Detection of Biscogniauxia mediterranea, the causal agent of charcoal rot disease on oak trees in Arasbaran forests and evaluation of its pathogenicity on oak under glasshouse conditions

The new emergining charcol rot disease of oak is a seirous threat for oak forestes in Iran. Biscogniauxia mediterranea has been determind as the cause of charcoal rot disease on oak, in Zagros region. However, there is no data available on the incidence of this disease in Arasbaran forests. With this research, we aimed to detect the causal agent of charcoal disease in the Hatam-Baig and Kaleibar regions in Arasbaran forests, Iran. Towards this aim, samples were collected from truck and branches of oak trees with dieback and decline symptoms as well as healthy oak trees in the region during June and September 2014. In total 14 isolates belonging to the genus Biscogniauxia were recovered from symptomatic and healthy oak trees. The isolates were identified as B. mediterranea using previously designed species-specific primer set for the ITS-rDNA region. Asexual morph of the species was developed on MEA culture medium. Sexual structures were not observed under natural conditions and efforts made to induce the sexual structures of the species in laboratory conditions were unsuccessful. The results of pathogenicity assay on two-years oak trees (Quercus macranthera), revealed that all of the isolates tested in this study were pathogenic under greenhouse conditions. This is first report on the detection of charcoal rot disease of oak trees and identification of the causal agent in Arasbaran forests.