Resistance to Fire Blight among Flowering Pears and Quince

Abstract

Fire blight, caused by the bacterium Erwinia amylovora (Burrill) Winslow et al., is one of the most destructive diseases of plants in the Rosaceae subfamily Maloideae. Artificial inoculations, using E. amylovora strain E2002a, were conducted to determine levels of resistance to fire blight among taxa of flowering pears (Pyrus L. spp.) and quince (Chaenomeles Lindl. spp.). The level of resistance was measured as the length of the fire blight lesion as a percentage of overall shoot length. Considerable variation in resistance was observed among both pears and quince. Pyrus ussuriensis Maxim. `Prairie Gem' was highly resistant with a lesion length of 1% of the total shoot length. Pyrus calleryana Decne. `Bradford' was intermediate with a 50% lesion length while P. calleryana `Chanticleer' was significantly more resistant with a lesion length of 31%. Nine pear taxa were highly susceptible and did not differ significantly from 100% disease severity (total shoot death). Chaenomeles speciosa (Sweet) Nak. `Contorta' was highly resistant with a lesion length of 15%. Six quince taxa, including C. × superba (Frahm) Rehd. `Cameo', `Texas Scarlet', and `Jet Trail' were highly susceptible while nine other taxa showed intermediate resistance.