Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/23/2002
Publication Date: N/A
Citation: Interpretive Summary: White or bot rot, a fungus that attacks apple, is an important disease in the mid-Atlantic and southern area of the U.S. Disease outbreaks can occur rapidly and losses can be severe, especially under prolonged warm, wet weather. Field evaluations for the incidence of rot diseases in apple can be difficult because of the similarity of symptoms caused by the various pathogens. Methods for evaluating rot diseases in the field are limited. 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 years studies permitted the selected apple cultivars to be classified from most susceptible to least susceptible to the white 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 cultivars were tested in the field and laboratory for their relative susceptibility to the white rot pathogen, Botryosphaeria dothidea. 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 with two criteria: disease severity of attached fruit in the field based on lesion growth (mm/degree-day) and disease severity of detached fruit in laboratory inoculations of wounded fruit (mean lesion diameter after 5 days). Based on the laboratory and field data from 2 years of study, cultivars were classified into three relative susceptibility groups: most susceptible: 'Fortune' and 'Pristine'; moderately susceptible: 'Golden Supreme', 'Creston' 'Ginger Gold', 'Sansa', 'Golden Delicious', 'Senshu', 'Orin' 'Sunrise', 'GoldRush', 'Arlet', 'Braeburn','Cameo', 'Enterprise', 'Fuji','Shizuka', 'Gala Supreme', and NY 75414; and least susceptible: 'Honeycrisp', 'Yataka', 'Suncrisp', and 'PioneerMac'. Compared to previous cultivar rankings, the results of the present study indicate that some new apple cultivars from the first NE-183 planting show greater resistance to Botryosphaeria dothidea than current standard cultivars.