bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural infection with raspberry bushy dwarf virus (RBDV) of the putatively RBDV‐resistant red raspberry cultivar Glen Moy, and the demonstration that it does not contain the RBDV resistance gene, Bu
Authors: JONES A TEIFION , McGAVIN WENDY J , MAYO M A , GRAHAM JULIE
Published: February 2008

When released to commerce in 1981, the red raspberry cv. Glen Moy was reported to be immune to the Scottish type isolate of raspberry bushy dwarf virus (RBDV‐D200). Field observations of this cultivar in localities where RBDV was prevalent tended to support this claim of its resistance, but in the past 6–10 yr, RBDV infection has been reported in this cultivar in Australasia, USA and in several commercial crops in England. Therefore, experiments were made to investigate the reason(s) for this apparent anomaly using RBDV‐infected material, putatively of cv. Glen Moy, from two locations in southern England and one each from Australia, New Zealand (NZ) and the USA. Genetic fingerprinting of genomic DNA from samples of these five RBDV‐infected raspberry sources confirmed their identity as cv. Glen Moy. Comparisons of some serological and genomic properties of the five Glen Moy RBDV isolates indicated that, whilst they shared many properties with previously well characterised isolates of this virus, they were distinguishable from them. Characterisation of the isolate from NZ maintained in raspberry showed that it did not have a Rubus host range characteristic of resistance‐breaking (RB) isolates, indicating that for this location, and probably also for those of Australia and the USA, RB isolates were not the cause of infection in cv. Glen Moy. When virus‐tested plants of cv. Glen Moy and 45 progeny seedlings from the cross between cv. Glen Moy and the RBDV‐susceptible cv. Autumn Bliss were graft inoculated with RBDV‐D200, all grafted plants became infected indicating that cv. Glen Moy does not contain the RBDV resistance gene, Bu. Possible reasons for the previously reported resistance of cv. Glen Moy to RBDV are discussed.
The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth and yield of winter cereals
Authors: BELL A C , BYRNE P M , WATSON S.
Published: February 2008

In 1986/1987 and 1987/1988 wild rabbits (Oryctolagus cuniculus) were trapped and enclosed in a 0.3 ha site in which two varieties of winter barley (Igri and Panda) and two of winter wheat (Norman and Mission) were grown in a split plot block design experiment. The level of rabbit population was varied to emulate natural variation in numbers throughout the growing season and was regulated to produce a peak density of 77 rabbits ha‐* in the first year, and 33 rabbits ha‐1! in the second year. Grazing was managed by the use of exclosure fences around plots to produce four treatment levels ‐ protected, autumn grazed, spring grazed and totally grazed regimes. Rabbit damage was assessed using stem and leaf damage indices several times through the growth of the crops. Yields were measured in terms of head number, grain weight and total yield.

There was no evidence of varietal preference among the four cereal varieties on the basis of damage assessments. In the first year the totally grazed treatment led to an increase in the number of unripe heads present at harvest which would indicate a delayed harvest date in a field crop. Winter wheat showed a trend towards higher yield loss in spring‐damaged plots, possibly linked to the time of tillering in this crop. Yield losses overall were highest in those plots grazed in either the autumn or throughout the entire season. The level of peak rabbit population did not appear to influence the degree of loss in either year. The results indicate that there may be a threshold of rabbit damage early in the growth of the crop which contributes most to the yield loss. This emphasises the importance of protecting a winter cereal crop at its establishment phase.
Antioxidant systems in the leaf apoplast compartment of Pinus pinaster Ait. and Pinus radiata D. Don. Plants exposed to SO2
Authors: DURAN‐CARRIL M V , BUJAN C RODRIGUEZ
Published: February 2008

The activities of guaiacol peroxidase (GuPOD), ascorbate peroxidase (ASAp), superoxide dismutase (SOD) and ascorbate/glutathione cycle (AGC) enzymes, together with ascorbate (ASC) and glutathione contents, were determined in apoplastic‐fluid and cell‐wall fractions of needles of Pinus pinaster Ait. and Pinus radiata D. Don. exposed for up to 6 months to SO2 (0.01 ppm or 0.30 ppm) in fumigation chambers. AGC enzyme activities (monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase) were in all cases undetectable, as was glutathione content. In needles of P. pinaster plants exposed to SO2, ascorbate content and all enzyme activities considered (except AGC enzymes) increased. The increases were most marked in response to the higher SO2 concentration. In needles of P. radiata, similar but less marked responses were observed. These findings suggest a) that enzyme activities and ascorbate contents increase in order to deal with the reactive oxygen intermediates produced during long‐term contamination with SO2, and b) that P. pinaster has more effective defences against contamination of this type than P. radiata.
The retting of flax after preservation with sulphur dioxide
Authors: EASSON D L , MOLLOY R. , ANDERSON R. , SHARMA H S S
Published: February 2008

