Ectomycorrhizal fungi of Larix laricina and the interspecific and intraspecific variation in response to temperature

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Abstract
The ability of tamarack to form ectomycorrhizae with different fungi was investigated by using a pouch technique. Ninety-one out of 109 fungal isolates from 25 different species formed ectomycorrhizae on larch seedlings. Tamarack displays strong specificity for ectomycorrhizal fungi identified as sporocarp-specific to larch under field conditions: Suillus grevillei, S. cavipes. Fuscoboletinus aeruginascens, F. spectabilis, F. paluster, and F. grisellus. These fungal species induced more rapid and extensive ectomycorrhizal development in growth pouches than the other less specialized fungi. Radial growth rates on Petri dishes of isolates of these six bolete species were observed at 10, 15, 20, 25, and 30 °C, to study interspecific and intraspecific variation. The results demonstrated strong intraspecific variations and suggest a great genetic variability of the physiological activity within ectomycorrhizal species. Interspecific comparisons, however, revealed that some species possessed characteristic behaviours in response to temperature. As compared with a "high-temperature fungus," Pisolithus tinctorius, the bolete species showed distinct adaptations and tolerances to low and high temperatures. No consistent relationship was established between geographical origin of the fungal isolates and their growth rates. The results are discussed in relation to the selection of ectomycorrhizal fungi potentially used inoculum in forestry practice.