Patterns of spread of the non-persistently transmitted bean yellow mosaic virus and the persistently transmitted subterranean clover red leaf virus in Vicia faba

Patterns of spread of two aphid borne viruses, the non-persistently transmitted bean yellow mosaic virus (BYMV) and the persistently transmitted subterranean clover red leaf virus (SCRLV), were compared simultaneously in field plots of Vicia faba minor grown in a Mediterranean climate (winter-spring growing season, and dry summer). Spread from a primary source was mapped following the artificial introduction of virus alone, or virus with vector, at the centre of the plots. BYMV spread rapidly from the virus source whether or not vectors were introduced with the virus. By contrast, SCRLV spread from the source only when plants were also artificially infested with the vector Aulacorthum solani. An attempt was made to evaluate the importance of secondary spread of both viruses by assessing the degree of clumping of infected plants that occurred outside the primary sites of virus introduction. BYMV-infected plants were clumped in each treatment irrespective of whether the virus was introduced alone or with vector, as well as in control plots. Clumping of SCRLV occurred only when the vectors were introduced on virus source plants at the beginning of the experiment. Times of spread were determined both by exposing trap plants at 4-weekly intervals throughout the 30 month trial period, and by analysing the rates of spread in experimental plots between June and November in one growing season. Both viruses spread in the spring when vectors were flying, but negligible spread of the viruses was observed in the autumn despite aphid flight activity. Times of flight of the four main aphid vector species were continuously monitored with yellow water traps. A major spring and a minor autumn flight peak were observed for Aphis craccivora, Macrosiphum euphorbiae, Aulacorthum solani and Myzus persicae. Aphid flights occurred predominantly in weeks when the mean temperature was in the range 13–17°C. Rainfall above 7 mm per week appeared to affect flights only when mean weekly temperatures were outside the range 13–17°C.     

The effect of time of sowing on the incidence of subterranean clover red leaf virus infection in broad bean (Vicia faba)

Yield losses in broad beans due to subterranean clover red leaf virus (SCRLV) in 1972/73 were 21, 30, 61 and 8% in plots sown in May, July, September and November respectively. The variations in yield loss resulted from differing levels of virus infection during periods in which harvestable pods were set because further pod set virtually ceased after symptoms of infection became apparent. The increases in infection were paralleled by increases in the infestation of Aulacorthum solani the aphid vector of SCRLV. Yield losses were greatest in the September-sown plots because the plants emerged at the commencement of the spring peak of aphid flight and were least in the November-sown plots which emerged after the peak of aphid flight had declined. However, potential yields decreased with deferment of sowing time and recorded yields were greatest from May-sown plots.
Yield losses due to SCRLV in 1973/74 were 79 and 91% for plots sown in May and September respectively. These larger yield losses resulted from an earlier and more rapid colonisation of plants by A. solani than in the previous year.
Choice of May as sowing date would not have controlled the disease satisfactorily in 1973/74 but would have been practical in the previous season when colonisation by A. solani was delayed so that little infection with SCRLV occurred before pod set had ceased.     

Rhizobium leguminosarum inoculation decreases damage to faba bean (Vicia faba) caused by broad bean mottle bromovirus and bean yellow mosaic potyvirus

Faba bean (Vicia faba) plants were inoculated with rhizobia and then their sap was infected with broad bean mottle bromovirus (BBMV) or bean yellow mosaic potyvirus (BYMV) in a field experiment. Both viral infections significantly decreased shoot and root dry weight, number of nodules, nodule dry weight, numbers of flowers and pods/plant, total plant N, grain yield and N₂ fixation. However, inoculation withRhizobium leguminosarum significantly increased all these parameters, both in healthy and virus-infected plants. Although BYMV was more destructive than BBMV, inoculation with rhizobia could be used, with other control measures, to limit damage by both viruses.The authors are with the Department of Biochemistry and Soil Science, Faculty of Agriculture, Shambat, Sudan.     

Control of subterranean clover red leaf virus in broad bean crops with aphicides

Apterous Rhopalosiphum padi on the first leaf of cereal plants, developed faster and were more fecund at seedling to stem extension of barley, at tillering to earing of oats and at stem extension and earing of wheat. Feeding site on a mature plant also affected the rate of development and fecundity of the aphids; the largest and most fecund developed on the stems of oat and wheat plants. The consequences of these variations in reproductive performance are discussed in relation to the population dynamics of R. padi and its possible pest status in Britain.     

