The only method for determining whether seeds are infected with a pathogenic virus is to grow them in the laboratory, greenhouse, or field until symptoms are evident. Seed-transmitted lettuce mosaic has received considerable attention.

WHEN nematode-infected seeds are converted into galls, as is the case for the grass and wheat seed nematodes (Anguina), the galls are easily detected by examining the dry seeds at low magnifications. When the nematodes are borne externally on the seeds for example, Aphelencoides ritzema-bosi with aster seeds and the stem nematode, Ditylenchus dipsaci, with clover seeds they cannot be detected by examining the dry seeds.

The Baerman funnel method has proved to be successful for detecting nematodes borne loosely on the seed-coat or in debris mixed with the seeds. A known amount of seeds wrapped in cheesecloth or a similar material is placed in a funnel immersed in water. The nematodes migrate from the seeds and the debris and can be collected, identified, and counted by microscopic examination.

ALTHOUGH information on methods for testing seed for seed borne pathogens is available in a number of publications, none covers completely all the methods that are in use.

L. C. Doyer in 1938 wrote one of the first manuals for the determination of seedborne diseases. In a publication of the Kew Mycological Institute in 1958, all the known seedborne pathogens are listed. It supersedes a similar compilation (Bulletin 245, 1931, West Virginia Agricultural Experiment Station) by C. R. Orton.

Many articles on the detection and classification of seedborne organisms have been contributed by Willard F. Crosier of the New York Agricultural Experiment Station and J. W. Groves and A. J. Skolko of the Department of Agriculture, Ottawa, Canada.

A number of methods of detecting seedborne diseases have been described by members of the Association of Official Seed Analysts, compiled by Alice M. Andersen and published in 1958 as a handbook by the Association of Official Seed Analysts. A section is devoted to seedborne diseases in the 1952 Agriculture Handbook No. 30, "Manual for Testing Agricultural and Vegetable Seeds."

Likewise, a section of the 1960 Proceedings of the International Rules for Seed Testing is devoted to the detection of pathogens. The European and Mediterranean Plant Protection Organization published reports on seed-borne diseases in 1954 and 1958.

Several organizations in North America are interested in testing seeds for seedborne diseases and other phases of seed pathology. These are the Association of Official Seed Analysts, the International Crop Improvement Association, and the Seed and Plant Material Certification Committee of the Phytopathological Society.

The Plant Disease Committee of the International Seed Testing Association has contributed much to the development of standardized testing procedures, particularly through the distribution of international referee samples containing seedborne organisms.

Routine testing of seeds for pathogens has made greater advances in Europe than in the United States. A number of countries test seeds for plant pathogens. The European testing laboratories are mainly government institutions and usually have mycologists or plant pathologists on their staffs to supervise testing seed for pathogens.

Seed testing in the United States is performed by many private, commercial, State, and Federal laboratories. Most of them have not been prepared to test for seedborne pathogens.

In the United States there was little legislation concerning the testing of seeds for seedborne pathogens and no formal labeling requirements in 1961 for seedborne organisms or diseases of interstate and imported field and vegetable seeds. A few quarantine restrictions pertain to inspection for certain harmful pests upon arrival in the United States. Certificates of health are issued in Europe to facilitate the movement of seeds in international commerce, principally for quarantine purposes. More than 90 different countries have quarantine regulations with respect to seed importation.

THE PRESENT state of testing seeds for seedborne pathogens is somewhat similar to that which existed for purity and germination in 1900 or so. There is a great need for cooperation, coordination, and standardization of national and international sampling and testing procedures.

Until such factors as sampling procedure, size of samples, length of incubation, incubation temperatures, type of lighting, types of substrata, and pH of the media are standardized, the results obtained have little meaning because they are not reproducible from one laboratory to another. Standardization and simplification of these procedures must be based on findings of research. Studies designed to correlate the incidence of pathogens in seed lots with the occurrence of disease in the field after sowing are needed. Only by such studies can scientifically based standards be established.

ALICE M. ANDERSEN is engaged in research on seeds in the Market Quality Research Division of the U.S. Department of Agriculture at Beltsville, Md. She holds degrees from the University of Nebraska. She is a member of the seed pathology and germination committees of the International Seed Testing Association.

CHARLES M. LEACH is an assistant Plant pathologist at the Oregon Agricultural Experiment Station. He was graduated from the Queen's University of Belfast and received his doctor's degree at Oregon State College. He is a member of the Seed and Plant Material Certification Committee of the American Phytopathological Society and has worked on various phases of seed pathology and diseases of forage legumes.