Rice volatile compound (E)--caryophyllene induced by rice dwarf virus (RDV) attracts the natural enemy Cyrtorhinus lividipennis to prey on RDV insect vectors

BACKGROUND: Rice dwarf virus (RDV)-induced rice plant volatiles (E)-beta-caryophyllene and 2-heptanol modulate the olfactory behavior of RDV insect vectors that promote viral acquisition and transmission. However, it remains elusive whether these two volatiles could influence the behaviors of the natural enemies of RDV insect vectors. Herein, we determined the effects of these two volatiles on the olfactory and predatory behaviors of Cyrtorhinus lividipennis (Hemiptera: Miridae), an important predator of RDV insect vectors in rice paddies.RESULTS: The results showed that C. lividipennis preferred RDV-infected rice plant odors over RDV-free rice plant odors. C. lividipennis was attracted by (E)-beta-caryophyllene, but showed no behavioral responses to 2-heptanol. The attraction of (E)-beta-caryophyllene towards C. lividipennis was further confirmed using oscas1 rice plants, which do not release (E)-beta-caryophyllene in response to RDV infection, through a series of complementary assays. The oviposition preference of the RDV vector insect Nephotettix cincticeps (Hemiptera: Cicadellidae) showed no significant difference between RDV-infected and RDV-free wild-type plants, nor between oscas1-RDV and oscas1 plants. However, the predation rate of C. lividipennis for N. cincticeps eggs on RDV-infected plants was higher than that on RDV-free plants, whereas there was no significant difference between oscas1-RDV and oscas1 plants.CONCLUSION: (E)-beta-caryophyllene induced by RDV attracted more C. lividipennis to prey on N. cincticeps eggs and played a crucial role in plant-virus-vector-enemy interactions. These novel findings will promote the design of new strategies for disease control by controlling the populations of insect vectors, for example recruiting more natural enemies by virus-induced plant volatiles.(c) 2023 Society of Chemical Industry.