Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2003
Publication Date: 4/1/2004
Citation: Biggs, A.R., Miller, S.S. 2004. Relative susceptibility of selected apple cultivars to fruit rot caused by botryosphaeria. Hortscience. 39:303-306, 2004 Interpretive Summary: Black rot, a fungus that attacks apple, is an important disease in the mid-Atlantic and southern areas of the United States. Disease outbreaks can occur rapidly and losses can be severe, especially under prolonged warm, wet weather. Identifying susceptible apple cultivars is important in selecting new varieties to be planted in these regions. Methods developed in previous studies by the authors were utilized in controlled field and laboratory inoculation studies for 21 relatively new and two established apple cultivars. Results from the two-year studies permitted the selected apple cultivars to be classified from most susceptible to least susceptible to the black rot organism. This information will aid apple growers and extension fruit specialists in selecting the most disease resistant apple cultivars for planting.
Technical Abstract: Twenty-three apple (Malus x domestica) cultivars were tested in the field and laboratory for their relative susceptibility to the black rot pathogen, Botryosphaeria obtusa. Wounded fruit were inoculated in the field at 2 to 3 weeks preharvest with mycelium from 14 to 21-day-old cultures. In the laboratory, detached fruit were inoculated similarly. Fruit were rated for relative susceptibility to the fungus by determining disease severity of attached fruit in the field based on lesion growth (mm/degree-day) and detached fruit in laboratory inoculations of wounded fruit (mean lesion diameter after 4 days). Based on the laboratory and field data from 2 growing seasons, cultivars were classified into three relative susceptibility groups: most susceptible: 'Orin', 'Pristine', and Sunrise'; moderately susceptible: 'Suncrisp', 'Ginger Gold', 'Senshu', 'Honeycrisp', 'PioneerMac', 'Fortune', NY 75414, 'Arlet', 'Golden Supreme', 'Shizuka', 'Cameo', 'Sansa', and 'Yataka'; and least susceptible: 'Creston', 'Golden Delicious', 'Enterprise', 'Gala Supreme', 'Braeburn', 'GoldRush', and 'Fuji'. Compared to previous cultivar rankings, the results of the present study indicate that no new apple cultivars from the first NE-183 planting show greater resistance to Botryosphaeria obtusa than current standard cultivars.