Volatile organic compounds to identify root and butt rot pathogen Armillaria spp.

PTRMS-TOF analysis of Armillaria volatomic profile was used as molecolar tools for the taxonomic identification of six European species of genus Armillaria: A. borealis , A. cepistipes, A. gallica, A. mellea, A. ostoyae and A. tabescens. This mycete is known as honey mushroom and it is one of the main opportunistic pathogenic fungus found in many forest and ornamental trees where it causes white root rot. It is also a saprotroph who allows the wood degradation and the easy transfer, by wood trade, the other more than 40 esotic species present in the other continents. Volatile Organic Compounds (VOC) pattern was analyzed for 77 strains of Armillaria by PTR- MS-TOF technique in order to discriminate the species. Armillaria strain were previously identified by DNA amplification by PCR. Samples were analyzed after 30 days of incubation to allow the mycelial growth on MEA substrate added with silver fir sawdust. Data analysis was performed using univariate and multivariate statistical tools. The analysis of variance (ANOVA) discriminated A. borealis by using acetylene concentration and A. cepistipes by using hexanal concentration. The distribution of specific masses concentration, as a function of species by boxplots, allows to discriminate A. tabescens, A. borealis, A. cepistipes and A. mellea. Principal component analysis allows discriminate the A. borealis and A. tabescens clusters. The future improvement of this approach is to identify some VOC which can discriminate invasive Armillaria species to develop a rapid and accurate identification diagnostic method based on gas chromatographic separation of these VOCs.