SUSCEPTIBILITY OF APPLE CULTIVARS TO BOTRYOSPHAERIA OBTUSA

The study was carried out in an apple orchard and a laboratory of the Institute of Agriculture, Kyustendil, Bulgaria in seven consecutive years from 1998 to 2004. The apple cultivars Liberty, Cortland, Freedom, Gloster, Florina, Gala, Granny Smith, Smoothy, COOP – 10 and Golden Delicious were evaluated for susceptibility after artificial inoculation of annual growths (shoots) and fruits. Susceptibility of the cultivars Granny Smith, Smoothy and COOP 10 on rootstock M9 and MM106 were evaluated at natural infection in the orchards. The annual growths (shoots) and fruits of all evaluated cultivars were susceptible to Botryosphaeria obtusa. The shoots of the cultivars Liberty and COOP 10 were most susceptible to the black rot. It was established that the rootstock had a strong influence over the cultivars susceptibility. The cultivars COOP 10, Granny Smith and Smoothy were more susceptible when was grafted on rootstock M9 than on MM106.