بررسی حساسیت و یا مقاومت عامل سوختگی باکتریایی گردو به سموم مسی و آنتی‌بیوتیک‌ها

Bacterial blight caused by Xanthomonas arboricola pv. juglandis is one of the most important bacterial diseases on walnut trees. This bacterium attacks all parts of the plant including: leaves, flowers, branches, stems and fruits. In favorable environmental conditions (moisture and rain), this bacterium can cause 70% damage in walnuts. One of the strategies for mitigating the impact of the disease and managing its progression is the utilization of copper-based compounds. From 2016 to 2019, this bacterium was isolated from walnut orchards in Mazandaran, Golestan, and Gilan provinces. This study evaluated the sensitivity or resistance of bacterial strains to copper compounds. Different concentrations of copper oxychloride (0.2, 0.5, 0.8, 1.5, and 3 g/liter), copper sulfate (20, 50, 100, 200, and 400 mg/liter), and antibiotics streptomycin (20, 50, and 100 mg/liter) and rifampicin (20, 50, and 100 mg/liter) were assessed in laboratory conditions. Each of these compounds was added to the Nutrient Agar medium and the bacterial strains were cultured on them. The results were evaluated after 24 to 48 hours. The results of this study showed that in the concentration of 0.2 g/liter of copper oxychloride, all isolates were able to grow, but in other concentrations of copper oxychloride, they did not grow and were sensitive. As well, all bacterial strains grew in concentrations of 20 and 50 mg/L of copper sulphate, while all the tested strains were sensitive to 100, 200 and 400 mg/L of copper sulphate. On the other hand, all bacterial strains were sensitive to all concentrations of streptomycin and rifampicin and were unable to grow in the presence of these two antibiotics. According to the copper and antibiotic resistance assays, the use of copper-based compounds along with other agronomic and cultural practices within the frame of integrated pest management, can be a suitable and effective option for the management of walnut bacterial blight in Iran. However, attention should be paid to the dose and frequency of using copper-based compounds, to reduce the risk of resistance development by bacterial strains.