The ability of a plant to restrict the activities of a pathogen so that its growth is not significantly affected. Complete resistance is termed * immunity. Resistance may be specific, i.e. effective against a particular strain of the pathogen, or nonspecific, i.e. effective against all strains. Specific resistance is usually controlled by one or a few major genes, e.g. resistance of barley to mildew and of flax to rust are inherited as single genes. Nonspecific resistance is conferred by the combined action of a number of minor genes. Such multigenic or field resistance is usually more stable and less likely to be overcome by mutants or recombinants of the pathogen. Environmental factors may influence the expression and degree of resistance. Compare susceptibility. See also hypersensitivity , phytoalexin. |
