SEED POTATOES

Potato plants may be grown from true potato seed, plant tissue culture or potato tubers. True potato seed forms in the small green berries, potato plants may produce. These berries look like small green tomatoes. True potato seed produces plants with random traits and will not be true to the varietal traits of the mother plant, thus may not produce the expected crop. Potato tissue culture is a way to maintain and propagate pathogen free and varietal pure foundation planting material. We use tissue cultured plantlets, delivered 10-15 per petri dish, to grow potato plant starts, which are later transplanted into our greenhouse. The resulting tubers harvested are minitubers, which become seed for the first generation of field cultivation. Tubers harvested from the first field generation are Field Year 1 (FY1). People are most familiar with the potato tubers encountered in fresh food markets or seed potatoes offered in garden centers or hardware stores in the spring of the year. The tuber forms on a modified stem of the potato plant, known as stolons, which grow in the dark environment beneath soil or mulch. These daughter tubers are basically clones of the mother plant and contain all that is necessary to grow an entirely new plant or plants. Potato tubers normally have a number of eyes, from which may sprout stems of a new plant. A potato tuber may be cut into as many pieces as it has eyes, thus producing that same number of new plants. Any potato tuber may be used as seed including supermarket potatoes (yes, conventional fresh supermarket potatoes are treated with a sprout inhibitor) or seed the old timer next door has been saving and growing and saving again for years (maybe Field Year 29?), this was the practice in Ireland prior to 1850. Modern practice includes governing regulations limiting the number of generations daughter tubers can be saved and replanted. Most jurisdictions allow seed to be certified out six generations, this known as limited generation. Each generation is replanted the following year to provide about an 8-to-10-fold increase in the quantity of tubers. This process is continued, out to a maximum of 6 years or until sufficient seed is available to provide for consumer food demand. Plants naturally acquire an external/internal microbiome from the surrounding environment. Some of these acquired microbes are pathogens which weaken or destroy the plant host. A one-time small infection may be enough to cause significant damage. In other cases, the number of pathogens may need to build-up before significant damage occurs. Because seed potatoes are basically clones of the mother plant, the microbiome acquired by the mother plant is passed down to the daughter tubers and each succeeding generation, potentially building to a damaging level. The Irish potato famine is a case-in-point. Not using certified seed is like playing Russian Roulet. With just you and your neighbors at risk it's likely not going to be significant loss, but pathogens can easily spread and on a commercial scale become a threat to national or world food security.