Detection and differentiation of phytoplasmas in Australia: an update

Abstract

Phytoplasmas were found in 33 plant species that were not described as host plants in an earlier Australian survey. Plants displayed characteristic symptoms of little leaf, proliferation, and floral abnormalities. Restriction fragment length polymorphism analysis revealed 13 different restriction patterns. 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 restriction 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) phytoplasmas. Seven new restriction fragment patterns have been detected and sequence analysis of the 16S/23S spacer region revealed that 3 of these phytoplasmas are related to the faba bean phyllody (FBP) group. The spacer region of a graminaceous phytoplasma was most similar to phytoplasmas from the sugarcane white leaf group. Another graminaceous phytoplasma was identical to a phytoplasma from Indonesia. The spacer region of a phytoplasma from poinsettia (PoiBI) was identical to the western X-disease phytoplasma from North America and Europe. The spacer region of a phytoplasma in stylosanthes contained no tRNAIle. Full-length 16S rRNA gene sequences from selected new phytoplasmas were determined to corroborate results obtained from the spacer region analyses. Three of these phytoplasmas (galactia little leaf, vigna little leaf, and stylosanthes little leaf) are, along with the PoiBI phytoplasma and the graminaceous phytoplasmas, members of phytoplasma groups that have not been reported before in Australia.

Plant hosts of the phytoplasmas and rickettsia-like-organisms associated with strawberry lethal yellows and green petal diseases

“…This is in contrast to previous disease surveys in northern Australia, which showed that the SPLL-V4 phytoplasma is associated with diseases that occur in a wide range of plant species (Davis et al , 2003Schneider et al 1999;Padovan and Gibb 2001). The identification of a single plant species positive for the SPLL-V4 phytoplasma compared with the TBB phytoplasma (16 species) suggests that in south-east Queensland, these phytoplasmas may not have a common vector and that the vector for the SPLL-V4 phytoplasma is not prevalent.…”

“…In Australia, Ca. P. australiense is also associated with the diseases strawberry green petal (SGP) (Padovan et al 2000b), papaya dieback (PDB; Gibb et al 1996;Liu et al 1996), Australian grapevine yellows (AGY; Padovan et al 1996) and mung bean witches' broom (MBWB; Schneider et al 1999). More recently, Ca.…”

“…P. australiense, the TBB phytoplasma has a wide host range including native and introduced plant species Schneider et al 1999;Padovan and Gibb 2001;Davis et al 2003). These TBB phytoplasma-associated diseases occur throughout Australia (Davis et al , 2003Schneider et al 1999;Padovan and Gibb 2001).…”

“…P. australiense has been consistently associated with a range of crop species, only a few non-crop host species have been identified during phytoplasma disease surveys in Australia (Davis et al , 2003Schneider et al 1999). The plant host range of a phytoplasma generally reflects the number of natural vector species that are capable of transmitting the organism and their feeding behaviour (Lee et al 2000).…”

Guazuma ulmifolia (Sterculiaceae), a new natural host of 16SrXV phytoplasma in Costa Rica

“…Phytoplasma brasiliense" in a Sterculiaceae tree species. Previous reports of phytoplasmas in a Sterculiaceae weed species, Waltheria indica, were done in Brazil (Kitajima & Costa, 1971) and Australia (Schneider et al, 1999;Wilson et al, 2001); the last of these belonged to group 16SrII (Gen Bank accession Y15870).…”