The status of crops that have a narrow genetic base, which could lead to increased threat of attack from pests and pathogens. Genetically vulnerable crops have a limited number of varieties and a narrow range of genetic resistance to pests and diseases. Modern breeding has narrowed the genetic base of crops, compared with what farmers grow in traditional systems. These systems are often characterized by many different varieties, often expressing different levels of susceptibility to a given pest or disease. This heterogeneity, as opposed to homogeneity in modern varieties, reduces risk of attack by pests and pathogens.