Virulence gene or genes in a pest which have not necessarily been identified but can be used for practical purposes in gene-for-gene relationships.

a feature of a pathogenic organism that enhances its ability to cause disease

Any gene product which enhances the ability of an organism to cause disease.

A structure or attribute of a microbe that enhances its capacity to produce symptoms of disease in an infected host.

Virulence factors are molecules produced by a pathogen that specifically influence their host's function to allow the pathogen to thrive. Factors that are used in general life processes, such as metabolism, may be vital to the pathogen's ability to thrive in the host, but are not considered virulence factors since they lack specific function to directly influence the host.