The presence of phytoplasmas in seven coniferous plant species (Abies procera, Pinus banksiana, P. mugo, P. nigra, P. sylvestris, P. tabuliformis and Tsuga canadensis) was demonstrated using nested PCR with the primer pairs P1 ⁄ P7 followed by R16F2n ⁄ R16R2. The phytoplasmas were detected in pine trees with witches' broom symptoms growing in natural forest ecosystems and also in plants propagated from witches' brooms. Identification of phytoplasmas was done using restriction fragment length polymorphism analysis (RFLP) of the 16S rDNA gene fragment with AluI, MseI and RsaI endonucleases. All samples showed RFLP patterns similar to the theoretical pattern of 'Candidatus Phytoplasma pini', based on the sequence of the reference isolate Pin127S. Nested PCR-amplified products, obtained with primers R16F2n ⁄ R16R2, were sequenced. Comparison of the 16S rDNAs obtained revealed high (99AE8-100%) nucleotide sequence identity between the phytoplasma isolates. The isolates were also closely related to four other phytoplasma isolates found in pine trees previously. Based on the results of RFLP and sequence analyses, the phytoplasma isolates tested were classified as members of the 'Candidatus Phytoplasma pini', group 16SrXXI.
The objective of our research was to assess if arbuscular mycorrhizal (AM) fungal colonization can modify the effect of infection by two aster yellows phytoplasma strains (AY1, AYSim) in Catharanthus roseus plants. Both phytoplasma strains had a negative effect on the root fresh weight, but they differed in symptoms appearance and in their influence on photosynthetic and transpiration rates of the periwinkle plants. AM plants showed significantly reduced shoot fresh weight, while the transpiration rate was significantly increased. AM fungal colonization significantly affected shoot height and fresh weight of the plants infected by each phytoplasma strains as well as the root system of plants infected with the more aggressive AYSim phytoplasma strain. Double inoculation did not reduce the negative effects induced with phytoplasma alone on the photosynthetic activity of phytoplasma-infected plants.
During a 3-year study, grapevines from 23 vineyards in Poland were surveyed for virus diseases and tested to determine the prevalence of the most economically important viruses by RT-PCR. The rate of positive samples was 2.2% for grapevine leafroll-associated virus 1 (GLRaV-1), 1.9% for grapevine leafroll-associated virus 2 (GLRaV-2), 1.5% grapevine leafrollassociated virus 3 (GLRaV-3), 1.9% for grapevine virus A (GVA), 0.2% for grapevine virus B (GVB), 0.2% for grapevine virus E (GVE), 0.65% for grapevine fanleaf virus (GFLV), 20.4% for grapevine fleck virus (GFkV) and 71.9% for grapevine rupestris stem pitting-associated virus (GRSPaV). These viruses were found to occur as single or mixed infections of different combinations in individual grapevines. The overall viral infection rate in the surveyed grapevines was 82.6%. GRSPaV is the most widely distributed virus of all the viruses currently detected in the region. DNA sequencing confirmed the identification of the viruses in selected samples, and analysis indicated that the Polish isolates shared a close molecular identity with the corresponding isolates in GenBank. To our knowledge, this is the first detection of GLRaV
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