Comparison of fire blight resistance screening protocols in two international breeding programmes

Experiments were carried out to compare fire blight resistance screening methodologies used in the German and New Zealand pipfruit breeding programmes. The small differences between the respective screening methodologies did not result in significant differences in the incidence of fire blight infection or the amount of resistance observed in plants. Differences in bacterial growth media, inoculum suspension and inoculation technique did not have a significant effect on the incidence of fire blight infection or the extent of resistance expression in various apple cultivars. Some of the Erwinia amylovora isolates had a significant effect on the level of disease expression on different cultivars. These differences can be used as tools to identify resistance quantitative trait loci in different cultivars. Results from these experiments have led to standardisation of screening methods between the two countries and provided confidence in comparing the findings of the New Zealand/German collaborative resistance research programme.