Develop and Distribute Reference Materials

CPPSI develops and distributes reference materials that facilitate the identification of plant pathogen strains or races. Reference materials are comprised of pathogen strain or race differentiating host sets, reference pathogen strains and an informative white paper. The white paper explains what the disease is, the nature of resistance to the disease, how to work with strains or races of the pathogen causal agent, how to evaluate resistance and susceptibility to a pathogen strain or race in a seedling test, and how to identify the pathogen strain or race in question. In addition, the white paper lists contacts for ordering seeds and reference pathogen strains or races.  

Differential hosts are sets of commercial plant varieties, each containing one or more genes for resistance to strains or races of a given plant pathogen. By inoculating an unknown strain of a given plant pathogen across the differentiating hosts, the strain can be identified based on the pattern of susceptible or resistant responses to that strain. Reference strains or races are known characterized isolates of a given pathogen. The response of the differential hosts to the reference strain or race is compared to that of your isolate in question to verify identification.  Reference responses are also used to substantiate that the test results are correct.

Library of Reference Materials

To launch the initiative, CPPSI members deployed a library of reference materials for four disease systems: tomato tobacco mosaic virus, pepper bacterial spot, melon fusarium wilt and spinach downy mildew. This was done to show that the CPPSI system of distribution would work for each type of plant pathogen: a virus, bacterium, fungus and an obligate plant pathogen.  Today, we expanded that library to include lettuce downy mildew, pepper Tomato spotted wilt virus, tomato Tomato spotted wilt virus and Watermelon fusarium wilt.

Seed of the differential hosts for each of these hosts can be ordered online through the USDA Germplasm Resources Information Network (GRIN). CPPSI material available in the USDA-GRIN system can be found by searching "CPPSI*". Refer to the GRIN links noted on the CPPSI website and in each of the white papers. For some hybrid host differentials, a Material Transfer Agreement (MTA) may be required to order seed.

To acquire the reference plant pathogen strains and races please refer to the contact information provided on the CPPSI website and in each white paper. It is the responsibility of those requesting pathogen strains to ensure they have the necessary permits to receive the plant pathogen strains or races by contacting the USDA Animal and Plant Health Inspection Service.