Role of herbivore-induced plant volatiles from Cnaphalocrocis medinalis infested rice genotypes in mediating host-location behaviour of the larval ectoparasitoid, Habrobracon hebetor

Herbivore-induced plant volatiles (HIPVs) are critical mediators of tritrophic interactions, providing parasitoids with reliable cues for host location and parasitisation. This study investigated whether HIPVs emitted by rice infested (I) with the rice leaffolder, Cnaphalocrocis medinalis (Guenee), affect the olfactory perception and behavioural responses of its larval parasitoid, Habrobracon hebetor (Say). Volatiles were collected from six rice genotypes (three resistant and three susceptible), each with three biological replicates. Gas chromatography–mass spectrometry (GC-MS) identified 37 volatile organic compounds (VOCs) in uninfested (U) and C. medinalis-I. plants across all genotypes. Uninfested plants served as the baseline for comparing infestation-related changes in volatile profiles. The antennal perception of female H. hebetor in response to VOCs from C. medinalis-I. rice plants was assessed using gas chromatography–electroantennographic detection (GC-EAD). Ten common VOCs consistently elicited antennal depolarisation across both resistant and susceptible genotypes. These compounds were subsequently evaluated for behavioural responses in female H. hebetor using a Y-tube olfactometer. β-ocimene, β-caryophyllene, 1,2,3,4-tetrahydronaphthalene, (R)-limonene, methyl jasmonate and methyl salicylate elicited positive orientation while xylene elicited significant avoidance in female H. hebetor. These findings demonstrate that individual HIPVs from C. medinalis-I. rice genotypes produce distinct behavioural effects on H. hebetor under controlled conditions. The study offers valuable insights into the identification of potential host-location cues for H. hebetor, which may contribute to the sustainable management of C. medinalis, warranting further validation in ecologically relevant volatile blends and field trials.