Plant resistance to pathogen infection:: Forms and mechanisms of innate and acquired resistance

Different forms and mechanisms of plant resistance are compared in this review, differentiating between innate and acquired resistance. Within innate resistance, general non-specific and specific host resistance are treated as regards the phenomena and mechanisms. Various forms of non-specific (e.g. non-host, basal, quantitative etc.) as well as specific resistance (extreme resistance, gene-for-gene resistance with the hypersensitive response, toxin resistance and gene silencing) are discussed. Within acquired resistance, the immune memory vs. stress memory of animal or plant hosts are compared. Furthermore, mechanisms of acquired resistance of plants are treated in relation to salicylate metabolism, systemic signalling, antioxidants and a recently discovered recombination signal inducing somatic mutations. It seems important for future research trends in plant pathology that several new resistance mechanisms have been discovered or at least re-evaluated, in addition to the specific HR-associated resistance, which has been the subject of the majority of previous research.