FIREBLIGHT EVALUATION OF ADVANCED ITALIAN SELECTIONS AND CULTIVARS OF PEAR

Three advanced selections and four cultivars from the ISF-FO pear breeding program were tested for their susceptibility to fire blight (caused by Erwinia amylovora) and compared to ‘Harrow Sweet’ and ‘Doyenné du Comice’, taken as tolerant and susceptible controls, respectively. The three advanced selections (ISF-FO 80-51-72, ISF-FO 80-57-83, and ISF-FO 80-104-72) were selected in a previous EU-funded program and resulted resistant or tolerant in field inoculation tests carried out at Dax (France). Nine E. amylovora strains were used in greenhouse assays in 1997 and 1998 at INRA Angers. For inoculation, the uppermost fully expanded leaf of grafted scions was cut with infected scissors previously dipped into bacterial suspension. One month after inoculation, the number of infected shoots and the length of necrosis were determined. The seven tested genotypes displayed a wide degree of susceptibility to Erwinia amylovora: the percentage of infected shoots ranged from 30% to 100%, while the average length of necroses varied from 5 to 37 cm. Interestingly, ISF-FO 80-104-72, originated from a cross between ‘Coscia’ and ‘Dr. Guyot’, showed an excellent tolerance profile in terms of average necrosis length, comparable to that of ‘Harrow Sweet’. The fact that ISF-FO 80-104-72 originated from a cross between susceptible parents is in agreement with the hypothesis that major fire blight resistance genes should be recessive in pear.