Protective action of salicylic acid against bean yellow mosaic virus infection in Vicia faba leaves

In this study, morphological, ultrastructural and physiological modifications of faba bean (Vicia faba cv Giza 461) leaves in response to bean yellow mosaic virus (BYMV) infection and salicylic acid (SA) treatments were examined. Under BYMV stress, leaves showed symptoms including severe mosaic, mottling, crinkling, size reduction and deformations. Three weeks after virus inoculation, photosynthetic rate, pigment contents and transpiration rate were significantly reduced in response to BYMV infection.

Ultrastructural investigations of BYMV-infected leaves demonstrated that most chloroplasts with increased stromal area became spherical in shape and some lost their envelopes, either partially or totally. The internal structures of chloroplast, grana and thylakoids were dilated. Two kinds of inclusions were detected in BYMV-infected leaves: straight or slightly curved bands sometimes coiled or looped at the end, and electron opaque crystals with varied shapes. BYMV-infected cells showed lower chloroplast number in comparison to the control.

Spraying of SA on faba bean leaves helped to reduce or prevent the harmful effects produced after virus infection. Application of 100 μM SA three days before inoculation restored the metabolism of infected leaves to the levels of healthy controls. SA treatment improved plant health by increasing the photosynthesis rates, pigment contents and levels of other parameters studied similar to control values.

Moreover, SA treatment increased plant resistance against BYMV. This was observed through induction of chloroplast number, reduction in percentage of infected plants, decrease in disease severity and virus concentration of plants treated with SA prior to BYMV inoculation. Cells of SA-treated samples showed well-developed chloroplasts with many starch grains and well-organized cell organelles.

The present results provide an overview of the negative effects on faba bean leaves due to BYMV infection from physiological and subcellular perspectives. Also, a role of SA involved in induction of resistance against BYMV infection in bean plants is discussed.     

Effect of mulching with cereal straw and row spacing on spread of bean yellow mosaic potyvirus into narrow-leafed lupins (Lupinus angustifolius)

Two field experiments examined the effect of straw spread on the soil surface on the incidence of bean yellow mosaic potyvirus (BYMV) in plots of narrow-leafed lupin (Lupinus angustifolius) sown at narrow (17.5 cm) vs wide (35 cm) row spacing and low (25–30 kg/ha) vs medium (50–60 kg/ha) seeding rates. Virus ingress was by vector aphids flying from adjacent pastures dominated by subterranean clover. In Expt 1, in which BYMV infection was extensive, straw greatly decreased the rate and amount of virus spread regardless of row spacing or plant density, decreasing infection more than 70% by the final assessment date. This effect of straw was attributed to decreased landing rates of incoming vector alates. In the plots without added straw, narrow row spacing decreased BYMV % infection by 38% by the last assessment date. Sowing at the medium seeding rate also decreased infection. The effect of wide row spacing seemed due to delayed canopy closure between rows which is likely to have increased the landing of aphids while the effect of medium seeding rate was attributed partly to the dilution effect of greater plant numbers and partly to the effects of partial canopy development in decreasing landing rates. In Expt 2, in which the incidence of BYMV infection was low, added straw again decreased BYMV spread, but by only 25–27% at final assessment; there were no effects of row spacing or seeding rate. In both experiments, an additional “reference” treatment was included which had a high (90–100 kg/ha) seeding rate, narrow rows and no straw. The dense canopy it developed also decreased BYMV incidence but less than in the plots with added straw in Expt 1. In Expt 1, adding straw and the resulting decrease in plants killed by BYMV, were associated with an overall increase in lupin grain yield of 20%. The greater plant densities resulting from the medium seeding rate also increased grain yield but row spacing did not affect it significantly. These results indicate that retaining stubble on the soil surface at seeding will assist in management of BYMV infection in lupin crops but that wide row spacing in the absence of retained stubble is undesirable.     

