IDENTIFICATION OF A PHYTOPLASMA CAUSING YELLOWS OF MONARDA

Monarda yellows occurring in southern Alberta was found to be associat ed with a phytoplasma. Using two pairs of universal primers, 16S ribos omal DNA fragments (about 1.5 and 1.2 kb) were amplified separately by polymerase chain reaction (PCR) from DNA samples that had been extrac ted from infected monarda. No such DNA bands were observed using DNA s amples from uninfected monarda. The DNA fragment (1.2 kb) amplified by nested-PCR was analysed and compared with western aster yellows (AY27 , Canada), eastern aster yellows (EAY, USA), French hydrangea aster ye llows (AYHF), Belgium hydrangea aster yellows (AYHB), clover prolifera tion (CP, Canada) and potato witches'-broom (PWB, Canada) by means of restriction fragment length polymorphism (RFLP) using endonucleases Al uI, MseI, HpalI, Sau3AI, KpnI and RsaI. The results showed that monard a yellows phytoplasma belongs to the aster yellows subclade and is dif ferent from CP and PWB. This is the first report of aster yellows phyt oplasma infecting monarda.