Gilroy, California, USA
June 2011

Source: Eurofins STA Laboratories newsletter, June edition
By Darrell Maddox

Seed health testing as a quality parameter began in earnest in the late 1980’s and with a few exceptions it has mostly been employed as a tool to determine if your seed field may have been contaminated with a seed borne pathogen. I like to look at seed health testing as having “ultimate goals” and “basic goals”. The ultimate goals of seed health testing are to minimize crop losses due to seed borne pathogens and to prevent their introduction or transfer into other geographic areas by limiting inoculums. But the basic goal of a seed health test is to provide accurate results and consistent detection of the pathogen at a predetermined level of contamination so you can reliably make risk management decisions and measure how well your integrated plant disease management practices are working in your seed production. I still believe that current seed health testing technology is not capable of predicting if seed contaminated with a seed borne pathogen will result in seed borne disease problems in commercial vegetables fields (for disease to occur the disease agent, susceptible host, and optimal environmental conditions must occur) after sale of the product. However, seed health tests are important tools in risk assessment and overall seed borne disease management. The best value on seed health testing to your company will be achieved when it’s part of an overall disease management process. Furthermore, you will need to show that you production practices are diligent in preventing seed borne pathogen introduction into your seed fields.

Prevention of seed borne disease is the primary key to your seed health program and prevention starts with a few key components:

• Start with clean seed and genetic material. This pertains to seed from your breeding program through your commercial seed lots. Know where the seed was produced and ascertain it was grown under a integrated disease management program.
• Isolate your seed fields in time and space. Also it is important to know what alternative hosts for pathogens of concern for any seed product. For example, many diseases, including several important seed borne diseases, that infect broccoli also infect oil rapeseed and radish. Consider having designated disease free “nurseries” for your breeder seed and high value stock seed production.
• Use good cultural control and agricultural practices. Weed control, water control, drainage control, arid climates, for example. And often overlooked is assessing your seed growers to ensure that good cultural practices are standard.
• Good sanitation and seed treatment. Remove field debris, clean equipment and tools, disinfect greenhouses, and educate workers; use seed treatments or disinfectants when applicable.
• Document your steps and use seed health testing at key control points. I have suggested testing your breeder seed/foundation seed, stock seed and most importantly as soon as you have control of your commercial product. Remember, most seed health testing should be done on seed that has not been treated or disinfected.

Finally, in the last year, as Chair of the American Seed Trade Association’s Phytosanitary Committee, it has become apparent that there are still misconceptions of seed health testing and misuse of seed health testing in everything from breeding to phytosanitary security, especially the later. During the implementation of the National Seed Health System (accreditation) or the International Seed Health Initiative (method standardization), there was never any intention of replacing the current phytosanitary system which relies on field inspection or certification with laboratory seed health testing. These programs were meant to increase confidence in seed health testing from companies, commercial labs and institutes by establishing accreditation processes and standardizing seed health testing methods. By providing this added level of confidence, seed health testing can now be used by our government officials (APHIS PPQ) to issue phytosanitary certificates when circumstances prevented a field inspection—thus not interrupting worldwide seed trade. In other words, using seed health tests in this manner has again added value to the seed industry, but it would be difficult to see the value of a phytosanitary security system that is entirely reliant on seed health testing, primarily because valid seed health tests do not exist on most of the pathogens that are of phytosanitary concern.

Darrell Maddox is the former President of Eurofins STA Laboratories (ESTA) and continues to provide seed health expertise to ESTA and their clients. Darrell currently directs Endless Sky Partners, LLC, a company providing seed quality and business development to the seed industry and related industries. Darrell is also the current chair of the ASTA Phytosanitary Committee and works closely with ASTA representatives and USDA APHIS officials to resolve phytosanitary issues that may affect seed trade worldwide.

Website: http://www.elskies.com/

Published: June 28, 2011