USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

1731 Research Park Dr.
Davis, CA 95618
(530) 759-1700
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Virulence in C. ribicola

Sugar pines with MGR that resisted early waves of infection for 14 years in a test plantation suddenly developed multiple infections from a new and virulent race of blister rust. Happy Camp, Siskyou Mountains California

Mixed resistant (HR) and susceptible (yellow) needle spot phenotypes on sugar pine with MGR.
(Spots are counted before they coalesce). Inoculum is from Thompson Ridge (TR).
virulent symptoms on needles
Frequency of vcr1 is determined by the proportion of total spots that are yellow.
Specificity of genetic interactions among major genes in the white pine/blister rust pathosystem.
MGR in western white pine is also neutralized by a virulent race. However, this race has no affect on MGR in sugar pine, and the race neutralizing MGR in sugar pine has no affect on MGR in western white pine. This is typical of gene-for-gene systems.