Molecular, serological and transmission electron microscopic analysis of the Barley yellow dwarf virus-PAV and the Cereal yellow dwarf virus-RPV in canary seed (Phalaris canariensis L.)

Canary seed (Phalaris canariensis L.) is a cereal crop belonging to the tribe Phalarideae of the Poaceae family. A prevailing virus infection, which causes dwarfing of plants and yellowing of leaves, was observed in canary seed fields in the Tekirdag province of Turkey. The aim of this study was to identify, clone and sequence the cereal viruses naturally occurring on P. canariensis by employing serological tests as DAS-ELISA and TAS-ELISA tests combined with transmission electron microcopy (TEM) and molecular analysis. One hundred and one plant samples showing symptoms were collected and tested serologically using polyclonal antisera against Barley yellow dwarf virus-PAV (BYDV-PAV) and Cereal yellow dwarf virus-RPV (CYDV-RPV). The results of both immunoassays showed that 48% of the samples were infected with BYDV-PAV, 2% with CYDV-RPV and 14% were mixed infection. 36% of the samples were uninfected or infected at level below detection. Aphid transmission experiments revealed that barley (cv. Rubina) exhibited characteristic of CYDV-RPV. Investigations of infected canary grass seedlings using transmission electron microscopy (TEM) supported the findings of serological tests and revealed the presence of isometric particles of approximately 25 nm in diameter. These results were also confirmed by using BYDV-PAV and CYDV-RPV specific primers. Sequence analysis of cDNA and probable translation products revealed a high level of homology to BYDV-PAV and CYDV-RPV isolates found in other plant species. The sequence data obtained from this research were deposited in the EMBL/GenBank Data Libraries under the accession nos. EGO19056 and EF372272

Detection and partial molecular characterization of Plum pox virus on almond trees in Turkey

Almond (Prunus dulcis) is one of the well known stone fruit species grown for its unripe fruits and delicious seeds in Turkey. In the Trakya region, however, some prevailing virus infections have reduced almond yields and quality. In ten districts of Trakya, 260 leaf samples were collected from affected almond trees in June 2010. DAS-ELISA assays and RT-PCR tests were employed for the identification of viruses. As a result of these detection studies, five of the 260 leaf samples gathered from symptomatic almond trees had Plum pox virus (PPV), 81 of them had Prunus necrotic ringspot virus (PNRSV), and 11 samples contained Prune dwarf virus (PDV). Only four out of 260 samples had a mixture of these viruses. Partial nucleotide sequences of five almond isolates of PPV were determined and compared with 17 other PPV isolates in databases. Computer analysis of obtained and published nucleotide sequences showed identity ranged from 75.72% to 96.87%. Of the five PPV almond isolates obtained, however, there was a close nucleotide identity of 95.82-96.61% to Turkish isolates. Phylogenetic analysis of nucleotides and amino acids showed that five PPV isolates of almond from the Trakya Region of Turkey were clustered in the same subgroup with PPV-T Turkish isolates in GenBank. Therefore we can consider almond isolates of PPV as PPV-T strain, like the two other isolates from apricot trees in Turkey