Weeds as alternative hosts for BSBV,BNYVV, and the vector Polymyxa betae (German isolate)

Journal of Plant Diseases and Protection - When grown in contaminated soil, several weed species proved to be alternative hosts for the Beet necrotic yellow vein virus (BNYVV), the Beet soil-borne...     

Distribution and properties of geographically distinct isolates of sugar beet yellowing viruses

From a total of 261 yellow sugarbeet leaves collected from 10 countries representing three continents, the incidence and distribution of strains of Beet mild yellowing virus (BMYV), Beet chlorosis virus (BChV) and Beet yellows virus (BYV) were analysed using serological and molecular methods. BMYV was found in all countries except Greece, and more frequently in the northern and western areas of Europe, whereas BYV predominated in Turkey, Spain, Greece, the USA and Chile. BChV, originally found in the USA and the UK in 1989, was identified in France, Spain, the Netherlands and Chile. Nine sugar beet poleroviruses, plus a reference isolate of Turnip yellows virus (TuYV, syn. Beet western yellows virus ), were further characterized and compared. Isolates obtained from sugar beet infected this species, but not oilseed rape or lettuce; all isolates except one infected Capsella bursa-pastoris . The coat-protein sequences of these isolates were highly similar, with the consensus sequence representing 89% of nucleotide residues. Within the coat-protein gene, two regions were identified that could represent specific epitopes to which monoclonal antibody BYDV-PAV-IL-1 could bind; this antibody is used to distinguish beet poleroviruses in ELISA. Comparison of the sequences at the 5' end showed that sequence homology existed only between isolates with the same host range. The first sequence data of polerovirus isolates from Chile are presented, showing that the coat protein and the 5' end of their genomes are highly similar to those of BMYV isolates found in Europe. Chilean polerovirus isolates may have been imported from the northern hemisphere in sugar beet breeding material.     

Biological, serological, and molecular variability suggest three distinct polerovirus species infecting beet or rape

Yellowing diseases of sugar beet can be caused by a range of strains classified as Beet mild yellowing virus (BMYV) or Beet western yellows virus (BWYV), both belonging to the genus Polerovirus of the family Luteoviridae. Host range, genomic, and serological studies have shown that isolates of these viruses can be grouped into three distinct species. Within these species, the coat protein amino acid sequences are highly conserved (more than 90% homology), whereas the P0 sequences (open reading frame, ORF 0) are variable (about 30% homology). Based on these results, we propose a new classification of BMYV and BWYV into three distinct species. Two of these species are presented for the first time and are not yet recognized by the International Committee on Taxonomy of Viruses. The first species, BMYV, infects sugar beet and Capsella bursa-pastoris. The second species, Brassica yellowing virus, does not infect beet, but infects a large number of plants belonging to the genus Brassica within the family Brassicaceae. The third species, Beet chlorosis virus, infects beet and Chenopodium capitatum, but not Capsella bursa-pastoris.     

Curly top survey in the Western United States

Curly top in sugar beet continues to be a challenging disease to control in the western United States. To aid in development of host resistance and management options, the curtovirus species composition was investigated by sampling 246 commercial fields along with nursery and field trials in the western United States. DNA was isolated from leaf samples and the species were identified using species-specific polymerase chain reaction primers for the C1 gene. Amplicons from 79 isolates were also sequenced to confirm identifications. Beet severe curly top virus (BSCTV) and Beet mild curly top virus (BMCTV) were widely distributed throughout the western United States, while only a few isolates of Beet curly top virus (BCTV) were found. In phylogenetic analysis, BSCTV, BMCTV, and BCTV isolates formed distinct groups in the dendrogram. Seven isolates not amplifiable with species-specific primers did amplify with curly top coat protein primers, indicating novel curtovirus species or strains may be present. Given the wide host range of the viruses responsible for curly top, frequent co-infections, and genetic diversity within and among species, establishing better host resistance, and controlling curly top will continue to be a challenge.     

