Plant-fungal interactions mediated by volatile signals

Previous exposure of plants to attack by pests or pathogens can alter the response of such plants to subsequent challenge. The molecular basis of this induced resistance is now well documented and the signal networks are being dissected through the analysis of mutants in plant genetic models such as Arabidopsis. Circumstantial evidence is accumulating that plants neighbouring those subject to attack or infection may also be altered in response, implicating the involvement of volatile signals. Experimental work to test the hypothesis that volatile emissions from plants infected by pathogens can induce resistance in adjacent plants, using barley seedlings and the necrotrophic fungi Rhynchosporium and Pyrenophora, is described. Practical exploitation of this phenomenon in crop protection, for instance through chemical elicitors or the use of responsive crop genotypes in variety mixtures, will depend upon identification of the key signals involved and a better understanding of the molecular and physiological basis of the induced resistance.