Disease development and beta-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 res istance conferred by the genes Lr29 and Lr34 to leaf rust, three near-isoge nic 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. tr itici. 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. Indu ction of beta-1,3-glucanase activity was observed in all lines, including P almiet, concurrent with the formation of substomatal vesicles and subsequen t differentiation of the pathogen. Following leaf rust infection, four majo r beta-1,3-glucanases were revealed with Western blot analysis. Higher leve ls of activity were detected in infected than in non-infected plants. The h ypothesis that resistance in lines carrying Lr29 or Lr34 is related to high er levels of beta-1,3-glucanase expression was not confirmed. (C) 1999 Acad emic Press.