Black stem rust (Ug99) Puccinia graminis f.sp. tritici (Ug99) is a serious disease of wheat and barley. While wheat in the United States is resistant to most strains of black stem rust, it is not ...

hope that one or more of the 600 varieties now being tested will overcome “Race 15B,” the new strain of black stem rust that is seriously threatening the U.S. wheat crop. Wheat rust has been ...