Experiments were carried out to compare the retting of moist flax preserved with sulphur dioxide with that of green dried flax, using whole straw samples. When retted in water at either a constant 20°C or 28°C dried flax was fully retted after 15 and 10 days respectively whereas the sulphur dioxide treated flax (20 g sulphur dioxide kg“1 flax DM) had undergone almost no retting after 20 days at 20dC or 10 days at 28°C. Pre‐soaking the treated flax for 24 h in water and changing the acidified water, raised the pH of the retting liquor to a more normal value but did not significantly increase the rate of retting. Addition of the pectinase enzyme preparation ‘Flaxzyme’ to retting liquor at the rate of either 1.5 g kg‐1 or 3.0 g kg‐1 water, and at a constant temperature of 20°C, substantially increased the rate of retting of both sulphur dioxide treated and dried flax. Optimum degree of retting was achieved at 24 h with the treated flax and at 97 h with the dried flax. Pre‐rinsing of the sulphur dioxide treated straw only served to reduce the rate of retting. It was concluded that natural water retting of sulphur dioxide treated flax is retarded by the presence of acidic residues of sulphur dioxide, while enzyme retting is enhanced by these. In further smaller scale experiments using bundles of cut flax straw Flaxzyme was added at concentrations ranging from 0–8.0 ml litre 1 to containers containing flax in water at ratios from 1:10 to 1: 600 flax:water and the producion of galacturonic acid was used as an indicator of retting progress. Retting took place more rapidly at higher flax to water ratios for a given enzyme concentration. This effect was attributed to the lower pH of higher flax to water ratios which created pH conditions closer to the pH optimum for the retting enzymes. When enzyme retting was compared at a range of buffered pH's the optimum was pH 4.0. At a buffered pH of 4.0 and a temperature of 19°C, retting of sulphur dioxide treated moist flax (flax to water ratio of 1:10) was achieved with Flaxzyme concentrations as low as 0.5 ml litre”‘,much lower than the previously reported minimum of 3.0 ml litre’.
Forecasting the airborne spread of Mycosphaerella fijiensis, a cause of black Sigatoka disease on banana: estimations of numbers of perithecia and ascospores
Authors: BURT P. J. A. , ROSENBERG L. J. , RUTTER J. , RAMIREZ F. , GONZALES O H
Published: February 2008

Banana leaves showing different levels of black Sigatoka disease were collected from an unsprayed plantation in Costa Rica during two separate periods representing the wet to dry season transition (October 1993 – February 1994) and the dry to wet season transition (April – September 1995). Laboratory studies were used to investigate the relationship between the release of Mycosphaerella fijiensis ascospores and the amount of inoculum on banana plants showing different levels of infection, as assessed by leaf necrotic area. The number of perithecia present in the necrotic area was used as an indication of potential ascospore loads and was investigated as a series of regression equations. A series of rewetting and incubation regimes was used to investigate spore release under field conditions (21°C and 100% relative humidity in the early morning and 28°C, 60% relative humidity on days when it rained in mid‐afternoon). Results suggest that rainfall, combined with a high temperature, may lead to peaks of ascospore release but without necessarily increasing overall numbers released over periods of up to 4 days and that a high level of spore release was less sensitive to changes in temperature once it had been initiated. The exact role of temperature in spore release is still unclear, however, as leaf samples kept at atypically low temperatures also released non‐germinating ascospores. An average of 4.5 ascospores was released per perithecium. This does not resolve ambiguities in the literature regarding the number of ascospores present in each perithecium. A linear model relating the average ascospore numbers and necrotic area, using quick estimates of the amounts of necrotic area on the leaves of a random sample of plants across a plantation, is proposed, to give an indication of the relative amount of airborne inoculum potentially available between different plantations.
Long‐term effects of asparagus virus 2 infection on growth and productivity in asparagus
Authors: JASPERS M. V. , FALLOON P. G. , PEARSON M. N.
Published: February 2008

An asparagus field trial was established with clonal plants to determine the long‐term effects of asparagus virus 2 (AV2) infection on spear production. Yield data, analysed by ANOVA, showed that AV2 infection caused significant (P < 0.05) decreases in spear yield which became more pronounced as the trial progressed. Mean marketable spear yields were reduced by 14%, 28%, 20%, 48% and 57% and reject spear yields were increased by 93%, 105%, 207%, 352% and 167%, during harvest years 1–5 respectively. Marketable spear yields from AV2–free plants increased annually to yr 5, but for AV2–infected plants, yields increased to yr 3 and decreased annually thereafter. Spears from AV2–infected plants were thinner than those from AV2–free plants, resulting in more reject thin spears by 109%, 88%, 220%, 499% and 216% during harvest yr 1–5, respectively. Further, data collected in yr 4 and 5 showed that AV2 infection had caused a 31 % reduction in mean spear diameter and reductions of 27% and 22% respectively, in diameter and height of fern stalks. Clearly, plants with smaller fern stalks were less able to accumulate carbohydrate reserves and therefore produced fewer, smaller spears and fern stalks the following spring. This may result in annual cycles of diminishing productivity in which the size and number of spears and fern stalks decrease with each successive year. The type and timespan of symptoms caused by AV2 infection in this trial are similar to those reported for asparagus decline syndrome and therefore it is likely that AV2 infection is a factor contributing to asparagus decline.
Effects of turnip mosaic virus and turnip yellow mosaic virus on the survival, growth and reproduction of wild cabbage (Brassica oleracea)
Authors: MASKELL L. C. , RAYBOULD A. F. , COOPER J. I. , EDWARDS M‐L , GRAY A. J.
Published: February 2008

