جداسازی و شناسایی قارچ‌های همراه با زوال درختان گردو (Juglans regia L.) در استان کرمان

Walnut (Juglans regia L.) is an important fruit tree in Iran. Branch cankers and trunk diseases are progressively becoming limiting factors for walnut trees cultivation. During 2016 to 2018, some orchards in Kerman province were surveyed to determine the presence of branch and trunk fungal pathogens on walnut trees. In addition to trunk pathogens, other fungal species were isolated, and their identification is presented here. Wood samples were collected from branches of affected trees showing dieback, canker and wood discoloration in cross sections. Necrotic wood tissues were cut into small pieces, surface sterilized in 1.5% sodium hypochlorite solution for 1 min, washed three times with sterile distilled water, air-dried under sterile conditions and plated onto streptomycin-amended malt extract agar (MEAS). Plates were incubated at 25 °C in the dark and all fungal colonies were transferred to a fresh medium. Isolates were first identified based on colony characteristics and microscopic observations. Total genomic DNA from representative isolates of each group was extracted and morphological identifications to species level were confirmed by sequence analysis of the internal transcribed spacer (ITS) nrDNA region using the primers ITS1 and ITS4 and a partial sequence of translation elongation factor 1-α gene (tef-1α) using the primers E1/E2. Based on morphological characteristics and DNA sequence comparisons, three fungal species including Fusarium brachygibbosum (three isolates), F. proliferatum (11 isolates) and Neocosmospora metavorans (10 isolates) were isolated from symptomatic walnut trees. To our knowledge, this study represents the first report about the presence of these species on walnut trees in the world.