Rhamnolipid Modified Silica Nanoparticles Control Rice Blast Disease by Enhancing Antifungal Activity In Vivo and Antioxidant Defense System of Rice (Oryza sativa L.)

Blast disease caused by Magnaporthe oryzae is a devastating disease that limits rice grain production. Here, we synthesized rhamnolipid (RL) modified silica nanoparticles (SiO 2 NPs) based on the excellent antimicrobial activity of RL against various phytopathogens and the role of SiO 2 NPs in alleviating plant diseases and investigated the roles and mechanisms of RL@SiO 2 NPs application in controlling rice blast disease. Two-week-old rice seedlings were sprayed with 100 mL/L of different materials before pathogen inoculation, and blast incidence was investigated 5 days after inoculation. The results showed that RL 0.1 @SiO 2 NPs were the most suitable mixture ratio in suppressing blast and enhanced plant resistance. Compared with the control, application of RL 0.1 @SiO 2 NPs significantly reduced rice blast disease incidence by 10.80% and the relative growth of fungus by 97.05% and increased the shoot dry biomass by 13.33%, which alleviated the infection pressure of rice blast fungus. Additionally, after RL 0.1 @SiO 2 NPs treatment, peroxidase, ascorbate peroxidase, and polyphenol oxidase activities in rice leaves were significantly increased by 47.02%, 34.26%, and 44.36%, respectively, the total phenolics content was significantly increased by 24.14%, and the malondialdehyde and hydrogen peroxide content was decreased by 5.28% and 14.58%, respectively. RL 0.1 @SiO 2 NPs also improved plant nutrient status and enhanced disease resistance of infected plants by restoring nutrient balance or ion homeostasis, including increased potassium concentration (23.84%) in leaves and Si concentration (60.34%) in roots and decreased magnesium (11.89%) and iron concentrations (30.55%) in rice leaves. In summary, our results suggest that RL 0.1 @SiO 2 NPs enhance rice plant resistance against blast by enhancing the antifungal activity in vivo, activating the antioxidant defense system, and affecting nutrient acquisition in rice seedlings. RL@SiO 2 NPs have shown potential application as green and efficient agricultural chemical substitutes in plant disease management.