Idaho winter seed test report

Published in the April 2014 Issue Published online: Apr 20, 2014 Phillip Nolte, UI extension seed potato specialist
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Some of the most exciting news in the Idaho seed potato industry has to do with the “big move” of the winter test plots to Waialua, Hawaii this year. The climate in Hawaii is so warm that the plots were ready for evaluation earlier this year than ever before. The big move was not without some issues, however, as a new planter had to be purchased, modified for drip irrigation and then shipped (on an actual ship!) to the islands. The move also required that all of the seed potatoes that were to be planted make a similar voyage across the Pacific Ocean.

The winter post-harvest test, or “winter grow-out” as it is often called, is one of the most important of the many inspections that seed potatoes are subjected to. The summer inspections, which most of you are familiar with, are important but they only go so far. The main difference between the summer and the winter tests is the nature of the information that is generated. For the most part, the summer results are an indication of what was in the seed crop when it was planted. The winter test, on the other hand, provides information on what is in the seed crop that was harvested and will be used to plant next year’s crop. Which of these two sources of information do you think is more important?

A number of the potato viruses, including potato virus Y (PVY) and potato leaf roll virus (PLRV) are often spread during the latter part of the growing season, which is usually too late for inspectors to see symptoms in any of the newly-infected plants because there are, to put it succinctly, none to be seen. The winter grow-out provides an opportunity to identify these late infections and provides more accurate information on the seed crop that will be planted.

Because PVY symptoms can be difficult to see even under the best of circumstances and the occurrence of new strains of the virus that don’t produce strong symptoms, the Idaho seed industry has established another line of defense: all of the seed lots in the winter test plots are tested for PVY using the industry standard ELISA (Enzyme-Linked Immuno Sorbent Assay) laboratory procedure. This procedure detects all strains of PVY, even those that are latent (symptomless) or those that cause mild or atypical symptoms.

The effect of ELISA testing on the Idaho seed industry, which was initiated for the 2007 crop, has been overwhelmingly positive, with steadily decreasing levels of PVY detected in Idaho seed lots during the seven years that the program has been in effect. This information is presented in the accompanying table.

(By the way, winter test information is available to anyone who purchases Idaho seed; all you need to do is ask your seed producer for it. You can also request a North American Plant Health Certificate from the seed certification agency. We strongly suggest that you do.)

This was only the first year at this new location for the winter grow-out, but the feedback has so far all been very favorable. It looks as though Idaho seed growers have a new home for the all-important winter grow out. Aloha!