Molecular Characterization of Cereal Yellow Dwarf Virus-RPV in Grasses in European Part of Turkey

Yellow dwarf viruses (YDVs) are economically destructive viral diseases of cereal crops, which cause the reduction of yield and quality of grains. Cereal yellow dwarf virus-RPV (CYDV-RPV) is one of the most serious virus species of YDVs. These virus diseases cause epidemics in cereal fields in some periods of the year in Turkey depending on potential reservoir natural hosts that play a significant role in epidemiology. This study was conducted to investigate the presence and prevalence of CYDV-RPV in grasses and volunteer cereal host plants including 33 species from Poaceae, Asteraceae, Juncaceae, Geraniaceae, Cyperaceae, and Rubiaceae families in the Trakya region of Turkey. A total of 584 symptomatic grass and volunteer cereal leaf samples exhibiting yellowing, reddening, irregular necrotic patches and dwarfing symptoms were collected from Trakya and tested by ELISA and RT-PCR methods. The screening tests showed that 55 out of 584 grass samples were infected with CYDV-RPV in grasses from the Poaceae family, while none of the other families had no infection. The incidence of CYDV-RPV was detected at a rate of 9.42%. Transmission experiments using the aphid species Rhopalosiphum padi L. showed that CYDV-RPV was transmitted persistently from symptomatic intact grasses such as Avena sterilis, Lolium perenne and Phleum exratum to barley cv. Barbaros seedlings. PCR products of five Turkish RPV grass isolates were sequenced and compared with eleven known CYDV-RPV isolates in the GenBank⁄ EMBL databases. Compared nucleotide and amino acid sequences of CYDV-RPV isolates showed that the identities ranged from 40.38 − 95.86 % to 14.04 − 93.38%, respectively. In this study, 19 grass species from the Poaceae family and two volunteer cereal host plants were determined as natural reservoir hosts of CYDV-RPV in the cereal growing areas of Turkey.

First Report of Barley yellow dwarf virus and Cereal yellow dwarf virus Affecting Cereal Crops in Azerbaijan

A field survey was conducted during the 2010/2011 growing season at the Absheron experimental station of the Genetic Resources Institute of Azerbaijan. A total of 49 cereal samples with yellowing and reddening symptoms were obtained from 12 bread wheats (Triticum aestivum), 25 durum wheats (T. durum), 11 wild or cultivated wheat relatives (T. dicoccoides, T. beoticum, T. monococcum, and T. turgidum), and one oat (Avena sativa). Samples were tested by tissue-blot immunoassay (2) using antisera against 7 cereal-infecting viruses: Barley stripe mosaic virus (BSMV), Wheat dwarf virus (WDV), Wheat streak mosaic virus (WSMV), Barley yellow mosaic virus (BaYMV), Barley yellow striate mosaic virus (BYSMV), Maize streak virus (MSV), and Barley yellow dwarf virus (BYDV). Strong positive reactions against the BYDV-PAV polyclonal antiserum were shown by 43 samples. To confirm, total RNAs from 10 of the positive samples (three bread wheat, three durum wheat, the oat, and one sample each of T. beoticum, T. turgidum, and T. dicoccoides) were submitted to RT-PCR with two primer pairs adapted in part from (3). Primers Luteo1F 5′TTCGGMSARTGGTTGTGGTCCA 3′ and YanR-new 5′TGTTGAGGAGTCTACCTATTTNG 3′ (adapted from primer YanR (3)) allow the specific amplification of viruses of the genus Luteovirus (including BYDV) while primers Luteo2F 5′TCACSTTCGGRCCGWSTYTWTCAG 3′ (adapted from primer Shu2a-F (3)) and YanR-new are specific for the genus Polerovirus (including Cereal yellow dwarf virus, CYDV). All 10 tested samples gave a positive amplification at the expected size (~545 bp) with the first primer pair, while only two samples, one from oat and one from the wild wheat relative T. dicoccoides, gave a positive amplification of the expected size (~383 bp) with the second primer pair. Sequencing of amplification products obtained with the Luteo1F/YanR-new primer pair confirmed the presence of BYDV-PAV in all samples (GenBank JX275850 to JX275857). The Azeri isolates were all similar (0 to 1.7% nucleotide divergence) except for one isolate (JX275855, from T. turgidum, 2.4 to 3.2% divergence). An Azeri BYDV-PAV isolate (JX275851, from bread wheat) showed 100% identity with a Latvian isolate (AJ563414) and with two isolates from Morocco (AJ007929 and AJ007918). These isolates belong to a group of widespread PAV isolates and are 99% identical with isolates from Sweden, the United States, China, France, and New Zealand. Sequencing of products obtained with the Luteo2F/YanR-new primers (JX294311 and JX294312) identified CYDV-RPV. The two Azeri sequences show ~3% nucleotide divergence and their closest relatives in GenBank are a range of CYDV-RPV isolates mostly from the United States, including EF521848 and EF521830, with ~4 to 5% divergence. Presence of CYDV was also confirmed using amplification with a CYD-specific primer pair (CYDV-fw-New 5′TTGTACCGCTTGATCCACGG 3′ et CYDV-rev-New 5′GTCTGCGCGAACCATTGCC 3′, both adapted from (1)) and sequencing of the amplification products. This is, to our knowledge, the first report of BYDV-PAV and CYDV-RPV infecting cultivated cereals and wild or cultivated wheat relatives in Azerbaijan. These viruses are responsible for serious disease losses in cereal crops worldwide (4). Their full impact on crops in Azerbaijan is yet to be seen. References: (1) M. Deb and J. M. Anderson. J. Virol. Meth. 148:17, 2008. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (3) C. M. Malmstrom and R. Shu. J. Virol. Meth. 120:69, 2004. (4) W. A. Miller and L. Rasochovà. Ann. Rev. Phytopathol. 35:167, 1997.