EN
Phytoplasmas are unculturable Mollicutes associated with aster yellows and witches' broom type diseases (AY) of several hundred plant species. Phytoplasma affected plants exhibited chlorosis, stunted growth, abnormal production of secondary shoots, flower malformation and early plant dieback. The aim of this review was to present the historical records of rescarch and current status of phytoplasma differentiation and classification based on RFLP analysis of the 16S rRNA gene. 246 described phytoplasmas have been classified into 20 major phylogenetic groups or subclasses. Article presents the current knowledge on genetic diversity of phytoplasmas, their geographical distribution and plant association as well as the research on phytoplasmosis in Poland.