Chiang Mai Journal of Science

     Red rot disease caused by Colletotrichum falcatum is a major production threat to several sugarcane varieties in Thailand. Biological control is an ecologically friendly alternative to manage the disease using microbial antagonism and associated metabolic products. In this study, four Aspergillus non-toxigenic strains (A37, A374, A400, and A561) were characterized using a genetic approach and evaluated for their antagonistic potential to suppress the growth of C. falcatum. The strain A561 had the maximum number of gene deletions, with 12 afl atoxin-producing genes being lost. In addition, the non-toxigenic characteristic of A561 was confi rmed using afl atoxin B1 (AFB1) enzyme-linked immunosorbent assay. A561 reduced the concentration of AFB1 by 98.57% (1.63 μg/kg) relative to the toxigenic control. The antagonistic activity of A561 was evaluated against C. falcatum using the competition plate method on potato dextrose agar (PDA) in vitro. The results revealed that A561 inhibited the mycelial growth of C. falcatum by 34.39%. In addition, 10% (v/v) culture fi ltrate of A561 on PDA produced mycelial inhibition of 53.21%. Non-toxigenic A561 had antifungal potential, suppressing the growth of C. falcatum.