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Genotypic diversity and reproductive biology of Thekopsora areolata, the causal agent of cherry spruce rust in Norway spruce seed orchards.

Åke Olson: Swedish University of Agricultural Sciences

<div>Swedish forestry is sustained by yearly planting of about 200 million Norway spruce seedlings, produced in seed orchards planted with superior trees. The seed orchards are intensively managed to produce large quantities of high quality seeds. However, today there are a deficit of plants originating from Swedish seed orchards mainly due to irregular flowering as well as to pest and pathogen infections. The fungal pathogen <em>Thekopsora areolata,</em> causal agent of cherry spruce rust, heavily affects Norway spruce seed production. Using newly developed microsatellite markers and a hierarchical sampling strategy, population structure and reproductive mode of <em>T. areolata</em> were investigated. From one location in Norway, two locations in Finland and five locations in Sweden, one aecium per infected cone was analysed. In addition, multiple aecia per scale and cone were sampled at two locations in Sweden. The results show an over-all high genetic diversity in <em>T. areolata</em> at all hierarchical levels with no genetic structure, indicating high gene flow and random mating. At the cone/scale level non-random mating was observed, for which several distinct hypotheses will be presented. Future research directions and management implications will be discussed.</div>