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1.
K. LINDSTEN 《EPPO Bulletin》1989,19(3):531-537
Some experiments with soil-borne beet viruses in cement tubes in a wire netting enclosure are described. It is confirmed that rhizomania (virus + vector) originating from German soil can survive and cause rhizomania in Sweden. Antisera produced in 1987 to one German BNYVV isolate and to one Swedish soil-borne beet virus isolate, 86-109, which is distinct from BNYVV, were used to check ELISA reactions in the tube beets. Positive ELISA was obtained not only for BNYVV but also for the 86-109 virus from tubes with German inoculum. Beets from tubes with Swedish inoculum reacted only against 86-109 antiserum. In 1988-09, ELISA of 118 sugarbeet plants from Öland and 73 from Skåne, collected in 42 different fields with spots resembling rhizomania, showed no or weak reactions against 86-109 antiserum, in contrast to plants collected in 1987. However, after transplanting the field plants into a warm glasshouse and using bait plants it was shown in ELISA and in transmission to Chenopodium quinoa that many of the bait plants became infected with the 86-109 and ‘related viruses’ but not with BNYVV. Viruses of the 86-109 type seem to be common both in Sweden and elsewhere but may escape detection, especially in mixed infections with BNYVV.  相似文献   

2.
Beet necrotic yellow vein virus (BNYVV) is the causal agent of rhizomania, the most serious sugar beet disease worldwide. Since the first finding in Japan in 1969, BNYVV became widespread throughout Hokkaido in a few decades and led to the introduction of Rz1-resistant sugar beet cultivars in the 1990s. Here, we report the historical progress of the BNYVV epidemic in Hokkaido from 1969 to 2019. Previous analysis on samples from 1991 showed that BNYVV isolates were classified into three strains (named O, D, and T) based on the RNA3-encoded p25 gene. The O-type viruses were widely detected in Hokkaido, while the D- and T-type viruses were detected in limited areas. The RNA5, encoding the p26 gene, was initially contained in some D- and O-type isolates but not in any T-type isolates. Interestingly, recent sample analysis revealed that RNA5-containing T-type viruses, seemingly more virulent than the other two strains, were widely detected in Hokkaido. Additionally, a small group of virus isolates harbouring a new p25 gene (named C) was found in limited areas. These results suggest that the T-type viruses, which accompanied RNA5, have been preferentially spread from a limited area to other districts over the last few decades and that this spread might be strongly associated with the recent introduction of Rz1-resistant sugar beet cultivars. BNYVV-positive samples also contained mainly beet soil-borne virus and traces of beet virus Q, both of which are the first to be recorded in Japan.  相似文献   

3.
Horizontal dispersal of beet necrotic yellow vein virus (BNYVV) by means of viruliferous zoospores ofPolymyxa betae was studied in greenhouse experiments. BNYVV was not detected in roots of sugar beet plants grown in silver sand for 4 weeks at a root-free distance of 5 cm from eitherP. betae- and BNYVV-infected plants or BNYVV-infested soil. Spread of BNYVV from inoculum sources in the field was studied in the absence and presence of tillage practices. Active dispersal in combination with root growth from and towards point sources of inoculum contributed only little to horizontal dispersal of viruliferous inoculum and spread of disease during the season, as determined for one soil type, two different years and in the absence of tillage and tread. In the second beet crop after application of inoculum to whole field plots, more BNYVV-infected plants were detected at 2 m than at 8 m distance from the infested plots in the tillage direction. In the third year, disease incidence at 8 m was high and equivalent to that at 2 m.  相似文献   

4.
Using field plots where rhizomania had not previously been detected, different inoculum levels of beet necrotic yellow vein virus (BNYVV) were created by application of infested soil. A susceptible sugar beet cultivar (cv. Regina) was grown for two consecutive years (1988 and 1989), in the presence or absence of drip irrigation. In soil samples taken in spring 1989, the different initial inoculum levels of 1988 could be distinguished using a quantitative bioassay estimating most probable numbers (MPNs) of infective units per 100 g dry soil. The first sugar beet crop resulted in a tenthousandfold multiplication of inoculum of BNYVV (viruliferousPolymyxa betae). Mean MPNs of BNYVV ranged from 0.6 and 7 per 100 g soil for the lowest inoculum level to 630 and 1100 per 100 g for the highest level, in plots without and with irrigation, respectively. In spring 1990, MPNs had again increased. In both years, the initial inoculum level of 1988 had a significant linear effect on log-transformed MPNs of BNYVV determined. Log-transformed MPNs for 1990 and 1989 showed a positive linear correlation, despite a decreasing multiplication ratio at higher inoculum levels. Drip irrigation during one or two years enhanced the increase in MPN of BNYVV, which was reflected by the enhancement of multiplication ratios at all inoculum levels. The totalP. betae population was also higher after growing two irrigated crops than after growing two non-irrigated ones.  相似文献   

