bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenicity and identification of the lilac pathogen, Pseudomonas syringae pv. syringae van Hall 1902
Authors: YOUNG J. M.
Published: February 2008

Comparative in planta studies with Pseudomonas syringae pv. syringae have established optimum conditions for disease expression in lilac in terms of inoculum concentration, host age and post‐inoculation conditions (temperature and day‐length). Reproducible disease reactions required an inoculum concentration exceeding the ED50, 5 × 106 cfu/ml, and a temperature for post‐inoculation incubation not exceeding 19°C. A revised host range of P. syringae pv. syringae, proposed on the basis of confirmation of pathogenicity of strains to lilac, comprises 44 species from monocotyledonous and dicotyledonous plants. Nine new hosts Abelmoschus esculentus, Bromus willdenowii, Camellia sinensis, Centrosema pubescens, Citrullus lanatus, Cotoneaster sp., Cucumis melo, Populus×euramericana and Triticum aestivum, are recorded.

A comparative laboratory study was made of strains of P. syringae pv. syringae using more than 30 selected biochemical and nutritional tests. The pathovar could be characterised on the basis of 11 of these which may prove to be useful determinative tests.
Recognition and differentiation of seven whitefly‐transmitted geminiviruses from India, and their relationships to African cassava mosaic and Thailand mung bean yellow mosaic viruses
Authors: HARRISON B. D. , MUNIYAPPA V. , SWANSON M. M. , ROBERTS I. M. , ROBINSON D. J.
Published: February 2008

Particles resembling those of geminiviruses were found by immunosorbent electron microscopy in extracts of plants infected in India with bhendi yellow vein mosaic, croton yellow vein mosaic, dolichos yellow mosaic, horsegram yellow mosaic, Indian cassava mosaic and tomato leaf curl viruses. All these viruses were transmitted by Bemisia tabaci whiteflies, all reacted with at least one out of ten monoclonal antibodies to African cassava mosaic virus (ACMV), and all reacted with a probe for ACMV DNA‐1, but scarcely or not at all with a full‐length probe for ACMV DNA‐2. Most of the viruses were distinguished by their host ranges when transmitted by whiteflies, and the rest could be distinguished by their pattern of reactions with the panel of monoclonal antibodies. Horsegram yellow mosaic virus was distinguished from Thailand mung bean yellow mosaic virus by its lack of sap transmissibility, ability to infect Arachis hypogaea, failure to react strongly with the probe for ACMV DNA‐2 and its pattern of reactions with the monoclonal antibodies.

Structures resembling a ‘string of pearls’, but not geminate particles, were found in leaf extracts containing malvastrum yellow vein mosaic virus. Such extracts reacted with two of the monoclonal antibodies, suggesting that this whitefly‐transmitted virus too is a geminivirus. All seven viruses from India can therefore be considered whitefly‐transmitted geminiviruses.
Further studies on cucumber mosaic virus infection of narrow‐leafed lupin (Lupinus angustifolius): seed‐borne infection, aphid transmission, spread and effects on grain yield
Authors: JONES R. A. C. , PROUDLOVE W.
Published: February 2008

Four field trials were done with narrow‐leafed lupins (Lupinus angustifolius) in 1988 ‐ 1989, to examine the effect of sowing seed with 5% and 0.5% cucumber mosaic virus (CMV) infection on subsequent virus spread, grain yield and percentage of infection in harvested seed. A proportion of the CM V‐infected seed failed to produce established plants and thus, plots sown with 5% and 0.5% infected seed contained 1.5‐2.9% and 0.2‐0.3% of seed‐infected plants respectively. The rate of virus spread by aphids was faster and resulted in more extensive infection at maturity in plots sown with 5% infected seed than with 0.5% infected seed. In three trials, sowing 5% infected seed resulted in yield losses of 34 ‐ 53% and CMV infection in the seed harvested of 6 ‐ 13%. The spread of CMV infection resulting from sowing 0.5% infected seed did not significantly decrease yield. However, late CMV spread in these plots caused > 1% seed infection. In the fourth trial, which was badly affected by drought, CMV spread only slowly, there was no significant effect of CMV on grain yield and the percentage of infected seed harvested was 3–5 times less than that in the seed sown.

When CMV‐infected seed was sown at different depths, target depths of 8 and 11 cm decreased the incidence of seed‐infected plants by c. 15% and c. 50% respectively compared with sowing at 5 cm. However, in glasshouse tests, treatment with the pre‐emergence herbicide simazine failed to selectively cull out seed‐infected plants.

The field trials were colonised by green peach (Myzus persicae), blue‐green (Acyrthosiphon kondoi) and cowpea (Aphis craccivora) aphids. When the abilities of these aphid species and of the turnip aphid (Lipaphis erysimi) in transmitting CMV from lupins to lupins were examined in glasshouse tests, short acquisition access times favoured transmission. With 5–10 min acquisition access times, overall transmission efficiencies were 10.8%, 9.4%, 6.1% and 3.9% for the green peach, cowpea, blue‐green and turnip aphids respectively.
A greenhouse technique to screen pigeonpea for resistance to Heterodera cajani*
Authors: SHARMA S. B. , ASHOKKUMAR P. , McDONALD D.
Published: February 2008

