Molecular biology and epidemiology of dianthoviruses.

The genus Dianthovirus is one of eight genera in the family Tombusviridae. All the genera have monopartite positive-stranded RNA genomes, except the dianthoviruses which have bipartite genomes. The dianthoviruses are distributed worldwide.

Use of heteroduplex mobility assay for identification and differentiation of phytoplasmas in the aster yellows group and the clover proliferation group.

ABSTRACT This paper describes the identification and differentiation of phytoplasmas by a highly sensitive diagnostic technique, DNA heteroduplex mobility assay (HMA). Closely related phytoplasma isolates of clover proliferation (CP), potato witches'-broom (PWB), and alfalfa witches'-broom (AWB) were collected from the field from 1990 to 1999. The entire 16S rRNA gene and 16/23S spacer region were amplified by polymerase chain reaction (PCR) from the field samples and standard CP, PWB, and AWB phytoplasmas and were subjected to restriction fragment length polymorphism (RFLP) analysis and HMA.

Optimization and Application of a Multiplex RT-PCR System for Simultaneous Detection of Five Potato Viruses Using 18S rRNA as an Internal Control.

Search for a host RNA molecule appropriate as an internal control for reverse transcription-polymerase chain reaction (RT-PCR) detection of viruses in potato (Solanum tuberosum) was conducted. The 18S ribosomal RNA (rRNA) was compared with the commonly used nad2 mRNA in terms of detection sensitivity and degradation kinetics. Detection of 18S rRNA was 5 magnitudes more sensitive than that of nad2 mRNA.

Clover proliferation phytoplasma: 'Candidatus Phytoplasma trifolii'.

Clover proliferation phytoplasma (CPR) is designated as the reference strain for the CP phylogenetic group or subclade, on the basis of molecular analyses of genomic DNA, the 16S rRNA gene and the 16S-23S spacer region. Other strains related to CPR include alfalfa witches'-broom (AWB), brinjal little leaf (BLL), beet leafhopper-transmitted virescence (BLTV), Illinois elm yellows (ILEY), potato witches'-broom (PWB), potato yellows (PY), tomato big bud in California (TBBc) and phytoplasmas from Fragaria multicipita (FM). Phylogenetic analysis of the 16S rRNA gene sequences of BLL, CPR, FM and ILEY, together with sequences from 16 other phytoplasmas that belong to the ash yellows (AshY), jujube witches'-broom (JWB) and elm yellows (EY) groups that were available in GenBank, produced a tree on which these phytoplasmas clearly clustered as a discrete group.

Molecular Characterization and Classification of Phytoplasmas Associated with Canola Yellows and a New Phytoplasma Strain Associated with Dandelions.

DNA isolated from symptomatic canola (Brassica napus, Brassica rapa) and dandelion (Taraxacum officinale) was used to amplify 16S ribosomal DNA fragments by polymerase chain reaction using two pairs of universal primers P1/P6 and R16F2n/R2. Restriction fragment length polymorphism (RFLP) analysis of the amplified DNA fragments using endonucleases AluI, HhaI, HpaII, MseI, RsaI, and Sau 3AI revealed two distinct types of phytoplasmas in canola with similar symptoms. One had the same RFLP profiles as the phytoplasmas in subgroup 16SrI-A, whereas the other one had RFLP profiles similar to those of phytoplasmas in subgroup 16SrI-B.