5.
Rhizomania, one of the most devastating diseases in sugar beet production, is caused by Beet necrotic yellow vein virus (BNYVV) and transmitted by Polymyxa betae. Previously, disease control was possible by cultivation of sugar beet hybrids carrying a major resistance gene Rz1, which restricts virus accumulation in taproots and suppresses symptom development. Over the last few years, BNYVV strains with four RNA components have arisen, which are able to overcome Rz1‐mediated resistance. All strains described so far possess an A67V amino acid exchange within the RNA3‐encoded P25 pathogenicity factor. In this study, BNYVV was isolated from Rz1 plants, collected in the United Kingdom, the Netherlands and Germany, displaying patches of strong rhizomania symptoms. Sequencing of the coat protein and P25 gene of three isolates showed 100% nucleotide sequence identity and detected AYPR as the P25 tetrad amino acid composition. The ability of this strain to accumulate to higher levels in young plants of Rz1 resistant but not in Rz1 + Rz2 resistant genotypes was initially demonstrated in a greenhouse assay in natural field soil from the Netherlands. This strain was loaded into a virus‐free P. betae population and compared to reference strains. The AYPR strain retained its resistance‐breaking ability in the Rz1 genotypes and displayed replication at a higher rate compared to the Rz1‐resistance‐breaking P type. The strain origin is unclear and it remains speculative whether the occurrence at different geographic locations is the result of independent selection or displacement of infested soil.  相似文献   

6.
Beet necrotic yellow vein virus (BNYVV) is transmitted by Polymyxa betae to sugar beet, causing rhizomania disease. Resistance-breaking strains of BNYVV, overcoming single (Rz1) or double (e.g. Rz1  +  Rz2) major resistance genes in sugar beet have been observed in France and recently in the USA and Spain. To demonstrate if resistance-breaking is dependent on inoculum density, the inoculum concentration of BNYVV and P. betae in soil samples where resistance-breaking had been observed was estimated using the most probable number (MPN) method. The MPN-values obtained displayed highly significant differences with respect to the virus concentration in various soils and did not correlate with the ability to overcome resistance. Virus quantification in susceptible plants demonstrated that soils containing resistance-breaking isolates of BNYVV did not produce higher virus concentrations. The MPN assay was repeated with Rz1  +  Rz2 partially-resistant sugar beets to see if the resistance-breaking is concentration-dependent. There was no correlation between soil dilution and increased virus concentration in Rz1  +  Rz2 plants produced by BNYVV resistance-breaking strains. Determination of the absolute P. betae concentration by ELISA demonstrated that all resistance-breaking soil samples contained elevated concentrations. However, the calculation of the proportion of viruliferous P. betae did not show a positive correlation with the resistance-breaking ability. Finally resistance-breaking was studied with susceptible, Rz1 and Rz1  + Rz2 genotypes and standardised rhizomania inoculum added to sterilised soil. Results from these experiments supported the conclusion that resistance-breaking did not correlate with virus concentration or level of viruliferous P. betae in the soil.  相似文献   

7.
Some partially resistant cultivars varied in their response to beet necrotic yellow vein virus (BNYW), which could be due to the occurrence of different pathotypes. In the past three different types of BNYVV could be identified. Since in the field no consistent cultivar×virus source interaction could be detected, greenhouse trials were carried out under more standardised conditions, starting with a similar initial density of BNYVV. Cultivars with different degrees of resistance varied in their response to various types of beet necrotic yellow vein virus (BNYVV). The B type appeared to be less damaging than the A and P types. The virus content in the tap roots and the ratio of the virus content in tap roots to that in lateral roots were both higher in P type than in A or B type infections indicating that the P type moves more rapidly in the plants than the two other BNYVV types. The percentage of plants in which the virus reaches only a low concentration (less than 56ng/ml of sap) is much lower in P type than in A or B type infections. Frequency distribution diagrams of individual plants showing different BNYVV levels reveal considerable differences between various cultivars.  相似文献   

