Reaction of Armillaria ostoyae to forest soil microfungi

Abstract

Fungi isolated from the oak (Quercus robur) rhizosphere were tested for their effects on rhizomorph formation and growth of 16 isolates of Armillaria ostoyae sampled in three localities in western Poland. The number of rhizomorphs, number of rhizomorph apices, and rhizomorph length and weight increased most in the presence of Penicillium lanosum, Penicillium notatum, Cylindrocarpon destructans, Penicillium spinulosum and Mycelium radicis atrovirens a and, to a lesser extent, in the presence of Nectria grammicospora. Inhibition of rhizomorph formation was caused by Trichoderma hamatum and Trichoderma viride in two A. ostoyae isolates and by M. radicis atrovirens a and P. spinulosum in one A. ostoyae isolate. It is suggested that variation in sensitivity to microbial stimulation within A. ostoyae is associated with the environmental and nutritional conditions of its original habitat. Isolates from nutrition-rich localities, with 20% of the land area covered by deciduous trees, were particularly susceptible to stimulation by rhizosphere fungi.

Culturable microfungi inhibitory to Armillaria rhizomorph formation from Fagus sylvatica stump roots and soil

“…This suggests the possibility of variation in (i) biochemical properties of saprotrophic microfungi or (ii) differences in sensitivity of Armillaria to microbial stimuli depending on its origin. Variation in the sensitivity of A. ostoyae isolates to forest soil fungi relating to the physical and chemical conditions of its former habitat was reported previously (Kwaśna et al., ).…”

“…Kwaśna (2001, 2002, 2003a,b) and Kwaśna et al. (, ) showed that microfungi from roots and rhizosphere of oak stumps can stimulate the formation and growth of Armillaria rhizomorphs in vitro, in a substrate of natural forest soil. Aspergillus kanagawaensis Nehira, Cylindrocarpon didymum (Harting) Wollenw., Hormiactis candida Höhn, M. macrocystis , Mycelium radicis atrovirens Melin, Ilyonectria radicicola , P. adametzii , P. daleae , P. janczewskii , Penicillium lanosum Westling , Penicillium notatum Westling, P. spinulosum , Sporothrix schenckii var.…”

“…Phialocephala dimorphospora W.B. Kendr., Pseudogymnoascus roseus Raiłło , T. niveum and T. opacum were less consistent, moderate “stimulants.” Trichoderma hamatum and T. viride were inhibitors (Kwaśna et al., ). Stimulation was observed more often in A. gallica and A. mellea and inhibition in A. ostoyae .…”

“…The wood of stumps does not form any mechanical barriers (callus) or chemical substances (i.e., resins, gums, phenols, monoterpenes, sterols or tannic acids in oak; nitrogen compounds in beech, birch and willow) which, in living trees, impregnate wood and have antiseptic activity. Kwaśna (, ,b, ,b,c, , , ,b, ), Kwaśna and Łakomy () and Kwaśna, Kotyńska, Łakomy, and Mallett (), Kwaśna, Łakomy, and Mallett () suggested that the saprotrophic mycobiota on/in stump roots are involved and contribute to colonization by Armillaria . The majority of fungi isolated from forest tree roots stimulated growth of Armillaria rhizomorphs in vitro.…”

“…Stimulation of growth of Armillaria rhizomorphs by fungi was observed in vitro. The substrate was prepared from forest soil, sand, peat and humus (1:1:1:1) and was intended to simulate the natural forest soil habitat (Kwaśna, ; Kwaśna & Łakomy, ; Kwaśna et al., , ).…”