Stylosanthes is a Host for Several Phytoplasmas, One of which Shows Unique 16S-23S Intergenic Spacer Region Heterogeneity

Stylosanthes sp. exhibiting characteristic symptoms such as little leaf, witchesʹ broom and ¯oral abnormalities were collected from north Queensland and the Northern Territory, Australia. Previous studies have shown that sweet potato little leaf V4 (SPLL-V4), tomato big bud (TBB), stylosanthes little leaf (StLL) and pigeon pea little leaf (PLL) phytoplasmas are associated with this disease. The detection of an additional phytoplasma type, vigna little leaf (ViLL) is reported herein. The range and severity of symptoms expressed by a€ected plants is highly variable and is not associated with a particular phytoplasma type. Similarly, host plants infected with a complex of two phytoplasmas did not have unique or more severe symptoms. Of the phyto- plasmas associated with stylosanthes little leaf disease, StLL is unique because it lacks the tRNAIle gene which is normally situated in the 16S-23S rRNA intergenic spacer region. This phytoplasma was shown to have a second operon containing the expected tRNAIle gene in all StLL samples examined. Sequence analysis suggests that the two 16S rRNA genes ampli®ed by polymerase chain reaction from StLL samples originate from the same phytoplasma. This the ®rst report of a phytopl- asma having ribosomal operons both with and without an intergenic tRNAIle gene.