وقوع بیماری شانکر نهال های آووکادو ناشی از قارچ Botryosphaeria dothidea در ایران

Avocado (Persea americana) is a fruit tree that is capable of growing in the tropical and Mediterranean regions. Avocado fruit is fleshy and shiny green with a large core and has a high nutritional value. This plant entered Iran in the 1960s. More than 50 hectares of orchards in the north of the country are under avocado cultivation. The fungus Botryosphaeria dothidea from the Botryosphaeriaceae family is the causal agent of decay and canker disease in many species of woody plants in the world. The present study was conducted to investigate the causative agent of canker disease on avocado seedlings in Mazandaran. Sampling of cankers formed on the stem of avocado carried out. After the usual disinfection steps, the samples were cultured on Potato Dextrose Agar (PDA) medium. After 3 days, grayish white colonies appeared around the samples. Colonies turned black after a week. Examining the morphological characteristics of the isolates showed their similarity with Botryosphaeria fungus. For molecular confirmation, the selected isolate was amplified from the internal Transcribed Spacer (ITS) region of rDNA using ITS1 and ITS4 primer pair and the PCR product was sequenced. The obtained sequences were compared with other sequences available in the gene bank (NCBI) and BLAST analysis showed 100% similarity with the sequence of Botryosphaeria dothidea. The pathogenicity test was done by placing a 0.5 cm2 piece of fungus mycelium (One week old colony) on avocado branches. Two weeks after inoculation, symptoms similar to those observed in infected gardens were created. From the inoculated samples, a fungus similar to the initial isolates was isolated. There are reports of cankers caused by this fungus in other areas of this crop cultivation in the world. This is the first report of B. dothidea as the causative agent of avocado canker in Iran.