گEvaluation of crop yield and resistance of different tomato cultivars to bacterial cankar

Tomato plants with symptoms of bacterial canker disease were observed and collected for the first time in Iran in 1988 from tomato fields located in Oroumieh region, West Azarbaijan, one of the important tomato cultivation areas in the country, and the bacterium Clavibacter michiganensis subsp. michiganensis was isolated and identified as the causal agent. Being considered as one of the most important diseases of tomato, bacterial canker causes wilting and dying of the plants and poses a serious threat to tomato production in the area. Since the use of resistant or tolerant varieties, which may produce satisfactory yields despite infection, could be effective in reducing losses, in this study crop yield and susceptibility to bacterial canker of 16 high-yielding tomato cultivars selected from regional trials were compared under field and greenhouse conditions during 2000-2001. In the field, treatments were arranged according to a randomized complete block design with three replications, and in the greenhouse completely randomized blocks with five replications were used. Seedlings were raised in seed beds and transplanted into the experimental field and into pots in the greenhouse at the same time. At the 6-8 leaf stage, all plants in one of the two rows in each experimental plot in the field and all test plants in the greenhouse, except the untreated check, were inoculated by injecting the turbid bacterial suspension into the leaf axils of three lower leaves. First symptoms, severity and progress of the disease as well as variations in the appearance of plants and fruits of the test cultivars induced by the bacterial canker organism were recorded weekly for two months. The results showed that the disease significantly affected crop yield, outer appearance of plants and fruits as well as fruit quality of the test cultivars, as compared with the untreated check. Differences in disease severity between cultivars were significant at p=0.01. The lowest infection rates were found in plants of the cultivars L 70, NVH 4473, Rover and L 144 in the greenhouse and L 144 and SP 97 in the field, respectively. High yields were obtained in this experiment from the cultivars L 144, Rover and Tiger, respectively.