May 31, 2005
Source: British Society for Plant Pathology, New Disease Reports, Vol. 10 [edited]
<http://www.bspp.org.uk/ndr/july2004/2004-20.asp>

A new yellowing disease in Phaseolus vulgaris associated with a whitefly-transmitted virus
E. Segundo, G. Martin, I.M. Cuadrado and D. Janssen, Unidad de Virologia, IFAPA, Autovia del Mediterraneo s/n, 04745 La Mojonera, Spain. Accepted for publication 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 plants. Affected plants were all observed in greenhouses infested with _Bemisia tabaci_ [Bt]. Reproducible symptoms were observed when the virus was transmitted from bean-to-bean by Bt (9/10) but not by mechanical inoculation (0/30).

Electrophoresis of double-stranded (ds) RNA extractions from field-collected samples and Bt-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 agarose-purified dsRNA species by Uneven PCR (Chen and Wu, 1997). Individual amplicons were cloned into pGEM-T Easy Vector (Promega, WI, USA), sequenced and then analyzed using Blastx (NCBI, Bethesda, USA).

The nucleotide sequence and deduced amino acid sequence from 1 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 percent and 67 percent), Beet pseudo-yellows virus (BPYV) (respectively 54 percent and 63 percent) and Tomato chlorosis virus (ToCV) (respectively 52 percent and 57 percent).

RT-PCR analysis with designed specific primers (forward primer 5'-TTATGTATGATCTAGGCGGAGGTC-3' and reverse primer 5'-CTGGGTCAATGATACAAGTTAGTC-3') produced an amplicon of the expected size (465 bp), when using total RNA extracts from diseased plants and viruliferous whiteflies.

This is the 1st report of a yellowing disorder in bean associated with a Bt-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.

References:

Celix A, Lopez-Sese A, Almarza N, Gomez-Guillamon ML, Rodriguez-Cerezo E, 1996. Characterisation of Cucurbit yellow stunting disorder virus, a Bemisia tabaci-transmitted closterovirus. Phytopathology 86, 1370-76.

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.

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[Closteroviruses belong to the family _Closteroviridae_ which consists of 2 genera (_Closterovirus_ and _Crinivirus_). These viruses are transmitted by aphids, whiteflies or mealybugs, depending upon the virus. The outbreak of BnYDV in early 2004 occurred in approximately 20 percent of all bean-producing glasshouses in 3 Spanish provinces (Almeira, Granada and Malaga) destined for the fresh market. Yield losses have been reported from 25-100 percent, depending on local conditions. Disease management will depend upon reducing populations of Bt as well has clearing away vegetation that might support the vector.

The delay in posting this piece is because I only found it recently. It is a 2004 piece but will have to be a 2005 posting.

Link: <http://www.serina.es/escaparate/verproducto.cgi?idproducto=6336&refcompra=NULO>
- Mod.DH]