Germination response of 12 onion varieties to inoculation with Xanthomonas euvesicatoria pv. allii Available to Purchase

Bacterial blight of onion (BBO) is a problematic disease affecting onion production in many countries. The disease is seed-borne hence difficult to manage. The study was premised upon exploring the effect of the bacteria on the germination percentage and germination energy of various commercial onion varieties. Twelve commercial varieties were sourced from the market and were inoculated with the bacteria then tested for germination percentage and germination energy. At day 5 of germination, although the highest bacterial concentration in the variety Karantansky had a significantly different germination percentage 9%, the concentrations 10⁶ and 10⁴ with germination percentages of 14% and 16% were statistically comparable to the control. For most onion varieties the level of germination inhibition increased with an increase in bacterial concentration. At day 14 of germination the highest concentration 10⁸ effected the highest level of inhibition whilst 10⁶ had moderate levels and the least inhibition was observed in the lowest concentration 10⁴. In the variety Chalcedony no seed germinated in any of the bacterial concentrations against a germination percentage of 8% in the control. In terms of germination energy, at day 5 of recording the highest inoculum concentration had the highest impact on 3 varieties, Myachkovsky 300, Carmen MS and Chalcedony with germination energy of 3, 2 and 0 respectively. Moreover, in germination energy at day 14 of recording it was revealed that in the majority of varieties the highest bacterial concentration 10⁸ effected the lowest germination energy followed by 10⁶ and 10⁴ respectively. However for varieties Chalcedony and Karantansky there were no variations amongst the concentrations though all treatments significantly differed from the control.