Wild plants of Brassica oleracea (wild cabbage) are commonly infected with turnip mosaic poty virus (TuMV), turnip yellow mosaic tymovirus (TYMV) and several other viruses. A field experiment in which plants were inoculated either with TuMV or TYMV showed that virus infection significantly reduced survival, growth and reproduction. Relative to water inoculated‐controls, plants infected with TYMV had greater mortality, were shorter, had a smaller leaf area and number, showed a greater amount of damage from herbivory and chlorosis, were less likely to flower and produced fewer pods and lower total seed output. Plants infected with TuMV did not appear to be adversely affected at first; however, mortality after 18 months was higher than control plants. Although TuMV infection had no effect on the number of plants flowering, the infected plants did produce fewer pods and a lower total seed output. We conclude that both viruses can significantly affect vegetative and reproductive performance of wild cabbage and hence that introgression of virus resistance (particularly when conferred by a major gene or a transgene) from a crop might increase plant fitness in natural populations of this species. Ecological risk assessments of virus resistance transgenes must do more than survey adult plants in natural populations for the presence of the target virus. Failure to detect the virus could be due to high mortality on infection with the virus.
Mode of action of fosthiazate used for the control of the potato cyst nematode Globodera pallida
Authors: WOODS S. R. , HAYDOCK P. P. J. , EDMUNDS C.
Published: February 2008

Fosthiazate (Nemathorin 10G Ishihara Sangyo Kaisha Ltd, Japan) is a new nematicide approved for use on potatoes Solanum tuberosum L. in die UK for die control of die potato cyst nematodes Globodera rostochiensis (Woll). Skarbilovich and G. pallida (Stone). Fosdiiazate delayed and suppressed hatch of die potato cyst nematode Globodera pallida in bom in vitro laboratory tests and a glasshouse pot experiment. In vitro hatch was temporarily inhibited by fosdiiazate concentrations above 0.09 μg ml‐1 and increasing me fosdiiazate concentration further prolonged the duration of hatch inhibition. Analysis of fosthiazate soil concentrations, using high‐pressure liquid chromatography, during me glasshouse experiment showed mat hatch was suppressed in the soil at concentrations above 0.5 mg kg‐1. Other factors such as the paralysis of hatched nematodes in the soil solution are also involved.
Temperature and heterogeneity of emergence time in oilseed rape
Authors: SQUIRE G. R.
Published: February 2008

Emergence of oilseed rape cultivars with known differences in germination profile was examined by controlled sowings in the field at mean temperatures between 2 and 10°C. Early percentiles, up to the 50th in two cultivars (Rocket and Martina) and up to the 20th in a third (Comet), responded to temperature similarly at all sowings, in that 1/time to emergence of a percentile (emergence rate) increased exponentially with temperature above an intercept of‐1°C. For these percentiles, emergence occurred at a similar thermally weighted time over the whole range of temperature, indicating the peak of the first flush of seedlings is predictable. Percentiles higher than those cited above displayed increasing non‐germination (probably secondary dormancy) as temperature declined towards winter. The maximum non‐germination ranged between 50% and 80% among the cultivars. In sowings during and just after winter, the emergence rate of these higher percentiles was lower than at a comparable temperature before winter. A portion of non‐germinating seeds of the two most heterogeneous cultivars overwintered and emerged synchronously in April from a range of pre‐ and post‐winter sowings, probably stimulated by increasing diurnal temperature amplitude from 7 to 15K. At low temperature, therefore, cultivars exhibited great heterogeneity in the emergence profile, those with more heterogeneity being more likely to give rise to temporally separate weed or feral populations. The findings are discussed in the context of weediness and transgene movement in the oilseed rape metapopulation.
Molluscicidal and slug‐repellent properties of anaerobically digested organic matter
Authors: SPEISER B.
Published: February 2008

Slug problems in arable crops and vegetables have increased drastically during the past few decades. Observations on slug damage to oilseed rape suggested that fresh, anaerobically digested organic material from a biogas production plant is molluscicidal. To find out whether digested matter can be used for the control of agricultural pest slugs, a series of exeriments were carried out. The laboratory experiments demonstrated strong mollusc repellent and molluscicidal effects of digested organic matter against the three most important pest slugs of Switzerland,Arion lusitanicus, A. distinctusandDeroceras reticulatum.The effects were restricted to fresh digested matter and were rapidly lost when the material was stored, and also after application in the field. In the field experiment, fresh digested matter greatly reduced slug damage to lettuce in comparison with the untreated plots. At present, the chemical nature of the molluscicidal compound(s) in digested matter is unknown, but environmental pollutants such as heavy metals can be ruled out. Current research aims at a new formulation which is easier to apply and has a longer‐lasting molluscicidal or slug‐repellent effect, and at optimising the dosage and number of applications.
Capture efficiency of insect natural enemies from tall and short vegetation using vacuum sampling
Authors: HOSSAIN Z. , GURR G. M. , WRATTEN S. D.
Published: February 2008

Experiments were conducted in lucerne to determine the efficiency of vacuum sampling of insects and whether this was affected by the height of vegetation sampled. Three insects of significance as predators of pests in Australian lucerne were studied: transverse ladybird beetle (Coccinella transversalisFabricius), pollen beetle (Dicranolaius bellulus(Guérin‐Méneville)), and spined predatory shield bug (Oechalia schellembergii(Guérin‐Méneville)). In a preliminary experiment comparing a commercially harvested area of lucerne with an unharvested area within the same crop, the proportions of released insects recaptured from unharvested lucerne were significantly lower than recoveries from the shorter, harvested lucerne. Resampling the tall lucerne after it was cut by hand gave cumulative recapture proportions which did not differ from those observed for the harvested lucerne. A second experiment with a randomised replicated design re‐tested the hypotheses of the preliminary experiment for two insect species. Very similar results were obtained. This verification showed that recapture efficiencies from tall lucerne ranged between 0.60 and 0.74 but that resampling after hand cutting gave cumulative recapture proportions in excess of 0.86 which did not differ from recapture proportions from short lucerne.
Discrimination of cachexia disease agents among citrus variants of hop stunt viroid
Authors: REANWARAKORN K. , SEMANCIK J. S.
Published: February 2008

