I trained a villager to be the farmer. No one else had more than a little bit of skill in farming. He became a master farmer very quickly. Silly me didn't notice that the little freak disliked fish, so when the fruit ran out he became USELESS. And to make it worse, not only did I have to train a new farmer, but the fish-hater had no skills in any other area and absolutely refused to learn. It took ages to get him to trainee in another skill.