Physiological Races and Pathotypes

Physiological Races and Pathotypes

The concept of physiological races was introduced by Barrus in 1911. Physiological races are strains of a single pathogen species differing in their ability to attack different varieties of the same host species. The varieties of a host species used to identity physiological races of a pathogen are known as differential hosts or host testers. Differential hosts are chosen on the basis of differences in their resistances to the pathogen, but the genes for resistance present in them are usually not known. Ideally, each of the differential hosts should posses a single resistance gene different from those present in the others, such a set of differentials is known as ideal differentials.