The correct option is 3: Puccinia graminis The correct causative agent for the highly destructive disease known as Black rust of wheat, or Stem rust, is the fungus Puccinia graminis. This specific pathogen is further classified as a forma specialis, Puccinia graminis f. sp. tritici, which specializes in infecting wheat (Triticum aestivum). As a true rust fungus, P. graminis is characterized by a complex life cycle, being macrocyclic and heteroecious,…Read More