USE OF HETERODUPLEX MOBILITY ANALYSIS (HMA) FOR DIFFERENTIATING PHYTOPLASMA ISOLATES CAUSING WITCHES-BROOM DISEASE ON POPULUS-NIGRA CV ITALICA AND STOLBUR OR BIG BUD SYMPTOMS ON TOMATO

Heteroduplex mobility analysis (HMA) was performed to distinguish Fren ch and German isolates of phytoplasmas from Populus nigra cv Italica w itches' broom. The French isolate was similar to the phytoplasma respo nsible for the European aster yellows while the German isolate was dif ferent but closely related to it. When phytoplasmas inducing similar ' stolbur' symptoms in tomato were compared to HMA, a high degree of gen etic differences was observed among the reference stolbur C (StC) isol ate, the European aster yellows and the other phytoplasmas inducing st olbur or big bud symptoms in tomato. Pseudo-stolbur B and D from Brazi l were differentiated from the reference St C using this method.