Morphological and molecular characterization of Elsinoë punicae, the causal agent of pomegranate scab disease in Golestan and Mazandaran provinces

In recent years a lesser known disease that causes necrotic spots on flower and fruit surface of pomegranate have been observed in orcahrds of Golestan and Mazandaran provinces, Iran. The present study was aimed to characterize and determine the causal agent of this disease. Towards this aim, during spring 2016 pomegranate orchards were inspected in Golestan and Mazandaran provinces and symptomtic flowers and fruits were collected and transported to the laboratory. Isolation was made using routine plant pathology methods on Potato dextrose Agar supplemented with sulphate streptomycin. Pure cultures were established using hyphal technqiue. Colonies on MEA grew very slowly (attained a diameter of 3-4 mm after 7 days at 25℃), raised, floded, dense aerial mycelium in centre, white in centre and pink in margin. Conidiomata did not develop in culture. Acervuli were observed on lesions in fruit surface, subcuticular, subepidermal, 50-200 µm diam; conidiophores dense, individual, short, and hyaline; conidiogenous cells hyaline to subhyalaine, phialidic.Conidia ellipsoidal, aseptate, hyalaine, 4-8 × 2-3.5 µm. The identity of the species was further investigated by PCR amplification and sequence of ITS-rDNA region. A BLAST serach against sequence data in GenBank, showed 100 percent similarity with somesequences avaibale in GenBank. Based on morphological and molecular data the fungus was identified as Elsinoë punicea. Inoculation of healthy pomegranate fruit (Yazd Cultivar) using mycelial suspension of the fungal isolates, resulted in the disease symptoms resembling those observed in field conditions; while, controls did not develop disease symptoms. The causal agent was re-isolated from inoculated tissues. With identification and determination of the causal agent, it is necessary to study the incidence of this disease in other pomegranate producing areas in country, biology of the causal agent, diseases cycle and finally provide proper management strategies for this disease.