Beet Yellows Virus Research Articles

Transmission of Beet Yellows and Beet Mosaic Viruses by Noncolonizing Aphid Vectors

A late Rhopalosiphum padi (L.), Acyrthosiphon kondoi Shinji, and Diuraphis no:xia (Mordvilko) transmitted beet yellows virus (BYV) and beet mosaic virus (BMV) in laboratory tests. In single probe acquisition tests, A. kondoi! and D. no:xia failed to transmit BMV, but both transmitted the virus successfully in free-choice arena tests. A. kondoi and D. no:xia are new vectors of beet yellows and beet mosaic virus. None of the three aphids colonize sugar beets but may be important in BYV and BMV epidemiology.

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.

The effects of yellowing viruses on yield of sugar beet in field trials, 1985 and 1987

SummaryThe separate effects of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) on yield of sugar‐beet cultivars inoculated at different growth stages were assessed in field trials in 1985 and 1987. Early or mid‐season inoculation decreased sugar yield by up to 47% for BYV, and up to 29% for BMYV. Infections after the end of July had no significant effect on yield. Both viruses caused significant increases in the juice impurities sodium, potassium and amino‐nitrogen after infecting plants early in the season. Yield losses associated with infection were determined by the causative virus, the time of infection, and susceptibility of the sugar‐beet cultivars.

Retrospective estimation of the data of infection with beet yellowing viruses in sugar-beet under field conditions

Sugar-beet plants, infected with beet yellows virus (BYV, closterovirus group) or beet mild yellowing virus (BMYV, luteovirus group) develop symptoms on the inoculated leaves on which aphids infected the plant. Symptoms develop also on the systemically-infected leaves to which virus has been transported via the phloem. Systemic infection occurs in the leaves which have just, or not yet appeared at the moment of infection of the plant. All other, older leaves remain uninfected. The infection-date can be estimated by assessing the date of appearance of the oldest systemicallyinfected leaf of a plant. This approach was tested in the field and gave good results.

The incubation period of beet yellowing viruses in sugar-beet under field conditions

In three years field trials, the incubation period, i.e. the time between infection and the appearance of symptoms, of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) increased with later infection during the growing season. The incubation period of BYV, a closterovirus, increased from 3 weeks in young plants infected before canopy closure, to 9 weeks in old plants infected in August. The incubation period of BMYV, a luteovirus, increased from 4 to 5 weeks in young plants to 9 weeks in old plants. Symptoms were observed c. one week earlier on the inoculated leaves than on those infected systemically, except on young BYV-infected plants. On these plants, symptoms developed in 3 weeks on both leaf types.The incubation period decreased at increasing temperature, a fixed temperature sum being required for the development of symptoms on plants of a certain age. This temperature sum increased with plant age. Symptom development was related to leaf growth; the systemic symptoms appeared after the infected leaves attained their final size. Young, expanding leaves did not show symptoms. Thus the development of symptoms seems to be related to physiological conditions occurring only in full-grown leaves. A low rate of leaf expansion may constitute the underlying reason for the long incubation period of virus symptoms in old plants and at low temperatures.The incubation period was not substantially affected by: (1) the number ofMyzus persicae used to inoculate the plants, (2) the number of leaves inoculated, (3) the development stage of the inoculated leaf and (4) the source plant of BMYV, beet or shepherd's-purse,Capsella bursapastoris. The incubation period can be used to obtain rough estimates of the infection-date of individual plants, given the date on which symptoms appear.

Detection of beet yellow stunt virus in England

Detection of beet yellow stunt virus in England

Virion RNA of Beet Yellows Closterovirus: Cell-free Translation and Some Properties

SUMMARY Virion RNA of beet yellows virus (BYV) is a messenger-sense RNA of about 14500 nucleotides containing no poly(A) or covalently linked protein. In υitro translation of BYV RNA yielded a prominent polypeptide of M r 250000, and some lighter products. None of the translation products was found to be immunoprecipitable with anti-BYV γ-globulins. The synthesis of all the BYV RNA-directed polypeptides was blocked by the cap analogue m7Gpp, thus suggesting the presence of a cap structure at the 5′ end of virion RNA.

Purification and Partial Characterization of Beet Yellow Stunt Virus

Purification and Partial Characterization of Beet Yellow Stunt Virus

Effect of dodecanoic acid on the colonisation of sugar beet by aphids and the secondary spread of virus yellows

SUMMARYThe effect of dodecanoic acid, a behaviour‐controlling chemical which alters aphid feeding behaviour and virus transmission efficiency, was studied under field conditions. In a first experiment, dodecanoic acid reduced the level of natural colonisation of sugar beet by Aphis fabae. A second experiment revealed no significant influence of dodecanoic acid on the secondary spread of the semi‐persistent beet yellows virus and the persistent beet mild yellowing virus.

