Biological Induction of Systemic Acquired Resistance in Arabidopsis. Scott Uknes. Agricultural Biotechnology Research Unit, CIBA-Geigy Corporation, 3054 Cornwallis Road, Research Triangle Park, NC 27709 U.S.A. Ann Marie Winter, Terrence Delaney, Bernard Vernooij, Alison Morse, Leslie Friedrich, Gordon Nye, Sharon Potter, Eric Ward, and John Ryals. Agricultural Biotechnology Research Unit, CIBA-Geigy Corporation, 3054 Cornwallis Road, Research Triangle Park, NC 27709 U.S.A. MPMI 6:692-698. Accepted 8 September 1993. Copyright 1993 The American Phytopathological Society.

Previously, Arabidopsis was shown to develop acquired resistance to a bacterial and a fungal pathogen following treatment with the activator compound 2,6-dichloroisonicotinic acid (INA). In this study, we show that a necrotizing pathogen, turnip crinkle virus (TCV), can induce systemic acquired resistance (SAR) in Arabidopsis against bacterial (Pseudomonas syringae) and viral (TCV) pathogens. The TCV-induced resistance results in both a decrease in visible disease symptoms and a reduction in the growth of the challenge pathogen. Levels of salicylic acid (SA), a likely endogenous signal for SAR, increased more than fivefold in response to TCV infection. In addition, exogenously applied SA induced resistance to the fungal pathogen Peronospora parasitica. Three genes induced to high levels by SA (PR-1, PR-2, and PR-5) were also induced by TCV inoculation. In addition, we show that INA treatment induces resistance to TCV, extending the previous observation of chemically induced resistance against bacterial and fungal pathogens to include protection against viral pathogens.