Relationship between dieback of Persian oak (Quercus brantii) and apparent and latent infection of Biscogniauxia mediterranea in Zagros forests

In field surveys of charcoal disease of Persian oak (CDO) trees caused by Biscogniauxia mediterranea in Iran, the fungal stroma-bearing (apparent infected) oaks have been regarded as infected trees. However, this disease has a latent phase that its ignoring leads to wrong estimations. Therefore, this research was performed to estimate percentage of latently infected oak trees and dieback related to the disease. Oak trees were sampled randomly to isolate fungi from inner bark in two regions of Zagros forests. Also altitude, diameter at breast height (DBH), crown diameter, CDO sign (fungal stroma), dieback severity (DS), severity of leaf loss by insects (SLLI), fire damage (FD), sign of damage by bark beetles (BB) and wood-boring insects (WBI) were recorded during sampling. The isolates of B. mediterranea were identified by characteristics of anamorph and teleomorph states and species specific primers (MED1-MED2). The results reveal that all oak trees have more or less dieback symptoms. Latent infection of causal agent of CDO occures in 12% of sign free oaks equivalent to 10% of all examined oak trees. Approximately, 16.7% of evaluated oaks tress has sign of CDO. On the whole, 26.7% of oaks have latent or apparent infection of B. mediterranea. CDO correlates positively with DS, FD, DBH, SLLI, BB and WBI, and negatively with altitude and crown diameter. The dieback severity of infected oaks with B. mediterranea is more than that of non-infected ones. Moreover, dieback severity of oak trees having apparent infection is more than that with latent infection.