Heterodera cajani is an important nematode pest of pigeonpea in India and a simple and reliable greenhouse procedure has been developed to screen pigeonpea genotypes for resistance to it. In pot experiments, white cysts of H. cajani were counted on the roots of the susceptible genotype ICPL 87 at 15, 30 and 45 days after seedling emergence in soils infested with different levels of H. cajani. The seedlings were rated for the number of white cysts per root system on a one (highly resistant, no cysts) to nine (highly susceptible, more than 30 cysts) scale. White cysts were not easy to see on wet roots but were clearly visible on slightly dried roots. Cyst counts and ratings were more uniform when roots of 30 day old seedlings were evaluated than when 15 or 45 day old seedlings were examined. Effects of different H. cajani infestation levels on the ratings were not significant although the use of higher inoculum densities (16 to 27 eggs and juveniles/cm3 soil) was effective in reducing variability. This procedure was used to screen 60 pigeonpea genotypes and all of them were rated seven or nine. Ten accessions of Atylosia spp. and Rhynchosia spp. were rated three.
The resistance of six potato cultivars to English populations of potato cyst‐nematodes, Globodera pallida and G. rostochiensis
Authors: WHITEHEAD A. G.
Published: February 2008

Six cultivars of potato (Santé, Morag, Paladin, Glenna and Fingal bred for resistance to both potato cyst‐nematodes (Globodera rostochiensis and G. pallida) and Valiant bred for resistance to G. pallida alone) were exposed to 28 English populations of G. pallida and eight English populations of G. rostochiensis in pots. Susceptible cv. Désirée potatoes served as controls for all 36 populations. Inoculum (Pi) was 12000 eggs in cysts per 400ml pot of soil.

Average increase of G. rostochiensis (Pf/Pi) on cv. Désirée was 23.5 but on cvs Sante, Glenna and Fingal it was < 1.0 and on cv. Morag it was 2.2. In contrast, cvs Paladin and Valiant were susceptible (average Pf/Pi = 17.4 and 26.5, respectively).

Against G. pallida populations, average Pf/Pi for cv. Désirée was 21.7; on cvs Paladin, Santé and Glenna it was 2.9, 2.6 and 2.4, respectively; cvs Morag and Fingal were less resistant (7.4 and 5.6, respectively) and cv. Valiant was quite susceptible (11.0).

Resistance to the different populations of G. pallida and G. rostochiensis varied but for the most resistant cultivars (Santé, Glenna and Paladin) the variation was usually small. The value of the six resistant cultivars studied to the integrated control of potato cyst‐nematodes in England and the genetic diversity of the nematode populations to which they were exposed are discussed.
Effects of Caenorhabditis elegans (Nematoda: Rhabditidae) on yield and quality of the cultivated mushroom Agaricus bisporus
Authors: GREWAL P. S. , RICHARDSON P. N.
Published: February 2008

Thirteen species of saprobic rhabditid nematodes (11 genera) were identified from samples of compost and casing material collected from mushroom farms in the British Isles. Caenorhabditis elegans, the most frequently found saprobe, was mass‐produced monoxenically and its effects on the cultivated mushroom, Agaricus bisporus (strain U3) were studied.

C. elegans did not multiply in well‐prepared, pasteurised, spawned compost, whereas casing material proved to be a highly suitable environment for its reproduction. An initial casing inoculum of 106 nematodes/crate of compost (7.5 kg), caused a significant reduction in mushroom yield. Losses in total mushroom yields of 11%, 20% and 26% were caused by initial inoculum rates of 106, 107and 2 × 107 nematodes/crate, respectively. Yields were negatively correlated with the initial nematode inoculation level and regression equations were derived. The nematode treatments caused fewer mushrooms to be produced and an absence of the usual distinctive flushing patterns.

C. elegans caused considerable deterioration in mushroom quality and characteristic distortion of mushrooms. Individual sporophores were mis‐shapen, notched and had brown or violet coloured grills. Up to 3.8%, 6.7% and 10.8% of total weight and 3.5%, 5.4% and 8% of total numbers of mushrooms were distorted at the three highest nematode inoculum rates tested. Weights and numbers of distorted mushrooms were positively correlated with the initial nematode population. C. elegans commonly colonised sporophores.
The effects of a paclobutrazol‐based growth regulator on the yield, quality and ease of management of oilseed rape
Authors: BAYLIS A. D. , HUTLEY‐BULL P. D.
Published: February 2008

A mixture of paclobutrazol and chlormequat chloride plant growth regulators (JF10405, Parlay C) was tested on field crops of two ‘double zero’ oilseed rape cultivars in two seasons. Application rate and timing of JF10405 were varied. Very large plots enabled the use of commercial farm equipment to treat and harvest the experiments.

Untreated plots showed considerable lodging at harvest in all experiments. Treatment with JF10405 had only small effects on the height of mature plants but, generally, reduced lodging substantially even at the lowest rate tested. All JF10405 treatments increased seed yields, several significantly so, particularly a 2.50 litre/ha rate, although the optimum timing varied between experiments. Seed oil contents were little affected, but levels of glucosinolates were significantly decreased in some instances. Treatments giving good control of lodging also took less time to harvest, especially when cutting against the direction of the lodging. The results‐are discussed in relation to the means by which these improvements in seed yield and quality were achieved, and crop management facilitated.
Variation in the glucosinolate content of oilseed rape (Brassica napus L.) leaves
Authors: DOUGHTY K. J. , PORTER A. J. R. , MORTON A. M. , KIDDLE G. , BOCK C. H. , WALLSGROVE R.
Published: February 2008

