Evaluation of Susceptibility Level of Old Pear Cultivars and Landraces to Fire Blight (Erwinia amylovora) in Field Conditions

摘要

Twelve older pear cultivars and Czech landraces, two new breeding and three commercially grown cultivars ('Beurre Bosc', 'Conference' and 'Williams') as standards were tested for their relative susceptibility level to fire blight after artificial inoculation in the climatic conditions of the Czech Republic. Tests were carried out in the research station of the Crop Research Institute in Slany in technical isolators covered insect proof net in suitable climatic conditions (temperature >15°C, relativehumidity >75%). Artificial inoculations were carried out in the period of strong extending growth by decapitation of shoot tips by scissors dipped in the bacterial suspension (concentration 10 cfu) of a mix of virulent strains of Erwinia amylovora. Thelevel of resistance was determined by the percentage of necrotic lesion development to total length of shoots (in cm) after 40 days. Calculated intensity of infection was transferred to 6-point evaluation scale: highly resistant 0.0-7.0%, resistant 7.1-13.0%, moderately resistant 13.1-26.0%, moderately susceptible 26.1-60.0%, susceptible 60.1-80.0% and highly susceptible 80.1-100.0%. From tested genotypes, only 'Avransska' was evaluated as resistant (0.0% infection intensity). The rresistance level of 'Avransska' was comparable to the newly bred US-62-537-48. Most of the testing genotypes were categorized as moderately susceptible, susceptible or highly susceptible.