Evaluation of micromycetes associated with green- ash ba rk in Buenos Aires (Argentina): their ab ility to degrade wood and tolerance to heavy metals

Background and aims: Environmental pollution can affect tree health and biodiversity of microorganisms, among them fungi, existing in the bark. Fraxinus pennsylvanica Marsh. is the most cultivated tree in Buenos Aires city. The purposes of this work were to screen the micromycetes present in green-ash wood and bark, to determine if the micromycetes most frequently associated with ash bark produce lignocellulolytic enzymes, to describe the anatomical changes they caused in wood and to evaluate their tolerance to Cu and Pb as indicators of environmental polution. M&M: Barks and wood were collected along an urban-periurban gradient. The decay caused in vitro in green-ash wood by the most frequently isolated micromycetes was evaluated, anatomical characters were described. The production of lignocellulolytic enzymes by these fungi and their tolerance to Cu and Pb was assessed. Results: Diplodia sp., Fusicoccum sp. and Sordaria sp. were the most frequently found micromycetes in green-ash bark, whereas Alternaria sp., Diplodia sp. and Phialophora sp. were isolated from wood. None of them caused symptoms of soft rot. They colonized ash wood in vitro but neither important wood weight losses were detected (3-5% after 6 months) nor micro anatomical relevant changes. Cellulolytic activity was produced by all the assayed micromycetes. All of them were able to grow with the addition of 250 mg/ Kg of Cu or 1000 mg/Kg of Pb. Conclusions: The micromycetes most frequently isolated did not affect tree health. Their tolerance to high concentrations of heavy metals suggests their potential as biomonitors of environmental pollution.