J. Vogel isolated a series of powdery mildew resistant mutants (pmr1 – pmr6) and a series of suppressor mutants of pmr5 (p5s1 – p5s10). A majority of these mutants exhibit some change in their cell wall composition or architecture suggesting that powdery mildew is highly adapted to its host cell wall and minor changes in the cell wall can restrict this pathogen. Two of the suppressors can mutations in TBR and two in RWA2, both genes involved in cell wall biosynthesis, suggesting these mutations cause compensating changes in the wall that no longer limit powdery mildew success. The remaining suppressor mutants encompass a broad range of gene suggesting suppression of the disease resistance of pmr5 can occur by other means.