The glucosinolates are thought to contribute to resistance to pests and diseases in members of the Cruciferae, including oilseed rape (Brassica napus) and they are known to accumulate in Brassica tissues after infestation by various pests. The present study investigated the changes in glucosinolate concentration in leaves of oilseed rape following inoculation with the dark leaf spot pathogen (Alternaria brassicae). Fourth and sixth leaves of the single‐low cultivar Bienvenu (low in erucic acid) and the double‐low cultivar Cobra (low in erucic acid and glucosinolate) were removed at intervals up to twenty days after inoculation and analysed for glucosinolate content using HPLC. Glucosinolates accumulated in inoculated leaves of both cultivars but the accumulation was greater for cv. Bienvenu, especially in sixth leaves. Among the glucosinolates, aliphatic compounds accumulated rapidly in cv. Bienvenu, but later declined. Indolyl and aromatic glucosinolates accumulated in both cultivars, but at a slower rate than the aliphatic glucosinolates. There were differences in the extent to which individual glucosinolates accumulated after inoculation. Disease symptoms were initially more extensive on cv. Cobra than on cv. Bienvenu but were similar on corresponding leaves of the two cultivars by the end of the experiment. However, sixth leaves had significantly less lesioning than fourth leaves. Glucosinolate accumulation in infected oilseed rape may restrict the spread of existing fungal infection or inhibit subsequent attempted infections, especially in younger leaves.
Incidence and severity of pest and disease damage to white clover foliage at 16 sites in England and Wales
Authors: LEWIS G. C. , THOMAS B. J.
Published: February 2008

From 1985 to 1987, leaves of white clover (Trifolium repens) cv. Grasslands Huia were examined for damage by pests and fungal diseases on seven occasions at up to 16 sites in England and Wales. Pest damage was recorded at all sites on all sampling dates. Over all sampling dates, the mean number of leaves damaged by slugs ranged from 23% to 67%, and that by weevils (Sitona spp.) ranged from 3% to 62%. Also, up to 30% of leaves were damaged by other, unidentified pests. At individual sites, total pest damage frequently exceeded 90% of leaves. The area of leaf damaged by pests ranged from 2 ‐ 12%. Fungal diseases were recorded in July and September but not in May, and were more prevalent in September 1985 than in September 1986 or 1987. Black blotch (Cymadothea trifolii) was the most frequently recorded disease, and the mean number of leaves damaged ranged from 4% to 21%. The mean area of leaves covered by lesions was 1–2%. Infections by viruses were assessed on two occasions, using indicator plants and electron microscopy, and only a very low incidence of arabis mosaic virus and red clover necrotic mosaic virus was recorded.
Studies on transmission of Indian peanut clump virus disease by Polymyxa graminis*
Authors: RATNA A. S. , RAO A. S. , REDDY A. S. , MOLT B. L. , REDDY D. V. R. , VIJAYALAKSHMI M. , McDONALD D.
Published: February 2008

The plasmodiophoromycete fungus, Polymyxa graminis was observed in the roots of Sorghum bicolor, S. sudanense, Pennisetum glaucum, Triticum aestivum, Cyperus rotundus, Eleucine coracana, Zea mays, Tridax procumbens and Arachis hypogaea collected from Indian peanut clump virus (IPCV)‐infested fields. Examination of roots of IPCV‐infected S. bicolor, S. sudanense, P. glaucum and T. aestivum grown in previously air dried field soil also showed the presence of cystosori of P. graminis. IPCV‐infested soil stored at room temperature for 3 years transmitted the virus to A. hypogaea, T. aestivum and S. bicolor. Roots extracted from IPCV‐infected P. glaucum and S. bicolor containing cystosori, and dried root fragments incorporated into sterile soil, transmitted the virus to A. hypogaea and T. aestivum. The root extracts contained primary zoospores of the fungus, presumably arising from cystosori. Utilising root fragments of S. sudanense containing cystosori as inoculum P. graminis was shown to infect both monocotyledonous and dicotyledonous plants. Profuse cystosorus production in rootlets only occurred in monocotyledonous plants. In dicotyledonous plants, in general, only few rootlets showed cystosori. Indian isolates of P. graminis appear to differ from isolates from temperate soils in that they can infect dicotyledonous plants and have a much wider host range.
Monoclonal antibodies against tomato spotted wilt virus: Characterisation and application*
Authors: ADAM G. , LESEMANN D. ‐E. , VETTEN H. J.
Published: February 2008

Mouse hybridoma cells, secreting monoclonal antibodies (MCA) against tomato spotted wilt virus, were produced and screened for virus specificity by an indirect triple antibody ELISA, using a rabbit polyclonal antiserum for antigen trapping. A Bulgarian virus isolate from tobacco was used for immunisation of mice and rabbits. One fusion eventually led to 10 stable hybridoma cell lines, all of which produced antibodies of IgG‐type though of different subgroups. Since none of the MCAs reacted with TSWV structural proteins after electrophoresis and transfer to nitrocellulose, other methods were chosen to examine their protein specificity. Purified viral cores and detergent‐solubilised envelope proteins were used as antigens for ELISA, or, alternatively, glycosylated viral envelope proteins were trapped onto microtitre plates coated with lectins in order to detect MCAs specific for them. Both methods, independently, led to the identification of two MCAs that were specific for envelope proteins of TSWV. Only these two antibodies reacted with intact TSWV particles when examined by immunogold labelling in the electron microscope. The reaction of all MCAs with 11 different TSWV isolates eventually led to the selection of one core‐ and one envelope‐specific antibody for routine use. Core‐specific MCAs revealed serological differences between isolates belonging to the common serotype (= lettuce serotype), but did not react with the serotype TSWV‐I. When comparing different ELISA procedures, broadest reactivity and highest sensitivity with different isolates were obtained in an indirect test procedure, using goat anti‐mouse antibody conjugates.
Improving the selectivity of water traps for monitoring populations of the cabbage root fly
Authors: FINCH S.
Published: February 2008

