The present invention provides a mutant wheat plant resistant to powdery mildew and producing method thereof wherein the mutant wheat plant comprises a loss of function mutation in a TaMLO Al TaMLO Bl and TaMLO Dl nucleic acid sequence. The present invention also provides a method for determining the presence or absence of a mutant TaMLO Al TaMLO Bl and TaMLO Dl nucleic acid or polypeptide in a wheat plant.