Using Oxytetracycline, Amikacin and Erythromycin in Controlling Mycelial Growth and Spore Germination of Rhytisma acerinum as Pathogen in Tar Spot Disease at Acer velutinum Boiss in Vitro

Abstract

Introduction : There are seven species and sub-species of Acer sp. in the Northern forest of Iran. One of the most important diseases of this tree in all over the world is tar spot. Two species of fungi, which cause this disease, are Rhytisma acerinum and R. punctatum from the category of Ascomycetidae. Studies on the Acer platinum sp. show that causative agent of this disease is R.punctatum which cause the early fall and make leaves turning yellow especially in the plant nurseries and forested areas. Therefore, investigating the use of antibiotics in treating this disease in the forest areas is necessary. The objective of the current research was to use Oxytetracycline, Amikacin and Erythromycin in Controlling mycelial growth and spore germination of R. acerinum as Pathogen in tar spot disease at Acer velutinum Boiss in vitro. Materials and methods: To control the disease of Maple tar spot in the condition of light and darkness, the medium containing oxytetracycline, Amikacin and Erythromycin were used. Four different dosage of 50, 100, 200, 500 microliter, of oxytetracycline 10% in the light and dark conditions in 100cc of distilled water and Amikacin 5% in four different dose of, 100, 200, 400 and 1000 microliter, light and dark conditions in 100 cc of distilled water and for erythromycin 5% four different dose of, 100, 200, 400 and 1000 microliter in 100 cc of distilled water in light and dark conditions each in three repetitions of medium were prepared. In this step, to evaluate the effect of light on the rate of the growth of mycelium and fungal colonies of R. acerinum, for each of the treatments with the different dosage, half of the repetitions were under the light condition and another half in dark condition (incubator). Then, after the growth, radiant growth was measured over one week. To investigate the fungi spore germination, above steps, were performed, as well. Results and Discussion: The results showed that among the mentioned antibiotics with different dosages, oxytetracycline with the dosage of 200 micro liter had the minimum effect on the coefficient of AUFGC. The results clarify that the effect of light and light-material on the coefficient of AUFGC and growth were not significant but the effect of the material on the coefficient of AUFGC and growth had a significant difference. Moreover, the results showed that growth of fungal and mycelia threads at the treatment of oxytetracycline with the dosage of 200 microliters in the medium were destructed and other dosages of this antibiotic (50, 100 and 500 microliters) were not effective in controlling the disease. According to the results, oxytetracycline 200 under light condition and dark condition had the maximum effect in preventing the mycelia growth of the fungi and the treatment of oxytetracycline with the dosages of 50, 100 and 500 microliters and erythromycin with the dosages of 100 and 200 microliters in dark condition had the least effect on the prevention of the mycelial growth of the fungi. Overall, the mycelial growth of the pitch stain disease, in addition to the witness treatment, in the mediums containing the antibiotics with the dosages of 50, 100 and 500 microliters had the most growth. Light or dark had not significant effect on the mycelia growth of the fungi or on the prevention of fungi growth but in controlling the germination of the spores, the treatments of light, material, and light-material showed a significant difference. In controlling the germination of the spores in addition to the oxytetracycline with the dosage of 200 microliters, other antibiotics also were effective at the same level regarding the compare means. Moreover, light or dark condition was effective in germination of the fungi spores so that in light condition, the spores of R. acerinum had more germination. Conclusion: Regarding the acquired results, it can be concluded that using antibiotics in controlling the disease of Maple tar spot can be effective and oxytetracycline with the dosage of too in 200 cc distilled water had the maximum effect on controlling R. acerinum. Although, using the antibiotics is effective in controlling the fungi, no need to say that other pre-treatments such as conservation of the trees and keeping the hygienic environment for these trees also is recommended for controlling of these diseases. However, the result of this study can be useful for the management of the forests and related organizations.

Keywords

• Pathogenic fungi
• Tar spot
• AUFGS coefficient
• forest management