Calcium chloride seed priming: A dual-action strategy for enhancing Cyrtorhinus lividipennis attraction and deterring brown planthopper infestations in rice

This investigation assessed the impact of calcium chloride (CaCl₂) seed priming on the direct and indirect defense mechanisms of rice (Oryza sativa L.) against the brown planthopper (BPH), Nilaparvata lugens (Stål). Our findings revealed that seeds primed with CaCl₂ significantly curtailed the survival and developmental rates of BPH nymphs and diminished the honeydew secretion by adult females. The feeding behaviour of BPH on CaCl₂-pretreated rice showed an extended non-proboscis handling (np) duration, while the phloem ingestion time (N4-b) and xylem ingestion time (N5) were reduced. Additionally, BPH nymphs exhibited a marked preference for H₂O-pretreated plants over CaCl₂-primed ones for both feeding and oviposition. Conversely, the natural enemy Cytorhinus lividipennis displayed a heightened preference for preying on BPH nymphs and eggs on CaCl₂-primed rice. The treatment with calcium led to an increased release of a diverse range of volatile compounds following BPH infestation, compared to H₂O pretreatment. Notably, the volatiles Methyl salicylate and 1-octen-3-ol were identified as the most effective deterrents for BPH and attractants for C. lividipennis, respectively, highlighting their potential role in mediating plant-insect interactions.