November 29, 2005
From: American Phytopathological Society, Plant Disease Notes, December 2005 [edited]
<http://www.apsnet.org/pd/searchnotes/2005/PD-89-1359B.asp>

First report of beet virus Q on sugarbeet in Iran
Sh. Farzadfar and R. Pourrahim, Department of Plant Virology, Plant Pests and Diseases Research Institute, P.O. Box 19395-1454, Tehran, Iran; A. R. Golnaraghi, Department of Plant Protection, Science and Research Campus, Islamic Azad University, P.O. Box 14515-775, Tehran, Iran; and A. Ahoonmanesh, Department of Plant Pathology, Esfahan University of Technology, Esfahan, Iran. Plant Dis. 89:1359, 2005; published on-line as
DOI: 10.1094/PD-89-1359B. Accepted for publication 6 Sept 2005.

During the 2001 growing season, a survey was conducted to determine the incidence of Beet necrotic yellow vein virus (BNYVV), Beet soilborne virus (BSBV), and Beet virus Q (BVQ) in Iran. A total of 2816 random and 76 samples with rhizomania were collected from 131 fields in the main sugar beet cultivation areas of 13 provinces in Iran.

All samples were tested using a tissue-blot immunoassay (TBIA) with commercial BNYVV (As-0799.1/CG6-F4), BSBV (As-0576.1), and SBV/BVQ (As-0576.2) antisera provided by S. Winter (DSMZ, Braunschweig, Germany). For randomly collected samples, the highest incidence of virus infection was found for BNYVV (52.3 percent), followed by BSBV (9.5 percent) and BVQ (1.5 percent). Co-infection of BNYVV with BSBV or BVQ was 6.6 percent and 0.9 percent, respectively. Infection with both BSBV and BVQ was found in 16 (0.6 percent) samples. In addition, 0.4 percent (12) of the samples were infected with all 3 viruses.

Our results indicated the presence of BVQ in samples from 10 fields located in Azarbayejan-e-gharbi, Esfahan, Fars, Kermanshah, Khorasan, Lorestan, and Semnan provinces of Iran, with or without rhizomania-like symptoms. The presence of viruses was confirmed using reverse transcription-polymerase chain reaction (RT-PCR) of RNA from 81, 19, and 14 root samples with positive reaction in TBIA to BNYVV, BSBV, and BVQ, respectively, with
previously described primers (3,4). The primers specifically amplified fragments of 501 bp, 602 bp, 399 bp, and 291 bp of the BNYVV RNAs 1 and 4, BSBV RNA-2, and BVQ RNA-1, respectively.

Our results indicated that the samples tested were also positive using RT-PCR. The putative vector for BNYVV, BSBV, and BVQ, _Polymyxa betae_, was also detected in 161 samples (from 127 fields) by amplification of a 170-bp fragment of the _P. betae_ repetitive EcoRI-like fragments using previously described primers (4). RT-PCR products from 72 BNYVV-positive sugar beet root samples from 58 fields that also gave positive reactions in TBIA were analyzed using single-strand conformation polymorphism (SSCP) as previously described with extracts from root beards of the susceptible sugar beet cvs. OPUS and IC1 grown in the soils infested with BNYVV types A and B (provided by A. Meunier, Unite de Phytopathologie-UCL-AGRO-BAPA, Louvain-la-Neuve, Belgium) as positive controls (3).

The patterns obtained with SSCP were uniform and showed widespread occurrence of BNYVV type A in almost all provinces surveyed. The fragments obtained for BNYVV RNAs 1 and 4 of an isolate from Qazvin (BNQ1) were
sequenced (GenBank Accession Nos. AY703452 and AY703455) and compared with other sequences available in GenBank using Clustal W, which revealed 99.3 and 99.6 percent identity with the Japanese S (D84410) and Italian type A (AF197552) isolates, respectively.

The economic importance of BVQ and its interactions with other sugar beet soilborne viruses remains a matter of debate. BNYVV and BSBV have been previously reported from Iran (1,2).

To our knowledge, this is the 1st report of the natural occurrence of BVQ in sugar beets in Iran.

