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Abstract
Powdery mildew is one of the most destructive plant diseases and causes dramatic yield losses in agricultural production. Mildiomycin (MIL) is an effective nucleoside antibiotics used to against such a devastating disease. In order to further improve the bioactivity of MIL, a cytosine-substituted mildiomycin analogue (MIL-C) was biosynthesized by supplementing 0.9 g/L cytosine into the fermentation medium as the precursor. The bioactivity of MIL-C against powdery mildew disease in vivo and in vitro were examined systematically, and compared to MIL and triadimefon. The minimum inhibitory concentration (MIC) of MIL-C in vitro was 78.8 mg/L, which was only half of that of MIL. Furthermore, in the greenhouse trials, the EC^sub 90^ value of MIL-C (52.89 mg/L) was much lower than that of either MIL (153.22 mg/L) or triadimefon (288.90 mg/L). In the field trials, the efficiency of MIL-C against powdery mildew of cucumber or pumpkin was better than that of MIL or triadimefon. Further acute toxicological and Ames tests proved that MIL-C was a potent bio-pesticide with good bio-compatibility and low toxicity, and its usage can be proposed to popularize for controlling the powdery mildew in the future. [PUBLICATION ABSTRACT]