Rice dwarf virus (RDV) is transmitted by insect vectors Nephotettix virescens and Nephotettix cincticeps (Hemiptera: Cicadellidae) that threatens rice yield and results in substantial economic losses. RDV induces two volatiles ((E)-β-caryophyllene (EBC) and 2-heptanol) to emit from RDV-infected rice plants. However, the effects of the two volatiles on the olfactory behavior of both non-viruliferous and viruliferous N. virescens are unknown, and whether the two volatiles could facilitate the spread and dispersal of RDV remains elusive. Combining the methods of insect behavior, chemical ecology, and molecular biology, we found that EBC and 2-heptanol influenced the olfactory behavior of non-viruliferous and viruliferous N. virescens, independently. EBC attracted non-viruliferous N. virescens towards RDV-infected rice plants, promoting virus acquisition by non-viruliferous vectors. The effect was confirmed by using oscas1 mutant rice plants (repressed EBC synthesis), but EBC had no effects on viruliferous N. virescens. 2-heptanol did not attract or repel non-viruliferous N. virescens. However, spraying experiments showed that 2-heptanol repelled viruliferous N. virescens to prefer RDV-free rice plants, which would be conducive to the transmission of the virus. These novel results reveal that rice plant volatiles modify the behavior of N. virescens vectors to promote RDV acquisition and transmission. They will provide new insights into virus-vector-plant interactions, and promote the development of new prevention and control strategies for disease management.
Keywords: Nephotettix virescens; olfactory behavior; plant volatiles; rice dwarf virus; virus dispersal.