Phytoplasmas are Plant Pathogens

Phytoplasmas are a group of wall-less phytopathogenic micro-organisms related to low G+C content, gram-
positive bacteria. Due to the lack of in vitro growth, it is difficult to characterize and classificate of these
plant patogens. Phytoplasmas, constituted a monophyletic group within the class Mollicutes have been classi-
fied according to 16S-rDNA phylogeny and RFLP profiles into 30 phylogenetic groups. These polymorphic
microorganisms with sizes variable from 200 to 800 nm cause hundreds of diseases worldwide and are
transmitted from plant to plant by sap-feeding hemipteran insects. Plants infected by phytoplasmas exhibit an
array of symptoms such as generalized yellowing, decline, necrosis, abnormal internodes elongation, stunt-
ing, development of green leaf like structures instead of flowers, sterility of generative organs etc.