Distinctions between phytoplasmas at the subgroup level detected by heteroduplex mobility assay

A total of 62 phytoplasma isolates were collected from North America, Europe and Asia and analysed by heteroduplex mobility assay (HMA) of the 16/23S spacer region amplified by the polymerase chain reaction. The results revealed wide genetic diversity among the phytoplasmas studied and a number of new phytoplasma strains were identified from known or new plant hosts in Alberta, Canada. Two distinctive subgroups were revealed by HMA in phytoplasmas associated with canola yellows, Chinese aster yellows, dandelion yellows and monarda yellows. In Alberta, two subgroups of the aster yellows group of phytoplasmas, I‐A and I‐B, were prevalent in naturally infected field crops and ornamentals in open gardens. The results indicated that HMA is a simple, but rapid and accurate, alternative method for the detection and estimation of genetic divergence of phytoplasmas when finer molecular characterization of phytoplasmas is required at the subgroup level.