Differential ability of ectomycorrhizas to survive drying.

To test the hypothesis that, depending on the fungal symbiont, ectomycorrhizas are differentially affected by severe drought stress, we developed a simple method to quantify the loss of vitality of excised ectomycorrhizal tips subjected to drying under controlled conditions. The method uses 96-well microtitration plates with one single ectomycorrhizal tip per well, and is based on measuring the loss of volume and the loss of electrolytes before and after the imposed stress. This approach very significantly discriminated the two ectomycorrhizal morphotypes formed with beech (Fagus silvatica) by Lactarius subdulcis and Cenococcum geophilum, which confirmed the ability of the latter fungal species to protect roots against desiccation already suggested by previous works. The new method should contribute to the present effort in deciphering the functional diversity of complex ectomycorrhizal communities.