Stilbocrea banihashemiana، یک بیمارگر نوظهور قارچی در درختان انار

The pomegranate tree (Punica granatum L.) is indigenous to the northern regions of the Iranian plateau, Afghanistan, Central Asia, North India, and Anatolia. In Iran, pomegranate ranks as the fifth most important horticultural product, accounting for nearly a quarter of the world's production. The rising demand for pomegranates in domestic and international markets has led to an expansion of pomegranate orchards, reaching 90,000 hectares by 2018. One of the primary challenges facing pomegranate production is canker disease, a detrimental threat that, if left unaddressed, can have severe consequences for producers. In recent years, the incidence of canker, dieback, and decline in pomegranate trees has increased across many orchards in the Fars Province, Iran. This research endeavor is focused on the identification of the fungal pathogens accountable for the aforementioned diseases through investigating trees exhibiting symptoms such as trunk and branch canker, dieback, and internal wood discoloration in the central regions of Fars Province. Initial morphological identification of fungal isolates revealed that some isolates from canker and branch dieback symptoms belong to an emerging ascomycete pathogen, Stilbocrea banihashemiana, of the Bionectriaceae family. Molecular identification using species-specific primer pairs, TEF-Sb1 (combination of TEF-SbF1 and TEF-SbR1) and TEF-Sb2 (combination of TEF-SbF2 and TEF-SbR2), targeting the translation elongation factor 1 alpha (tef1) gene, confirmed the morphological identification. Additionally, sequencing results of the RNA polymerase II subunit (rpb2) gene of the two representative isolates corroborated the identification. Pathogenicity assessments on detached branches and one-year-old saplings of three commercially important pomegranate cultivars (‘Rabab’, ‘Kadro’, and ‘White’) demonstrated the pathogen's ability to induce symptoms of necrosis and wood discoloration in all three cultivars. The varying susceptibility of these cultivars to the most aggressive isolate was assessed using four pathogenicity characteristics (upward, downward, and horizontal lesion progression and internal longitudinal progression of lesions) on inoculated one-year-old saplings. Statistical analysis of these pathogenicity traits revealed that the commercially significant cultivar ‘Rabab’ is significantly more susceptible to this pathogen comparing the other two cultivars. This study represents the first global report of S. banihashemiana as a causal agent of canker and branch dieback in pomegranate trees.