EVALUATION OF GROWTH MEDIA AND IN-VITRO CONDITIONS FOR THE ASSESSMENT OF Aspergillus flavus GROWTH AND AFLATOXIN B1 IN GRAPES

Aflatoxin B-1 (AFB(1)) is one of the toxic secondary metabolites of fungi belonging to the genus Aspergillus. AFB(1) causes hepatotoxicity and carcinogenicity. Mostly, cereals, nuts, fruits, and stored commodities are prone to their attack. It has great health and economic importance. Under suitable conditions, fungus shows maximum pathogenicity which leads to the abundant production of AFB(1). This study encompasses the selection of the most pathogenic strain producing abundant AFB(1). For this purpose, 50 isolates were tested and YF18 was the most pathogenic. This isolate was then evaluated on 15 culture media which concluded that Yeast Extract Sucrose (YES) agar and Yeast Peptone Dextrose (YPD) agar media proved best for the optimal growth of A. flavus and abundant yield of AFB(1). Moreover, the culture media showing optimal growth under different levels of growth conditions i.e., temperature, pH, and water activity, and their effect was verified with the aid of correlation and response surface methodology. The culture media were checked at five levels of temperature (15 degrees C, 20 degrees C, 25 degrees C, 30 degrees C, and 35 degrees C), pH (3.5, 4.0, 4.5, 5.0 and 5.5), and water activity (0.80, 0.85, 0.90, 0.95, and 0.995) were tested, confirming that temperature of 30 degrees C, pH of 5.5 and water activity level of 0.995 significantly enhanced the growth of A. flavus and production of AFB1 (P<0.05); while correlation, as well as response surface methodology, also concluded the level of conditions appropriate for mycelial growth and AFB(1) yield. Afterward, the isolate YF18 was applied to the grapes and biochemical parameters were evaluated. The biochemical analysis concluded that fungal infected grapes showed less acidity, TSS, total sugars, TPC, and DPPH as compared to non-treated grapes while the berry size and berry weight was also reduced in infected grapes. The isolate was subjected to 16S rDNA analysis for identification which revealed that fungus is A. flavus and the aflR gene was responsible for activation and release of aflatoxin B-1. The present study will help to devise management strategies to reduce the incidence of fungus and its respective toxin.