Isolierung und Charakterisierung von pilzlichen Erregern des Schwarzen Rindenbrandes an Apfelbäumen mit Hilfe des „Apfeltests".

During the previous years characterized by summer-drought, black canker disease of apple and pear has become a problem in different parts of Germany. The aim of the current work was therefore to develop basic techniques for isolation of the inciting pathogens from apple trees and their characterization in the laboratory. The experiments included the standard isolation of putative pathogens by placing symptomatic tissue on agar media as well as a method described in the literature as „apple test". For the latter, symptomatic bark pieces are inserted into apple fruits and colonization of the apple tissue is visible as rotting spots. Candidate pathogens can be easily isolated from the colonized apple tissue. After placement of tissue from the trunk of the top of an apple tree expressing wilt symptoms, Trametes versicolor, Diaporthe eres and Diplodia seriata (one of several agents known to cause black canker disease) were isolated. Together with Diplodia malorum, the latter species was also obtained after placement of symptomatic bark pieces on potato dextrose agar. Insertion of diseased bark into apple fruits led to the isolation of further isolates of D. malorum, three isolates of Diplodia bulgarica, Lambertella corni-maris, Penicillium sp. and Sclerotinia sclerotiorum. After inoculation with pure cultures into apple fruits, the latter three, all Diplodia-isolates and Diaporthe eres were pathogenic and caused fruit rots. The Diplodia isolates were further characterised regarding speed of hyphal growth and spore morphology. [ABSTRACT FROM AUTHOR]