Traps placed within brassica crops to monitor changes in cabbage root fly activity could be made more selective by painting black the inner wall of the standard fluorescent yellow water‐traps. Traps could also be made more selective by covering them with cylinders of Netlon mesh, although this procedure reduces the numbers of cabbage root fly caught by about 70%. Of the single‐coloured traps tested, those painted “marigold” yellow were the most selective in capturing female cabbage root flies. Although white and certain blue traps were as effective as the best yellow traps at capturing cabbage root flies, such traps should be avoided, as they catch 4–5 times as many of the closely‐related bean seed fly. The presence of bean seed flies makes cabbage root fly identification more difficult and adds considerably to the time required to sort trap catches.
The impact of two insecticides on predatory ground beetles (Carabidae) in newly‐sown grass
Authors: ASTERAKI E. J. , HANKS C. B. , CLEMENTS R. O.
Published: February 2008

Field scale experiments carried out over three years showed that chlorpyrifos reduced the numbers of several carabid beetle species caught in pitfall traps. Fonofos seed treatment was also shown to affect selected species. Consideration of the biology of individuals of groups of species provided explanations of why some species such as Nebria brevicollis, Notiophilus spp., Bembidion spp., and Trechus quadristriatus were severely affected by one or other of the chemicals, whereas other species (e.g. Amara spp., Harpalus spp.) were able to survive or recolonise pastures shortly after chemical application. Measurements of elytral and pronotal widths and counts of mature eggs in N. brevicollis, which was trapped in reduced numbers over a long period, were made and provided some information about the mode of action of these chemicals.
Arabis mosaic nepovirus coat protein in transgenic tobacco lessens disease severity and virus replication
Authors: BERTIOLI D. J. , COOPER J. I. , EDWARDS M. L. , HAWES W. S.
Published: February 2008

Tobacco plants expressing the coat protein of a lilac isolate of arabis mosaic virus (ArMV) poorly supported the replication of this virus and did not display any of the signs of systemic invasion produced in their untransformed counterparts or in transgenic plants expressing a different gene (β‐glucuronidase). These effects, were manifest whether the inoculum was virions or RNA. This is the first report of such coat protein protection with a nepovirus.
Restricted virus multiplication in potatoes transformed with the coat protein gene of potato leafroll luteovirus: similarities with a type of host gene‐mediated resistance
Authors: BARKER H. , REAVY B. , KUMAR A. , WEBSTER K. D. , MAYO M. A.
Published: February 2008

Plants of two potato cultivars were transformed with disarmed Agrobacterium rumefaciens (LBA4404) containing a binary expression vector. The vector contained sequences that encode the coat protein of potato leafroll luteovirus (PLRV) under the control of the 35s promoter of cauliflower mosaic virus. RNA transcripts from the integrated viral gene were readily detected in the transgenic plants. PLRV coat protein was detected in only some of these plants when using sensitive immunoblotting techniques. Tubers were collected from transgenic plants that became infected following inoculation either by viruliferous aphids or by grafting with scions from infected plants. When these tubers were used to grow plants with secondary infection, less virus accumulated in each plant of some transgenic lines than in control plants. The PLRV concentration, estimated at different sampling times, in plants of cv. Désirée (transgenic line B1) and cv. Pentland Squire (transgenic line C4) was about 15% and 30% respectively of that in control plants. Among a number of conventionally‐bred clones of potato, some were resistant to virus multiplication and were found to accumulate little virus. The coat protein‐mediated resistance in transgenic potato plants is discussed in relation to the conventional gene‐mediated resistance found in some breeding clones.
Sugar‐beet treatments, water supply and depth of sowing
Authors: DURRANT M. J. , MASH S. J.
Published: February 2008

With variation in rainfall patterns, evaporation, seedbed soil structure and depth of sowing, sugar‐beet seed and seedlings can be subjected to damaging extremes of water availability. Under controlled conditions, seed given progressively longer pre‐sowing treatments (steeped for 12 h at 25°C or advanced for 4 days at 25°C) was more tolerant of non‐optimal conditions than seed given a brief steep (20 min at 15°C). The prolonged steep treatment accelerated emergence and increased establishment (3% on average) in the field, compared with the brief steep. Advanced seed consistently gave the quickest emergence, produced as many plants as the prolonged steep, and was less affected by depth of sowing so its introduction should improve the establishment phase of the sugar‐beet crop.
The effect of galls induced by the gall fly Procecidochares utilis on vegetative growth and reproductive potential of crofton weed, Ageratina adenophora
Authors: ERASMUS D. J. , BENNETT P. H. , STADEN J. VAN
Published: February 2008

Reproductive potential and vegetative growth of Ageratina adenophora (Spreng.) K. & R. (crofton weed) were measured under ambient conditions to evaluate the efficacy of the gall fly, Procecidochares utilis Stone as a biocontrol agent for this weed. Galls induced by the fly resulted in the production of underdeveloped capitula and a reduction in the number of capitula and filled achenes per capitulum. Galling had no effect on subsequent germination of the seed produced. Where vegetative growth was concerned the effect of galling ranged from a temporary cessation of growth to death of stems above the gall. Although galling promoted production of side shoots, the dry mass of above‐ground material was markedly reduced.
Epidemiology of tobacco leaf curl virus in India
Authors: VALAND G. B. , MUNIYAPPA V.
Published: February 2008