Effects of cereal borders, admixture with cereals and plant density on the spread of bean yellow mosaic potyvirus into narrow-leafed lupins (Lupinus angustifolius)

In studies of virus control measures, field experiments in 1987–1991 investigated the effects of cereal and fallow borders, admixture with cereals and plant density on spread of bean yellow mosaic potyvirus (BYMV) from pastures dominated by subterranean clover (Trifolium subterraneum) into plots of narrow-leafed lupins (Lupinus angustifolius). Virus spread was mainly monocyclic because BYMV killed infected lupin plants and between systemic movement and death there was only a brief period for BYMV acquisition and transmission to other plants by vector aphids. In plots with cereal borders, the rate and extent of BYMV spread into the lupins was decreased; at final assessment the numbers of infected plants were 43–60% less than in plots with fallow borders. Admixture with cereals also decreased the rate and extent of BYMV spread into lupin plots, numbers of infected plants being decreased by 76–96% at the time of final assessment. When lupins were sown at different seeding rates to generate a range of plant densities and weeds were removed, high densities decreased BYMV infection. The higher incidences of BYMV infection in sparse stands were attributed partly to smaller plant numbers and partly to incoming viruliferous vector aphids being more attracted to plants with bare earth around them, than to a plant canopy. BYMV infection decreased grain yield of samples from infected lupin plants by 94–100%. In plots with 34% infection and sparse stands, grain yield was decreased by about one third. Plotted progress curves for the accumulated numbers of alate aphids of the BYMV vector species Acyrthosiphon kondoi and Myzus persicae resembled those for numbers of BYMV infected plants in 1990, but in 1991 only the curve plotted for M. persicae did so. There was a 2 week delay between the curves for aphid numbers and virus counts which reflected the time taken for obvious systemic necrotic symptoms to develop in lupins.     

Necrosis in field beans (Vicia faba) induced by interactions between bean leaf roll, pea early-browning and pea enation mosaic viruses

Mixed infections with two or three viruses - bean leaf roll (BLRV), pea early-browning (PEBV) and pea enation mosaic (PEMV) - were detected in plants showing leaf curling, stunting and necrosis in a crop of field beans grown for seed in 1980. In glasshouse tests, field bean plants infected with any one of these viruses showed no necrosis, and plants infected with PEBV and PEMV together showed symptoms of PEMV only. However, mixed infection with BLRV and PEMV almost invariably induced severe stunting and leaf necrosis, and infection with BLRV and PEBV often induced both leaf and stem necrosis and sometimes caused early death. Thus it seems that the necrotic symptoms seen in the field were induced by interactions between BLRV and the other viruses. No transmission of PEBV was detected through seed harvested from the crop, but up to 5% transmission was detected through seed from experimentally-infected plants. The infected seedlings were symptomless.     

The occurrence and effects of red clover necrotic mosaic virus in red clover (Trffbliumpratense)

In 1976, red clover necrotic mosaic virus (RCNMV) was identified in red clover variety trials at the Scottish Colleges of Agriculture and at the trial centres of the National Institute of Agricultural Botany (NIAB) in Northumberland, Dyfed, Devon and Cambridge. In 1977, RCNMV was also found in two commercial crops of red clover in South Wales. The only previous finding of this virus in Britain was in 1971.
In red clover leaves RCNMV causes veinal chlorosis, often followed by severe necrosis and deformation; the plants become stunted. All cultivars tested were infected either in field or glasshouse experiments and three of the four most susceptible cultivars were tetraploids. Yield losses in cv. Hungaropoly averaged 57% over three cuts. RCNMV was transmitted manually but not through seed or by aphids {Acyrthosiphon pisum and Myzus persicae) or weevils (Apion spp. and Sitona lineatus). Seedlings became infected when grown in pots containing RCNMV-infected plants or soil from infected sites, and the roots of infected test seedlings contained an Olpidium sp. which may be the vector.
White clover mosaic virus (WCMV), also common in red clover at some sites, was less damaging than RCNMV and in a glasshouse experiment decreased yield by only 22%. An unidentified seed-borne virus with spherical particles c. 33 nm in diameter was the only virus detected in clover seedlings screened for RCNMV.     

Translocation of selenium in the bean plant (Phaseolus vulgaris) and the field bean (Vicia faba)

Selenium distribution in the bean plant ( Phaseolus vulgaris L. cv. Contender) was studied using autoradiographs of the whole plant and of sections of organs. A few hours after the incubation of the roots with (⁷⁵Se) selenate, a major part of the selenate accumulates in the roots, while the fraction conveyed towards the aerial organs is unevenly distributed, resulting in accumulation of ⁷⁵Se in the young leaves, the buds and the epicotyl. This distribution results from a general translocation of selenium through the xylem. A secondary process of redistribution is then immediately linked to the transport of ⁷⁵Se labeled products (such as seleno-amino acids) in the phloem from the mature leaves. A similar pattern of translocation of selenium was found in the field bean ( Vicia faba L. cv. Aguadulce) by using aphids that insert their stylets into the sieve tubes. Measurement of the radioactivity of these insects shows that the ⁷⁵Se content of the phloem sap was reduced to low levels when all the mature leaves were excised. The mature leaves thus serve as relaying organs, redistributing the selenium which is carried in by the movement of water through the xylem.     

