January 11, 2005
Source: American Phytopathological Society, Plant Disease Notes [edited]

First report of Barley yellow mosaic virus in barley in Spain
MA Achon, M Marsinach, Area de Proteccio de Conreus, Centre UdL-IRTA Rovira Roure 191, 25198 Lleida, Spain; C Ratti, C Rubies-Autonell, DiSTA, Via Filippo Re 8, 40126-Bologna, Italy. Plant Dis 2005; 89: 105, published
online as DOI: 10.1094/PD-89-0105A, 2005. Accepted for publication 7 Sep 2004.

Recently, the presence of Barley mild mosaic virus (BaMMV) and the weakly serological detection of Barley yellow mosaic virus (BaYMV) were reported in Spain (1); both viruses are members of the genus Bymovirus (family
_Potyviridae_). Random and symptomatic surveys were conducted during February and March of 2003 in barley fields in north eastern Spain to determine the occurrence of BaMMV and BaYMV.

Leaves from 316 samples collected in 15 fields were analyzed using enzyme-linked immunosorbent assay (ELISA) with commercial antisera specific for BaYMV and BaMMV (Loewe Biochemica, Munich) as well as antisera against both viruses (provided by T Klumen). Positive ELISA samples were further analyzed using reverse transcription-polymerase chain reaction (RT-PCR) with specific primers that amplify 445 bp of BaMMV (1) and 433 bp of BaYMV (2).

Complete agreement was observed between the ELISA and RT-PCR results. Mixed infections of BaYMV and BaMMV were detected in 10 samples, BaYMV in 5 samples and BaMMV in 3 samples. Samples positive for both viruses that exhibited clear mosaic symptoms were collected in 2 fields.

RT-PCR products from 5 BaYMV-infected samples were cloned and sequenced and showed 96 to 98 per cent identity to BaYMV isolates previously reported from Europe (Genbank Accession Nos. AJ1515479-85 and X95695-7) and 92 to 95 per cent identity with isolates reported from Asia (GenBank Accession Nos. AB023585-96, AJ132268, AJ224619-22, AJ224624-28, AF536944-46, AF536948-58, D01091, D00544, and Z24677). Sequence identity of Spanish isolates was 96 to 99 per cent.

To our knowledge, this is the 1st report of BaYMV infecting barley in Spain and illustrates the association of both Bymoviruses infecting barley.

References:
(1) MA Achon, et al. Plant Dis 2003; 87: 1004.
(2) D Hariri, et al. Eur J Plant Pathol 2000; 106: 365.

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[BaYMV and Barley mild mosaic virus (BaMMV) are transmitted by the soil-inhabiting and spore-forming bacillus _Polymyxa graminis_. Both viruses occur on barley in Europe and Asia and are economically important,
soilborne pathogens of winter barley. Until recently, laboratory diagnosis of these pathogens has relied upon ELISA using polyclonal antiserum. Because of inherent virus particle instability, combined with the inability
to sap-transmit BaYMV, high quality antiserum has been difficult to obtain and ELISA is often unsatisfactory. As an alternative approach, 2 TaqMan assays (1 BaYMV-specific and the other BaMMV-specific) have been developed.
These assays have been validated for 3 seasons, by testing samples in parallel with ELISA. TaqMan assays are a more reliable detection method than ELISA, especially with late-season and mixed infection samples. Both
fungi acquire the viruses following encystment on host roots, which then germinate to form a pre-penetration swelling termed an adhesorium. The protoplast is "injected" into the plant host cell by a bullet-like mechanism, causing infection in the root. The protoplast then grows into a multinucleate plasmodium which eventually converts into a sporangium to release further zoospores. As an alternative, the multinucleate plasmodium can convert into numerous thick-walled resting spores which are released when the host cells decay and can survive as an inoculum pool for many years in soil.

Additional reference: Brunt AA, Crabtree K, Dallwitz MJ, Gibbs AJ, Watson L, Zurcher EJ (eds.) (1996 onwards). Plant Viruses Online: descriptions and lists from the VIDE database. Version: 20 Aug 1996.
<http://biology.anu.edu.au/Groups/MES/vide/>

Links:
<http://www.apsnet.org/pd/searchnotes/2003/0604-01N.asp>
<http://wheat.pw.usda.gov/ggpages/bgn/22/a22-12.html>
<http://www.rothamsted.bbsrc.ac.uk/ppi/links/pplinks/bymoviruses/>
<http://helios.bto.ed.ac.uk/bto/microbes/chytrid.htm>
<http://www.rothamsted.bbsrc.ac.uk/ppi/staff/mike_pdf/MPP_review.pdf>  
-Mod.DH]