The incidence of disease caused by tobacco leaf curl geminivirus (TbLCV) in ten tobacco growing areas of India ranged from 1.2% to 77%. The highest incidence of disease was observed in Andhra Pradesh (77%) followed by Gujarat (59%), Karnataka (17%), Bihar (11.6%) and West Bengal (5.4%). Under field conditions, an average of 32 adult whiteflies (Bemisia tabaci) per plant were recorded in Andhra Pradesh followed by Gujarat (20), Karnataka (12), Bihar (8) and West Bengal (5). In sequential sowings at Bangalore, all the plants were infected within 90 days in plots planted from February to June. Infection in plots planted later was progressively less. There was a positive correlation between whitefly catches and the final incidence of leaf curl disease in plantings. TbLCV was transmitted by Bemisia tabaci to 35 plant species, including Beta vulgaris, Capsicum annuum, Carica papaya, Cymopsis tetragonoloba, Lycopersicon esculentum, Sesamum indicum, Phaseolus vulgaris and Petunia hybrida. Forty five TbLCV isolates from different parts of India induced four distinct types of symptoms on tobacco cultivars Samsun and Anand 119. Group 1 isolates caused severe curling and cup‐shaped enations; group II isolates induced pale green leaves, pit‐like depressions and thorny enations: group III isolates caused leathery leaves, narrow and tiny protruding enations between the veins, and group IV isolates induced irregular thickening and swelling of veins and green flap‐like enations on veins. Nylon net covers protected tobacco seedlings in nursery beds for 45 days. Ricinus communis and Helianthus annuus sown around the tobacco nursery bed as barrier crops attracted adult whiteflies and decreased the number found on tobacco.
The transmissibility of a potyvirus by an aphid vector: reliability of measurements under controlled conditions
Authors: LABONNE G. , LUPOLI R. , QUIOT J. ‐B. , YVON M.
Published: February 2008

Reproducibility of measurements of the transmission rate of a given potyvirus by a given aphid vector was assessed using a standardised transmission procedure. The plant‐virus‐vector system studied was: Cucurbita pepo ‐ Papaya ringspot virus ‐ Aphis gossypii.

Several elements concerning the rearing and handling of the aphids were analysed. One of these, the climatic conditions under which the aphids were reared, influenced the transmission rate of the virus. Six trials were carried out to measure the rate of transmission of the virus from a defined leaf surface area. The measurements appeared to be reliable. A two year experiment was carried out to compare transmission rates at different dates. Although strong variations were observed in some source plants, the transmission rates obtained for samples of 10 source plants were stable, with a 10% coefficient of variation.

The results show that transmissibility of the virus is a stable property which is independent of the trial date. They are discussed in relation to standardised elements of the transmission process.
Comparative transmission of, and varietal reaction to, three isolates of rice tungro virus disease
Authors: DAHAL G. , DASGUPTA I. , LEE G. , HULL R.
Published: February 2008

Comparative transmission by leafhoppers of three tungro isolates obtained from the Philippines, India and Malaysia, and of an infectious clone of the Philippine isolate of rice tungro bacilliform virus (RTBV) by agroinoculation, was conducted on 12 rice cultivars. The symptoms, including height of inoculated plants were recorded and the efficiency of RTBV and rice tungro spherical virus (RTSV) transmission was determined by enzyme‐linked immunosorbent assay. In most cases, the reduction of height and leaf symptoms of plants infected with RTBV and/or RTSV by the three isolates were similar in any given cultivar. On cultivar ASD7, the Malaysian isolate showed more severe yellow orange leaf discolouration symptoms than the Indian isolate which in turn had more severe leaf discolouration than the Philippine isolate. On the other hand, cultivars ASD 7 and Ptb 18 produced the most severe yellow orange leaf discolouration when agroinoculated with an infectious RTBV clone of the Philippine isolate. There was some variation in the transmission profile of the two tungro viruses among the three isolates. However, there was no one clear set of characteristics by which one could use cultivars to distinguish isolates.

The amount of viral DNA in agroinfected plants of cultivars Utri merah, Balimau putih, Utri Rajapan and ARC 11554 was low, while the amount was high in cultivars TN1, ASD7, Ptb 18 and TKM 6. There was high correlation between the amount of viral coat protein by ELISA and viral nucleic acid by DNA hybridisation on 10 agroinoculated rice cultivars; this might indicate that similar proportions of the total RTBV DNA are encapsidated in each cultivar.
Interactions of the Solanum spp. of the Etuberosa group and nine potato‐infecting viruses and a viroid
Authors: VALKONEN J. P. T. , BRIGNETI G. , SALAZAR L. F. , PEHU E. , GIBSON R. W.
Published: February 2008

All 26 accessions of Solanum brevidens, one accession of S. etuberosum and one accession of S. fernandezianum tested were all extremely resistant to potato leafroll virus (PLRV) and potato viruses Y (PVY) and A (PVA). S. brevidens and S. etuberosum were also resistant to Andean potato mottle virus (APMV) and moderately resistant to potato virus X (PVX), whereas S. fernandezianum was susceptible to these viruses. Additionally, S. brevidens was resistant to sap‐inoculated potato viruses M (PVM) and S (PVS). All the Etuberosa accessions were susceptible by graft‐inoculation to PVM, PVS, potato virus T (PVT) and Andean potato latent virus (APLV). Infections by the above mentioned viruses were symptomless in all of the Etuberosa spp. S. etuberosum and S. fernandezianum were infected by mechanical inoculation with potato spindle tuber viroid, S. etuberosum developing severe stunting and leaf‐curl symptoms, but S. brevidens was infected only by graft‐inoculation.

