ارزیابی مقاومت ارقام مختلف گوجه فرنگی نسبت به بیماری خال زدگی باکتریایی

Tomato bacterial speak caused by Pseudomonas syringae pv. tomato (Pst), is one of the economic disease that occurs worldwide, wherever tomatoes are grown. Use of resistant cultivars is an effective strategy to reduce the damage of this disease. In this study, a total of 25 different tomato cultivars including 14 standard cultivars and 11 commercial hybrids were evaluated in response to the disease. The experiment was conducted in a completely randomized design with four replications. Plant incubation was carried out in two methods. In first method, bacterial suspension (1×105 CFUml-1) was injected in the lower epidermis of the tomato leaves. In second one, carborundum powder used for scratching the leaf surfaces, and bacterial suspension of 1×105 CFUml-1 sprayed on seedling foliage. Incubated seedling was kept under the plastic cover at 25 °C and 95-98% RH for 48 hours. After that, greenhouse conditions adjusted at 27 °C day/21 °C night with 50-70% RH. Symptom was appeared between 3 to 9 days after inoculation. Symptoms were appeared as chlorotic spots that gradually turned to necrosis spots with yellow halo. After 25 days, the number of spots was counted and their diameter was measured. To determination of cultivar resistance, numerical index from 1 to 5 was used according to percentage of symptom area on leaves. Results showed 15 to 100 % infection to Pst in different tomato cultivars. Significant difference at 1% level was observed between cultivars. Spots were observed in Hyb.8320, 2270, CalJ N3, Early urbana, Falat CH and Urmia native cultivar earlier than others. In the final measurement, the size of spots and the diameter of yellow halo were higher in these cultivars. Cultivars of Hyb.1585, Hyb. Superset and Primax were evaluated as the most tolerant cultivars. None of the studied cultivars were resistant to disease.