How can you tell if a seed potato is disease free?
The American potato seed industry is difficult to navigate. Each region or state has its own seed certification rules, which creates inconsistency.
“Seed potato programs differ depending on the markets they serve. If a state has significant commercial production, [its] main goal may be to provide seed to their commercial farms,” says Nina Zidak, Montana State University, Associate Research Professor, seed potato certifier.
There is no commercial potato industry in Montana, so the focus is on seeds, Zidak said.
The goal of the seed potato certification program is not to provide disease-free seeds, but to make sure the seeds meet accepted quality standards, says Kasia Duellman, associate professor and seed potato specialist at the University of Idaho.
“Seed certification programs provide independent, third-party verification of the quality of seed potatoes,” says Alan Vestra of the Idaho Crop Improvement Association, Southeast Region Manager. Certification agencies determine what determines the quality of a potato. This does not mean that the certification body cannot claim the absence of certain diseases.
“In many programs, the standards indicate zero tolerance for some diseases and tolerance for others,” Duellman says. "Some diseases are not tolerated only for high reproduction seeds or for all generations intended for certification."
This means that any seed lots with a detected disease will not be certified, Duellman says. In other cases, however, a tolerance may be set. “If the tolerance is exceeded, the quality of the seed lot is either reduced or it is rejected,” she says.
Certification may also vary by generation. High reproduction (basic) seeds are usually sold to other growers who propagate them up to a year before they are useful to commercial growers. They buy later generations of potato seeds, usually generations 3 and up. The standards may be higher for an earlier generation, as any problems with these seeds will only multiply as they are grown by seed growers and then by commercial growers.
The University of Montana Certification Program has an impeccable reputation. This may be due to the fact that this state's growers are concentrating on seed production. “We're looking to produce seeds that can be re-certified for seed potato production in other states,” says Zidak.
Because certificate programs vary so much, we heard a lot of opinions about what each program should include.
Representatives of the University of Montana test all basic plantings and 1st generation for mosaic virus (PVY). They also conduct post-harvest testing, sending samples from all growers' fields to Hawaii for growing during the season. The team inspects and takes a leaf from each plant and then sends them back to the lab. Leaves are tested for three viruses: PVY, potato virus X (PVX) and potato virus A (PVA).
The Wisconsin Seed Potato Certification Program checks not only the crop twice in the summer and after harvest, but also storage and shipping points. According to Russell Groves, professor and extension specialist at the University of Wisconsin and interim director of the Wisconsin Seed Potato Certification Program, as improvements are constantly being made, it is critical to update diagnostic test protocols for pathogen detection and procedures to limit cultivar mixing.
Documentation is also key. It is not uncommon for seeds to cross state lines where they need to qualify for another certification program. "Another aspect of a robust certification program is the removal of infected plants," says Brian A. Charlton, acting director of Oregon State University's Klamath Basin Potato Department.
However, certification alone cannot replace a strong relationship between seed suppliers and growers. “In my opinion, trust and participation is more important than testing,” says Reagan Grabner, vice president of CSS Farms, a seed producer in Washington state. "A seed grower and a commercial grower must have a close relationship and agree on what it means to deliver a high quality product."