Description of a cachexia disease specific oligonucleotide is presented which may be employed as a probe in molecular hybridisation as well as a primer in reverse transcriptase‐polymerase chain reaction (RT‐PCR) procedures to segregate cachexia‐inducing citrus viroids (CVd) from the non‐cachexia variant, CVd‐IIa, known to introduce commercially desirable effects on tree growth and performance. The cachexia‐specific probe also demonstrates the ability to discriminate between the severe cachexia variants, CVd‐IIb and CVd‐IIc, and moderate to mild variants, Ca903 and Ca909.
Comparison of subjective and objective methods to assess flax straw cultivars and fibre quality after dew‐retting
Authors: SHARMA H. S. S. , FAUGHEY G. J.
Published: February 2008

Subjective and objective methods were compared for the assessment of the quality of unretted and retted straw, and the fibres obtained after dew‐retting of four flax cultivars, Ariane, Evelin, Laura and Viola. Maturity of straw, degree of retting, ease of decortication after retting, divisibility, handle, cleanliness and colour were assessed as subjective factors and of these, degree of retting and handle appear to be useful for assessing quality. The samples were also analysed for physical and chemical differences using a range of objective methods. Straw quality could not be graded using height and maturity, although stem diameter and technical length could indicate quality. Changes in N, lipid and ash content, as a result of retting, were observed. The increase in the proportions of fibre fractions present in retted compared with unretted straw, due to microbial degradation of pectin, could be identified by thermal analysis. Analyses of the fibre samples to determine fineness, strength, cellulose, hemicellulose, lignin and minerals were carried out and significant differences in some of the parameters were identified. Cultivar Laura produced the best fibre. Fibre fineness, ash, lipid, caustic weight loss and fibre fractions as determined by thermal analysis were found to be important objective parameters for quality assessment. The assessment of fibre samples performed subjectively by an expert grader and by selected objective methods gave similar quality rankings.
A laboratory assessment of the relative susceptibility of Molinia caerulea (L.) Moench and Calluna vulgaris (L.) Hull to a range of herbicides
Authors: MILLIGAN A. L. , PUTWAIN P. D. , MARRS R. H.
Published: February 2008

There is a concern that Molinia caerulea (L.) Moench may be increasing in upland moorland communities at the expense of Calluna vulgaris (L.) Hull and other ericaceous species. In order to develop a strategy for the control of Molinia, laboratory studies were carried out to determine the dose‐response relationships of seven graminicides and glyphosate on both Molinia caerulea and Calluna vulgaris. Plants were grown under laboratory conditions and sprayed with increasing doses of herbicide using a precision sprayer. Results were highly variable, indicating the great morphological plasticity of these two species, making determination of the ED50 difficult. Glyphosate, quizalofop‐ethyl and sethoxydim successfully reduced various measures of Molinia growth to 50% of control levels (ED50 estimates ranged from 0.41–0.67 kg a.i. ha‐1, 0.18–1.20 kg a.i. ha‐1and 0.37–0.49 kg a.i. ha‐1respectively). In contrast, only glyphosate reduced Calluna growth significantly (ED50s ranged from 0.025–0.45 kg a.i. ha‐1), whilst selective herbicides left it undamaged. A comparison of the results for Molinia and Calluna suggests that there is no application rate of glyphosate which will reduce Molinia effectively whilst leaving Calluna undamaged. Recommendations for field testing of selective herbicides are discussed.
The effects of priming treatments using seaweed suspensions on the water sensitivity of barley (Hordeum vulgareL.) caryopses
Authors: MÖLLER M. , SMITH M. L.
Published: February 2008

Two seaweed suspensions, one prepared fromAscophyllum nodosum(Linnaeus) Le Jolis (ANS), another fromLaminaria hyperborea(Gunn.) Foslie (LHS), were evaluated for their effects on the water sensitivity of barley (Hordeum vulgareL.) seeds. Priming in either seaweed suspension did not reduce viability. Priming in ANS was beneficial to seeds germinated in elevated water levels. The suspension ofA. nodosumreduced the water sensitivity of barley seeds better than either water or polyethylene glycol (PEG) priming treatments. ANS also reduced the microbial population on the seeds by 86%. The hygroscopic properties and the antibiotic effect of the suspension ofA. nodosumresulted in greater oxygen availability to the embryo, enabling more seeds to germinate under oxygen deficient conditions.
Floral biology of ‘Bulida’ apricot trees subjected to postharvest drought stress
Authors: RUIZ‐SANCHEZ M. C. , EGEA J. , GALEGO R. , TORRECILLAS A.
Published: February 2008