Host range and molecular analysis of Beet leaf yellowing virus,Beet western yellows virus-JP and Brassica yellows virus in Japan

Beet western yellows virus (BWYV; genus Polerovirus, family Luteoviridae) is one of the most important viruses causing yellowing disease of many field and vegetable crops. This study isolated different poleroviruses from sugar beet, spinach, radish and brassica in Japan, and identified them as BWYV-JP, Beet leaf yellowing virus (BLYV), Brassica yellows virus (BrYV) and BrYV-R (radish strain) based on host range and molecular analysis. Among over 100 plant species from 19 families inoculated with the vector Myzus persicae, about half of the species in 13 families were infected with some of these viruses. BLYV shared a similar host range to Beet mild yellowing virus (BMYV). These had a much more limited host range than BWYV-JP, which resembled BWYV-USA. The host range of BrYV was similar to that of Turnip yellows virus (TuYV). Phylogenetic analyses at the 5′ portion (replication-related gene) of the genome showed that BLYV, BMYV, BWYV (-JP and -USA) and Cucurbit aphid-borne yellows virus (CABYV) formed one large group, whereas BrYV and TuYV were grouped together. BLYV and BWYV were most closely related to each other, and were more closely related to CABYV than to BMYV. However, at the 3′ end (coat protein gene), BLYV and BWYV-JP formed a distinct group, separated from the BrYV group, which in turn was more closely related to BWYV-USA, BMYV, TuYV and Beet chlorosis virus, a group originating from outside Asia. Thus, this study presents host range differences and phylogeographical relationships of BWYV-like poleroviruses that are distributed worldwide.     

Antagonistic effects of natural Pseudomonas putida biotypes on Polymyxa betae Keskin,the vector of Beet necrotic yellow vein virus in sugar beet

Journal of Plant Diseases and Protection - This in vivo study investigated the ability of fluorescent Pseudomonas spp. to suppress Polymyxa betae, a vector of Beet necrotic yellow vein virus...     

Beet necrotic yellow vein virus genome reassortments in a resistant sugar beet variety showing–in a small area in France–strong rhizomania symptoms

Journal of Plant Diseases and Protection - The genome composition of Beet necrotic yellow vein virus (BNYVV) was analysed in rootlets of field-grown sugar beets belonging to a variety which in...     

Spinach curly top virus: A Newly Described Curtovirus Species from Southwest Texas with Incongruent Gene Phylogenies

ABSTRACT A curtovirus associated with a disease of spinach was isolated in southwest Texas during 1996. Disease symptoms included severe stunting and chlorosis, with younger leaves curled, distorted, and dwarfed. Viral DNA was purified and an infectious clone obtained. Agroinoculation using a construct bearing full-length tandem repeats of the cloned viral genome resulted in systemic infection of species in six of seven plant families tested, indicating that the virus has a wide host range. Symptoms produced in spinach agroinoculated with cloned viral DNA were similar to those observed in the field. Viral single-stranded and double-stranded DNA forms typical of curtovirus infection were detected in host plants by Southern blot hybridization. The complete sequence of the infectious clone comprised 2,925 nucleotides, with seven open reading frames encoding proteins homologous to those of other curtoviruses. Complete genome comparisons revealed that the spinach curtovirus shared 64.2 to 83.9% nucleotide sequence identity relative to four previously characterized curtovirus species: Beet curly top virus, Beet severe curly top virus, Beet mild curly top virus, and Horseradish curly top virus. Phylogenetic analysis of individual open reading frames indicated that the evolutionary history of the three virion-sense genes was different from that of the four complementary-sense genes, suggesting that recombination among curtoviruses may have occurred. Collectively, these results indicate that the spinach curtovirus characterized here represents a newly described species of the genus Curtovirus, for which we propose the name Spinach curly top virus.     

Distribution and phylogenetic analysis of the 3′UTR and coat protein gene of Iranian Beet black scorch virus

Journal of Plant Diseases and Protection - Beet black scorch virus (BBSV) was surveyed in major sugar beet cultivation areas in Iran in 2008–2013 growing seasons. A total of 148 out of 308...     

甜菜夜蛾的生物防治及其展望

近些年来,甜菜夜蛾在我国淮河以南地区蔬菜等作物上频繁发生,已成为一种灾害性害虫。由于在无公害蔬菜生产中对化学农药残留要求高,因此生物防治受到人们的广泛关注与重视。本文综述了甜菜夜蛾生物防治进展以及对生物防治的展望。     

Molecular characterization and detection of European isolates of Soil-borne wheat mosaic virus

Sequencing of a recently identified isolate of Soil-borne wheat mosaic virus (SBWMV) from the UK confirmed its identity as a European strain of the species and provided further evidence for taxonomic divisions in the group. Two RT–PCR protocols were developed for the detection of all SBWMV strains and for the specific detection of the European SBWMV strain, and were tested successfully on 21 isolates of SBWMV from a range of countries. Both protocols worked well using either purified total RNA in one- or two-step RT-PCR, or immunocapture (IC) RT–PCR. The sensitivity of IC RT-PCR was 100 times greater than ELISA. Neither set of primers produced any PCR product with either Wheat spindle streak mosaic virus or Wheat yellow mosaic virus which are frequently associated with SBWMV, or with the related viruses Indian peanut clump virus , Potato mop-top virus , Beet soil-borne virus and Beet necrotic yellow vein virus . This new diagnostic protocol will improve disease management by enabling correct identification of the causal pathogen and earlier detection than is possible serologically.     

