Juha Kaitera, Leena Aarnio, Tiina Ylioja, Jouni Karhu. (2021). Naohidemyces vaccinii sporulates on wild species of ground flora in Finnish Norway spruce seed orchards but Thekopsora areolata does not on other species than Prunus. Silva Fennica vol. 55 no. 5 article id 10568. https://doi.org/10.14214/sf.10568

Keywords: Picea abies; cherry-spruce rust; epidemics; Prunus; blueberry rust; Naohidemyces vaccinii

Highlights: Cherry-spruce rust, Thekopsora areolata, was not found on any of the common species of ground vegetation in Finnish Norway spruce seed orchards; Blueberry rust, Naohidemyces vaccinii, was common on Vaccinium myrtillus and occasional on V. vitis-idaea in all seed orchards; Thekopsora areolata occurs only on Prunus in Finnish Norway spruce seed orchards.

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Thekopsora areolata (Fr.) Magnus is a serious cone pathogen that reduces seed crop of Picea abies (L.) Karst. and other Picea spp. Natural sporulation of T. areolata was investigated in nine Norway spruce seed orchards suffering from severe successive T. areolata epidemics in Finland. Habitats occupied by Vaccinium myrtillus L., V. vitis-idaea L., Empetrum nigrum L. and Calluna vulgaris (L.) Hull, and a number of other wild species belonging to ground flora were investigated for Thekopsora areolata uredinia 9–10 times in May–September 2018–2019. Occurrence of Thekopsora uredinia was estimated in current-year leaves of the plants in ca. 25 sample plots of 1 m² in each seed orchard. A sample of plant leaves with rust uredinia or necrotic pustules were collected from each plot. No rust fruiting stages of T. areolata were found on any of the test species of ground flora. However, rust uredinia were observed regularly on leaves of V. myrtillus and V. vitis-idaea in all seed orchards between mid-July and the end of September. Rust sporulation started on V. myrtillus in July and on V. vitis-idaea in August. Based on symptoms, uredinia and spore morphology, the rust on both V. myrtillus and V. vitis-idaea was identified as blueberry rust, Naohidemyces vaccinii (Jørst.) S. Sato, Katsuya & Y. Hirats. ex Vanderwegen & Fraiture. The uredinial stage of the rust on Vaccinium spp. were described. No evidence of natural sporulation of T. areolata on wild plant species other than Prunus was observed in Finnish Norway spruce seed orchards.

Kaitera, Natural Resources Institute Finland (Luke), Natural Resources and Bioproduction, FI-90570 Oulu, Finland E-mail: juha.kaitera@luke.fi
Aarnio, Natural Resources Institute Finland (Luke), Natural Resources and Bioproduction, FI-00790 Helsinki, Finland E-mail: leena.aarnio@luke.fi
Ylioja, Natural Resources Institute Finland (Luke), Natural Resources and Bioproduction, FI-00790 Helsinki, Finland E-mail: tiina.ylioja@luke.fi
Karhu, Natural Resources Institute Finland (Luke), Natural Resources and Bioproduction, FI-90570 Oulu, Finland E-mail: jouni.karhu@luke.fi

article id 10422, category Research article

Juha Kaitera, Jouni Karhu. (2020). Temperature range for germination of Thekopsora areolata aeciospores from Finnish Norway spruce seed orchards. Silva Fennica vol. 55 no. 1 article id 10422. https://doi.org/10.14214/sf.10422

Keywords: Picea abies; cherry-spruce rust; cones; epidemics; rust diseases

Highlights: Cherry-spruce rust was able to germinate at very low temperature (6 °C) close to the temperature when thermal growth starts; Optimum spore germination occurred between 15–24 °C; High temperature of 30 °C drastically reduced germination; Temperature had the most significant effect on germination, while spore source had less significant effect and agar media a non-significant effect on germination in a Fixed Effects model.

Abstract | Full text in HTML | Full text in PDF | Author Info

Cherry-spruce rust caused by Thekopsora areolata (Fr.) Magnus is a serious cone pathogen of Norway spruce [Picea abies (L.) Karst.]. The rust causes great economical losses in seed orchards specialized in the production of high quality seeds. Germination range of T. areolata aeciospores from rust populations (spore sources) in seven Finnish Norway spruce seed orchards was tested on water agar and malt agar at nine temperatures varying between 6–30 °C. The temperature range of spore germination was high varying between 6 °C and 27 °C, while germination was retarded at 30 °C. The peak in germination rate of all spore sources occurred between 15–24 °C. In a model with fixed effects of agar media, temperature and spore source, temperature had the most significant effect on germination. Spore source had a less significant effect, while agar media had a non-significant effect on germination. The rust was able to germinate at low temperatures corresponding to temperatures when the thermal growing season starts at 5 °C in the spring. As spores from cones from both the spruce canopy and the ground showed very similar germination ranges, it indicated the great capacity of all spores of the rust to germinate early in the spring. Hot temperatures with over 30 °C drastically reduced germination of the rust.

Kaitera, Natural Resources Institute Finland (Luke), Natural resources and bioproduction, Paavo Havaksentie 3, FI-90014 University of Oulu, Finland E-mail: juha.kaitera@luke.fi
Karhu, Natural Resources Institute Finland (Luke), Natural resources and bioproduction, Paavo Havaksentie 3, FI-90014 University of Oulu, Finland E-mail: jouni.karhu@luke.fi

Category : Research note

article id 401, category Research note

Kari Taulavuori, Marian Sarala, Jouni Karhu, Erja Taulavuori, Eero Kubin, Kari Laine, Jarmo Poikolainen, Erkki Pesonen. (2005). Elongation of Scots pine seedlings under blue light depletion. Silva Fennica vol. 39 no. 1 article id 401. https://doi.org/10.14214/sf.401

Keywords: Scots pine; blue light; elongation; high latitude

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The effect of blue light (400–500 nm) removal on the elongation of Scots pine (Pinus sylvetris L.) seedlings was investigated in a field experiment in Northern Finland during two growing seasons. The seedlings were grown in plexiglass chambers and ambient control plots. The blue wavelengths were removed from the light spectrum by using chambers made of orange plexiglass. The results of nearly daily measurements showed that the elongation of Scots pine seedlings was increased by the removal of blue light only at high latitudes.

Taulavuori, Department of Biology, University of Oulu, PO Box 3000, FI-90014, Oulu, Finland E-mail: ktaulavu@cc.oulu.fi
Sarala, Department of Biology, University of Oulu, PO Box 3000, FI-90014, Oulu, Finland E-mail: ms@nn.fi
Karhu, Muhos Research Station, Finnish Forest Research Institute, Kirkkosaarentie 7, FI-91500 Muhos, Finland E-mail: jk@nn.fi
Taulavuori, Department of Biology, University of Oulu, PO Box 3000, FI-90014, Oulu, Finland E-mail: et@nn.fi
Kubin, Muhos Research Station, Finnish Forest Research Institute, Kirkkosaarentie 7, FI-91500 Muhos, Finland E-mail: ek@nn.fi
Laine, Department of Biology, University of Oulu, PO Box 3000, FI-90014, Oulu, Finland E-mail: kl@nn.fi
Poikolainen, Muhos Research Station, Finnish Forest Research Institute, Kirkkosaarentie 7, FI-91500 Muhos, Finland E-mail: jp@nn.fi
Pesonen, Vantaa Research Centre, Finnish Forest Research Institute, PO Box 18, FI-01301, Vantaa, Finland E-mail: ep@nn.fi

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