Identification and prevalence of fungi causing charcoal rot in oak forests of Iran

Oaks (Quercus) are among the most important trees found in forests Iran and rest of the world. Over the last decade, oak charcoal disease (OCD) has become more common in numerous forest areas in the Zagros and Hyrcanian regions, largely due to reduced rainfall and multiple droughts. This disease causes local or systemic necrosis, wilting, and even death of infected oak trees within one or more years. In addition, there is a complex interaction between trees and biotic and abiotic environmental factors. This study was conducted in 2020-2021 on oak trees in seven provinces of the country, namely Khuzestan, Ilam, Lorestan, Kurdistan, Khuzestan, Isfahan and Golestan, to analyze and determine the current status of oak trees in terms of OCD and the causative fungal pathogens. For this purpose, samples of infected oak trees were collected and then the causal agents of the disease isolated and identified morphologically. Detection of the samples was confirmed by sequencing the fungal ITS1-5.8S-ITS2 and ß-tubulin gene. The results showed that the most prevalent fungal pathogens of OCD in the samples were Biscogniauxia mediterranea and Obolarina persica. The prevalence of these fungi in the studied provinces varied, with the highest prevalence of B. mediterranea in Lorestan and the highest prevalence of O. persica in Ilam. The results of this study complemented the existing relatively limited data on the prevalence of each fungal pathogen of OCD in different provinces. In addition, the current status of oak infection in each of the studied regions was clarified.