Disease development and β-1,3-glucanase expression following leaf rust infection in resistant and susceptible near-isogenic wheat seedlings

To determine the association of pathogenesis-related (PR) proteins with resistance conferred by the genes Lr29 and Lr34 to leaf rust, three near-isogenic wheat lines [Palmiet (Pa), Pa/Lr29 (Pa*4/RL6080[Lr29]) and Pa/Lr34 (Pa*4/RL6058 [Lr34])] were infected with the fungus Puccinia recondita f sp. tritici. Activity levels and an immunological profile of the PR protein, beta 1,3-glucanase, were recorded in relation to fungal structure development. Compared with the susceptible control, Palmiet, infection and colonization of leaf tissue were inhibited in lines containing either Lr29 or Lr34. Induction of beta-1,3-glucanase activity was observed in all lines, including Palmiet, concurrent with the formation of substomatal vesicles and subsequent differentiation of the pathogen. Following leaf rust infection, four major beta-1,3-glucanases were revealed with Western blot analysis. Higher levels of activity were detected in infected than in non-infected plants. The hypothesis that resistance in lines carrying Lr29 or Lr34 is related to higher levels of beta-1,3-glucanase expression was not confirmed. (C) 1999 Academic Press.