Whereas some things are fairly straightforward to grow from their own last-crop seeds, resowing potatoes from some you already have often results in disease.

I grow a lot of different things in my backyard. From one lettuce, coriander, radish, pumpkin or tomato plant, I can collect loads and loads of seeds to regrow. In the case of a lettuce plant, it's thousands of seeds.

Potatoes are trivial to grow from old shrivelled supermarket stock (and sometimes scraps with the eyes intact) but 80+% of crops I've grown this way have been riddled internally with disease.

Pictures here: https://www.google.com.au/search?q=potato+disease&source=lnm...