Often, the gene gives the plant resistance to only one race of a pathogen. It is sometimes called qualitative resistance because plants are either resistant or susceptible, without intermediate levels. It usually is effective against all races of a pathogen. This type of resistance is often called quantitative because there are intermediate levels ranging from resistant to susceptible. Often, polygenic resistance does not give a plant as high a level of resistance as major-gene resistance.
Tolerance also describes the reaction of a plant to a disease.
Tolerance has two meanings. It may refer to a moderate level of polygenic resistance or to the ability of a plant to maintain yield when the plant is diseased. This characteristic is a separate from resistance to infection. The type of resistance available depends on the specific disease. Most hybrids and varieties have some level of polygenic resistance to the common diseases.