Unlike other major field crops, potatoes are reproduced vegetatively, from other potatoes. Therefore, a part of each year’s crop – from 5 to 15 per cent, depending on the quality of the harvested tubers – is set aside for re-use in the next planting season. Most farmers in developing countries select and store their own seed tubers. In developed countries, farmers are more likely to purchase disease-free “certified seed” from dedicated suppliers.
Extract from International Potato Centre https://cipotato.org/potato/how-potato-grows/