اثر چند قارچکش شیمیایی در ممانعت از رشد رویشی عامل بیماری مرگ گیاهچه بادام زمینی Aspergillus niger در شرایط آزمایشگاه

Aspergillus niger fungus is present in most of the groundnut cultivated soils and is one of the common groundnut pathogens. This pathogen usually appears up to 30 days after cultivation. Damage caused by it has been reported up to 50% in groundnut farms. This fungus can cause seed rot and death before the seedlings sprout. The most obvious symptom is the sudden wilting of young plants. Root and crown rot caused by Aspergillus is in the form of black mold, which typically grows on the surface of the root and crown. The above research was conducted to investigate the inhibitory effect of some chemical compounds on the mycelial growth of Aspergillus niger in laboratory conditions. Infected samples with disease symptoms from Astaneh Ashrafieh county were transferred to the laboratory and pieces of root and crown tissue of diseased plants with dimensions of 3 to 5 mm were placed on potato dextrose agar (PDA) medium in petri dishes and the cultures were kept at a temperature of 25 degrees Celsius in an incubator for three days to isolate the disease-causing fungus. Purification of isolates was done by single spore method. For pathogenicity test, the seeds of the common groundnut variety in Guilan province were planted in pots with a diameter of 10 cm, containing light sterile soil and ten percent of fungus inoculum, including a mixture of sand and corn flour in a ratio of 7:3, and the pots were kept in the greenhouse at a temperature of 25±2 degrees Celsius. Fifteen days after inoculation, symptoms of root rot and seedling death were examined and the pathogen was isolated again. In the continuation of the present study, the effectiveness of some chemical fungicides including methyl thiophanate WP70%, captan WP50%, tebuconazole DS2%, difenoconazole DS3%, triticonazole + pyraclostrobin FS12% (Insure Perform), metalaxyl M + fludioxonil FS3.5% (Maxim X L) and metalaxyl-mancozeb WP72 were tested in inhibiting the vegetative growth of the disease-causing fungus on PDA medium. The disease-causing fungus was grown on PDA culture medium for seven days before the start of the experiment. The investigated fungicides were added to the PDA medium in the same concentrations or more or less than the recommended concentrations of the manufacturing companies, and in the control Petri dish, the medium without fungicide was used. Then, the Petri dishes were kept at 25 degrees Celsius and the diameter of the fungus was measured daily for ten days. Based on the comparison of the inhibition rate of fungus vegetative growth by different concentrations of chemicals, it was determined that captan, Insure Perform, tebuconazole, and difenoconazole have the highest inhibition rate of fungus vegetative growth and methyl thiophanate has the lowest rate.