Determining the relative roles of different aphid species as vectors of cucumber mosaic and bean yellow mosaic viruses in lupins

Glasshouse and field studies were done to determine the relative roles of different colonising and non-colonising aphid species as vectors of two non-persistently transmitted viruses, cucumber mosaic cucumovirus (CMV) and bean yellow mosaic potyvirus (BYMV) in narrow-leafed lupin (Lupinus angustifolius) crops in Australia. The abilities of nine different aphid species in transmitting CMV from infected to healthy lupins and BYMV from infected subterranean clover to healthy lupins were compared in the glasshouse using 5–10 min acquisition access feeds. The percentage transmission efficiencies found with lupin-colonising aphid species were (CMV/BYMV): Acyrthosiphon kondoi (6/15), Aphis craccivora (10/14) and Myzus persicae (11/77). With non-colonising species the respective efficiencies were: Brachycaudus rumexicolens (0.9/0), Lipaphis erysimi (4/8), Rhopalosiphum maidis (9/6), R. padi (5/5), Sitobion miscanthi (2/11) and Therioaphis trifolii (4/5). When flying aphids were trapped in the field in four successive years (1993–1996) on vertical nets downwind of virus-infected lupins, 13 different species were caught at a “wheatbelt” site and 18 at an urban irrigated site. Of 2833 aphids caught at the “wheatbelt” site, 64 transmitted CMV to lupin test plants. At the irrigated site, numbers of aphids transmitting CMV/numbers caught were 12/186 while the corresponding numbers for BYMV were 11/727. M. persicae, A. kondoi and R. padi transmitted both viruses, while additional vectors of CMV found were A. craccivora, Acyrthosiphon pisum, B. rumexicolens, L erysimi, R. insertum, T. trifolii and Toxoptera citricidus. Averaged over four years, A. kondoi accounted for 50% of CMV transmissions at the “wheatbelt” site, M. persicae for 16% and R. padi for 22%, and these three species were caught in the greatest numbers, comprising 28%, 13% and 37% respectively of the total catch. At the irrigated site R. padi accounted for half the CMV transmissions, while R. padi and A. kondoi together accounted for most of the BYMV transmissions. R. padi, A. kondoi, M. persicae and T. citridus were the most common aphid species at this site. These findings suggest that M. persicae, A. kondoi and R. padi are the aphid species likely to be most important as vectors of CMV and BYMV in narrow-leafed lupins grown in mediterranean-type climatic zones of southern Australia.     

The effect of temperature and water stress on the timing of leaf death in Vicia faba

The timing and pattern of leaf death was studied in three field experiments from observations of the area and dates of death of individual leaves. Two linear regression lines adequately described the pattern of leaf death on the plant in all experiments and treatments. These represented an initial phase with a slow rate of leaf death changing to a second phase with a more rapid rate of leaf death. The change from the first to second phase of leaf death occurred when the maximum seed dry weight was reached. The rates of both the first and second phases of leaf death increased with temperature. This was confirmed in an experiment in growth rooms. The rate of leaf death in both phases of plants grown at three constant temperatures increased linearly with temperature from 14 °C to 22 °C. The rate of leaf death in phase 2 increased with increasing solar irradiance and vapour pressure deficit. The rate of leaf death in both phases increased with increasing water stress in three irrigation treatments in the field.     

Genetic mapping of the bean golden yellow mosaic geminivirus resistance gene bgm-1 and linkage with potyvirus resistance in common bean (Phaseolus vulgaris L.)

