LAUSR

BACKGROUND Management of rice false smut is based mainly on chemical control, which poses many challenges in safety and environment. The other option, biological control with biofungicides doesn't have such problems but is still not as reliable due to the low systemic ability, and lower and unstable efficacy. To that end, it is necessary to combine application of chemical fungicides and BCAs, and elucidate their synergistic mechanism. RESULTS A combination of tebuconazole and a proven BCA, Bacillus subtilis H158, was evaluated to control rice false smut. Tebuconazole at low application rates stimulated the growth of B. subtilis, prolonged the effective period of B. subtilis by enhancing its persistence on the surface of rice plants, accelerated the biofilm formation of the BCA to facilitate colonization, promoted induced systemic resistance (ISR) in rice by regulating defense-related enzymes and genes, and reduce the natural resistance of the pathogen by suppressing the key gene for fungal resistance to tebuconazole. However, tebuconazole at high application rates had adverse effects on these aspects and showed antagonistic combination effects with B. subtilis. The combination of B. subtilis with tebuconazole at low application rates showed great synergistic effects, but that at high application rates showed only antagonistic effects in field experiments over two consecutive years. CONCLUSION The combination of B. subtilis with tebuconazole had significant synergistic effects when the chemical was applied at the low rates. The synergistic effects are the result of multiple mechanisms involved in BCA, rice, and the fungal pathogen. This article is protected by copyright. All rights reserved.