M. A. Achon

Complete genome sequences of Maize dwarf mosaic and Sugarcane mosaic virus isolates coinfecting maize in Spain

SummaryThe genomes of Spanish isolates of Maize dwarf mosaic virus (MDMV-Sp) and Sugarcane mosaic virus (SCMV-Sp) were completely sequenced. Nucleotide sequence identities of SCMV-Sp to those of other SCMV isolates ranged from 79 to 90%. MDMV-Sp shared 85% nucleotide identity with the only other fully sequenced isolate of MDMV. MDMV-Sp and SCMV-Sp differed from each other by 31% in their nucleotide sequences. Phylogenetic analyses showed that SCMV isolates group by host rather than by geographical location. Two significant recombination signals were identified in the NIa and NIb regions of the SCMV-Sp genome.

The population genetics of maize dwarf mosaic virus in Spain

The population genetics of maize dwarf mosaic virus (MDMV) in Spain was assessed by analysis of the P1-HC region. Restriction fragment length polymorphism analysis of 363 isolates revealed that the MDMV population consisted of 69 haplotypes. Sequence analysis of 112 isolates confirmed a high degree of nucleotide sequence diversity (0.143), which was higher for P1 than for the HC. Twelve sequences showed a single different recombination event. Selection pressure analysis revealed that the P1-HC region was under strong negative selection. The MDMV population was spatially structured but not structured temporally or by host. Phylogenetic analysis split the sequences into five major groups.

First report of barley yellow mosaic virus in barley in Spain.

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 northeastern 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 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 two fields. RT-PCR products from five BaYMV-infected samples were cloned and sequenced and showed 96 to 98% identity to BaYMV isolates previously reported from Europe (Genbank Accession Nos. AJ1515479-85 and X95695-7) and 92 to 95% 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 were 96 to 99%. To our knowledge, this is the first report of BaYMV infecting barley in Spain and illustrates the association of both Bymoviruses infecting barley. References: (1) M. A. Achon et al. Plant Dis. 87:1004, 2003. (2) D. Hariri et al. Eur. J. Plant Pathol. 106:365, 2000.