The mycobiota in nonmycorrhizal roots of healthy and declining oaks

Abstract

A detailed survey of the mycobiota in roots of declining and healthy-looking oak trees was conducted at two sites in eastern Austria that clearly differed in humus and soil type and pH. Overall colonization of living and dead oak roots was 97.7% and 98.5%, respectively. Colonization frequency of the cortex was nearly twice that of the central cylinder in living roots. The species assemblage comprised 126 fungal taxa. Species composition varied greatly between sites and less between living and dead roots from the same site. Fungal association on living roots at Nieder weiden was dominated by Cadophora fastigiata Lagerb. & Melin, which occurred in 50% of roots, and Cylindrocarpon destructans (Zinssm.) Scholten. Together with Cryptosporiopsis melanogena Kowalski & Halmschlager and Basidio mycete R157, these two species were also the major components in dead roots. At Patzmannsdorf, the fungal community in living roots was dominated by Cystodendron sp. 1, Cadophora-like R018, and Cryptosporiopsis radicicola Kowalski & Bartnik, whereas in dead roots Xylaria hypoxylon (L. ex Hooker) Grev. was the dominant species. No substantial differences were found between the root mycobiota in healthy and declining trees. Apart from Armillaria ostoyae (Romagnesi Herink and Cylindrocarpon destructans, the majority of isolated species were considered endophytes or saprophytes that are most likely not involved in the dieback of oak roots.Key words: root fungi, Quercus robur, Quercus petraea, endophytes, fungal community, oak decline.