Vitex agnus-castus methanolic extract showed strong antifungal activity against Pythium ultimum in tomato under both in vitro and in vivo conditions. The 0.2% extract delayed the mycelial growth of the fungus and showed significant antifungal activity against P. ultimum on tomato seedlings with an efficacy comparable to that of the synthetic fungicide. To determine the involvement both of plant extract and pathogenic fungus in PR gene induction, tomato plants were treated with V. agnus-castus extract and/or inoculated with P. ultimum. The expression of four PR genes (PR-1, PR-2, PR-5, PR-6) was monitored at five time points within 48 h of the extract treatment and fungal inoculation. The PR-1 and PR-4 genes were activated directly by V. agnus-castus extract up to 12 h after treatments; at 24 h, the direct activation by plant extract disappeared and a synergistic inducing effect of extract and pathogen applied simultaneously on the plant was observed. The PR-6 gene was not activated directly by the V. agnus-castus extract but only when applied together with the pathogen; activation of the PR-6 gene occurred 24 h after treatments and the gene expression increased at 48 h. There was no activation of PR-5 gene by the plant extract. The ability of V. agnus-castus extract to enhance plant defence responses upon pathogen inoculation might be further investigated. The activation of various PR genes suggests that induction of defence responses by V. agnus-castus extract in tomato may be regulated by more than one signalling pathway. © 2012 Elsevier Ltd.

Export Date: 22 November 2012Source: ScopusArticle in Press