Sugarcane White Leaf Phytoplasma Research Articles

Sequence Analysis of Extrachromosomal DNA of Sugarcane White Leaf Phytoplasma.

Sequence Analysis of Extrachromosomal DNA of Sugarcane White Leaf Phytoplasma.

Characterization and classification of phytoplasmas from wild and cultivated plants by RFLP and sequence analysis of ribosomal DNA

Restriction fragment length polymorphism and sequence analysis of PCR-amplified ribosomal DNA were used to identify and classify phytoplasmas associated with diseases of various wild and cultivated plants. The diseases examined were either not known before or the presumable causal agents were not yet identified and characterized or were only known from other geographic areas. New diseases examined were those causing virescence and phyllody of Bunias orientalis and Cardaria draba. Both were associated with strains of the aster yellows phytoplasma. The same type of aster yellows phytoplasma was also found to be associated with yellows and phyllody diseases of Portulaca oleracea, Stellaria media, Daucus carota ssp. sativus, and Cyclamen persicum. In German and French DNA samples from diseased Trifolium repens, the clover phyllody phytoplasma was identified, which could clearly be distinguished from other phytoplasmas of the aster yellows group. Strains of the stolbur phytoplasma were detected in big bud-affected tomatoes and almost exclusively in Convolvulus arvensis. In Cirsium arvense and Picris echioides two distinct phytoplasmas were identified which showed relationship to the sugarcane white leaf phytoplasma group but may represent a new group or subgroup. In Conyza (syn.: Erigeron) canadensis a phytoplasma of the X-disease group was detected. A strain from Gossypium hirsutum showed the same restriction profiles as the faba bean phyllody phytoplasma.

Detection of DNA of Phytoplasmas Associated with Phyllody Disease of Sesame in Thailand.

Sesame phyllody (SP) caused by phytoplasmas occurs in many countries in the tropics. DNA extracted from sesame plants with phyllody in Thailand, purified for the phyllody-specific fraction with repeated bisbenzimide-CsCl equilibrium density gradient centrifugation and fragmented by restriction enzyme HindIII was cloned into a plasmid-Escherichia coli system. Recombinant plasmids which reacted with the peroxidase-labeled DNA of SP-affected sesame plants but not with the labeled DNA of healthy sesame plants were selected. Southern analysis revealed that the inserts of some recombinant plasmids consisted of fragments of chromosomal DNA of the phytoplasma, whereas the inserts of the other recombinant plasmids consisted of fragments of two types of extrachromosomal DNAs of the phytoplasma. Hybridization using the cloned chromosomal and extrachromosomal DNA fragments associated with the SP phytoplasmas as probes as well as the PCR procedure to amplify the 16S rDNA of phytoplasmas was effective in assaying SP phytoplasmas in the field. Cloned DNA probes hybridized strongly with SP specimens whereas most of them hybridized weakly with rice yellow dwarf, sugarcane white leaf, gentian witches' broom, and tsuwabuki witches' broom specimens. Preferential dot hybridization and restriction enzyme cutting pattern analysis of the 16S rDNA of several phytoplasma isolates found in Northeast Thailand indicated that the SP phytoplasmas are more closely related to some phytoplasmas associated with phyllody and witches' broom type symptoms than to phytoplasmas associated with white leaf symptoms including sugarcane white leaf phytoplasma.