Molecular detection of diverse mycoplasma-like organisms (MLOs) associated with grapevine yellows and their classification with aster yellows, X-disease, and elm yellows MLOs.
Polymerase chain reactions (PCR) and restriction analyses of PCR-amplified DNA were used to detect and differentiate MLO strains associated with grapevine yellows detected in naturally diseased grapevines in Virginia, USA (cultivar Chardonnay) and Italy (cultivar Caveccia). At least 3 major groups of grapevine-infecting MLOs were delineated. FDVA1 MLO, discovered in yellows-diseased grapevines in Virginia, and flavescence dorée MLO strain FDU from northern Italy were classified with X-disease MLOs; grapevine yellows-associated MLO strains FDG from Germany, CA1, CH1, SAN1 and SAN2 from northern Italy, and FDB and FDR from southern Italy were classified with aster yellows MLOs; and flavescence dorée MLO strain FDF from France was classified in the elm yellows MLO group. It is suggested that grapevine yellows may be a complex of several diseases of diverse aetiologies.