The genes conferring resistance to PVY and PVX in S. brevidens and S. etuberosum appeared to be different from those currently utilised by plant breeders.
Growth and development of Avena fatua (Wild‐oat) in the field
Authors: COUSENS R. , WEAVER S. E. , PORTER J. R. , ROONEY J. M. , BUTLER D. R. , JOHNSON M. P.
Published: February 2008

The growth and development of field‐grown Avena fatua plants were studied for autumn and spring sowings in two consecutive years. The duration of various growth stages from sowing until anthesis was quantified in terms of thermal time (accumulated degree days) or photothermal time (degree days modified by photoperiod). Base temperatures and photoperiods for developmental phases were estimated as those which minimised the coefficient of variation among sowing dates. Relationships were derived between leaf emergence, canopy height, plant leaf area, and photothermal time. Stem extension and flowering occurred earlier in autumn‐sown plants than spring‐sown plants. Autumn‐sown plants produced more leaves on the main stem, and had greater leaf area and above‐ground biomass at anthesis than spring‐sown plants.
Postharvest biological control of Penicillium digitatum decay on citrus fruit by Bacillus pumilus
Authors: HUANG YONG , WILD B. L. , MORRIS S. C.
Published: February 2008

A new antagonist/pathogen combination is reported, with Bacillus pumilus showing strong antagonistic activity against Penicillium digitatum. B. pumilus (1.6 × 1010 to 1.6 × 1012*cfu ml‐1) gave significant control of P. digitatum infection in Valencia orange, which was as effective as imazalil (500 μg ml‐1) and was significantly better than benomyl treatment (500 μg ml‐1). When lower concentrations of B. pumilus (1.9 × 107 to 1.9 × 109 cfu ml‐1) were tested on Washington Navel orange and Lisbon lemon fruit, the antagonist caused significant control of P. digitatum infection at two inoculum levels (6.5 × 104 and 6.5 × 105 spores ml‐5). Concentrations of both the pathogen and the antagonist affected the biocontrol effect.
Transcription amplification of polymerase chain reaction products of bean yellow mosaic virus RNA extracted from gladioli corms
Authors: ROSNER ARIE , STEIN ADINA , LEVY SAMUEL
Published: February 2008

The RNA genome of bean yellow mosaic virus (BYMV) was detected in gladioli corms by reverse transcription and polymerase chain reaction (PCR). However, a positive signal was not obtained from some infected corms because the virus concentration was below the sensitivity limits of PCR. Virus was detected in these corms by using a modified protocol in which transcription of the PCR products by T7 RNA polymerase yielded an additional 10‐ to 100‐fold signal amplification.

The relative concentrations of BYMV in gladioli corms were evaluated using PCR. Virus accumulation in corms was found to be a 100 times lower than in leaves, and be within the range of picogram quantities of viral RNA per gram fresh weight of corm tissue.
Pathogenicity of three RPV isolates of Barley Yellow Dwarf Virus on barley, wheat and wheat alien addition lines
Authors: BANKS P. M. , WATERHOUSE P. M. , LARKIN P. J.
Published: February 2008

Barleys with and without the Yd2 resistance factor, wheat alien addition stocks with other barley yellow dwarf virus (BYDV) resistance factors and true wheats were challenged with three Australian isolates of BYDV‐RPV. Yd2 resistance was effective against two of the BYDV‐RPV isolates and inoculated barleys which carry Yd2 did not develop BYD symptoms and shoot growth was not affected. However, barleys with Yd2 were susceptible to the third BYDV‐RPV isolate. All barley lines inoculated with the third virus isolate developed typical BYD symptoms (yellowing), shoot growth was reduced compared to uninfected controls and virus titres determined by ELISA were high and similar in barleys with and without Yd2. In contrast, resistances from Thinopyrum intermedium and Agropyron pulcherrimum in wheat backgrounds were effective against all three BYDV‐RPV isolates. Shoot growth of inoculated plants with either of these resistance factors did not differ from uninfected controls and virus titres determined by ELISA were very low.
Accumulation of potato virus Y is enhanced in Solatium brevidens also infected with tobacco mosaic virus or potato spindle tuber viroid
Authors: VALKONEN JARI P. T.
Published: February 2008

The accumulation of potato virus Y˚(PVY˚) and potato leaf roll virus (PLRV) was studied in plants of Solanum brevidens co‐infected with each of six viruses or a viroid. Virus could not be detected by ELISA in plants of S. brevidens infected solely with PVY. However, accumulation of PVY was increased c. 1000‐fold in plants doubly infected with tobacco mosaic virus or potato spindle tuber viroid (PSTVd). PVY titres in doubly infected plants of S. brevidens were between 1% and 0.1% of those found in the PVY‐susceptible interspecific Solanum hybrid DTO‐33. Double infections of 5. brevidens by PVY and alfalfa mosaic virus or potato viruses M, S, T or X did not significantly enhance PVY accumulation. Accumulation of PLRV was not enhanced in plants co‐infected with any of the six viruses or PSTVd.
Spread of potato leafroll virus is decreased from plants of potato clones in which virus accumulation is restricted
Authors: BARKER H. , WOODFORD J. A. T.
Published: February 2008

