Physiological variation between tree-associated populations of Suillus granulatus as determined by in vitro mycorrhizal synthesis experiments

Abstract

Mycorrhizal synthesis studies revealed that allopatric populations of Suillus granulatus differ in host specificity. Isolates of Suillus granulatus originated from Nepal (associated with Pinus wallichiana), Korea (Pinus densiflora), and the U.S.A. (Pinus strobus). Functional compatibility of the mycorrhizal association was used to measure host specificity. Useful characters for measuring mycorrhizal compatibility were defined as those which revealed statistical differences between the uninoculated controls and mycorrhizal treatments and which were stable within one population. Useful characters, as defined by these two tests, were shoot wet weight, total wet weight, percentage mycorrhizal short roots, shoot dry weight, total dry weight, and Hartig net penetration. Data for these characters were subsequently used in anova tests to determine whether allopatric populations of Suillus granulatus differ in functional compatibility. Isolates associated with Pinus strobus were most compatible with Pinus strobus and least compatible with the other trees, whereas isolates from Pinus wallichiana and Pinus densiflora showed variable compatibility with all three trees. Phenetic analyses used to determine how similarly the isolates responded with the hosts confirmed these results. We conclude that isolates associated with Pinus strobus are most specific for this host, whereas isolates from the other two trees are not host specific. The implications of these results are discussed in light of future investigations regarding the relatedness of these tree-associated isolates. Key words: Boletaceae, Suillus, Pinus, ectomycorrhizae.