Abstract
ABSTRACTShoots of Calluna vulgaris, Erica carnea, Juniperus communis subsp. nana, Picea abies, and Pinus mugo subsp. mugo covered with felty, melanized epiphytic mycelia typical for brown felt blight caused by Herpotrichia pinetorum were collected at several locations in the Swiss Alps. Most cultures prepared from the mycelia on J. communis subsp. nana and P. abies were H. pinetorum, whereas the majority of cultures from P. mugo subsp. mugo and C. vulgaris were identified by internal transcribed spacer ITS1-5.8S-ITS2 sequencing and morphology as Allantophomopsis cytisporea. The fungus tolerates low temperatures, has an optimum between 16°C and 24°C, and ceases to grow at 28°C. 35°C is lethal. A. cytisporea is known as the causal agent of cranberry black rot on Vaccinium macrocarpon but has never been described as a snow mold. A. cytisporea is an endophyte in C. vulgaris but seems able to kill leaflets and whole shoots during winter. The epiphytic mycelium can expand from C. vulgaris to neighboring shoots of P. mugo subsp. mugo and J. communis subsp. nana below the snow where it forms epiphytic mycelial mats reminiscent of H. pinetorum. H. pinetorum has a strong antibiotic effect against A. cytisporea at 4°C and 20°C, whereas A. cytisporea grows faster at these temperatures. The effects of climate change on the interaction between the two snow mold fungi and their consequences on regeneration of woody plants at timberline are discussed.
Highlights
Snow blight pathogens such as Herpotrichia pinetorum and Gremmenia (Phacidium) infestans affect natural regeneration of conifers in alpine, subalpine, and boreal zones and probably play a decisive role in determining conifer regeneration near timberline (Hartig 1888; Gäumann, Roth, and Anliker 1934; Roll-Hansen 1989)
Shoots of Calluna vulgaris, Erica carnea, Juniperus communis subsp. nana, Picea abies, and Pinus mugo subsp. mugo covered with felty, melanized epiphytic mycelia typical for brown felt blight caused by Herpotrichia pinetorum were collected at several locations in the Swiss Alps
Most cultures prepared from the mycelia on J. communis subsp. nana and P. abies were H. pinetorum, whereas the majority of cultures from P. mugo subsp. mugo and C. vulgaris were identified by internal transcribed spacer ITS1-5.8S-ITS2 sequencing and morphology as Allantophomopsis cytisporea
Summary
Snow blight pathogens such as Herpotrichia pinetorum and Gremmenia (Phacidium) infestans affect natural regeneration of conifers in alpine, subalpine, and boreal zones and probably play a decisive role in determining conifer regeneration near timberline (Hartig 1888; Gäumann, Roth, and Anliker 1934; Roll-Hansen 1989). During a study about the population structure of H. pinetorum in the region of Arosa, Switzerland, three of more than eighty strains prepared from melanized mycelial mats covering shoots of juniper Not all of the brown to black mycelial mats covering dead shoots of young conifers are due to colonization by H. pinetorum. This observation was the starting point for the present study. C. vulgaris was included because this plant species and its accompanying vegetation close to melting snow patches in the alpine zone were repeatedly observed to be covered by mats of felty gray brown mycelia reminiscent of H. pinetorum (Figure 1 and Table 1). Recognition of the mats is best right at the edge of the retreating snow cover in spring
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