اولین گزارش از وقوع Septoria citri همراه با لکه های روی میوه‌ی پرتقال تامسون ناول

During the winter and early spring of 2018 and 2019, necrotic spots were observed on Thomson navel orange (Citrus sinensis (L. ) Osbek ) fruits in citrus orchards and in Mazandaran. Early symptoms of spot appear as small, red-brown to pale-brown, 1 to 2 mm in diameter an Confused with copper injury and other abiotic and biotic agents. Advanced lesions are sub-circular, blackish, sunken and are up to10-15 mm. samples, were collected from citrus orchards and were transferred to laboratory, cut into 2- to 3-mm pieces, surface sterilized with 75% ethanol for 10 s followed by 3 min in 0.5% sodium hypochlorite, rinsed three times with sterile distilled water, and cultured on potato dextrose agar (PDA). A slow-growing fungus with dark colored mycelium that produced pycnidia was consistently isolated. Conidia were hyaline, elongate, straight or slightly curved, unicellular, but sometimes with one septum, and measured 9.0 to 25.4 × 1.0 to 2. μm. Preliminary morphological identification of the fungal isolates resembling Septoria sp. Pathogenicity tests were carried out with selected isolations on using detached fruits by inoculating 10 fruits. A spore suspension (1 × 106 spores per ml) of the fungus was sprayed on fruit by a needle (1 mm in diameter) to a depth of 2 mm and washed in sterile water. After inoculation, the fruits were incubated 10 days at 10-15 ° C and 100% relative humidity. The fungus was re-isolated from inoculated tissues. Ten non inoculated fruits were dipped in sterilized water and served as control. Non-inoculated fruits remained healthy. The pathogenicity test was carried out twice. Preliminary morphological identification of the fungal isolates resembling Septoria spp. To confirm the species of the fungus, DNA was extracted from a single spore isolate and the internal spacer regions (ITS) were amplified with universal primers ITS4 and ITS6. The amplicon was sequenced and analyzed using BLASTn, and showed a homology of 99% with a corresponding sequence of Septoria citri. The same disease was observed on other fruits belonging to the Rutaceae family, such as lemon fruit and clementine in Italy , lemon in Greece, and on orange and lemon in Australia, To our knowledge, this is the first report of the presence of Septoria citri on orange fruits in Iran.