Leaf rust caused by Puccinia triticina Eriks. (Pt) is a destructive foliar disease that threatens world wheat production. Breeding and deployment of resistant cultivars are the most profitable and environmental friendly method to prevent disease losses. It was found that when the wheat leaf rust resistance gene Lr13 was introduced into some wheat varieties by hybridization, the hybrid necrosis was often caused in F1 plants. Complementary wheat genes Necrosis 1 (Ne1) and Necrosis 2 (Ne2) on chromosome arms 5BL and 2BS, respectively, cause hybrid necrosis. Ne2 shows extremely tight genetic linkage with leaf rust resistance gene Lr13. However, the function and relationship of Lr13/Ne2 remained unknown for decades.