References:
(1) Sh. Farzadfar et al. Plant Dis. 86:187, 2002.
(2) K. Izadpanah et al. Iran. J. Plant Pathol. 32:155, 1996.
(3) R. Koenig et al. J. Gen. Virol. 76:2051, 1995.
(4) A. Meunier et al. Appl. Environ. Microbiol. 69:2356, 2003

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[The gist of this piece is that _Polymyxa betae_ (Pb) is thoroughly established in Iranian soils. During a survey on soilborne viruses in sugarbeet, 2 viruses with rod-shaped particles were isolated, in addition to beet necrotic yellow vein furovirus (BNYVV). The Ahlum isolate proved to be serologically closely related to beet soilborne virus (BSBV), which was 1st described in England and has since been found in all sugarbeet growing areas worldwide. Recent data revealed that the 2nd serotype (Wierthe) should be considered a distinct virus species named Beet virus Q (BVQ). These 2 pomoviruses are also transmitted by Pb. Although their contribution to rhizomania remains a matter of debate, it is not uncommon to find them associated with rhizomania-infested fields. Moreover, occurrence of 3 different viruses, transmitted by a similar vector, within a single sugar beet raises questions regarding the epidemiology of rhizomania syndrome.

Virus particle of the Genus _Pomovirus_ are morphologically similar to other rod-shaped viruses, i.e. in the genera _Furovirus_, _Pecluvirus_, _Hordeivirus_, _Tobravirus_, _Tobamovirus_ and _Benyvirus_. The derived amino acid sequences for the putative RNA 1-encoded proteins also suggest relatively close relationships to the genera _Furovirus_, _Pecluvirus_, _Hordeivirus_ and somewhat more distant ones to the genus _Tobamovirus_. Affinities not only to genera _Pecluvirus_, _Hordeivirus_ and _Benyvirus_, but also to genera _Potexvirus_ and _Carlavirus_, are suggested by the derived amino acid sequences of their triple gene block-encoded proteins. The folding properties of the 5-UTRs of their genomic RNAs suggest affinities to the genus _Tymovirus_, those of the 3'-UTRs to genera _Tymovirus_, _Tobamovirus_ and _Hordeivirus_.

BVQ was isolated together with BNYVV from a sugarbeet tap root obtained from a rhizomania field near Braunschweig, Germany. Like BNYVV, it causes local lesions on _C. quinoa_, but those of BVQ appear about 5 days earlier after mechanical inoculation. They both have a more irregular shape with a tendency to spread along the veins. Systemic infections of _C. quinoa_ were not observed. BVQ and BNYVV were separated from originally mixed infections by single lesion transfers. BVQ could not be transmitted to _Nicotiana benthamiana_ or _Nicotiana clevelandii_, nor could it be re-transmitted by mechanical means to sugarbeet leaves or roots. It is possible that this isolate can be transmitted only by a soilborne vector, or it may have lost its infectivity for beets after several years of cultivation on _C. quinoa_. BVQ proved to be extremely difficult to purify; nevertheless, an
antiserum was obtained with a partially purified virus preparation which, despite some additional reactivity with constituents of healthy _C. quinoa_, could be used in immunocapture RT-PCR, immunosorbent electron microscopy (IEM) and the immunoelectron microscopical decoration test.

BVQ has been repeatedly observed by IEM repeatedly during the past decade in sugarbeet samples from various areas in Germany and abroad, indicating that it is widely spread. The most frequently detected virus was BSBV,
followed by BVQ and then BNYVV. In no case was BVQ found alone. BVQ has been found in Bulgaria, Belgium, France, Germany, Hungary, Italy, and the Netherlands, but not from Turkey. From an epidemiological point of view, although the role of BNYVV in rhizomania syndrome is well established, there is controversy regarding the role of Pb in seedling growth and in severe stunting of sugar beet, and still others reject the notion that Pb
has any effect on sugar beet growth. The controversy is emphasized by the study of 2 other viruses, which were possibly undetected in the Pb used in previous studies.

Our study confirms the ubiquitous presence of BSBV in sugar beet fields. It was present in more than 80 percent of the analyzed samples, with a frequency much higher than that observed for BNYVV. The limited number of
samples tested does not preclude further detection possibilities on different sugar beet cultivars or on different species. In all cases, BNYVV occurred with BSBV and often with BVQ as well. It would be very interesting to check a possible interaction of pomoviruses with BNYVV.

Links:
<http://vir.sgmjournals.org/cgi/reprint/79/8/2027>
<http://aem.asm.org/cgi/content/full/69/4/2356>
<http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/fs_pomov.htm>
- Mod.DH]

[see also in the archive:
2003
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Rhizomania, sugar beet - USA (Great Lakes region) 20030210.0356
Rhizomania, sugar beet - Egypt 20030719.1769
2002
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Rhizomania, sugar beet - USA (Oregon, Washington) 20020124.3369
Beet viruses, sugar beet - Syria 20021218.6089
2001
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Beet pomovirus Q, sugar beet - Belgium 20011219.3065]