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

Abstract

Blast disease caused by Magnaporthe oryzae is a devastating disease that limits rice grain production. Here, we synthesized rhamnolipid (RL) modified silica nanoparticles (SiO₂NPs) based on the excellent antimicrobial activity of RL against various phytopathogens and the role of SiO₂NPs in alleviating plant diseases and investigated the roles and mechanisms of RL@SiO₂NPs 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@SiO₂NPs were the most suitable mixture ratio in suppressing blast and enhanced plant resistance. Compared with the control, application of RL_0.1@SiO₂NPs 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@SiO₂NPs 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@SiO₂NPs 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@SiO₂NPs 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@SiO₂NPs have shown potential application as green and efficient agricultural chemical substitutes in plant disease management.