Resistance Responses of Birch Betula spp. Against Leaf Rust Fungus Melampsoridium Betulinum : Shoot and Foliage Diseases in Forest Trees. Proceedings of a Joint Meeting of the Working Parties Canker and Shoot Blight of Conifers (S2.06.02) Foliage Diseases (S2.06.04)

Florenz

1995

S. 292-297

11 Lit. Ang.

Bandaufführung

77439

Appressorium formation and location of the urediniospores of Melampsoridium betulinum were studied with scanning electron microscopy by use of sterile in vitro and mature leaves of the clones of Betula pendula and Betula pubescens. Appressorium formation could be induced on sterile leaves. Comparisons between different host - rust combinations indicated that even in the incompatible interactions between Betula pubescens clones and rust isolates derived from Betula pendula, the proportions of appressoria formed over stomata were in the range of the compatible interactions. Thus the lower infection level in the incompatible system of Betula pubescens host and Betula pendula rust is probably not a result of failure to locate appressoria over stomata. In another experiment, seven Betula pendula clones were screened with an extended number of different birch rust isolates, three Betula pendula isolates originating from south and central Finland and four Betula pubescens isolates from south, central and north Finland. According to the area under the disease progress curves (AUDPC) derived from pustule frequencies on leaf discs, clones differed significantly in their rust resistance. As in previous inoculation experiments, no hypersensitive reactions to any rust isolate were found among Betula pendula clones.