Distribution and Rate of Movement of the Curtovirus Beet mild curly top virus (Family Geminiviridae) in the Beet Leafhopper

ABSTRACT A polymerase chain reaction (PCR)-based method for the detection of the curtovirus Beet mild curly top virus (BMCTV, previously named the Worland strain of Beet curly top virus) was developed and used to investigate the BMCTV-beet leafhopper interaction. Using PCR and a BMCTV-specific primer pair, an approximately 1.1-kb BMCTV DNA fragment was amplified from adult leafhoppers and from the organs involved in circulative transmission: the digestive tract, hemolymph, and salivary glands. The temporal distribution of BMCTV in the leafhopper was determined using insects given acquisition access periods (AAPs) ranging from 1 to 48 h on BMCTV-infected shepherd's purse plants. BMCTV was detected in the digestive tract after all AAPs, in the hemolymph after AAPs of 3 h or greater, and in the salivary glands after AAPs of 4 h or greater. The amount of virus detected in the hemolymph and salivary glands increased with AAP length. The virus persisted for up to 30 days in leafhoppers (given a 3-day AAP on BMCTV-infected plants) maintained on corn plants, a nonhost for BMCTV, but transovarial transmission was not detected. These results are consistent with a persistent but nonpropagative mode of circulative transmission.     

Aphid transmissibility of different European beet polerovirus isolates

Different field isolates of the ‘beet poleroviruses’ Beet mild yellowing virus (BMYV) and Beet chlorosis virus (BChV) (genus Polerovirus, family Luteoviridae) collected in France and Poland were evaluated for transmissibility from and to sugar beet plants by different aphid species. In general, both BMYV and BChV were efficiently transmitted by Myzus persicae and by a French clone of Macrosiphum euphorbiae. In contrast, transmissibility of the two poleroviruses by an English clone of M. euphorbiae was evidently weaker, although the aphid samples contained the virus as demonstrated by RT-PCR. None of the BMYV or BChV isolates was transmitted by Aphis fabae or Myzus ascalonicus. In attempting to correlate biological properties with molecular variations, the RT proteins were sequenced. Some amino acid point variations, presumably affecting aphid transmissibility, were identified.     

A generic RT‐PCR assay for the detection of Luteoviridae

This study, using RT‐PCR, is the first comprehensive assessment since 1991 of a generic detection method for the Luteoviridae. Thirteen Luteoviridae species were detected using three separate sets of low‐degeneracy generic primers with RT‐PCR to amplify 68‐, 75‐ and 129/156‐bp regions of the Luteoviridae coat‐protein gene. Species detected include all members of the genus Luteovirus [Barley yellow dwarf virus (BYDV)‐PAV, BYDV‐PAS, BYDV‐MAV (129 and/or 156 bp amplicons), Soybean dwarf virus, Bean leafroll virus (68 bp amplicon)] and eight of nine species from the genus Polerovirus [Beet western yellows virus, Beet chlorosis virus, Beet mild yellowing virus, Turnip yellows virus, Potato leafroll virus, Cucurbit aphid‐borne yellows virus, Cereal yellow dwarf virus‐RPV (68‐bp amplicon) and Sugarcane yellow leaf virus (75‐bp amplicon)]. These primers were not able to detect Carrot red leaf virus, Sweet potato leaf speckling virus (both belong to unassigned Luteoviridae) and Pea enation mosaic virus‐1 (genus Enamovirus). A synthetic positive control containing all primer sequence priming sites was designed to facilitate this method as a generic tool for use with a variety of host plants. The Luteoviridae primers described in this study present a simple infection‐detection tool of benefit to biosecurity authorities in nursery‐stock surveillance, disease management or outbreak prevention, and may also be useful in detection of as‐yet undiscovered species within the Luteovirus and Polerovirus genera.     

