Nucleotide sequence of beet western yellows virus RNA.

The nucleotide sequence of the genomic RNA (5641 nt) of beet western yellow virus (BWYV) isolated from lettuce has been determined and its genetic organization deduced. The sequence of the 3'terminal 2208 nt of RNA of a second BWYV isolate, obtained from sugarbeet, was also determined and was found to be very similar but not identical to that of the lettuce isolate. The complete sequence of BWYV RNA contains six long open reading frames (ORFs). A cluster of three of these ORFs, including the coat protein cistron, display extensive amino acid sequence homology with corresponding ORFs of a second luteovirus, the PAV isolate of barley yellow dwarf virus (BYDV) (1,2). The ORF corresponding to the putative viral RNA-dependant RNA polymerase, on the other hand, resembles that of southern bean mosaic virus. There is circumstantial evidence that expression of the BWYV RNA polymerase ORF may involve a translational frameshift mechanism. The ORF immediately following the coat protein cistron may be translated by in-frame readthrough of the coat protein cistron amber termination codon. Similar mechanisms have been proposed for expression of the corresponding ORFs of BYDV(PAV) (1).     

Cytology of beet yellows virus infection inTetragonia

Summary This is the third paper of the series dealing with beet yellows virus infection ofTetragonia expansa Murr. It concerns the different kinds of aggregates of virus and the state of the virus particles in the different cells. In vascular parenchyma cells, the aggregates of virus are variable but are consistently intermingled with host cell components. In the sieve elements, the virus may fill the cell lumen solidly either without obvious order or in stacks of layers each as wide as the particle is long. The virus particles appear to be commonly disorganizing in parenchyma cells with degenerating protoplasts and in sieve elements solidly packed with virus. The factors possibly determining the conformation of viruses in plant cells and the terminological problems regarding designations of aggregates of virus particles and other products appearing in infected cells are discussed.This work was supported in part by National Science Foundation grant GB-5506.     

Cytology of beet yellows virus infection inTetragonia

Summary This paper is the second in the series dealing with the ultrastructure ofTetragonia expansa Murr. infected with the beet yellows virus. It considers the relation of the virus to the conducting cells in the phloem and the xylem. Virus particles occurred in mature sieve elements, their amount increasing as the infected leaf became older. In older leaves some sieve elements were completely blocked with virus. Virus particles were seen in pores of sieve plates, in plasmodesmata interconnecting sieve elements and parenchyma cells, and in those between parenchyma cells. Mature and immature tracheary elements also contained virus particles. Presence of inclusions composed of vesicles and virus in some immature tracheary elements may indicate that virus multiplies in these cells. No vesicles and no virus particles were discovered in immature sieve elements.This work was supported in part by National Science Foundation grant GB-5506.     

Effects on Myzus persicae (Sulz.) and transmission of beet yellows virus of applying certain trace elements to sugar beet

Applications of lithium chloride (LiCl), zinc sulphate (ZnSO₄) or nickel sulphate (NiSO₄) to the roots of sugar-beet plants in the glasshouse encouraged settling on the leaves of adult apterae from a clone of Myzus persicae (Sulz.); conversely, treatment with boric acid (H₂B₂O₇) inhibited aphid settling. Larviposition of M. persicae was increased by NiSO₄ and tin chloride (SnCl₂). Viruliferous M. persicae transmitted beet yellows virus (BYV) more efficiently to plants treated with LiCl or H₂B₂O₇ than to those treated with copper sulphate (CuSO₄), ZnSO₄ or SnCl₂. The sulphate and chloride anions of the applied chemicals appeared to have little effect on M. persicae and virus transmission. It is suggested that applications of trace elements to sugar beet affected M. persicae and virus transmission by changing the concentrations of trace elements in the aphids' diet and by altering the metabolism of the leaf tissues in the host plant.     