Tubers of eight potato clones infected with potato leafroll luteovirus (PLRV) were planted as ‘infectors’ in a field crop grown, at Invergowrie, of virus‐free potato cv. Maris Piper in 1989. The mean PLRV contents of the infector clones, determined by enzyme‐linked immunosorbent assay (ELISA) of leaf tissue, ranged from c. 65 to 2400 ng/g leaf. Myzus persicae colonised the crop shortly after shoot emergence in late May and established large populations on all plants, exceeding 2000/plant by 27 June. Aphid infestations were controlled on 30 June by insecticide sprays. Aphid‐borne spread of PLRV from plants of the infector clones was assessed in August by ELISA of foliage samples from the neighbouring Maris Piper ‘receptors’. Up to 89% infection occurred in receptor plots containing infector clones with high concentrations of PLRV. Spread was least (as little as 6%) in plots containing infectors in which PLRV concentrations were low. Primary PLRV infection in guard areas of the crop away from infectors was 4%. Some receptor plants became infected where no leaf contact was established with the infectors, suggesting that some virus spread may have been initiated by aphids walking across the soil.
Distribution and prevalence of the entomopathogenic nematode Steinernema feltiae in Scotland
Authors: BOAG B. , NEILSON R. , GORDON S. C.
Published: February 2008

The distribution of insect parasitic nematodes in Scotland was investigated between April 1988 and April 1989 using the wax moth, Galleria mellonella, larvae as bait. Of the 1014 samples examined only 2.2% were found to be positive and all the nematodes recovered and identified belonged to the one species Steinernema feltiae. A more detailed investigation into the distribution of S. feltiae in a 1 ha block indicated that it had a very aggregated distribution.
Parasitism of grain legumes by Alectra species (Scrophulariaceae)
Authors: RICHES C. R. , HAMILTON K. A. , PARKER C.
Published: February 2008

In glasshouse pot experiments in the United Kingdom, the host preference of nine seed samples of Alectra vogelii from Eastern, Western and Southern Africa and of two samples of A. picta from Cameroon and Ethiopia, to cultivars of cowpea, groundnut, bambara and mung bean, was assessed. A susceptible cowpea cultivar, Blackeye, and four cultivars of groundnut were attacked by all samples of both parasitic species regardless of whether the host of origin was cowpea, groundnut or bambara.

Five “strains” of A. vogelii were distinguished using two criteria: their ability to parasitise bambara and/or mung bean and their ability to parasitise cowpea B301 and bambara TVU 870. The latter proved in an associated experiment to be resistant to collections of the parasite from some locations. Strain 1, including populations from Mali, Nigeria and Cameroon, attacked all groundnuts, cowpea cultivar Blackeye, but not cowpea line B301, mung bean or bambara. Strain 2, from Botswana, differed in attacking B301 and mung bean. Three other strains were identified which attacked susceptible lines of all four legume species. Strain 3 from Kenya failed to attack either cowpea B301 or bambara TVU 870, strain 4 from Malawi attacked cowpea B301, but not bambara TVU 870, while strain 5 from Northern Transvaal, South Africa, attacked bambara TVU 870, but not cowpea B301. Cowpea B359 was resistant to A. vogelii samples from all locations and also to A. picta, which has a similar host preference to strain 1 populations of A. vogelii from West Africa. Two out of 13 groundnut lines tested showed low susceptibility to A. vogelii from Cameroon suggesting there is scope for selecting resistance in this crop also.
Improving slug baits: the effects of some phagostimulants and molluscicides on ingestion by the slug, Deroceras reticulatum (Miiller) (Pulmonata: Limacidae)
Authors: HENDERSON I. F. , MARTIN A. P. , PERRY J. N.
Published: February 2008

The effects of seven potential phagostimulants and of four molluscicidal compounds on feeding were examined by confining slugs with agar gels containing the chemicals in varying concentrations. Sugars generally increased the amount of gel ingested; sucrose more than glucose, lactose and fructose. Feeding increased with increasing sucrose concentration to a maximum and then fell progressively: the optimum concentration lay between 2.5% and 5%. The sweeteners saccharin and aspartame at concentrations up to 2.5% did not increase feeding. Addition of the molluscicides metaldehyde, methiocarb and ferric acetylacetonate to gels containing 2.5% sucrose progressively reduced feeding at concentrations of 0.001% and above. Metaldehyde reduced ingestion more than methiocarb and ferric acetylacetonate was intermediate. The molluscicidal herbicide Ioxynil deterred feeding completely at concentrations of 0.001%. The implications for slug bait development are discussed.
Sensitive detection of mycoplasmalike organisms in field‐collected and in vitro propagated plants of Brassica, Hydrangea and Chrysanthemum by polymerase chain reaction
Authors: BERTACCINI ASSUNTA , DAVIS ROBERT E. , HAMMOND ROSEMARIE W. , VIBIO MONICA , BELLARDI MARIA GRAZIA , LEE ING MING
Published: February 2008

A polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field‐collected and in vitro micropropagated plants. PCR with template DNA extracted from symptomatic, naturally‐infected samples of Brassica, Chrysanthemum and Hydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infected Ranunculus (with phyllody disease) or Gladiolus with (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case of Ranunculus and the presence of substances in Gladiolus which inhibited the PCR. The MLO‐specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field‐collected Hydrangea and less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field‐collected Brassica. The findings illustrate highly sensitive detection of MLOs in both field‐grown and in vitro micropropagated infected plants.
Use of a model and toxicity data to predict the risks to some wild plant species from drift of four herbicides
Authors: BREEZE VICTOR , THOMAS GAVIN , BUTLER RUTH
Published: February 2008

The dose responses of 14 wild plant species (two grasses, two legumes, one annual and nine perennial dicotyledons), not usually recognised as weeds, to four herbicides (asulam, glyphosate, MCPA and mecoprop) were measured in glasshouse experiments. Glyphosate was the most toxic; seven of the species tested had EDu, values (measured as shoot dry weight) of < 1.0 μg/plant, compared with only one species for MCPA and mecoprop. Asulam was the least toxic.

