Detection of rhizomania in Belgium : diversity and characterization of Beet necrotic yellow vein virus RNAs-2 and -3
(2005)
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- Authors
- Supervisors
- Bragard, Claude
- Abstract
- The worldwide extension of the rhizomania disease is one of the most severe constraints for sugar beet crops over the past 30 years. The disease, an abnormal proliferation of rootlets associated with a loss of weight and sugar content,is caused by a Benyvirus, the Beet necrotic yellow vein virus(BNYVV) and its vector, a soil Plasmodiophorid, Polymyxa betae. With the view of characterizing the spread as well as the type of the virus in Belgium, more than 100 soils were collected in 2000 and 2001. Using RT-PCR, the Beet necrotic yellow vein virus was detected in 41% of the samples, hence demonstrating a prevalence unknown before. A multiplex RT-PCR technique was developed to assess the co-occurence of the BNYVV along with the Beet soil-borne virus (BSBV) and Beet virus Q (BVQ), two pomoviruses also associated with sugar beet, together with their vector, P. betae. Systematic co-occurence of BNYVV with BSBV and/or BVQ were observed, in samples from different countries like Belgium, Bulgaria, France, Germany, Hungary, Italy, Sweden, The Netherlands and Turkey. The sequencing of the BNYVV RNA-3 P25-encoding region for twenty seven selected Belgian sources confirmed the presence of previously described types A and B, and allowed the distinction of two sub-types named A1 and A2. Variations at the amino acid residues 68 to 70 as well as larges deletions possibly sugar beet genotype-dependant have been evidenced. Comparison of the sequence of RNA-2 P75 open reading frame from ten 10 Belgian sources and sequences from sources originating from France, Kazakhstan, Japan and China confirmed these results. The analysis of nucleotide sequences of capsid protein epitopes and motifs involved in the transmission of the virus by P. betae revealed that they are well conserved. In silico analysis showed that a potential dimerization/dsRNA-binding domain is also present on P75 as well as a possible recombination site. This study showed the range of variations observed for both BNYVV RNA-2 P75 and RNA-3 P25, allowing to precise the types of virus observed in Belgium. Though the rare aggressive P-type was not observed, variations between A-types underlines the potential risk for the emergence of new aggressive types. A discussion points out how to take into account these results with the view of developing an integrated management strategy of the disease.
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Citations
Meunier, A. (2005). Detection of rhizomania in Belgium : diversity and characterization of Beet necrotic yellow vein virus RNAs-2 and -3. https://hdl.handle.net/2078.5/97497