The source of potato blight is from the genetic similarity of the potatoes grown, as potatoes clone themselves when grown from potato seed (small potatoes) rather than "true" potato seeds, from their flowers. They are naturally selected, then naturally cloned en masse.

Lab grown meat will have the same problem assuming the cells have little to no genetic diversity. Even if grown in a sterile environment, they could become susceptible to a blight-like organism (virus, bacteria, fungus, etc) once on grocery store shelves.