Bean golden yellow mosaic virus (BGYMV) is a whitefly-transmitted geminivirus of the Begomovirus family that causes important yield losses to common beans grown in tropical and sub-tropical countries of Latin America and the Caribbean. A major resistance gene that has been widely deployed in this region is the recessive locus bgm-1 that prevents the development of severe yellowing typical of the disease. In this study, we developed a co-dominant sequence-characterized amplified region (SCAR) marker, SR2, based on a previously identified random amplified polymorphic DNA (RAPD) marker that is tightly linked to the bgm-1 resistance gene and identified the position of the locus in the common bean genome through comparative mapping using two genetic maps for the species. The SR2 marker was mapped relative to bgm-1 in a segregating population of recombinant inbred lines developed from the resistant × susceptible cross of DOR476 × SEL1309. Polymorphism was shown to be based on a 37 bp insertion event in the SR2 allele associated with susceptibility compared to the allele associated with resistance and the marker mapped at a distance of 7.8 cM from the resistance gene. The SR2 marker was significantly associated with overall disease symptoms and with three of the four symptoms associated with the disease (yellowing or chlorosis, flower abortion, foliar deformation) in a greenhouse trial in Colombia with the mechanically transmissible BGYMV–Guatemala strain. In both the DOR364 × G19833 and BAT93 × Jalo EEP558 mapping populations, SR2 was located near the end of linkage group b03 (chromosome 5) suggesting a sub-telomeric position. The position of the bgm-1 resistance gene was estimated to be close to that of bc-1, a strain-specific resistance gene for Bean common mosaic virus (BCMV), based on linkage of SR2 with the SCAR marker SBD5 in the DOR364 × G19833 mapping population. The implications of linkage between these two recessive resistance genes are discussed, as this is the first association between resistance genes against both a begomovirus and a potyvirus. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

The effect of red and far-red light on proton secretion from mesophyll-cell protoplasts of Vicia faba L.

The influence of red and far-red irradiation on the transport of H⁺ and ⁸⁶Rb⁺ through the plasmalemma was studied using parenchymal protoplasts isolated from Vicia faba leaves. The results indicate that red light stimulates H⁺ secretion and the uptake of ⁸⁶Rb⁺. Moreover, it has been demonstrated that far-red irradiation acts antagonistically with respect to red light in both these processes.     

Intraspecific variation in zucchini yellow mosaic virus transmission by Myzus persicae and the impact of aphid host plant

Three isofemale lines of Myzus persicae (Sulzer), two lines collected from and reared on a brassicaceous host, and one line collected from and reared on a malvaceous host, were evaluated for their efficiency of transmitting Zucchini yellow mosaic virus (family Potyviridae, genus Potyvirus, ZYMV). In the first experiment, the transmission efficiencies of two clones from Brassicaceae (B1 and B2) were 52.0 and 60.8%, respectively, and these transmissions were not significantly different. In a second experiment, the transmission efficiencies of the clone on Malvaceae (M1) and clone B2 were significantly different at 35.6 and 55.7%, respectively. Further experiments evaluated host-related mechanisms that may have contributed to the differential transmissions observed between clones M1 and B2. Studies on short-term feeding showed that aphids continuously reared on okra, Abelmoschus esculentus (L.) Moench (malvaceous host), and those that were reared on okra and allowed a 24-h preacquisition feeding period on mustard, Brassica juncea (L.) Czern (brassicaceous host), had significantly lower transmission than aphids continuously maintained on mustard. Aphids reared on mustard and allowed a 24-h preacquisition feeding period on okra had intermediate transmission efficiency. In long-term host association studies, we found that aphids reared on mustard had significantly higher transmission efficiency than those reared on okra, and aphids reared first on okra and then switched to mustard had a transmission efficiency that was intermediate and not significantly different from the other two treatments. Our study reveals the existence of intraspecific variation in the transmission of ZYMV by M. persicae, and it suggests that to accurately assess the transmission capability of ZYMV by this species, multiple clones should be examined. Furthermore, the host plant on which the aphid is reared as well as the host plant on which it feeds just before virus acquisition contribute to ZYMV transmission efficiency of M. persicae.     

Incidence, field spread, seed transmission and effects of broad bean stain virus and Echtes Ackerbohnenmosaik-Virus in Vicia faba in eastern Scotland

In eastern Scotland seed-borne infection with broad bean stain virus (BBSV) and/or Echtes Ackerbohnenmosaik-Virus (EAMV) was detected in five of 39 seed lots of field bean in 1975 and in four of 21 commercial crops of field bean or broad bean sampled in 1975 or 1976. Tests failed to detect the main weevil vector of these viruses, Apion vorax, in 1975 and 1976 but Sitona weevils were found in most crops and were numerous in many, reaching maximum numbers in August. No spread of BBSV and EAMV was detected in commercial crops containing seed-borne infection. In experimental field bean crops containing plants manually inoculated with virus, no virus spread was detected in 1975, and only 0–015% uninoculated plants became infected with EAMV in 1976. Sitona, therefore, was an inefficient vector. The percentage of virus infection in seed harvested from field bean plants manually inoculated 3, 5, 7 and 11 wk after emergence in the field was 1–5, 2–7, 0–4 and 0–06 for BBSV and 0–5, 2-1, 0–6 and 0 for EAMV respectively. Seed harvested from unrogued and rogued plots of field bean grown from seed containing 3–4% seed-borne infection produced 0–05% and no infected plants, respectively. Yield losses in field bean plants manually inoculated with virus before flowering were up to 20% but were much greater in plants infected through the seed. Loss in yield was largely caused by a decrease in number of seeds per pod. The absence of A. vorax, the late arrival of Sitona weevils in the crop and their inefficiency as vectors, and the smaller effects of BBSV and EAMV on crop yield than in southern England appear to make eastern Scotland very suitable for the production of bean seed free from BBSV and EAMV.     

