Detection of Phytoplasmas in Declining Pears in Southern Australia

Forty-nine pear tree samples collected in Victoria, most of them showing decline symptoms, were tested by polymerase chain reaction (PCR) analysis to detect phytoplasmas. Two universal phytoplasma-specific primer pairs, fP1/rP7 and fU5/rU3, were tested, but only fU5/rU3 amplified the phytoplasma DNA adequately. Nested PCR with universal and group-specific primers, however, proved more effective. Thirty pear trees reacted positively in a nested PCR assay. Restriction fragment length polymorphism (RFLP) analysis with the restriction enzymes MseI and AluI of the PCR fragment amplified with the primer pair fU5/rU3 revealed patterns identical to those from the sweet potato little leaf phytoplasma. This is the first report of a phytoplasma in pear in Australia.