Resistance to powdery mildew in mutant lines of the susceptible wheat cultivar Hobbit 'sib'

Mutant lines of the wheat (Triticum aestivum) cultivar Hobbit 'sib', produc ed by irradiation with fast neutrons, were evaluated for their response to powdery mildew (Erisyphe graminis f.sp. tritici) at various growth stages t o identify and characterize resistance. Two mutants, I3-54 and I3-48, were found to be significantly more resistant than Hobbit 'sib', with the resist ance being expressed in both seedlings and adult plants. Fungal hyphal deve lopment was slower in both the mutants than in Hobbit 'sib' between 18 and 24 h after inoculation, and fewer haustoria were formed in the mutants, par ticularly in I3-54, 72 h after inoculation. Constitutive expression of a th aumatin-like protein gene was detected in both I3-48 and I3-54 but not in H obbit 'sib'.