First Detection of Wheat dwarf virus in Barley in Spain Associated with an Outbreak of Barley Yellow Dwarf

Severe dwarfing, yellowing, and crop failure were observed on barley in northeastern Spain during March and April of 2003. Leaves from 106 plants collected from 15 barley fields were analyzed using enzyme-linked immunosorbent assay (ELISA) with commercial antisera (Loewe Biochemica, Munich) specific for Barley mild mosaic virus (BaMMV), Barley yellow mosaic virus (BaYMV), the PAV and MAV serotypes of Barley yellow dwarf virus (BYDV), Barley yellow striate mosaic virus (BYSMV), Barley stripe mosaic virus (BSMV), Brome mosaic virus (BMV), Brome streak mosaic virus, (BStMV), Cereal yellow dwarf virus (CYDV), Wheat streak mosaic virus (WSMV), Wheat spindle streak mosaic virus (WSSMV), Soilborne cereal mosaic virus (SBCMV), and Wheat dwarf virus (WDV). In 70 samples, BYDV-PAV was the sole virus detected; in 20 other samples, this virus was detected in association with WDV, WSMV, BaMMV, and/or BaYMV. Mixed infections were further analyzed using reverse transcriptase-polymerase chain reaction (RT-PCR) or PCR with specific primers that amplify 445 bp of BaMMV (3), 433 bp of BaYMV (1), 600 bp of WSMV (primer 1: 5'CGAAACGCAGCG TTATTTC3', primer 2: 5'CATCTGAAG GGCTTGACG3'), and 1,200 bp of WDV (4). Eight samples gave the expected amplicons for WDV, two samples gave the expected amplicon for BaMMV, and one sample gave the BaMMV and BaYMV amplicons. No samples gave the amplicon for WSMV. In addition, 10 samples that were positive with ELISA for BYDV, either as a single or as multiple infections with other viruses, were analyzed with specific primers that amplify 600 bp of the BYDV genome (2) and all gave the expected RT-PCR product. ELISA and RT-PCR results agreed completely for WDV and BYDV samples, but agreed poorly for BaMMV and BaYMV (three of seven ELISA-positive samples). PCR products of WDV were subsequently cloned and sequenced. Sequence analysis confirmed the presence of WDV in these barley samples. This report shows the high occurrence of BYDV in barley fields and its association with BaMMV, BaYMV, and WDV infections that induces barley crop failure. To our knowledge, this is the first detection of WDV in Spain. References: (1) M. A. Achon et al. Plant Dis.87:1004, 2003. (2). E. S. G. Canning et al. J. Virol. Methods 56:191, 1996. (3) D. Hariri et al. Eur. J. Plant Pathol. 106:365, 2000. (4) A. Kvarnheden et al. Arch Virol. 147:206, 2002.