8.
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is vectored by Polymyxa betae. The disease can only be controlled by growing partially resistant sugar beets, which quantitatively reduce virus replication and spread. None of the known major resistance genes (Rz1, Rz2, Rz3), alone or in combination, are able to prevent BNYVV infection entirely. Here we report for the first time the identification of a Spanish soil, containing an A-type BNYVV with RNA 1-4, displaying Rz1 resistance-breaking abilities comparable to soils from the USA and to those from France containing the French (Pithiviers) P-type BNYVV with RNA 5. A resistance test with several soil samples vs. different sugar beet cultivars was conducted under standardised conditions. Sugar beets were analysed after 12 weeks of greenhouse cultivation for taproot weight, BNYVV and relative P. betae content. The soil samples from Spain, France and the USA produced high virus contents and strong rhizomania symptoms in Rz1 plants, indicative of resistance-breaking abilities. In addition, all resistance-breaking soil samples produced detectable virus concentrations in plant lateral roots of the Rz1 + Rz2 cultivar, and plants grown in the Spanish soil sample also had reduced taproot weight and displayed severe rhizomania disease symptoms. Additionally, the main pathogenicity factor P25, responsible for the formation of BNYVV symptoms, showed high sequence variability in the amino acid tetrad at position 67–70. The results suggest the geographically independent selection of BNYVV resistance-breaking isolates following the uniform cultivation of Rz1-containing sugar beet cultivars.  相似文献   

9.
The plasmodiophoromycete Polymyxa betae is an obligate root parasite that transmits Beet necrotic yellow vein virus (BNYVV), the cause of sugar beet rhizomania disease. Currently, control of this disease is achieved through the use of cultivars with monogenic (Rz1) partial resistance to the virus. To improve the level and durability of this resistance, sources of resistance to the virus vector, P. betae, were sought. Over 100 accessions of the wild sea beet (Beta vulgaris ssp. maritima) from European coastal regions were evaluated for resistance in controlled environment tests. Quantification of P. betae biomass in seedling roots was achieved using recombinant antibodies raised to a glutathione‐s‐transferase expressed by the parasite in vivo. Several putative sources of resistance were identified and selected plants from these were hybridized with a male‐sterile sugar beet breeding line possessing partial virus resistance (Rz1). Evaluation of F1 hybrid populations identified five in which P. betae resistance had been successfully transferred from accessions originating from Mediterranean, Adriatic and Baltic coasts. A resistant individual from one of these populations was backcrossed to the sugar beet parent to produce a BC1 population segregating for P. betae resistance. This population was also tested for resistance to BNYVV. Amplified fragment length polymorphism and single‐nucleotide polymorphism markers were used to map resistance quantitative trait loci (QTL) to linkage groups representing specific chromosomes. QTL for resistance to both P. betae and BNYVV were co‐localized on chromosome IV in the BC1 population, indicating resistance to rhizomania conditioned by vector resistance. This resistance QTL (Pb1) was shown in the F1 population to reduce P. betae levels through interaction with a second QTL (Pb2) found on chromosome IX, a relationship confirmed by general linear model analysis. In the BC1 population, vector‐derived resistance from wild sea beet combined additively with the Rz1 virus resistance gene from sugar beet to reduce BNYVV levels. With partial virus resistance already deployed in a number of high‐yielding sugar beet cultivars, the simple Pb1/Pb2 two‐gene system represents a valuable additional target for plant breeders.  相似文献   

10.
The genome of most Beet necrotic yellow vein virus (BNYVV) isolates is comprised of four RNAs. The ability of certain isolates to overcome Rz1-mediated resistance in sugar beet grown in the United States and Europe is associated with point mutations in the pathogenicity factor P25. When the virus is inoculated mechanically into sugar beet roots at high density, the ability depends on an alanine to valine substitution at P25 position 67. Increased aggressiveness is shown by BNYVV P type isolates, which carry an additional RNA species that encodes a second pathogenicity factor, P26. Direct comparison of aggressive isolates transmitted by the vector, Polymyxa betae, has been impossible due to varying population densities of the vector and other soilborne pathogens that interfere with BNYVV infection. Mechanical root inoculation and subsequent cultivation in soil that carried a virus-free P. betae population was used to load P. betae with three BNYVV isolates: a European A type isolate, an American A type isolate, and a P type isolate. Resistance tests demonstrated that changes in viral aggressiveness towards Rz1 cultivars were independent of the vector population. This method can be applied to the study of the synergism of BNYVV with other P. betae-transmitted viruses.  相似文献   

11.
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is an important disease affecting sugar beet. Control is achieved through planting of resistant varieties; however, following the introduction of Rz1, new pathotypes that overcome resistance have appeared. To understand how BNYVV overcomes resistance, we examined quantitative protein differences during compatible and incompatible interactions when sugar beet is infected with either a traditional A-type strain or with an Rz1 resistance breaking strain. Proteomic data suggest distinct biochemical pathways are induced during compatible and incompatible sugar beet interactions with BNYVV. Pathways including the detoxification of reactive oxygen species, UB/proteasome, and photosynthesis should be studied in more depth to characterize roles in symptom development.  相似文献   

