Induced systemic resistance against systemic viruses : a feasible approach?

Induction of resistance to plant viruses causing localized infections has been widely used to study HR and SAR mechanisms. However, in Nature true virus diseases are produced by viruses able to systemize in the plant and SAR is scarcely effective against them. Thus, a more successful strategy relays in the induction of resistance against both the virus and its vector. In this work, using the pathosystem bean common mosaic virus (BCMV)-Phaseolus vulgaris we made attempts of inducing resistance separately to both the pathogen and the aphid vector Myzus persicae, with the aim of dissecting the two resistance levels inducible with the most used chemical elicitors. Results showed that BTH and chitosan are able to reduce the infection degree in BCMV mechanically inoculated plants, however not preventing the infection. On the other hand, chitosan and 2-isobutyric acid (IBA), applied as root-drench, could reduce aphid population by half. Therefore, combining the two effects and using chitosan, partially effective against both the virus and the vector, it could be possible to raise an acceptable resistance level in the field, where BCMV is actively spread by aphids. To verify this hypothesis, experimental transmission with viruliferous aphids in chitosan and IBA treated plants are now in progress.