Effect of Silicon Application to the Rice Plants on Feeding Behaviour of the Brown Planthopper, Nilaparvata lugens (Stål) Under Elevated CO2

Silicon (Si) is known to enhance plant resistance in rice and many other Poaceae plants by priming chemical defence, physiological, and mechanical barriers. However, the impact of soil application of Si on the feeding behaviour of rice Brown Planthopper (BPH) under climate change conditions remains unknown. This study aims to investigate the effects of Si on BPH feeding behaviour under elevated CO 2 levels (570 ± 25 ppm) and elevated temperature (≃ 3 °C higher than ambient) in open-top chambers (OTCs) during the Kharif season of 2019 and 2020. The results of the study showed that honeydew excretion by BPH was reduced by Si amendment, indicating reduced feeding by the pest under both ambient and elevated CO 2 and temperature conditions. The deposition of callose in the sieve tube of rice leaf sheath was identified as one of the main reasons, along with silicification, for reduced feeding in response to BPH infestation. Both Si-amended and non-amended plants showed a positive response to BPH infestation by depositing callose. In Si-amended plants, BPH infestation induced higher expression of the callose synthase-encoding gene ( OsGSL1 ) and lower expression of the gene encoding callose hydrolase ( Gns5 ) compared to non-amended plants. The dynamic expression of these two genes indicated higher callose deposition in Si-amended plants. The benefits of Si, which include reduced feeding by BPH through callose deposition, mechanical barrier via silicification, and positive alteration of photosynthesis-related parameters, suggest its potential as an alternative strategy for BPH management under climate change conditions.