The capacity in plant and microbe is symbolized below as 1P and 1H, respectively . This symbolization is not intended to represent one gene in each organism, but rather a complex genotype. This corresponding genetic capacity is often referred to as an incompatibility system. Incongruous organisms may also have the genetic information that codes for incompatibility, but cannot be observed at an organismal level since the corresponding genes are not brought together. Some investigators suggest that, in some cases, two or more corresponding gene pairs operate together to bring about incompatibility, where either pair does not operate alone.
Environment affects both congruity and incompatibility.