Drip irrigated ‘Búlida’ apricot trees (Prunus armeniaca L., on Real Fino apricot rootstock) were submitted to drought stress by withholding irrigation for two different postharvest periods for two consecutive years. The first treatment (T–1) started immediately after harvest, and lasted 11/2 months, while the second treatment (T–2) started when the first treatment finished and lasted 2 months. These stress treatments were compared with a control treatment (T–0), which was irrigated throughout the year so that it received an amount of water equivalent to 100% of the crop evapotranspiration (ETc) demand. Flowers from the three treatments showed similar quality (fresh weight, petal surface area and pistil length) and frequent macrostyle (stigma located above the anthers). A lower percentage of pollen germination was observed in grains from the following year's bloom in plants from the T–1 treatment. The T–1 drought stress also induced a significant decrease in fruit yield, due to an increase in fruitlet drop, which led to significantly lower fruit set. The T–2 treatment did not affect these processes and was not critical as regards apricot yield. The fruits harvested met the required standards of quality in all treatments.
Rice Ragged Stunt Oryzavirus: role of the viral spike protein in transmission by the insect vector
Authors: GUOYING ZHOU , XIONGBIN LU , HUIJUAN LU , JUANLI LEI , SHENGXIANG CHEN , ZUXUN GONG
Published: February 2008

A 39 kDa protein, known as the viral spike protein or one of the protein components forming the viral spike, encoded by genomic segment 9 (S9) of Rice Ragged Stunt Oryzavirus (RRSV) was obtained by enzymatic cleavage of a fusion protein expressed by S9 cDNA in bacteria with proteinase factor Xa. The feeding of an insect vector — the rice brown planthopper (Nilaparvata lugens) on purified expressed 39 kDa protein before the inoculation of the insects on diseased rice plants could completely inhibit the vector transmission ability of the insect. The presence of a 32 kDa insect cell membrane protein which could bind to 39 kDa viral spike protein indicated that the inhibition might be resulted from the competition in the interactions of 39 kDa protein and intact virus with the virus receptors on the insect cells. These results suggest that the spike proteins of the plant reoviruses are essential for the virus infection in the interactions of virus, insect vectors and host plants. These results are also useful in the practical applications.
Detection of wheat‐alien recombinant chromosomes using co‐dominant DNA markers**
Authors: KHAN IMTIAZ AHMED
Published: February 2008

A study of homoeologous recombination along almost the complete genetic length of two homoeologous chromosomes in the Triticeae was conducted. Sears' phlb mutant was used to induce homoeologous pairing between chromosomes 7A of common wheat and 7Ai–l of Agropyron intermedium. 390 ph1b ph1b homozygous F3 progeny were screened using six co‐dominant DNA markers (RFLP loci). 63 of the progeny (16%) were putative recombinants, showing dissociation of RFLP markers within the arm(s). Progeny tests of self‐fertile putative recombinants confirmed the dissociation phenotypes observed in the F3 progeny. No recombination could be confirmed in 117 F3 progeny plants having the Ph1– allele (control population). Frequencies and distribution of chiasmata along the chromosome arm 7AS were analysed using additional RFLP markers. The patterns of recombination between the two homoeologous chromosomes were found similar to those reported for homologous recombination between the same markers on short arms of group 7 chromosomes of Triticeae.
Cell cycle inhibition of potato root tips treated with Imazethapyr
Authors: SPACKMAN V. M. T. , COBB A. H.
Published: February 2008

Imazethapyr inhibits the progression of the cell cycle in potato (Solanum tuberosum L.) root tips. A variety of existing methods were developed and adapted for the determination of mitotic index in potatoes. Significantly lower numbers of mitotically dividing cells were recorded after just 30 min of incubation with imazethapyr (0.35 μM) and the effect was characterised as an inhibition of mitotic entry. Imazethapyr inhibits a key enzyme in the biosynthesis of the branched‐chain amino acids, valine, leucine and isoleucine. The inhibition of mitotic entry can be considered to be a secondary manifestation of a primary metabolic change induced by imazethapyr.
A review of the status of the New Zealand flatworm in the UK
Authors: CANNON R. J. C. , BAKER R. H. A. , TAYLOR M. C. , MOORE J. P.
Published: February 2008

The indigenous terrestrial planarian fauna (three species) of the UK is outnumbered by introduced exotics, of which there are at least nine species. The New Zealand flatworm,Arthurdendyus triangularis, is one of the most widespread and apparent of these non‐indigenous earthworm predators, particularly in Northern Ireland and central Scotland. Despite its having been in the UK for at least 35 yr, our knowledge of the biology and ecology of this species remains somewhat limited.

In Scotland,A. triangularisoccurs predominantly in botanical and domestic gardens, and is not generally considered to be a problem on agricultural land. The situation in Northern Ireland is different; although predominantly found in domestic gardens, it appears to have colonised grass leys many localities although the impact on earthworm populations remains ambiguous. In England, records are increasing, predominantly from northern regions.

Studies have indicated that earthworm species vary in terms of their vulnerability to predation byA. triangularis;surface‐active and anecic species are considered to be most at risk. However,A. triangulatusand earthworm populations are known to coexist, apparently in a state of dynamic equilibrium, in a number of localities.

Naturally‐occurring planarian populations are often severely constrained by food supply, but individuals survive lengthy periods of starvation. Such behaviour may preclude the natural recolonisation of habitats by prey species. Very much higher rates of population growth can be achieved where food is not limited, and where favourable conditions result from horticultural practices. The mobility of the prey species may determine the dispersal strategy of the flatworm predator, and a propensity not to move away from centres of prey density might account for the relatively low rate of colonisation of agricultural land byA. triangulatus.Additionally, reliance on protected refuges, may explain the present, somewhat limited distribution in the UK, particularly in southern England.

