Fungi in the rhizosphere of common oak and its stumps and their possible effect on infection by Armillaria

About 16 fungal communities were isolated from the rhizospheres of thick (0 .5-1 cm diameter) and thin (0.5-1 mm diameter) roots of living trees and st umps of common oak (Quercus robur). The density of fungi was 2-5 x greater on thick roots from stumps than from living trees. The diversity of fungi w as similar in the living trees and stumps. Some of the fungal species whose density was greater in rhizospheres of stumps than of living trees, e.g. C hrysosporium merdarium, C. pannorum, Cylindrocarpon destructans, C. didymum , Mortierella gracilis, M. hygrophila, M. microspora var. macrocystis. M. v inacea, Penicillium adametzii, P. daleae, P. janczewskii, Phialophora cycla minis, Pseudogymnoascus roseus and Sporothrix schenckii, stimulated the for mation of rhizomorphs of Armillaria ostoyae and A. gallica in oak-wood segm ents. It is presumed that the increase in density of fungi stimulating the rhizomorph production may favour the infection of oak stumps by A. ostoyae and A. gallica. (C) 2001 Elsevier Science B.V. All rights reserved.