Comparative Relative Susceptibility of NE-183 Apple Cultivars to Fruit Rot Pathogens in West Virginia

Abstract

Twenty-three apple ( Mainsx domesticaBorkh.) cultivars were tested over a 5-year period with controlled inoculations in the field and laboratory for their relative susceptibility to the pathogens that cause common preharvest ("summer") fruit rot diseases in the mid-Atlantic region of the United States. Pathogens tested were isolates of Colletotrichum acutatum, Botryosphaeria dothidea, and B. obtusa, the causal agents for bitter rot, white rot, and black rot respectively. Wounded (for Botryosphaeriaspp.) or nonwounded (for C. acutatum) fruit were inoculated in the field and laboratory at 2 to 3 weeks preharvest with mycelium (for Botryosphaeriaspp.) or conidia (for C.acutatum) from axenic cultures. Fruit were rated for relative susceptibility to the different fungi by determining disease severity of attached fruit in the field based on lesion growth and detached fruit in laboratory inoculations of wounded fruit. Based on the laboratory and field data from 5 growing seasons, cultivars were classified into three relative susceptibility groups: most susceptible: 'Pristine', 'Fortune', 'Sunrise', 'Orin', and 'Arlet'; moderately susceptible: 'Sansa', 'Ginger Gold', 'Golden Supreme', 'Honeycrisp', 'PioneerMac', 'Suncrisp', 'Cameo', 'Senshu', 'Shizuka', 'Yataka', and NY75414; and least susceptible: 'Enterprise', 'Golden Delicious', 'Creston', 'GoldRush', 'Gala Supreme', 'Braeburn', and 'Fuji'. Results of the present study indicate that new apple cultivars from the first NE-183 planting vary in their resistance to the different rot fungi and none, perhaps with the exceptions of 'Gala Supreme' and 'Fuji,' shows uniform resistance to the spectrum of summer rot pathogens included in these experiments.