EFFECT OF RUST INFECTION ON CELL-WALLS OF BARLEY AND WHEAT - IMMUNOCYTOCHEMISTRY USING ANTI-BARLEY THIONIN AS A PROBE

Polyclonal antiserum prepared against barley cell wall thionin was use d to localize and quantitate immunoreactive material on the cellular l evel in healthy and rust-infected leaves of barley and wheat. Three ty pes of sites were used for the immunocytochemical analysis: as control sites, mesophyll cell walls were selected in uninoculated leaves, and in leaves that were inoculated with rust but where the sites were not in contact with the pathogen; these were compared with mesophyll cell walls that were in contact with intercellular rust hyphae in inoculat ed leaves. Similar amounts of cell wall thionin were detected in all 3 barley cultivars before inoculation. At sites where intercellular hyp hae of Puccinia hordei had made contact with mesophyll cell walls, les s thionin was found in the compatible host cv. Larker, but in incompat ible hosts (cvs. Gold and Bolivia) the thionin concentration did not d iffer from that of the controls. Two cultivars of wheat were studied w ith respect to immunoreactive material in their mesophyll cell walls, the universal rust suscept cv. Little Club and the highly rust-resista nt cv. Khapli. Before inoculation, leaves of cv. Khapli contained abou t twice the amount of immunoreactive material in mesophyll cell walls than those of cv. Little Club. This relation was unchanged in walls th at had made contact with P. graminis tritici, but in non-contacted wal ls of infected cv. Little Club leaves, the concentration of this mater ial had risen to levels typical for those of cv. Khapli. Tests for imm unoreactive material with pre-embedding cytochemistry yielded negative results, indicating that it is not exposed on the surface of mesophyl l walls in barley and wheat.