It is difficult to estimate the potential distribution ofA. triangulatus, because of the lack of fundamental knowledge of its ecoclimatic requirements. A better understanding is needed of the precise habitat requirements (and constraints) ofA. triangulatus, particularly where this species appears to have adapted to rural conditions.
Host‐plant susceptibility to the carrot fly, Psila rosae. 2. Suitability of various host species for larval development
Authors: DEGEN THOMAS , STÄDLER ERICH , ELLIS P R
Published: February 2008

Several apiaceous and two asteraceous species were tested for their suitability to support larval development of the carrot fly. Plants grown in pots or transplanted from seed beds into pots, were inoculated with a specific number of eggs. Pupae and non‐pupated larvae were collected 6–7 wk after inoculation. Both the number and weights of pupae produced varied widely among the species. Cultivated carrots Daucus carota sativus often gave rise to only moderate numbers of pupae, but these invariably attained the highest weights. Pimpinella major was the only apiaceous plant tested that did not yield any carrot flies. The two asteraceous plants Cichorium intybus and Tanacetum vulgare failed to support larval development. Total carrot fly biomass produced per plant was influenced by both the host species and the root weight. Emergence rates of adult flies were positively correlated with pupal weights. Small individuals tended to have a longer total developmental time from egg to adult fly.
Host‐plant susceptibility to the carrot fly, Psila rosae. 3. The role of oviposition preferences and larval performance
Authors: DEGEN THOMAS , STÄDLER ERIC , ELLIS P R
Published: February 2008

The acceptability of various plant species to ovipositing carrot flies was weakly, but significantly correlated with the host's suitability for larval development. Both adult host‐plant preferences and larval performance as determined in laboratory experiments explained a part of the variation in susceptibility among the various test plants observed in the field. Across the whole set of plant species examined, antixenosis contributed more substantially to resistance than antibiosis, while the reverse seemed to be true for carrot cultivars.
Comparative effects of three insect growth regulator insecticides and a dipteran‐active strain of Bacillus thuringiensis on cropping of the cultivated mushroom Agaricus bisporus
Authors: WHITE P F
Published: February 2008

Three insect growth regulator insecticides and an entomopathogenic strain of Bacillus thuringiensis (GC327), products effective against the mushroom sciarid, Lycoriella auripila, were compared for their effect on mushroom cropping. Cyromazine and diflubenzuron were applied as a surface drench to mushroom compost before or after pasteurisation (at filling or spawning, respectively); admixed into casing material (at casing); or at a combination of these times. Hexaflumuron and GC327 were applied only at filling and casing, respectively. The presence of the target pest, L. auripila, had no effect on treatment trends, although it was accounted for in the analysis by use of a yield model. The trial was notable for the disparate effects that cyromazine and diflubenzuron casing treatments had on mushroom cropping. Cyromazine treatments that included application at casing resulted in increases in yield, compared to the untreated control whereas, with diflubenzuron, the opposite was true, with treatment at casing alone causing the greatest reduction overall (10%). GC327 applied at casing was also conspicuous for giving a 13% increase in yield. Treating the crop at casing with either cyromazine or GC327, therefore, resulted in a 15% or 24% increase in yield, respectively, compared to a similar treatment with diflubenzuron. Hexaflumuron applied at filling caused increases in yield compared to application of cyromazine at filling and cyromazine or diflubenzuron at spawning. There were also effects on crop timing. The addition of a cyromazine casing treatment normally caused the distinct flushes of mushrooms to be produced significantly earlier than the untreated control (up to 2.5 days), as did GC327. With diflubenzuron, the earlier flushes were only produced by those treatments that did not include a casing application. The combinations that included a casing treatment with diflubenzuron initially produced mushroom flushes earlier than the untreated control. They became either synchronous with the control or they were delayed. From the crop tolerance perspective, therefore, cyromazine and GC327 would be the sciarid control products of choice for a commercial mushroom grower.
Water and temperature relations of softrot bacteria: growth and disease development
Authors: SCHOBER B M , ZADOKS J C
Published: February 2008

The effect of water availability and the temperature of the growth substrate on growth and disease development of softrot bacteria were studied using artificial media and plant material. Water availability was measured as the osmotic potential of a solution (ψosm) and was assessed for solutions of PEG4000 and KNO3 as artificial osmotica and for plant tissue of chicory heads. Growth of softrot bacteria was found at water potentials from ψ= ‐0.12 MPa to ψ= ‐8.0 MPa but the lag phase of the growth curve increased with decreasing water potential. The relative growth rates of the three softrot pathogens showed a sigmoidal relationship with water potential, the relative growth rates decreasing rapidly at water potentials lower than ψ= ‐1.5 MPa. The water potential of harvested chicory heads decreased with storage time of the harvested crop but was still within the growth limits for softrot bacteria. In relation to temperature, the relative growth rate of Erwinia carotovora subsp. carotovora (Ecc) was highest at 10°C, of Erwinia carotovora subsp. atroseptica (Eca) at 15°C and of Pseudomonas marginalis (Pm) at 5°C. Chicory heads of two cultivars, Rumba and Salsa, inoculated with Ecc, had a significantly higher disease severity at 30°C (0.72 for Rumba and 0.47 for Salsa) than at lower or higher temperatures. In conclusion, temperature and water availability during forcing of chicory were not factors limiting populations of softrot bacteria. Possibilities for crop protection thus only avail during chicory root storage. During storage a high death rate combined with a low growth rate of the softrot bacteria may result in a decrease of bacterial populations below the minimum densities needed for infection during the forcing of chicory heads.
Isolation, characterisation and identification of a potyvirus from Dioscorea alata L. (water yam) in Nigeria
Authors: ODU B O , HUGHES J d'A , SHOYINKA S A , DONGO L N
Published: February 2008

