A small group of plant scientists work tirelessly around the world to keep plant disease at bay. Now, they’re trying to find a strain of wheat resistant to stem rust, which is threatening the world’s wheat supply. Host Jeff Young talks with author Susan Dworkin whose book, “The Viking in the Wheat Field: A Scientist’s Struggle to Preserve the World’s Harvest,” follows the life of a man who was devoted to saving seeds from plants all over the world so that we will be able to fight future diseases.