RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS WITHIN THE APPLE PROLIFERATION MYCOPLASMALIKE ORGANISM

Genetic homogeneity of the mycoplasmalike organisms (MLOs) associated with apple proliferation (AP) disease was examined by comparing samples collected in south-western Germany, France, Italy, and Romania by Southern blot analysis. The material examined consisted of two periwinkle-maintained strains of the AP-MLO, samples from witches' brooms of 48 symptomatic trees, and root samples from 14 latently infected trees. Six cloned chromosomal DNA fragments of one of the periwinkle-maintained strains were used as probes. These probes, which were specific for the AP-MLO and other European fruit MLOs, hybridized with DNA of all samples which indicates that the MLOs examined were closely related with one another. However, restriction fragment length polymorphism was observed among the samples. Four hybridization patterns occurred which were interrelated by common bands. Therefore, the AP agent can be regarded as a taxonomic entity. The variability among the isolates seems not to be due to their geographical origin but might be related to pathological traits.