Use of Heteroduplex Mobility Analysis (HMA) for Differentiating Phytoplasma Isolates Causing Witchesʹ Broom Disease on Populus nigra cv Italica and Stolbur or Big Bud Symptoms on Tomato

Heteroduplex mobility analysis (HMA) was performed to distinguish French and German isolates of phytoplasmas from Populus nigra cv Italica witches" broom. The French isolate was similar to the phytoplasma responsible for the European aster yellows while the German isolate was different but closely related to it. When phytoplasmas inducing similar ʹstolbur" symptoms in tomato were compared to HMA, a high degree of genetic differences was observed among the reference stolbur C (StC) isolate, the European aster yellows and the other phytoplasmas inducing stolbur or big bud symptoms in tomato. Pseudostolbur B and D from Brazil were differentiated from the reference St C using this method