|Stockwell, Virginia - Oregon State University|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/4/2009
Publication Date: N/A
Interpretive Summary: Fire blight is one of the most serious diseases of plants in the Rose family, which includes apples, pears and quinces. Quince is considered to be one of the most susceptible hosts. In this study several quince, pear and apple cultivars were inoculated with the fire blight bacteria in a greenhouse so that their relative susceptibility could be compared. The apple and pear cultivars used are international standards in fire blight research and ranged from the most susceptible to the most resistant know. The length of fire blight lesions three weeks after inoculation with a virulent bacteria isolate was used to compare all the fruit tree cultivars to each other. The apple and pear cultivars responded as expected, with the longest lesions in cultivars reported to be very susceptible and the shortest lesions or no lesions at all in the ones reported to be very resistant. We expected all the quince trees to be as susceptible to fire blight as the most susceptible apples and pears. Surprisingly, the response of all six quince cultivars used in the study was intermediate between the most susceptible apples and pears and the most resistant. None of the quince trees, however, exhibited strong resistance to fire blight.
Technical Abstract: Fire blight caused by Erwinia amylovora (EA) is one of the most serious diseases of plants in the family Rosaceae, and Quince (Cydonia oblonga Mill.) is considered one of the most susceptible host genera. Apple (Malus sp.) and pear (Pyrus sp.) cultivars ranging from most susceptible to most resistant have been identified and are used as international standards. The response of six quince cultivars to a virulent isolate of EA was compared to that of four standard apple and seven pear cultivars. Young leaves of actively growing, recently grafted trees (6 trees/cultivar) were inoculated by cutting with scissors dipped in a suspension of EA strain Ea153 at 1 x 10E9 CFU/ml and maintained in a greenhouse. Assays were conducted in May 2008, and repeated in September. Length of fire blight lesions after 3 weeks ranged from 0 to 24 cm. ‘Jonathan’ apple and ‘Forelle’ pear developed the longest lesions. Apples ‘G-41’ and ‘Robusta 5’ and pear ‘Old Home’ were the most resistant with either no disease symptoms or lesions < 1.0 cm. No significant difference in lesion length was found between quince cultivars ‘Aromatnaya’, ‘Limon’, ‘Quince A’, ‘Smyrna’ and ‘Van Deman’. Disease severity in quince was comparable to standard apple and pear cultivars considered intermediate in susceptibility. Apple and pear standards responded as expected to inoculation with EA and each of the quince cultivars was more resistant to fire blight than the most susceptible apple or pear clones.