named ‘ViBact’ using DMRS agar. Lactobacillus strains were grown in MRS broth for 48 hours in anaerobic jar, centrifuged and cell free broths were tested for inhibitory action on Aspergillus niger using agar well diffusion technique. Cell free broth was applied to infected onion and observed for progress of disease symptoms. Results: 10 strains of Lactobacillus spp. showing typical morphology of Gram positive rods were isolated from a commercial probiotic. 4 strains of Lactobacillus spp. showed significant inhibitory action on Aspergillus niger in agar well diffusion method. Large zones of inhibition were shown by strains 2 and 8.The largest zone of inhibition of 18 mm was shown by strain 2. When the cell free broth of this strain was applied to infected onion for 1 hour, further progression of symptoms of the disease was not seen whereas the infected onion without this treatment showed progression of typical symptoms after one week.