Just finished listening to a book on this subject, among others.
The problem was made much worse by propagating the potato by planting eyes rather than seed. This means the plants are basically clones.
Since the Irish potatoes were pretty much all descended from a very few plants brought over a couple centuries earlier, you had an entire island planted with a monoculture of almost genetically identical plants. No resistance whatsoever.
It’s common practice among potato growers to grow next years crop from last years remaining tubers. (eyes)
If a potato plant gets to the point where it is flowering and creating new seed pods, tuber production falls dramatically, and existing tubers can get stressed to the point they are not worth a crap.
Now people DO grow them with the intent of crossing them and creating new hybrids (Luther Burbank!!) but in the years I’ve gardened, I never even heard of anyone starting potato plants from fertilized potato seeds.
Remember, potatoes are of the solanum (Nightshade) family, and the possibility always exists that a new hybrid crop could pick up stuff from another native solanum species.
You could end up with some real KILLER potatoes!
;-)
Bananas have the same problem.
The banana republics were developed using cuttings from the Gros Michael banana, on terms similar to that of the Union-Pacific: Railroads were built to plantations with land on alternating sides of the road going to the railroad builder (Standard Fruit or United Fruit). When fungus hit the Gros Michael, they tried to expand cultivation, but the fungus followed.
Eventually cultivation of the Gros Michael was not viable, and there were no bananas available. (Yes, we have no bananas.....). Banana cultivation was eventually restarted with the Cavendish banana, a formerly rare variant derived from Asia. It took more careful handling (boxes not stems), but its cultivation eventually expanded to Asia, where a fungus mutated to affect it. That fungus is now spreading.
Some ancient asian bananas have seeds. Uganda has over 70 species of banana.