It
was blight that caused the Irish famine Snadger, you're right. The main problem was that there were only a couple of varieties in common use there at the time. In South America where the spud originated, farmers will plant a field up with about 2 dozen varieties, then if some succumb to pestilence of any kind, they will still get a crop from the others. A lesson to us all about biodiversity.
Same thing happened with maize in the USA in the 70s. This is another reason for keeping some of the Heritage varieties in circulation. We never know when we will need their genetic input to breed disease resistance into our modern crops. Once it's gone, it's gone.
(Little personal rant over!)
