Investigation of Resistance of Some Lettuce Varieties against Lettuce Bacterial Leaf Spot Disease Agent Xanthomonas hortorum pv. vitians and the Susceptibility of the Disease Agent to Copper

Bacterial Leaf Spot (BLS), caused by Xanthomonas hortorum pv. vitians (Xhv), is a significant disease affecting lettuce cultivation and causing crop losses. In this study, eight lettuce varieties were tested against the most virulent strain (HBXcv1) of X. hortorum pv. vitians using two inoculation methods: hand sprayer and needle syringe. The symptoms appearing on lettuce plants ten days after bacterial inoculation using the spraying method were evaluated. The varieties' tolerance levels were determined using the Duncan Multiple Range Test (DMRT), with Carmesi RZ Lolo being the most tolerant variety (DMRT mean of 0.25 at 5% significance level) and Cospirina being the most susceptible variety (DMRT mean of 216.55 at 5% significance level). After bacterial inoculations using a syringe with a needle, similar reactions were observed in lettuce as those obtained from spray inoculations. Among different lettuce varieties, Carmesi RZ Lolo showed the most tolerance to the effect of HBXcv1. No symptoms were found in lettuce leaves after 10 days of inoculation. On the other hand, Cospirina, Nun 06118, and Presidential lettuce varieties were determined to be sensitive to HBXcv1. In the second part of the study, the susceptible level of Xhv HBXcv1 strain to different copper sulfate (CuSO4) concentrations was investigated using Nutrient Agar and Casitone Yeast extract agar. HBXcv1 strain was found to be resistant to 50ppm CuSO4 and susceptible to 100ppm and 200ppm. These results contribute to understanding the response of lettuce varieties to BLS. It has been found that copper-containing mixtures may be effective in the chemical control of Xhv infections.