A yam potyvirus was isolated from Dioscorea alata samples collected in Nigeria. The virus was not transmissible mechanically but was transmitted by Aphis craccivora to four cowpea cultivars (Ife Brown, IT84S‐2114, IT82E‐10 and TVu2657), and from which it could be mechanically transmitted between the cowpea cultivars. In infectivity‐ tests using cowpea extracts, the virus had a dilution end point of 10‐4, a thermal inactivation point of 60–65°C and longevity in vitro of 2 days at room temperature. The virus coat protein had an estimated molecular weight of 32 100 daltons. The virus was identified as an isolate of Dioscorea alata virus (DAV; syn. yam virus 1) due to its biological characteristics and its serological reaction with antiserum raised against DAV. The virus is not related to yam mosaic virus, but distantly related to blackeye cowpea mosaic virus and cowpea aphid‐borne mosaic virus.
Effects of natural sequence variation on symptom induction by citrus viroid III
Authors: OWENS R A , THOMPSON S M , FELDSTEIN P A , GARNSEY S M
Published: February 2008

The potential use of viroids as citrus dwarfing agents has been studied for more than 30 yr, and Semancik, Rakowski, Bash & Gumpf (1997) have recently shown that infection of ‘Valencia’ scions growing on trifoliate orange rootstocks by either citrus viroid Ia, IIa, or IIIb results in a desirable dwarfed tree canopy phenotype and enhanced fruit production. Viroids exist in vivo as populations of closely related sequence variants, and we are interested in isolating variants of citrus viroid III specifically adapted to induce desirable levels of dwarfing in different citrus cultivars. As the first step toward selecting suitable variants from large populations of mutagenised RNA transcripts, we examined the biological properties of several naturally‐occurring variants of CVd‐IIIb. Five sequence variants were cloned and slash‐inoculated into Etrog citron. Four of these including the type sequence CVd‐IIIb were infectious, and most of the sequence changes initially present were maintained in the respective progeny. Two changes in the putative pathogenicity domain of CVd‐III were associated with a marked reduction in symptom expression in Etrog citron. These results suggest that, with a suitable screening assay, it should be possible to select stable variants with different dwarfing properties from populations of mutagenised CVd‐III RNAs synthesised in vitro.
Severity of infection of Moroccan barley yellow dwarf virus PAV isolates correlates with variability in their coat protein sequences
Authors: BENCHARKI B. , MUTTERER J. , YAMANI M El , ZIEGLER‐GRAFF V. , ZAOUI D. , JONARD G.
Published: February 2008

Biological properties and deduced amino acid sequences of the overlapping coat and 17kDa proteins were compared for 12 barley yellow dwarf virus PAV‐type isolates collected at different locations in Morocco. The biological variability of the 12 isolates was investigated by inoculation to a set of as many as eight barley cultivars and an oat cultivar. Significant biological variability was observed among the Moroccan PAV–type isolates, with the isolates falling into two clusters. Cluster 1 contained isolates MA9501, MA9502, MA9504, MA9512 and MA9513, and cluster 2 the MA9415, MA9505, MA9508, MA9511, MA9514, MA9516 and MA9517. Isolates of cluster 2 produced more severe symptoms and stunting than did those of cluster 1 when inoculated to appropriate index plants. In parallel, the nucleic acid sequences were obtained for the region containing the cistron coding for the coat protein (CP) and 17 kDa protein for all 12 isolates by reverse transcription followed by the polymerase chain reaction. Sequence homology grouping yielded the same two clusters of the isolates as found by measuring biological variability. Comparisons of the CP sequences between the two clusters revealed 87.4% to 90.5% nucleotide identity and 82.6% to 87.6% amino acid identity. Comparison with other sequenced isolates demonstrated that the CP's of cluster 1 were closely related to the Australian (Vic‐PAV), the North American (NY–PAV, P–PAV), and Japanese (JPN–PAV) PAV–type isolates. The CP's of cluster 2, on the other hand, were closely related to the North American PAV–129 isolate. Finally, an RFLP test on CP gene–derived PCR products has been developed which distinguishes between the two clusters of the PAV–type isolates.
Use of lichen secondary metabolites as antifeedants to protect higher plants from damage caused by slug feeding
Authors: CLARK S J , HENDERSON I F , HILL D J , MARTIN A P
Published: February 2008

Extracts of 15 species of lichen were tested for antifeedant properties against the field slug Deroceras reticulation (Müller) (Mollusca: Pulmonata). All but three showed some activity and two of these were from endolithic species. The most effective extract was from Letharia vulpina. The major active compound from this species, vulpinic acid, was tested for dose response, applied as a foliar spray to turnip plants and as a dressing to wheat seeds in laboratory experiments. It provided effective protection against slug feeding under these conditions.
High temperature during storage favours infection potential of resting spores of Polymyxa graminis of Indian origin
Authors: LEGREVE A. , VANPEE B. , DELFOSSE P. , MARAITE H.
Published: February 2008

