Morphological and molecular characterization of Diplodia seriata,the causal agent of canker and twig dieback disease on mulberry in Iran

Mulberries are cultivated for different purposes: for feeding larvae of silkworm, Bombyx mori, as fresh and dry food resources, in wood instrument industry, in pharmaceutical industry and as outdoor ornamental trees in Iran. In recent years, twig and branch canker disease symptoms have been noticed on mulberry trees in northwestern parts of Iran. Diplodia isolates were repeatedly recovered from symptomatic tissues. Based on cultural and morphological features, the isolates were identified as Diplodia seriata. The identity of the isolates was further confirmed using sequence data from internal transcribed spacer (ITS)-rDNA and ef-1α gene. A phylogenetic analysis using ITS sequence data clustered the isolates obtained in this study together with known Diplodia seriata isolates of other woody hosts from GenBank. Inoculation studies carried out on white mulberry twigs using an excised shoot method revealed that the isolates are pathogenic on this host. D. seriata have been reported from other woody host plant species such as Juglans nigra and Vitis vinifera in Iran, however, to the best of our knowledge, the occurrence of D. seriata on mulberry trees is new for Iran. The distribution and reaction of different Morus spp. to D. seriata remain to be studied.