Molecular identification of a 16SrIII-B phytoplasma associated with cassava witches’ broom disease

Cassava plants displaying typical symptoms commonly associated with phytoplasmas, such as witches’ broom, general stunt, leaves with chlorosis, deformation, and reduced size, were observed in fields located in the state of São Paulo, Brazil. Molecular analysis using specific primers evidenced that the phytoplasma found in all positive samples was affiliated with group 16SrIII (X-disease group). Based on the virtual RFLP patterns and similarity coefficient calculations, the phytoplasma was classified as a member of the group 16SrIII, subgroup B (16SrIII-B). Phylogenetic analysis showed this phytoplasma as closely related to the reference strain for the subgroup 16SrIII-B. Representatives of 16SrIII-B have been described in several cultivated species in Brazil and cassava is an additional host species for this phytoplasma.