Molecular characterisation of <Emphasis Type="Italic">Rice stripe necrosis virus</Emphasis> as a new species of the genus <Emphasis Type="Italic">Benyvirus</Emphasis>

The complete nucleotide sequences of RNAs 1 and 2 of Rice stripe necrosis virus (RSNV) were determined and compared to the corresponding genomes of all sequenced, rod-shaped plant viruses. The genome organisation of RSNV RNA1 and RNA2 is nearly identical to that of Beet necrotic yellow vein virus (BNYVV) and Beet soil-borne mosaic virus (BSBMV), definitive species of the genus Benyvirus. As demonstrated for BNYVV and BSBMV, the RNA1 of RSNV also encodes a single ORF with putative replicase-associated motifs, which distinguishes benyviruses from all other viruses possessing rod-shaped particles. As described for BNYVV, RNSV RNA-2 also contains six ORFs: the capsid protein gene, the read-through protein gene, a triple gene block gene that codes for three different proteins, and a 17 kDa cysteine-rich protein. RNAs 3 and 4 (or 5 in the case of BNYVV), identified in natural infections of BNYVV and BSBMV, were not detected in any of the 44 RSNV cDNA clones obtained in this investigation. Nevertheless, phylogenetic and amino comparative acid sequence analyses demonstrated that RSNV is more closely related to BNYVV and BSBMV than to any other rod-shaped plant virus characterised to date.     

The occurrence of beet pseudo-yellows virus in England

Beet pseudo-yellows virus (BPYV) has been identified in England for the first titne, in lettuce, following transmission by the greenhouse whitefly ( Trialeurodes vaporariorum ) to healthy plants. Infected plants had leaves with severe interveinal chlorosis and slight downward curling, and were gerterally smaller than healthy plants. Indirect ELISAs with an antiserum raised against the Californian isolate of BPYV were positive with extracts produced from infected plants. Infected but not healthy plants contained a single species of double-stranded RNA of about 7.5 × lO⁶Da, a size similar to that found with beet yellows virus, the type member of the closterovirus group.     

甜核·苏云菌对水稻二化螟的防效

为减少化学农药在稻田的使用,在四川新都进行了2种生物农药混配制剂〖CD*2〗甜核·苏云菌防治水稻二化螟试验和示范。结果表明：采用PB 16手动喷雾器防治试验,甜核·苏云菌对水稻二化螟的枯心、白穗和虫伤株的防治效果分别为98.0%、99.56%和99.29%,采用东〖CD*2〗18机动喷雾器喷雾示范,甜核·苏云菌对二化螟的枯心、白穗和虫伤株的防治效果分别为96.44%、97.83%和96.69%,效果良好,可以在大面积生产中推广应用。     

Rhizomania disease of sugar beet in England

Rhizomania disease was first detected in the UK in 1987, in a single crop in Suffolk. Affected plants had pale leaves, often upright, narrow and rolled; roots were small, often with constrictions, warty outgrowths, proliferation of fibrous roots, and vascular staining. Disease occurred in strips at right angles to one another, parallel with directions of cultivation, suggesting that the previous beet crop had also been infected. Beet necrotic yellow vein virus was detected by ELISA, by electron microscopy, and by transmission to indicator species. It was sometimes associated with beet soil-borne virus. The affected crop was destroyed with herbicide. No other outbreaks were detected in subsequent surveys of crops in 1987.     

First Record of A and B Type Beet necrotic yellow vein virus in Sugar Beets in Sweden

Natural infections of sugar beet with Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania, have been detected for the first time in Sweden in two small areas, one on the island of Öland and one in the Southeastern part of Scania. Single strand conformation polymorphism analyses of PCR products revealed that the infections on Öland were produced by A type BNYVV, whereas those in Scania were caused by the B type. This suggests that BNYVV has been introduced into Sweden at least twice. Alternatively, the virus may have invaded sugar beet from unknown native hosts. BNYVV RNA 5 was not detected in the samples investigated.     

Development of a recombinant antibody ELISA test for the detection of Polymyxa betae and its use in resistance screening

An ELISA test was developed for the quantitative detection of the obligate parasite Polymyxa betae , the vector of Beet necrotic yellow vein virus (BNYVV), in infected sugarbeet roots. The test used monoclonal and polyclonal antibodies raised to a recombinantly expressed glutathione-S-transferase (GST) from P. betae . A close correlation was found between the number of P. betae zoospores in serially diluted suspensions and absorbance values in the ELISA test. Time-course studies of plants grown in naturally infested soils in controlled environment tests demonstrated the value of the ELISA test in screening for P. betae resistance. In preliminary tests, P. betae -resistant accessions of the wild sea beet ( Beta vulgaris ssp. maritima ), which might be used to restrict the transmission of BNYVV, were identified.