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Characterization and Distribution of Mating Type Genes in the Dothistroma Needle Blight Pathogens

First, sixth, and tenth authors: CBS Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, Netherlands; second, eighth, and ninth authors: Forestry and Agricultural Biotechnology Institute (FABI), Department of Genetics, University of Pretoria, Pretoria 0002, South Africa; third author: Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand; fourth author: Forest Research, Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH, United Kingdom; and fifth and seventh authors: University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada.

Dothistroma septosporum and D. pini are the two causal agents of Dothistroma needle blight of Pinus spp. in natural forests and plantations. Degenerate primers amplified portions of mating type genes (MAT1-1-1 and MAT1-2) and chromosome walking was applied to obtain the full-length genes in both species. The mating-type-specific primers designed in this study could distinguish between the morphologically similar D. pini and D. septosporum and between the different mating types of these species. Screening of isolates from global collections of D. septosporum showed that only MAT2 isolates are present in Australian and New Zealand collections, where only the asexual form of the fungus has been found. In contrast, both mating types of D. septosporum were present in collections from Canada and Europe, where the sexual state is known. Intriguingly, collections from South Africa and the United Kingdom, where the sexual state of the fungus is unknown, included both mating types. In D. pini, for which no teleomorph is known, both mating types were present in collections from the United States. These results provided new insights into the biology and global distribution of two of the world's most important pine pathogens and should facilitate management of the diseases caused by these fungi.

Additional keywords: ascomycetes, heterothallic, Mycosphaerella, sexual reproduction.