The Occurrence of Phytoplasmas in Apple Trees Showing Branch Twisting

Apple trees showing malformation of branches were found at different locations in the Czech Republic. Ultrathin sections of tissues from diseased trees showed the presence of pleomorphic bodies resembling phytoplasma. Nested-polymerase chain reaction (PCR) assays with primers amplifying16S–23S ribosomal RNA (rRNA) sequences specific for phytoplasma and the subsequent restriction fragment length polymorphism (RFLP) analyses allowed to classify the detected phytoplasmas in the aster yellows group, subgroup 16SrI-C in 12 trees, single (11 plants) or mixed with phytoplasma belonging to subgroup 16SrI-B (1 plant). Phytoplasma of apple proliferation group (16SrX-A subgroup) were identified in cv. Matcˇino. Apple tree cv. Prˇesˇticke´ ru˚ zˇove´ was infected by phytoplasma of the 16SrX-A and 16SrI-B subgroups. No phytoplasmas were detected in asymptomatic apple trees.