بررسی وقوع و پراکنش بیماری لکه باکتریایی (خال زدگی) گوجه فرنگی در کشت گلخانه و مزرعه استان های مختلف ایران

In general, tomato (Lycopersicon eseulentum Mill) bacterial spot disease causes damage to leaves, stems and fruits. The infection of the plant in the early stages of growth causes slow growth and general weakness of that. During1402 and 1403 (spring), sampling was carried out from the fields and greenhouses of tomato cultivation areas in Khorasan Razavi, Fars, Sistan and Baluchistan, Khuzestan, Isfahan and Hormozgan provinces. Suspected plants with symptoms of bacterial diseases (dark brown water-soaked lesions and spots on leaves and fruits) were placed in paper envelopes and transported to the laboratory. The samples were washed under running tap water to remove the soil particles, disinfected in 1% sodium hypochlorite for 40 seconds to remove the saprophytic agents, and then washed three times with sterile distilled water. Marginal areas of infected and healthy tissue were crushed in a mortar containing sterile distilled water and a loop full of the resulting suspension was cultured on Luria-Bertani Agar medium and kept in an incubator at 26ᵒ C for 72 hours. Relatively small, yellow, domed-shaped colonies were transferred to YDC agar (yeast extract-dextrose-CaCO3) medium by single cloning method and were cultured on it. After 48 hours, the lemon-yellow mucoid colonies appeared on the culture medium were transferred to sterile microtubes containing water and glycerol mixture for storage. The isolates were then subjected to biochemical and physiological analysis, and the preliminary results showed that they belong to the genus Xanthomonas sp.. The pathogenicity test was performed on tomato plants in greenhouse, and two weeks after inoculation, symptoms of spotting was appeared. In the following, the identity of the strains was confirmed by molecular methods (PCR and sequencing) and it was determined that the strains belong to species X. perforans. The preliminary results of this research indicated the spread of the tomato spot disease in different provinces of Iran (Khorasan Razavi, Fars, Sistan and Baluchistan and Khuzestan). Distribution of the disease agent takes place through contaminated seeds, rain and wind. Considering the fact that the infected plants are the main source of the inoculum, it is recommended to implement quarantine rules and sieve the contaminated seeds to prevent their transmission to other areas in order to control the dissemination of the disease in the country.