Results were used to indicate the risk to each species from drift damage. A model of spray drift, based on that developed by Thompson & Ley (1982) for evaporating droplets, was rescaled to allow for field application rates and used to predict the distances travelled by given doses of herbicide. This gave acceptable agreement with reports for drift damage in the field, and predicted that only glyphosate sprayed at the highest recommended concentration might be unsafe to some of the species examined. The two herbicides sometimes used as volatile formulations (MCPA and mecoprop) did not cause damage at the small doses likely to result from exposure to vapour in the field.
Partial antibiosis to Rhopalosiphum padi in wheat and some phytochemical correlations
Authors: KAZEMI M. H. , van EMDEN H. F.
Published: February 2008

The fecundity of the aphid Rhopalosiphum padi during the first ten days of reproduction was measured on five wheats at three growth stages. The wheats were of UK and Iranian origin, but also involved both spring and winter wheats as well as hexaploid and tetraploid types. Aphids which had already been reared on the respective variety for at least one generation were transferred to the experimental plants. The tetraploid Emmer showed some resistance in comparison with the hexaploid UK varieties at later growth stages, whereas the Iranian variety Moghan 2 appeared relatively resistant only at the tillering stage. The other Iranian variety, Ommid, was resistant at all growth stages, and appears to be the most resistant hexaploid wheat variety to R. padi so far identified.

Correlations of aphid fecundity with plant chemistry were attempted with total phenolic compounds, hydroxamic acids and amino acids. All three of these chemical groups have previously been reported as correlated with plant resistance to cereal aphids. Even just for the results at the tillering stage, no correlation could be found for phenolics or hydroxamic acids, but a multiple regression based on the levels of alanine, histidine and threonine accounted for over 95% of the variation in aphid fecundity at all 15 data points (5 wheats × 3 growth stages). No cause or effect relationship is necessarily implied.
Vector specificity of barley yellow dwarf virus serotypes and variants in southwestern Idaho
Authors: HALBERT SUSAN E. , CONNELLY B. JUNE , LISTER RICHARD M. , KLEIN ROBERT E. , BISHOP GUY W.
Published: February 2008

Plants with symptoms of barley yellow dwarf virus (BYDV) obtained in infection feeding assays of aphids collected in the field in Idaho between 1986 and 1988 were tested for virus transmissibility by possible aphid vectors. Isolates obtained during 1987–1988 were also tested with a range of polyclonal antisera which distinguished PAV, MAV, SGV, RPV and RMV serotypes. In 1989 some Idaho (ID) BYDV isolates, maintained as standards for comparison, were serotyped and tested for aphid transmissibility, using 11 species of aphids.

There was not always the expected correspondence between serotype and vector specificity for ID isolates. For isolates obtained from field‐collected Rhopalosiphum padi, vector transmissibility and serotype corresponded with previous reports; however, 44% of isolates which were serotyped as RMV were also transmissible by species other than Rhopalosiphum maidis. Similarly, the transmissibility of the ID laboratory standards did not always conform to the reported vector specificity of serotypes. The laboratory ID‐MAV culture was transmitted by Metopolophium dirhodum and Myzus persicae as well as by Sitobion avenae. The laboratory ID‐SGV culture was transmitted by R. padi and 5. avenae as well as by Schizaphis graminum. The ID‐RPV culture was transmitted by S. graminum and Rhopalosiphum insertum as well as R. padi. Both of two laboratory ID‐RMV cultures were transmissible by R. insertum and R. padi transmitted one of them. The results indicate that, for isolates collected in Idaho, vector specificity cannot be assumed from their serotypes.
Ultrastructural changes associated with June Yellows in strawberry and with leaf yellowing symptoms of viral and genetic origin in Fragaria, Rubus and Ribes
Authors: WATKINS C. A. , ROBERTS I. M. , JONES A. T.
Published: February 2008

Light and electron microscopy was used to study the ultrastructural effects of June Yellows (JY) in leaves of strawberry. Four cultivars of strawberry, affected to different extents by JY, were compared with healthy (JY‐free) cv. Cambridge Favourite and with strawberry infected with strawberry crinkle rhabdovirus, Fragaria vesca infected with strawberry mottle virus (SMotV), raspberry and black currant showing virus‐induced yellowing and with strawberry and raspberry showing chaemeric yellow sectors in the leaves. Except for isometric virus‐like particles detected in SMotV‐infected F. vesca, no virus‐like particles or structures of other pathogenic agents were found in any of the tissues examined. Leaf cells of JY‐affected strawberry showed severe disruption of chloroplasts and plasmalemma, whorls of membranous vesicles and decreased vacuole size. The extent and severity of these abnormalities increased with increased severity of JY symptoms but, even in leaves with mild JY symptoms, chloroplast abnormalities were obvious. In the most severely affected leaves, the cells lacked discrete vacuoles and extensive hypertrophy was seen in other organelles such as nuclei and mitochondria. Few, if any, ultrastructural abnormalities were observed in virus‐infected strawberry or F. vesca, or in chaemeric leaves of strawberry and raspberry. By contrast, in raspberry and black currant with yellowed leaves caused by virus infection, the cells showed enlarged chloroplasts, decreased vacuole size and vesicle formation. However, chloroplast enlargement and disruption in this material seemed due to increased size of starch grains which were largely absent from swollen chloroplasts of JY‐affected strawberry. The ultrastructural abnormalities observed in JY‐affected strawberry are, therefore, not inconsistent with the possibility that a pathogenic agent may be involved in the condition.