Influence of Xanthomonas euvesicatoria pv. allii on germination of 12 onion varieties

Onion bacterial blight is a problematic disease affecting onion production in many countries. The disease is seed-transmitted, hence difficult to control. The study was based on the effects of bacteria on germination percentage and germination energy of various commercial onion varieties. Twelve commercial varieties were obtained from the market and inoculated with bacteria and then tested for germination percentage and germination energy. For most onion varieties, the level of germination inhibition increased with increasing bacterial concentration. On the 5th day of recording, the germination of onion seeds of the variety Karantansky which were inoculated with bacteria at a concentration of 108 CFU/ml differed significantly from the germination of seeds in the control variant. At the same time, seed germination was similar to the control when using bacteria at a concentration of 10⁶ cfu/ml. On the 14th day of record, it was found that the highest concentration (10⁸ CFU/ ml) caused the highest level of inhibition in most onion seeds, while moderate levels were observed at 10⁶ CFU/ ml and the lowest concentration (10⁴ CFU/ml) caused the least inhibition. In the cultivar Khaltsedon, seeds did not germinate at any of the bacterial concentrations compared to 8 % germination in the control. Regarding germination energy, the highest concentration of inoculum on the 5th day of record had the greatest effect in 3 varieties: Myachkovsky 300, Carmen MS and Khaltsedon with germination energy of 3, 2 and 0 %, respectively. In most varieties, the highest bacterial concentration of 10⁸ CFU/ml had the least effect on germination energy, followed by 10⁶ CFU/ml and the highest of 10⁴ CFU/ml on the 14th day of record. However, there were no differences in the effect of concentrations for the varieties Karantansky and Khaltsedon, although all treatments differed significantly from controls (p < 0.05).