Detection and differentiation of phytoplasmas in Australia: an update

Phytoplasmas were found in 33 plant species that were not described as host plants in an earlier Australian survey. Plants displayed characteristic sy mptoms of little leaf, proliferation, and floral abnormalities. Restriction fragment length polymorphism analysis revealed 13 different restriction pa tterns. The majority of phytoplasmas showed a restriction pattern identical to that of either the tomato big bud (TBB) or sweet potato little leaf V4 (SPLL-V4) phytoplasma. Phytoplasmas from 6 plant species showed a restricti on pattern similar to that of the pigeonpea little leaf (PLL) phytoplasma. One phytoplasma from garden bean displayed a restriction pattern identical to that found in papaya dieback and Australian grapevine yellows (AGY) phyt oplasmas. Seven new restriction fragment patterns have been detected and se quence analysis of the 16S/23S spacer region revealed that 3 of these phyto plasmas are related to the faba bean phyllody (FBP) group. The spacer regio n of a graminaceous phytoplasma was most similar to phytoplasmas from the s ugarcane white leaf group. Another graminaceous phytoplasma was identical t o a phytoplasma from Indonesia. The spacer region of a phytoplasma from poi nsettia (PoiBI) was identical to the western X-disease phytoplasma from Nor th America and Europe. The spacer region of a phytoplasma in stylosanthes c ontained no tRNA Ile. Full-length 16S rRNA gene sequences from selected new phytoplasmas were determined to corroborate results obtained from the spac er region analyses. Three of these phytoplasmas (galactia little leaf, vign a little leaf, and stylosanthes little leaf) are, along with the PoiBI phyt oplasma and the graminaceous phytoplasmas, members of phytoplasma groups th at have not been reported before in Australia.