Studies on beet western yellows virus in oilseed rape (Brassica napus ssp. oleifera) and sugar beet (Beta vulgaris)

Oilseed rape (Brassica napus L. ssp. oleifera) was studied as a potential overwintering host for the sugar-beet yellowing viruses, beet yellows virus (BYV) and beet mild yellowing virus (BMYV), and their principal vector, Myzus persicae. In spring 1982, plants infected with a virus which reacted positively in enzyme-linked immunosorbent assay (ELISA) with BMYV antibody globulin were found in oilseed-rape crops; none of the plants contained virus which reacted with BYV antibody globulin. This virus was subsequently identified as beet western yellows virus (BWYV). No leaf symptoms could be consistently associated with infection of oilseed rape, but the virus was reliably detected by sampling any leaf on an infected oilseed-rape plant. Some isolates from oilseed rape did infect sugar beet in glasshouse tests, but the proportions of inoculated plants which became infected were low. Apparently there is therefore little danger of much direct transmission of BWYV by M. persicae from oilseed rape to sugar beet in spring. BWYV was introduced to and spread within oilseed-rape crops in autumn by M. persicae, and autumn-sown oilseed rape proved to be a potentially important overwintering host for M. persicae. In a survey of 80 autumn-sown crops of oilseed rape in East Anglia, northern England and Scotland in spring 1983, 78 were shown to be extensively infected with BWYV. Experimental plots of oilseed rape with 100% BWYV-infection yielded approximately 13.4% less oil than plots with 18% virus infection, the result of a decrease in both seed yield and oil content.     

Occurrence of beet western yellows virus in sugar beet in Czechoslovakia

The beet western yellows virus (BWYV) was identified in sugar beet plants with leaf yellowing symptoms. When transmitted toSinapis alba L. the virus isolate caused severe symptoms of yellowing and violetting of the interveinal leaf tissue of this plant. By aphidsMyzus persicae (Sulz.) the virus isolate was transmitted toLactuca sativa L.,Raphanus sativus L. var.radicula Pers.,Baphanus sativus L. ssp.sativus L. ap., and toBrassica oleracea L. var.gemmifera DC. InLactuca sativa plants the virus induces a yellowing along with thickenning and brittleness of leaves and with mild dwarfing of the plants. InBaphanus sativus var.radicula andBaphanus sativus ssp.sativus plants it brings about a yellowing of the leaf margins with a change in consistency as was the case in lettuce, and inBrassica oleracea var.gemmifera it causes violet spots on the lower leaf sides. The transmission was proved in repeated experiments by a backtransmission to beet andSinapis alba and further transmission from beet toSinapis alba. The transmission of the virus isolate toVicia faba L.,Datura stramonium L., andPetunia hybrida hort. was unsuccessful. In the course of transmissions the isolate properties did not change. In its host range the virus resembles the Duffus’ strain 3 BWYV, isolated from beet in the U.S.A. This is the first characteristic of an Europian BWYV isolate, as obtained from naturally infected beet plants.     

Detection of beet yellows virus in sugar beet leaves and roots by enzyme-linked immunosorbent assay (ELISA)

Using the enzyme-linked immunosorbent assay (ELISA) beet yellows virus (BYV) could be detected reliably in the leaves of sugar beet andTetragonia expansa Pall. and in the roots of sugar beet. Specifio γ-globulin of BYV antiserum was coupled to horse radish peroxidase by periodate oxidation. Optimum dilutions of antigen (extract from infected leaves) were1: 50 to 1: 200 for BYV detection in sugar beet andT. expansa leaves and1: 2 to 1: 5 for detection in sugar beet roots. Extracts from beet roots are not to be purified by ultracentrifugation, however, by the described method virus can be demonstrated only in 80–90% of naturally infected sugar beet roots. The method is specific, no increase of extinction values was found in healthy or beet western yellows virus infected plants. Presence of virus can be demonstrated by visual as well as photometric evaluation. Results confirmed the suitability of peroxidase application for detection of plant viruses by ELISA.     