The infection potential of sporosori of Polymyxa graminis involved in the transmission of the Indian peanut clump virus (IPCV) was assessed by culturing bait plants exposed to various concentrations of sporosorus suspensions and then determination of the numbers of plants that became infected. Storage of air‐dried inoculum at temperatures above 30°C resulted in an increase in the infection potential compared to that of sporosori stored at 15°C or 20°C. In contrast, when the sporosori were stored at ‐20°C or freeze‐dried, their infection potential was low. These results confirm the adaptation of P. graminis isolates associated with IPCV transmission to the tropical environment. The implication of storage temperature for the epidemiology of Indian peanut clump virus and for the assessment of the infection potential of the vector in the soil is discussed.
In vitro root induction in axillary microshoots of Quercus robur L.
Authors: PUDDEPHAT I J , ALDERSON P G , WRIGHT N A
Published: February 2008

Whilst considerable efforts have been made to optimise shoot multiplication and rooting in oak, little attention has been paid to the impact of conditions used for multiplication on subsequent root formation. An optimised technique for rooting of oak microshoots has been developed to assess the effect of cytokinin treatments applied to shoot multiplication cultures on the subsequent rooting of microshoots. We found IBA to be more effective at inducing root formation in microshoots than NAA. Efficient rooting of oak microshoots (80%) was achieved after 35 days on medium supplemented with 1.0 mg litre‐1 IBA. Lower concentrations of IBA reduced the frequency of root formation and significantly increased the time taken for microshoots to form roots. High concentrations of IBA (3.0 mg litre‐1) produced similar rooting frequencies but with significantly increased numbers of roots formed by each microshoot. However, high concentrations of IBA stimulated the production of basal callus. Rooting of microshoots was unaffected by the concentration of BA used during shoot multiplication, although basal callusing was greater in microshoots taken from multiplication medium supplemented with the highest concentration of BA (1.0 mg litre‐1) and rooted on medium supplemented with 3.0 mg litre IBA. Reducing the period of exposure to auxin to 7 days by transferring microshoots to auxin‐free medium increased the frequency of root formation (84%), led to more rapid root formation and a reduction in basal callus formation.
Response of two strains of Nostoc muscorum to metal stress and salinity
Authors: PANDEY U. , CHATTERJEE C.
Published: February 2008

Two strains of a cyanobacterium Nostoc muscorum, wild‐type N. muscorum (Cds) and an isolate having resistance to the heavy metal cadmium (Cdr), were selected for characterisation of their growth potential and physiological assays in certain defined stress environments.

The chosen determinants were copper (heavy metal) and NaCl (salt stress). The observations on growth, heterocyst frequency, chlorophyll and nucleic acid contents, photosynthetic O2 evolution, 14C incorporation and acetylene reduction suggested that the strain Cdr was also resistant to copper. This strain, however, was found to be more sensitive to NaCl in comparison to its wild‐type counterpart. NaCl was found to enhance sugar accumulation in Cds and was more inhibitory to acetylene reduction rates than to the photosynthetic activities. The interaction between Cu and NaCl appeared to be antagonistic as the depression of growth and physiological activities by a mixture of the two was lesser than that caused by either of these. These observations form the first report on the response of a metal resistant strain of cyanobacterium to salinity.
Rapid identification of adult whiteflies in plant consignments using monoclonal antibodies
Authors: SYMONDSON W O C , GASULL T. , LIDDELL J E
Published: February 2008

A rapid and simple method for the identification of adult whiteflies (Homoptera: Aleyrodidae) would be valuable, both to facilitate pest management decision making and, more importantly, to prevent the introduction of new pests into non‐infested areas. Considering the enormous economic losses that have resulted in the recent past from the accidental introduction of harmful species, there is a clear and urgent need for a reliable antibody‐based test kit that would allow non‐specialist growers, extension workers and customs authorities to identify whiteflies. As a first step in this process, this paper describes the development and characterisation of monoclonal antibodies capable of distinguishing between major pest species of whitefly, and application of these antibodies in an enzyme‐linked immunosorbent assay (ELISA). A monoclonal antibody is described that reacts strongly with both male and female Trialeurodes vaporariorum (Westwood) but not with either Bemisia tabaci (Gennadius) or B. argentifolii Bellows & Perring. A second antibody is reported that gives a strong response to female Bemisia sp. that does not react with T. vaporariorum of either sex. The two antibodies used in combination provide a powerful means of distinguishing between adult whitefly, particularly at low levels of infestation in plant consignments, when pupae cannot easily be found.
Characterisation of Cydia pomonella granulovirus from codling moths in a laboratory colony and in orchards of British Columbia*
Authors: EASTWELL KENNETH C , COSSENTINE JOAN E , BERNARDY MICHAEL G
Published: February 2008

Sequence analyses indicate that a granulovirus isolated from a laboratory colony of codling moth in British Columbia, Canada is identical or very similar to the Mexican isolate of Cydia pomonella granulovirus (CpGV‐M). In addition to codling moth, the vims was found to cause mortality of secondary leafroller pests of North American orchards, including the fruit tree leafroller and the obliquebanded leafroller. A survey in apple growing regions of British Columbia indicates that 23% of the wild population of codling moth larvae carry CpGV.