Of course the prolific 'Lumper' was highly susceptible to blight (like all the other varieties of that time). But the variety has survived to become an 'heirloom' potato, valued for its rarity. This means that to grow it today, the grower has to apply the weekly doze of fungicide to keep the dreaded tuber blight out of his pre-packs for the supermarket. If you want a different variety to tempt the customer, why not choose one that tastes good and has resistance to blight and do your bit to save the planet?
Salaman in his "The history and social influence of the potato" tells a nice little tale. A poor boy in Ireland (pre-famine) was beaten in his school exams by a rich boy called Laughlin. He protested that it was unfair as Laughlin had the great advantage of dining off 'Gregors Cups', a much higher quality variety than the one he had to eat.
Read more about Lumpers in the National Geographic http://news.nationalgeographic.com/news/2013/03/130315-irish-famine-potato-lumper-food-science-culture-ireland/#finished