Studies of the distribution of yellowing viruses in the sugar beet root crop from 1981 to 1984

Two viruses, beet yellows virus (BYV) and beet mild yellowing virus (BMW), cause yellowing of sugar beet, their principal vector being Myzus persicae. Although the viruses have different properties which are likely to influence their spread within root crops, for the purpose of control they have been treated in the past as one disease. This paper describes the results of a crop survey carried out in co‐operation with agricultural staff of British Sugar plc from 1981 to 1984 in which leaves from plants with symptoms of virus yellows were tested by enzyme‐linked immunosorbent assay (ELISA) for BYV and BMW. The two viruses differed in their incidence and distribution within the national sugar beet root crop; BMW was the main cause of yellowing and occurred in all parts of the growing region while BYV, which has the more severe effect on yield, was more limited in distribution. The survey located areas in southern East Anglia which are at greatest risk from BYV infection. The possible need to modify control measures depending on which virus threatens to invade the crops is discusssed. A high proportion of leaves visually identified as infected was found to contain neither BYV nor BMYV, emphasizing the difficulties of identifying virus‐infected plants by field symptoms.

The combined use of mineral oils and pyrethroids to control plant viruses transmitted non‐ and semi‐persistently by Myzus persicae

SUMMARYA mixture of the pyrethroid WL85871 (an enriched form of cypermethrin) and the mineral oil SC811 intoxicated adult apterae of an insecticide‐susceptible clone of the peach‐potato aphid Myzus persicae at a similar rate to a treatment containing only WL85871, but the mixture killed more. Mixtures of WL85871 andSC811 also gave better control of both acquisition and inoculation by M. persicae of the non‐persistent potato virus Y (PVY) than either component alone. A mixture of the pyrethroids deltamethrin, cypermethrin and PP321 with SC811, or a mixture of WL85871 with the mineral oil Bayol 52 also decreased acquisition of PVY, and a mixture of WL85871 with SC811 decreased acquisition of another non‐persistently transmitted virus, beet mosaic virus. Control with mixtures was generally better than that provided by each component applied separately. When testing acquisition or inoculation of the semi‐persistent beet yellows virus, fewest plants were infected in treatments incorporating both WL85871 and SC811.

The effect of previous host plant on the fecundity of Myzus persicae and its ability to transmit beet yellows virus

SUMMARY Myzus persicae transferred to rape produced offspring with higher survival, larger weight and faster development than aphids transferred to beet, irrespective of whether they had been reared on rape or beet. Aphids transferred from rape to beet produced fewer offspring than those reared continuously on rape. On beet, rape‐reared adults produced progeny with lower survival, slower development, smaller adult size and lower fecundity than the progeny of beet‐reared individuals, but there were no differences in these characteristics associated with host plant after one generation. Aphids from rape were less than half as efficient in transmitting beet yellows virus as aphids reared continuously on beet but after one subsequent generation on beet this difference had disappeared completely. These results are discussed in relation to field conditions.

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

SUMMARYOilseed 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.

Detection of beet yellows virus in sugarbeet plants by enzyme-linked immunosorbent assay (ELISA)

Beet yellows virus can be detected in leaf extracts of infected sugarbeet plants by ELISA. The use of discs was studied and proved to be a valuable and qualitatively reliable method. Leaf material could be stored at 4o or 22°C for at least six days without affecting the detection of this virus by ELISA. A dramatic decrease in ELISA values was found when leaf extracts were frozen.

Effects of aphid alarm pheromone derivatives and related compounds on non‐ and semi‐persistent plant virus transmission by Myzus persicae

SUMMARYA derivative, prepared from the aphid alarm pheromone (E)‐β‐farnesene and the saturated straight 14‐carbon chain dialkyl ester of acetylene dicarboxylic acid, was the most active compound tested for inhibiting acquisition by the aphid Myzus persicae of the non‐persistently transmitted potato virus Y (PVY). Derivatives lacking, or with shorter, or branched or partially‐unsaturated carbon side‐chains were less active. The one derivative tested also inhibited inoculation of PVY, and acquisition of beet mosaic virus (also non‐persistent) and the semi‐persistent beet yellows virus. However, it had no obvious effect on aphid probing behaviour; related compounds lacking the (E)‐β‐farnesene moiety also inhibited acquisition of PVY.

