Gene-for-gene

Gene-for-gene interaction is a model of antagonistic coevolution between hosts and pathogens, first formalized by Harold Henry Flor in 1942. The model posits that for every gene conferring resistance in the host, there is a corresponding gene conferring virulence in the pathogen. The interaction is governed by a simple genetic rule: the pathogen can only infect the host if it possesses a virulence allele that matches the host's resistance allele. If the host lacks the resistance allele, or if the pathogen lacks the matching virulence allele, infection fails.

The genetic architecture is a matching game with the following payoff structure: each host resistance gene (R) is matched by a pathogen avirulence gene (A). When the host carries R and the pathogen carries A, the host recognizes the pathogen and mounts a defense. When the pathogen carries a mutated virulence allele (a) that evades recognition, infection succeeds. The dynamics produce a Red Queen race in which host populations must continuously generate new R alleles while pathogen populations must continuously generate new virulence alleles.

The gene-for-gene model is the simplest formalization of the evolutionary arms race that characterizes host-parasite coevolution. It has been empirically validated in plant-pathogen systems, including flax rust, wheat stem rust, and potato late blight. The model has also been extended to animal-pathogen interactions and has influenced the design of artificial immune systems in computer security.