E. Segundo, G. Martín, I.M. Cuadrado and D. Janssen*
Unidad de Virología, IFAPA, Autovia del Mediterraneo s/n, 04745 La Mojonera, Spain
Accepted: 19 Mar 2004
During the autumn of 2003, a new disease was observed in French bean (Phaseolus vulgaris) grown commercially in Spain. Symptoms resembling nutritional disorders consisted of interveinal mottling and yellowing in leaves, combined with stiffness or brittleness, and were produced on the middle to lower parts of the plant. Affected plants were all observed in greenhouses infested with Bemisia tabaci. Reproducible symptoms were observed when the virus was transmitted from bean-to-bean by B. tabaci (9/10) but not by mechanical inoculation (0/30). Electrophoresis of double-stranded (ds) RNA extractions from field-collected samples and B. tabaci-inoculated plants revealed a high molecular weight dsRNA doublet, consistent with the bipartite genome of criniviruses (Celix et al., 1996). cDNA transcripts were produced and amplified by RT-PCR from the agarose-purified dsRNA species by Uneven PCR (Chen and Wu, 1997). Individual amplicons were cloned into pGEM-TÂ® Easy Vector (Promega, WI, USA), sequenced and then analyzed using Blastx (NCBI, Bethesda, USA). The nucleotide sequence and deduced amino acid sequence from one amplicon (GenBank accession AY543165) showed the highest percentage identity with the heat shock protein 70 homologue from members of the genus Crinivirus such as Cucurbit yellow stunting disorder virus (CYSDV) (respectively 57 % and 67%), Beet pseudo-yellows virus (BPYV) (respectively 54% and 63%) and Tomato chlorosis virus (ToCV) (respectively 52% and 57%). RT-PCR analysis with designed specific primers (forward primer 5'-TTATGTATGATCTAGGCGGAGGTC-3' and reverse primer 5'-CTGGGTCAATGATACAAGTTAGTC-3') produced amplicon of the expected size (465 bp), when using total RNA extracts from diseased plants and viruliferous whiteflies. This is the first report of a yellowing disorder in bean associated with a B. tabaci-transmitted virus, with molecular and epidemiological features consistent with criniviruses (Wisler et al., 1998). Based on the host range and the unique partial genome sequence, we suggest the name Bean yellow disorder virus (BnYDV) to describe this new virus.
This work was supported with project PIA 03/31 from the Junta de AndalucÃa (Spain).
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Chen X, Wu R, 1997. Direct amplification of unknown genes and fragments by Uneven polymerase chain reaction. Gene 185, 195-9.
Wisler GC, Duffus JE, Liu H-Y, Li RH, 1998. Ecology and epidemiology of whitefly-transmitted closteroviruses. Plant Disease 82, 270-79.
©2004 The Authors