Untersuchungen zum Erreger der Ringfleckigkeit an Stieleichen (Quercus robur)

Oak trees showing leaves with chlorotic ring spots have been observed in an area of Berlin (Spandau Forest). Leaves from infested trees were used for investigations on virus purification and mechanical transmission. Electron microscopic visualisation of the virus particles was unsuccessful, as was their mechanical transmission to herbaceous indicator plants. The use of specific primers to detect ring spot disease on mountain ash showed that both ring spot disease forms do not stem from the same causal agent. Whilst the amplified DNA fragment of mountain ash consists of 224 bp, those of diseased oak trees had lengths of 150 bp and 550 bp. These two fragments amplified in diseased oak leaf tissue probably result from an unspecific reaction of the primers with the cDNA. Further investigations are considered necessary.