Distribution of minerals in quinoa (Chenopodium quinoa Willd.) seeds

The distribution of minerals in quinoa (Chenopodium quinoa Willd.) seed was examined using energy dispersive X-ray microanalysis (EDX) in combination with scanning electron microscopy (SEM). Phosphorus, K, and Mg coincided in localization in embryonic tissue. Since phytin globoids have been known to localize in protein bodies in embryonic cells of quinoa seed, it is thought that P is attributed to phytic acid and that K and Mg form to phytate. Calcium and K were present in the pericarp, where the cell wall is thickly developed, suggesting that these minerals are associated with pectin. Sulfur occurred in embryonic tissues, which would be derived from sulfur amino acid residues of storage proteins concentrated in the tissues. Abrasion of quinoa seeds resulted particularly in decrease in Ca content.     

Leader proteinase of beet yellows virus functions in long-distance transport

The 66-kDa leader proteinase (L-Pro) of the Beet yellows virus (BYV) possesses a nonconserved N-terminal domain and a conserved, papain-like C-terminal domain. Previous work revealed that the N-terminal domain functions in RNA amplification, whereas the C-terminal domain is required for autoproteolysis. Alanine-scanning mutagenesis was applied to complete the functional analysis of L-Pro throughout the virus life cycle. This analysis indicated that the C-terminal domain of L-Pro, in addition to being required for proteolysis, also functions in RNA amplification and that these two functions are genetically separable. Examination of the role of L-Pro in BYV cell-to-cell movement revealed that none of the 20 examined replication-competent mutants was movement defective. In contrast, six of the L-Pro mutations affected the long-distance transport of BYV to various degrees, whereas three mutations completely abolished the transport. Because these mutations were located throughout the protein molecule, both domains of L-Pro function in virus transport. We conclude that in addition to previously identified functions of L-Pro, it also serves as the BYV long-distance transport factor.     

The use of monoclonal antibodies to detect beet mild yellowing virus and beet western yellows virus in aphids

Information on infectivity of the aphids which invade sugar beet root crops each Spring is required for forecasting incidence and providing advice on control of virus yellows. Monoclonal antibodies, produced in the USA to barley yellow dwarf virus (BYDV) and in Canada to beet western yellows virus (BWYV), were used to distinguish between sugar-beet-infecting strains of the luteovirus beet mild yellowing virus (BMYV), and the non-beet-infecting strains of the closely-related BWYV in plant and aphid tissue. Totals of 773 immigrant winged Myzuspersicae and 124 Macrosiphum euphorbiae were caught in water traps in a crop of sugar beet between 25 April and 5 August 1990. Using the monoclonal antibodies and an amplified ELISA, 67%M. persicae and 19%M. euphorbiae were shown to contain BWYV; 8%M. persicae and 7%M. euphorbiae contained BMYV. In studies with live winged aphids collected from the same sugar beet field during May, 25 of 60 M. persicae and two of 13 M. euphorbiae transmitted BWYV to the indicator host plant Montia perfoliata; two M. persicae and two M. euphorbiae transmitted BMYV. In another study three of 65 M. persicae and one of three M. euphorbiae in which only BWYV was detected, transmitted this virus to sugar beet.     

藜麦及其资源开发利用

藜麦Chenopodium quinoa Willd.英文名:quinoa,原产于南美洲安第斯山区,是印加土著居民的主要传统食物,至今已有5 000~7 000多年的利用和种植历史。古代印加人将它称之为"粮食之母"。藜麦在20世纪80年代,被美国宇航局用于宇航员的太空食品。联合国粮农组织认为藜麦是唯一的单一植物即可满足人体基本营养需求的食物,正式推荐藜麦为最适宜人类的完美的全营养食品。本文对藜麦的植物形态、生态特性、营养价值以及在我国种植展望作了综合报道。     

Forecasting the incidence of virus yellows in sugar beet in England

A new forecasting system for virus yellows incidence in sugar beet in the UK has been devised using multiple regression analyses. The forecast equations include data on (1) the previous year's virus incidence, (2) temperature in January and February and (3) the timing of the spring migration of Mytus persicae. Forecasts using the first two of these variables account for 63% of the variance in virus incidence in the main beet growing area of Eastern England and give growers information in time to decide on whether to apply aphicidal granules at drilling to control the vectors of the disease. Forecasts using all three variables account for 87% of the variance in virus incidence and can forewarn growers and the sugar industry of the likelihood of an epidemic. Forecasts for the northern and western regions of the beet growing area are derived from the forecast for the eastern region.     