12.
Beet necrotic yellow vein virus (BNYVV) generally has a four-segmented positive-sense RNA genome (RNAs 1–4), but some European and most Asian strains have an additional segment, RNA5. This study examined the effect of RNA5 and RNA3 on different sugar beet cultivars using a Polymyxa-mediated inoculation system under field and laboratory conditions. In field tests, the degree of sugar yield served as an index for assessing the virulence of BNYVV strains. Japanese A-II type isolates without RNA5 caused mostly 15%–90% sugar yield reductions, depending on the susceptibility of sugar beet cultivars, whereas the isolates with RNA5 induced more than 90% yield losses in the seven susceptible cultivars, but small yield losses in one Rz1-resistant and Rizor cultivars. However, a laboratory-produced isolate containing RNA5 but lacking RNA3 caused higher yield losses in Rizor than in susceptible plants, and induced scab-like symptoms on the root surface of both susceptible and resistant plants. In laboratory tests, A-II type isolates without RNA5 had low viral RNA accumulation levels in roots of Rizor and Rz1-resistant plants at early stages of infection, but in the presence of RNA5, viral RNA3 accumulation levels increased remarkably. This increased RNA3 accumulation was not observed in roots of the WB42 accession with the Rz2 gene. In contrast, the presence of RNA3 did not affect RNA5 accumulation levels. Collectively, this study demonstrated that RNA5 is involved in the development of scab-like symptoms and the enhancement of RNA3 accumulation, and suggests these characteristics of RNA5 are associated with Rz1-resistance breaking.  相似文献   

13.
The effect of resistance of sugar beet cultivars to beet necrotic yellow vein virus (BNYVV) on virus content of resting spore clusters of the vectorPolymyxa betae was studied in controlled environments and in naturally infested fields. The total number of resting spore clusters formed in roots of a partially resistant and a susceptible cultivar did not differ when assessed 6 and 12 weeks after inoculation with viruliferous resting spores. Transmission experiments showed that in partially resistant plants, having a low virus content in the roots, the population of resting spores formed was less viruliferous than that in susceptible plants with a high virus content. Consequently, growing a resistant cultivar can be expected to delay the build-up of virus inoculum in soil.In a trial field sampled in 1991, the inoculum potential of BNYVV (most probable number of viruliferousP. betae propagules) in soil was lower after growing a partially resistant cultivar than after growing a susceptible one. On the other hand, in four sites sampled in 1990, inoculum potential in soil was hardly increased by growing sugar beet and was not significantly affected by the cultivar grown.  相似文献   

14.
The host range of beet necrotic yellow vein virus (BNYVV) and Polymyxa betae was determined by growing plants in naturally infested soils from rhizomania outbreaks in England. Apart from Beta vulgaris , plant species infected by BNYVV were included in the families Chenopodiaceae ( Atriplex patula, Chenopodium bonus-henricus, C. hybridum, C. polyspermum and Spinacia oleracea ), Amaranthaceae ( Amaranthus retroflexus ) and Caryophyllaceae ( Silene alba, S. vulgaris, S. noctiflora and Stellaria graminea ). Only P. betae isolates from B. vulgaris, C. polyspermum and S. oleracea were found to be able to transmit BNYVV back to sugar beet. When a range of weed plants from infected fields were tested, none were found to be infected by BNYVV. Therefore, it seems likely that the weed hosts play only a minor role in the spread of rhizomania disease compared to that of sugar beet, other Beta vulgaris crop types or spinach.  相似文献   

15.
Rhizomania is one of the most damaging and widely spread diseases in major sugar beet growing regions of the world. The causal agent, beet necrotic yellow vein virus (BNYVV), is transmitted via the fungus Polymyxa betae, which retains it in the field for years. In this study, an RNA silencing mechanism was employed to induce resistance against rhizomania using intron‐hairpin RNA (ihpRNA) constructs. These constructs were based on sequences of the BNYVV 5′‐untranslated region of RNA‐2 or the flanking sequence encoding P21 coat protein, with different lengths and orientations. Both transient and stable transformation methods produced effective resistance against rhizomania correlated with the transgene presence. Among the constructs, those generating ihpRNA structures with small intronic loops produced the highest frequencies of resistant events. The inheritance of transgenes and resistance was confirmed over generations in stably transformed plants.  相似文献   

