Attached and detached leaves of 60 potential host species were inoculated in the greenhouse and laboratory with aeciospores of Cronartium ribicola J.C. Fisch. from six Finnish locations and of Cronartium flaccidum (Alb. & Schw.) Wint. from 20 locations in Finland and Sweden in 2011. Candidate hosts represented 16 plant families: Solanaceae, Verbenaceae, Asclepiadaceae, Grossulariaceae, Paeoniaceae, Balsaminaceae, Gentianaceae, Scrophulariaceae, Loasaceae, Tropaeolaceae, Acanthaceae, Myricaceae, Phrymaceae, Plantaginaceae, Orobanchaceae, and Apocynaceae. Inoculations of C. flaccidum produced uredinia after 2 weeks and (or) telia after 4 weeks of incubation on 25 hosts. Inoculation trials identified several new hosts for C. flaccidum in Fennoscandia, namely Impatiens balsamina, Swertia fedtschenkoana, Loasa tricolor, Myrica gale, Verbena canadensis, Saxifraga spp., Paeonia obovata, and Veronica daurica. Myricaceae and Saxifragaceae represent new host families for these rusts. Cronartium ribicola formed uredinia or telia on 10 species: Ribes spp. (7 species/cultivars), Pedicularis palustris subsp. palustris, Bartsia alpina, and Loasa triphylla. Results suggest wider alternate host ranges for both C. flaccidum and C. ribicola than previously recognized. Spores were virulent regardless of their source location, suggesting a lack of host-specificity among Fennoscandian populations of Cronartium.Key words: alternate hosts, Scots pine blister rust, white pine blister rust.

Susceptibility of potential alternate host plants to pine stem rusts belonging to Cronartium spp. was artificially tested in Finland during 2012-2013. Forty-three species representing 11 plant families were inoculated in the laboratory; 34 species (11 families) were inoculated in the greenhouse with aeciospores of Cronartium flaccidum or C. ribicola. Twenty-one selected species (10 families) were also exposed to natural inoculum of C. flaccidum in the field in two severely affected Pinus sylvestris stands. After 5-8 weeks' incubation, C. flaccidum sporulated on 17 species (nine families) in the laboratory, 17 species (eight families) in the greenhouse and seven species (five families) in the field. Cronartium ribicola sporulated on three species (three families) in the laboratory or greenhouse. All of the hemiparasitic plants that belong to Orobanchaceae were infected by C. flaccidum, and several species supported rust sporulation when exposed to natural inoculum. Susceptible species belonged to genera Veronica,

Aeciospores of Cronartium ribicola and C. flaccidum were collected from several locations in Finland and used to inoculate Pedicularis spp. and some known and suspected alternate hosts in 2008-2009. In all trials, C. ribicola formed uredinia and telia on leaves of Ribes nigrum. No uredinia or telia of C. ribicola formed on older leaves of Pedicularis spp. but both uredinia and telia were found on young leaves of P. palustris ssp. palustris. Cronartium flaccidum produced uredinia and ⁄ or telia on leaves of P. palustris ssp. palustris, P. lapponica, Vincetoxicum hirundinaria and Melampyrum sylvaticum. Neither rust infected P. sceptrum-carolinum, Vaccinium myrtillus, Calluna vulgaris or Ledum palustre. Similar to rusts in Asia and North America, the results showed that European C. ribicola exhibit more variable host reactions and wider alternate host ranges than earlier described. Pedicularis palustris may play a role in the spread of Cronartium in natural forests.

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Habitat destruction, invasive species, climate change and other threats to plant diversity are requiring increased conservation efforts. Priority is appropriately given to in situ conservation, but the important contribution that ex situ conservation can make is increasingly being recognised. In Finland, extensive seemingly intact natural areas have so far led authorities to consider ex situ conservation activities largely unnecessary. Botanic gardens, with estimated living collections of 80 000 plant species worldwide, cultivate valuable plant material that can be used in recovery and reintroduction programmes. Recently, gardens all over the world have started to survey their collections. The results to date have revealed some very valuable collections but also highlighted inadequate databasing, narrow genetic representation and various genetic problems. As a part of an EU Life+ funded initiative, 4 Finnish botanic garden collections were investigated in order to find nationally threatened vascular plant species of known wild origin. Accessions were assessed for their potential use in future reintroduction programmes by ranking the quality of origin data and genetic intactness. Seventy-seven accessions from 56 vascular plant target taxa were found cultivated as living plants, representing 18% of Finland's nationally threatened taxa. The findings of this Finnish survey are similar to studies completed for botanic gardens elsewhere showing that there are deficiencies in intraspecific and within-population diversity. However, the accuracy of origin data and genetic intactness of the accessions were comparatively high. This survey forms the basis of the current development of a national plant ex situ action plan.