Molecular detection of the Australian grapevine yellows phytoplasma and comparison with grapevine yellows phytoplasmas from Italy

A diagnostic test using the polymerase chain reaction is described for the detection of phytoplasma DNA in grapevines collected from South Australia and Victoria. Grapevines with Australian grapevine yellows disease tested positively for a phytoplasma but those with ‘restricted spring growth syndrome’ (formerly called ‘grapevine decline’) tested negatively. Restriction fragment length polymorphism analyses were done to determine the relationships between phytoplasmas of the Australian grapevine yellows and of representatives from both the aster yellows group (which includes phytoplasmas of grapevine yellows from Italy) and the elm yellows group (which includes phytoplasmas of flavescence dorée). Results showed that Australian grapevine yellows is associated with a unique phytoplasma that is more closely related to the phytoplasmas of the aster yellows group than to those of the elm yellows group.