Abstract
Phytoalexins are antimicrobial compounds accumulating in infected plants. Accumulation of phytoalexins has been observed after infections by fungi, bacteria, viruses, and nematodes. Their formation is often associated with cellular necrosis. Evidence exists that the accumulation is based on enhanced de novo synthesis of phytoalexins in living cells adjacent to the necrotic tissue. Antifungal activity of phytoalexins is directed against different pathogenic and nonpathogenic fungi. In some instances, they may contribute to nonhost resistance; in other cases, they might be involved in plant resistance against pathogens. Numerous abiotic inducers of phytoalexin formation are known and highly potent ‘elicitors’ of phytoalexins have been isolated from fungal cell walls and culture fluids. Keen and associates reported that races ofPhytophthora megasperma produce specific elicitors of phytoalexin formation which are active only in resistant interactions. Albersheim and associates purified and characterized phytoalexin-eliciting β-glucans from the same fungus which unspecifically induce phytoalexin accumulation in resistant, susceptible, and also in nonhost plants. Research on elicitors should provide powerful tools for the elucidation of phytoalexin biosynthesis and the role of phytoalexins in plant resistance.
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