Recent advances in the genetics of disease resistance.

Breeders selecting for disease resistance need measures of general resistance because they have limited potential for multiple trait selection. Among mechanisms of resistance, active immunity appears to have the best potential for measuring general resistance. The search for selection criteria to improve general resistance may be aimed at single genes, such as the major histocompatibility complex, or at measures of immune response that are controlled by multiple genes. Current research approaches require testing potential genes or phenotypes with several criteria of resistance to determine their general nature. Extreme selection for one measure of immuno-responsiveness may lead to failure in another type of immunity. If this is true true, a balanced breeding approach is required.