Evaluation of some morphological features and pathogenic diversity of Ophiognomonia leptostyla isolates causal agent of walnut anthracnose after prolonged storage

In this study survivability, morphological characteristics and pathogenicity of 12 isolates of Ophiognomonia leptostyla, which is known as causal agent of walnut anthracnose, have been evaluated after 13-years of storage on filter paper in oat meal agar (OMA) and -20°C. The recovery rate varied from 0 to 89 percent and seventy-five percent of stored isolates were shown to be viable. In macroscopic and microscopic studies of revived cultures, the morphology of colonies was uniform for all isolates. Production of asexual bodies (acervular conidiomata) was preserved by all isolates. Fertile perithecia with asci and ascospores were not detected in pure fungal cultures after three months incubation at 8-10°C in darkness. In pathogenicity experiments, there was not a significant variability in infection severity for different isolates, and the first symptoms were observed on leaves 12-16 days after inoculation. Stability of morphological characteristics, ability to sporulation and retaining the pathogenicity of isolates confirmed that transferring of acervuli on filter paper in OMA medium could be a suitable, safe, simple and cost-effective tool to preserve O. leptostyla isolates in a viable state.