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Ecology and Epidemiology

Parasitization of Pine Stem Rust Fungi by Monocillium nordinii. A. Tsuneda, National Research Council of Canada visiting fellow, Northern Forest Research Centre, Canadian Forestry Service, Environment Canada, 5320122 Street, Edmonton, Alberta, Canada T6H 3S5; Y. Hiratsuka, research scientist, Northern Forest Research Centre, Canadian Forestry Service, Environment Canada, 5320122 Street, Edmonton, Alberta, Canada T6H 3S5. Phytopathology 70:1101-1103. Accepted for publication 17 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1101.

Monocillium nordinii that occurred in sori of Cronartium coleosporioides and Endocronartium harknessii in Alberta, Canada, was a destructive mycoparasite of these pine stem rust fungi. Detailed study of the parasitic process in the E. harknessii-M. nordinii interaction showed that hyphae of M. nordinii grew between the surface wart layers of rust spores and that swollen appressoriumlike bodies often were formed where contact was made. The host cytoplasm occasionally developed a papilla beneath the area of contact during the early stages of parasitism; however, the host cell eventually lost most of its cytoplasm, except oil bodies, in most cases. Penetration of the rust spores by the Monocillium hyphae usually appeared to occur after the host cells were killed. Monocillium generally formed many conidiophores and conidia on the host spores. Eventually the surface morphology of the infected rust spores was greatly degraded. It is suggested that antifungal metabolites of M. nordinii are involved in this parasitic process.

Additional keywords: mycoparasitism.