16.
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17.
A survey was carried out to investigate the current situation concerning rhizomania disease incidence in sugar beet cultivation of Greece. A systematic field evaluation over locations and years revealed a consistent disease severity pattern according to favourable agroclimatic conditions and pointed to the so far effectiveness of the Rz1 gene-based resistance, as no major disease outbreaks were observed. Molecular analyses aiming at the characterization of the type and genetic diversity of the virus further confirmed the widespread occurrence of BNYVV in the country, as evidenced by RT-PCR amplification of all five known genomic molecules and nested-PCR assays. None of the isolates contained an RNA 5, typically found in pathotype P. On the basis of RFLP patterns, all BNYVV isolates analysed were classified as pathotype A. Sequence determination of the full-length RNA 3-encoded p25 protein, responsible for symptom development, revealed amino acid motifs ACHG/VCHG in the hypervariable region aa67–70. The presence of valine in position 67 did not appear associated with increased pathogenicity and resistance breaking properties, as earlier reported.  相似文献   

18.
The potential for using the composting process to sanitize plant waste infected with one of three plant pathogens was investigated using bench‐scale composting equipment. Two of these pathogens, the potato wart disease fungus Synchytrium endobioticum and Potato spindle tuber viroid (PSTVd) are currently subject to European quarantine regulations. The third, Polymyxa betae, a parasite of sugar beet, is regulated in some European countries when in association with Beet necrotic yellow vein virus (BNYVV), the causal organism of rhizomania disease of sugar beet. Survival of test organisms following various combinations of compost temperature, exposure time and moisture was determined using RNA‐based detection methodology and/or plant‐based bioassays. Mathematically definable relationships between compost treatment (temperature/time) and organism viability were identified for P. betae and S. endobioticum; these give some indication of the practicality of using composting for dealing with infected wastes. However, for PSTVd, the considerable variability in measured susceptibility of the viroid to the composting process meant that no such definable relationship could be determined and further work would be needed to extrapolate to practical situations.  相似文献   

19.
S. A. HILL 《EPPO Bulletin》1989,19(3):501-508
Concern about the introduction of rhizomania to UK heightened when the disease was confirmed in The Netherlands in 1983. A series of precautionary measures supported by legislation was quickly enacted to reduce this risk. Extensive surveys of harvested beet and of growing crops failed to reveal any infection until 1987 when a single isolated outbreak was found near Bury St Edmunds in Suffolk. Plants in the affected field showed typical rhizomania symptoms and laboratory tests confirmed the presence of beet necrotic yellow vein furovirus (BNYVV). Further investigation of isolates from the outbreak field revealed the presence of beet soil-borne furovirus in addition to BNYVV and sometimes both were present in mixed infections. Intensive surveys in the immediate area of the outbreak, both by field inspections of growing crops and by soil bait testing, confirmed infection only in the one field and the margin of the adjacent field. Immediate containment measures were followed by soil sterilization with methyl bromide to minimize the movement of infection from the area. Surveys of beet will continue, but results to date suggest that the distribution of the disease is limited in extent.  相似文献   

20.
Tamada T  Uchino H  Kusume T  Saito M 《Phytopathology》1999,89(11):1000-1006
ABSTRACT Two mutant strains of beet necrotic yellow vein virus (BNYVV) containing deletions in RNA 3 were obtained by single lesion transfers in Tetragonia expansa. The deleted regions encode either 94 or 121 amino acids toward the C-terminal part of the 25-kDa protein (P25). Wild-type and mutant virus strains were inoculated by Polymyxa betae to sugar beet seedlings of susceptible and partially resistant cultivars. No differences were found in virus content in rootlets between mutant and wild-type viruses or between susceptible and resistant cultivars after culture for 4 weeks in a growth cabinet. However, when virus-inoculated seedlings were grown in the field for 5 months, the wild-type virus caused typical rhizomania root symptoms (69 to 96% yield loss) in susceptible cultivars, but no symptoms (23% loss) developed in most plants of the resistant cultivar, and BNYVV concentrations in the roots were 10 to 20x lower in these plants than in susceptible plants. In contrast, the mutant strains caused no symptoms in susceptible or resistant cultivars, and the virus content of roots was much lower in both cultivars than in wild-type virus infections. Wild-type RNA 3 was not detectable in most of the taproots of a resistant cultivar without any symptoms, suggesting that replication of undeleted RNA 3 was inhibited. These results indicate that the P25 of BNYVV RNA 3 is essential for the development of rhizomania symptoms in susceptible cultivars and suggest that it may fail to facilitate virus translocation from rootlets to taproots in the partially resistant cultivar.  相似文献   

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