Sixty-four apple cultivars and selections of potential interest to apple producers and plant breeders in the Czech Republic were tested for their relative resistance to the fire blight pathogen over six years. Level of fire blight resistance was evaluated according to the extent of lesion development on the shoots tips after artificial inoculation in experimental plots under insectproof nets. Cultivars Quinte (resistant) and Yellow transparent (high susceptible) were included in the tests. Of 64 apple cultivars and selections tested, none were high resistant, 3.1% were evaluated as resistant, 10.9% moderately resistant, 57.8% moderately susceptible, 21.9% susceptible and 6.3% high susceptible. Resistant apple genotypes, showing blight necrosis of shoots of 11–12%, were only cultivars Selena and Quinte. Moderately resistant genotypes (blight necrosis 13.1–25.0%) were Kordona, Golden Smoothee, Julia, HL 323, Melodie, HL 421 and S 634/3. High susceptible genotypes (blight necrosis more then 80.1%) were comprised cultivars Vesna, Topas, Yellow transparent and Vanda. The remaining genotypes were moderately susceptible (blight necrosis 26.1–60.0%) and susceptible (blight necrosis 60.1–80.0%). During six experimental years, quantitative variability was recorded in the blight score. Differences between cultivars in susceptibility to fire blight were often statistically significant.

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Sedlák J., Paprštein F., Korba J., Šilerová J. (2015): Development of a system for testing apple resistance to Erwinia amylovora using in vitro culture techniques. Plant Protect. Sci., 51: 1-5.The suitability of different in vitro artificial inoculation methods for testing apple resistance to fire blight was evaluated. Six proliferation MS media containing BAP, TDZ or 2iP were tested to determine favourable conditions for shoot development. Out of the tested cytokinins, only media with BAP proved to be useful for all tested cultivars for artificial inoculation with Erwinia amylovora. Out of three tested inoculation methods, removal of 3 mm of the shoot apex with scissors and transfer of bacterial suspension by pipette (method 1) appeared to be the most suitable technique. This method enabled the determination of susceptibility of two cultivars due to the different speed of fire blight symptom development.

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