Natural Products-Based Botanical Bactericides Discovery: Novel Abietic Acid Derivatives as Anti-Virulence Agents for Plant Disease Management

The discovery of natural product-based pesticides is critical for agriculture. In this work, a series of novel tricyclic diterpenoid derivatives decorated with an amino alcohol moiety were elaborately prepared from natural abietic acid, and their antibacterial behavior was explored. Bioassay results indicated that compound C₂ exhibited the most promising bioactivity (EC₅₀ = 0.555 μg mL^–1) against Xanthomonas oryzae pv. oryzae (Xoo), about 73 times higher than the effect of commercial thiodiazole copper (TC). Results of in vivo bioassays showed that compound C₂ displayed significantly higher control of rice bacterial leaf blight (curative activity: 63.8%; protective activity: 58.4%) than TC (curative activity: 43.6%; protective activity: 40.8%), and their bioactivity could be improved maximally 16% by supplementing the auxiliaries. Antibacterial behavior suggested that compound C₂ could suppress various virulence factors. Overall, these findings suggested that new botanical bactericide candidates could control intractable plant bacterial diseases by suppressing virulence factors.