Epiphytic micro-organism communities of Armillaria mellea fruiting bodies and their potential use as biocontrol agents

Armillaria mellea root rot is an important disease of several woody and herbaceous plants worldwide. In Trentino (northern Italy), A. mellea attacks grapevines, affecting their vigour and productivity and, eventually, killing the plants. At present, the control of Armillaria root rot by chemical and agronomical methods is inadequate, ineffective, or unfeasible. Due to the recent increase of the disease in some areas a method for its control became highly desirable. The use of biological control agents (BCAs), could be a potential tool to protect vines from new infections. Thus, 112 epiphytic micro-organisms were isolated in 2003 from basidiocarps collected from infected grapevines (13) and apple (1). These micro-organisms were identified and the percentage of filamentous fungi, yeasts and bacteria was determined. There was a high variation in the distribution and relative proportion of epiphytic organisms among different basidiocarps. The isolated micro-organisms were then evaluated for their ability to act as BCAs by in vitro dual culture. A. mellea and the different micro-organisms were inoculated in a Petri dish and incubated at 25 degree C. After 5, 10, 15, 20 days from inoculum the growth rate of the two organisms was compared and the inhibition rate of A. mellea mycelium and rhizomorphs estimated. Few microorganisms showed a promising antagonistic activity against the pathogen in these tests.