THE IMPORTANCE OF THE TYPE OF Erwinia amylovora INOCULUM IN SCREENING OF APPLE GENOTYPES SUSCEPTIBILITY TO FIRE BLIGHT

Abstract

Terminal shoots of 3 apple cultigens ('Free Redstar'. 'Ligolina' and J-79) growing in the greenhouse, were inoculated with 2 types of inoculum: either a mixture of 4 E. amylovora strains or with each strain separately. The strains were isolated from apple, pear or hawthorn plants in various regions of Poland. Differences in virulence level among strains were found. However, there was not a case where the same strain showed different virulence with the different genotypes inoculated. The severity of fire blight was reflected by type of inoculum and virulence of strain used.