Plant–virus–vector interactions: Tobacco rattle virus infection alters root volatile emissions to attract nematode vectors

Plant–virus–vector interactions mediate important ecological processes and can significantly reduce crop production. Almost all plant viruses require vectors for transmission and use sophisticated mechanisms to achieve this: they manipulate host plants to release volatile chemical that attract their vectors. This chemoattraction has been demonstrated in above-ground interactions but has never been studied in viruses transmitted by soil-dwelling nematodes. Tobacco rattle virus (TRV) is an important pest of potato, transmitted by trichodorid nematodes. This work uses a model plant system to investigate the effects of TRV infection on host root architecture, root volatile release and chemoattraction of its nematode vectors.
TRV infection alters root structure, producing a smaller and more compact root system. It modifies root volatile profiles compared to uninfected plants, which leads to trichodorids preferentially moving towards infected plants. The TRV genome contains genes known as 2b and 2c; implicated for nematode transmission. Mutations in these genes reduce the severity of root architecture symptoms, remove differences in the profile of volatiles released from infected roots compared with uninfected ones and, in the case of 2b, make plants less attractive to nematodes than plants infected with viruses without mutations. The release of the volatile 2-ethyl-1-hexanol significantly increased in roots infected by TRV. When added to uninfected plants, it made them more attractive to nematodes than untreated counterparts.
This work demonstrates TRV manipulates the production of host root volatiles, leading to increased attraction of trichodorid vectors. 2b and 2c are important in this interaction and 2-ethyl-1-hexanol is a strong component of the attractant signal. This new knowledge shows nematode transmitted viruses use similar mechanisms to attract their vectors as their better-studied aboveground counterparts and contributes to the study of volatile- mediated rhizosphere interactions with implications for agricultural pest control.