The effect of salinity on N fixation and assimilation in Vicia faba

Production of the faba bean in semi-arid and coastal areas maybe limited by the salt sensitivity of faba bean symbiosis. Accordingly,this study was done to analyse the effects of salt on the effectivesymbiosis of faba bean (Vicia faba L. var. minor cultivar Alborea)and salt-tolerant Rhizobium leguminosarum biovar. viciae strainGRA19. After 4 weeks of growth, the nutrient solutions weresupplemented with 50, 75 and 100 mM NaCl for 21 d. Plants wereharvested four times at weekly intervals, beginning at 4 weeks.Vicia faba tolerated low (50 mM NaCl) but not higher levels(75 and 100 mM NaCl) of salt stress. Salinity affected shootgrowth more than root growth. At the end of the culture, thetotal nitrogen content in the shoot was affected more than plantgrowth; conversely, in the root, growth was influenced morethan total nitrogen content. In nodules, nitrogen fixation (acetylenereduction activity) was more sensitive to salinity than ammoniumassimilation (glutamine synthetase and glutamate synthase). Key words: Glutamate synthase, glutamine synthetase, N₂ fixation, Rhizobium leguminosarum, salinity     

Sorption of caesium,iodine and sulphur in solution to the adaxial leaf surface of broad bean (Vicia faba L.)

The interception by crop canopies of radionuclides in rainfall can be important in determining radiation exposures to animals and man. Data were obtained on the sorption and desorption of radionuclides on the adaxial surfaces of fully expanded bean leaves by exposing them to ionic forms of caesium (Cs⁺), iodine (I⁻) or sulphur (SO₄²⁻) over a six order of magnitude concentration range. The accumulation of each element was determined as a time course over a 48 h period using radioactive labels (¹³⁷Cs, ¹²⁵I or ³⁵S, respectively). Time- and concentration-dependent sorption of each element to the leaf surface was analysed to determine: (a) the leaf surface-solution distribution coefficient (K_d) at equilibrium and (b) the sorption and desorption rate coefficients for each element over the range of concentrations investigated. It was expected that Cs⁺ would show a stronger tendency to sorb to the leaf surface than both I⁻ and SO₄²⁻ because of the cation exchange properties of the cuticular membrane. The K_d for Cs⁺ was approximately 90× greater than that for SO₄²⁻ but 5× less than that for I⁻. This is thought to be due to either (a) the highly organophilic nature of iodide and the relatively high iodine number of cuticular waxes on plant leaf surfaces or (b) the possible oxidation of I⁻ to I⁰ or IO₃⁻, with consequently enhanced leaf surface sorption. Based on data obtained in this study, ranges and best estimates of sorption and desorption rate coefficients are presented for Cs⁺, I⁻ and SO₄²⁻ for use in modelling the interception of radioactive Cs, I and S in rainfall by crops.     

The DNA-A component of a plant geminivirus (Indian mung bean yellow mosaic virus) replicates in budding yeast cells

Understanding the biochemistry of DNA replication of the plant DNA viruses is important for the development of antiviral strategies. Since DNA replication is little studied in plants, a genetically tractable, easily culturable, eukaryotic model system is required to pursue such studies in a facile manner. Here we report the development of a yeast model system that supports DNA replication of a chosen geminivirus strain, Indian mung bean yellow mosaic virus. The replication of plasmid DNA in the model system relies specifically on the virus-derived elements and factors. Usage of this model system revealed the role of at least one hitherto unknown viral factor for viral DNA replication. The episomal characteristic of single-strandedness of replicated plasmid DNA was shown, and the expression of viral genes was also confirmed. This model system is expected to shed light on the machinery and mechanism involved in geminiviral DNA replication in plants.