Early-season predation impacts the establishment of aphids and spread of beet yellows virus in sugar beet

The potential of predators to impact the establishment of aphid vectors and the spread of beet yellows virus in sugar beet was examined. Myzus persicae carrying beet yellows virus (BYV) were released on six interior sites and six edge sites in each of four fields at the end of May. Aphids established at low densities and BYV was spread in circular patches around the infested plants at all sites. The number of diseased plants per patch at the end of September ranged from a field-average of 130 to 210 in the four fields. There was a weak tendency towards better aphid establishment and greater virus spread in fields in less complex landscapes. Edge sites had less virus spread than interior sites in one field, more virus spread in two other fields, and there was no statistically significant difference in the fourth field. In the field where virus spread was lowest at edge sites, we used predator exclosure and direct observation to manipulate and quantify the effects of early season predation. On a warm day in early June, 81% ofAphis fabae exposed to predators on young beet plants disappeared during a 24 h period, compared to 10% of aphids protected by clipcages. Intermediate levels of predator exclusion, allowing aphids to walk away but restricting predator access, showed that predation was responsible for aphid disappearance.Cantharis lateralis L. (Coleoptera: Cantharidae) was the most frequently observed foliar predator (>90%). It was found eating aphids on several occasions. The incidence of predators was 1.8 per plant per h in the field interior and 3.8 per plant per h. near the edge. In the same field, aphids and virus were released in six edge and six interior sites, that were surrounded by 0.5 m high plastic open-top barriers (‘exclosures’). Pitfall trapping inside the barriers reduced potential soil predator densities to ca. one-tenth of the open field level and arrivals of flying predators were reduced. Inside the exclosures, aphid establishment was enhanced, and virus spread at exclosure sites was increased by about 50% compared to open sites. Foliar and pitfall sampling yielded the following predators:Cantharis lateralis, C. rufa L. (Coleoptera: Cantharidae),Coccinella septempunctata L.,C. undecimpunctata L. (Coleoptera: Coccinellidae),Pterostichus cupreus (L.),Harpalus rufipes (de Geer),Patrobus atrorufus (Strom),Trechus quadristriatus (Schrk.),Bembidion lampros (Herbst) (Coleoptera: Carabidae). In a laboratory no-choice trial (with 10M. persicae /day offered), each of these species ate aphids with consumption rates varying from 1.7 to 9.2 aphids/day. The results show that early predation substantially impacted aphid establishment in one field, and resulted in reduced virus spread. Results in the other fields show that these results cannot be easily generalized.     

金藜麦耐盐性分析及营养评价

对我国沿海地区新收集种质资源金藜麦(Chenopodium quinoa Willd.)进行了耐盐性及营养品质评价。结果表明:金藜麦在对盐胁迫相对敏感的芽期和苗期表现出相对较高的耐盐性;子粒蛋白质含量为14.2%,蛋白营养价值优于牛奶以及小麦、水稻、玉米、大豆等作物;子粒中富含维生素B、E等以及钙、锰、铁、铜、锌等矿质元素,特别是钙含量高达190.16 mg/100g,是小米钙含量的35倍;且金藜麦子粒含有丰富的必需脂肪酸,如亚油酸(3.58 g/100g)和亚麻酸(0.44 g/100g),天然抗氧化剂维生素E含量为7.66 mg/100g。这些研究结果表明,新收集的金藜麦种质资源具有较高的营养价值和耐盐性,将为我国藜麦研究和种植提供重要的种质资源。