Pathological and Molecular Identification the causal agent of Cittrange rootstock rot in Citrus Orchards the East of Mazandaran

Recently, a devastating decline has been observed in some citrus groves established with cittrange rootsock. The most conspicuous symptom is a frustose rootstock and decline. The suspicious infected samples were collected at different stages of growth and transported to the laboratory. The samples were rinsed under top water and disinfested with 70% ethyl alcohol. Pieces of each sample was separated with a sterile blade and cultured on potato dextrose agar (PDA) medium. Obtained fungal isolates were purified and pathogenicity of the isolates was tested by A mycelial plug (5 mm diam.) obtained from the margin of a fungal colony was placed in the wound with the mycelium facing towards the stem, and the wound was wrapped with Parafilm. Based on the morphological characteristics including colony form, conidia specific feature, and growing on agar cum Foeniculum vulgare stipes, studied fungal isolates were identified as Diaporthe novem Santos. Genomic DNA extraction was done from fungal isolates and amplification was done with ITS1, ITS4 and Bt regions primers and the amplicons were sequenced. Also the sequencing results confirmed fungal species mentioned above. This is the first report of fruit drop and dieback disease and the causal agent identification on local tangerine in north of Iran.