Alarm pheromone secretion by insecticide‐susceptible and ‐resistant Myzus persicae treated with demeton‐S‐methyl; aphid dispersal and transfer of plant viruses

SUMMARYThe insecticides demeton‐S‐methyl and pirimicarb induced cornicle secretion, and thereby alarm pheromone release, in Myzus persicae. Secretion was earliest in young and insecticide‐susceptible aphids.In laboratory experiments to assess the behavioural significance of this effect, demeton‐S‐methyl applied to colonies of R1 (moderately resistant) aphids killed the majority, but caused the remainder to disperse. The timing and degree of dispersal depended on the size and composition of the colonies. Beet yellows virus was transferred by dispersed aphids, but less frequently when recipient indicator seedlings were treated with demeton‐S‐methyl. R2 (strongly resistant) aphids soon dispersed from colonies containing susceptible nymphs (which secrete alarm pheromone early) and transmitted readily even to treated seedlings.The non‐persistent potato virus Y was transferred by dispersed R: aphids and no protection was afforded by treatment of the seedlings.

The Structure and Characterization of a Closterovirus, Beet Yellows Virus, and a Luteovirus, Beet Mild Yellowing Virus, by Scanning Transmission Electron Microscopy, Optical Diffraction of Electron Images and Acrylamide Gel Electrophoresis

SUMMARY Attempts were made to determine more precisely the structure and properties of a closterovirus, beet yellows virus (BYV), and a luteovirus, beet mild yellowing virus (BMYV), by scanning transmission electron microscopy, optical diffraction of electron images and acrylamide gel electrophoresis. It was shown that BYV has a mol. wt. of 76.5 × 106, including an RNA of 4.15 × 106. The pitch of the helix is 3.7 nm and there would be 8.5 protein subunits per turn. BMYV particles have a diameter of 26 nm and a total mol. wt. of 6.5(±0.45) × 106. The mol. wt. of the protein subunit is about 24000 and that of the RNA 2 × 106.

A controlled environment study of the effect of leaf physiological age on the movement of apterous Myzus persicae on sugar‐beet plants

SUMMARYApterous Myzus persicae were found to move frequently from leaf to leaf on sugar‐beet plants in controlled environment conditions. It is suggested that aphid movement can be related to changes in the rate and content of translocate flow during leaf development. These changes make newly‐emerged leaves nutritionally favourable to colonising aphids and make expanding leaves slowly wane in favourability during the process of ‘sink to source’ conversion leading to aphid dispersal from the leaf. Variation in temperature was not found to alter the rate of aphid movement or the period (measured in thermal time) that aphids spent on particular leaves. However, the lower temperature was found to increase the rate of aphid development, aphid size and fecundity; these effects could also be due to nutritional factors.This dispersal behaviour may be a tactic to maximise food intake by a polyphagous aphid and increase the probability that nymphs are deposited on nutritionally‐favourable leaves. The implications of the interleaf dispersal of apterous M. persicae for within‐ and between‐plant spread of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) are discussed.

Aphid alarm pheromone derivatives affecting settling and transmission of plant viruses

1,4-Cycloaddition reactions between (E)-β-farnesene (the aphid alarm pheromone) and dienophiles, such as SO2 and RO·CO·C ≡ CCO·OR, gave products more stable and less volatile than the parent compound. In laboratory experiments, the numbers ofMyzus persicae (Sulz.) settling and nymphs deposited on plants were decreased by some of the reaction products. Acquisition, and thereby transmission, of the semipersistent beet yellows virus and the nonpersistent potato virus Y, was decreased.

Detection of sugarbeet yellowing viruses in leaf extracts by enzyme-linked immunosorbent assay (ELISA)

Beet mild yellowing virus (BMYV) and beet yellows virus (BYV) can be detected in leaf extracts of infected sugarbeet by ELISA tests. These tests are especially useful in the case of greenhouse-grown beets since the latter often are symptomless. Using this sensitive assay, it was found that the host range of beet yellowing viruses is wider than previously thought. La jaunisse de la betterave en France est provoquée par deux virus morphologiquement très différents mais souvent associés: les virus de la jaunisse modérée et de la jaunisse grave de la betterave. Nous avons montré que—même en l'absence de symptômes foliaires nets, comme cela est souvent le cas pour des betteraves cultivées sous serre—ces 2 virus peuvent être décelés par la méthode ELISA dans des extraits de feuilles de betteraves infectées. L'utilisation de cette technique fine a permis de montrer que les gammes d'hôtes de ces deux virus étaient plus larges que celles décrites précédemment. En particulier, Capsella rubella et Nicotiana clevelandii apparaissent comme des plantes hébergeant le virus de la jaunisse modérée, alors que Papaver dubium, Sinapis alba et Tetragonia echoniata sont hôtes du virus de la jaunisse grave.