bluuebunny/crossref_metadata_2025 huggingface dataset:
Differentiation of citrus tristeza closterovirus (CTV) isolates by single‐strand conformation polymorphism analysis of the coat protein gene
Authors: RUBIO LUIS , AYLLONl M ANGELES , GUERRI JOSÉ , PAPPU HANNU , NIBLETT CHUCK , MORENO PEDRO
Published: February 2008

Citrus tristeza closterovirus (CTV) isolates of several geographical origins were compared for variations in their coat protein (CP) gene by analysis of single‐strand conformation polymorphism (SSCP). The CP gene of 17 isolates was reverse transcribed, amplified by polymerase chain reaction (PCR), and 22 clones were inserted into a plasmid vector. These clones were sequenced and found to have between 91.7% and 99.8% sequence homology. Clones were amplified and the PCR products denatured and compared by SSCP analysis in 8% polyacrylamide gels. Using two different electrophoretic conditions, the patterns were different for 16 or 17 clones. Four pairs of clones (T36/T66, P1/Q2, 03/8Q, and E1/E2) differing by 10, 2, 1 and 1 nucleotides, respectively, could not be distinguished using either condition. When these clones were compared by SSCP after digestion with Eco91I (BstEII) three of the pairs (T36/T66, P1/Q2, and 03/8Q) could be differentiated, whereas the clones E1 and E2 (differing by 1 nucleotide) remained indistinguishable. Thus, SSCP analysis combining two electrophoretic conditions and restriction of eight clones with Eco91I allowed discrimination between 21 of the 22 CP gene clones selected.

SSCP analysis may provide a procedure to identify and differentiate CTV isolates based on comparisons of several genes or gene regions. It is rapid and cheap and may drastically reduce the amount of sequencing necessary for accurate comparisons.
Alfalfa mosaic and cucumber mosaic virus infection in chickpea and lentil: incidence and seed transmission
Authors: JONES R A C , COUTTS B A
Published: February 2008

Samples collected in 1994 and 1995 from commercial crops of chickpeas and lentils growing in the agricultural region of south‐west Western Australia were tested for infection with alfalfa mosaic (AMV) and cucumber mosaic (CMV) viruses, and for members of the family Potyviridae using enzyme‐linked immunosorbent assay (ELISA). In 1994 no virus was detected in the 21 chickpea crops tested but in 1995, out of 42 crops, AMV was found in two and CMV in seven. With lentils, AMV and/or CMV was found in three out of 14 crops in 1994 and 4 out of 13 in 1995, both viruses being detected in two crops in each year. Similar tests on samples from chickpea and lentil crops and plots growing at experimental sites, revealed more frequent infection with both viruses. No potyvirus infection was found in chickpeas or lentils in agricultural areas either in commercial crops or at experimental sites. However, bean yellow mosaic virus (BYMV) was detected along with AMV and CMV in irrigated plots of chickpeas and lentils at a site in Perth.

When samples of seed from infected crops or plots of chickpeas and lentils were germinated and leaves or roots of seedlings tested for virus infection by ELISA, AMV and CMV were found to be seed‐borne in both while BYMV was seed‐borne in lentils. The rates of transmission found through seed of chickpea to seedlings were 0.1–1% with AMV and 0.1–2% with CMV. Seed transmission rates with lentil were 0.1–5% for AMV, 0.1–1% for CMV and 0.8% for BYMV. Individual seed samples of lentil and chickpea sometimes contained both AMV and CMV. With both species, infection with AMV and CMV was sometimes found in commercial seed stocks or seed stocks from multiplication crops of advanced selections nearing release as new cultivars. Seed‐borne virus infection has important practical implications, as virus sources can be re‐introduced every year to chickpea and lentil crops or plots through sowing infected seed stocks leading to spread of infection by aphid vectors, losses in grain yield and further contamination of seed stocks.
Influence of post‐treatment temperature, solvents and emulsifiers on the toxicity of cypermethrin to larvae of Spodoptera litura (Fab.)
Authors: JAGLAN R S , SIRCAR P.
Published: February 2008

Larvae of the tobacco caterpillar, Spodoptera litura (Fab.) were topically bioassayed with cypermethrin emulsion formulation and proprietary EC in combination with different solvents and emulsifiers for their toxicity at 16 ± 2°C and 27 ± 1°C. Among different solvents, the descending order of efficacy (with relative toxicity in parenthesis) against 9 ± 1 day old larvae of S. litura (Fab.) at 16 ± 2°C than 27 ± 1°C was: xylene (7.41), aromex (5.54), cyclohexane (4.93), C‐IX (3.93), benzene (2.40) and toluene (2.26). With emulsifier, the order was: Triton X‐100 (7.41), SN4S (4.60), Teepol (2.90), Tween‐80 (1.49), Swascofix DP‐50 (1.28), SN4R (1.10) and S52B (1.07). However, the proprietary cypermethrin EC was 2.31 times more toxic at 16 ± 2°C than at 27 ± 1°C.
A review of the physiology of potato tuber dormancy
Authors: WILTSHIRE J J J , COBB A H
Published: February 2008

A review of the scientific literature relating to the physiology of potato (Solanum tuberosum) tuber dormancy is presented. Effort has been concentrated on an up‐to‐date overview of the current state of understanding, rather than comprehensively covering the very extensive literature going back over many decades. The format chosen follows the fate of the crop. After defining tuberisation and dormancy, the physiological activity of the dormant tuber is reviewed and the storage environment is considered from both a physical and chemical standpoint. Advances in chemical control and the potential for molecular biology are highlighted.
Influence of soil applied nitrogen (NPKS 25: 5: 5:5) on Brevipalpus phoenicis Geijskes (Acari: Tenuipalpidae) mite incidence and damage symptoms on tea
Authors: SUDOI V. , KHAEMBA B M. , WANJALA F M E.
Published: February 2008

Application of nitrogenous fertilisers (NPKS 25: 5: 5:5) for yield of tea and to induce tolerance to the red crevice (Brevipalpus phoenicis Geijskes) mite was found to be rates between 150 and 200 Kg N ha‐1 yr‐1 rates above 400 Kg N ha‐1 encouraged the build up of mites on tea. Damage symptoms resulting from mite infestation declined with increase in application of nitrogenous fertilisers.

The levels of nitrogen in the leaf tissues increased with soil applied nitrogen and also was related to the mite numbers found on the leaves suggesting a link. The symptoms of the discoloured necrotic leaf base that accompanied mite infestation was significantly (P≤ 0.05) and linearly correlated (r = 0.60) to mite numbers in the control plot. The levels of applied nitrogen were negatively correlated to % leaf necrosis suggesting a tolerance leading to reduction in necrotic symptoms with fertiliser applications.
Characterisation of a new virus from escarole
Authors: CRESCENZI A. , NUZZACI M. , STRADIS A DE , COMES S. , PIAZZOLLA P.
Published: February 2008

A new virus associated with mosaic, yellowing and necrotic symptoms in escarole has been isolated recently in southern Italy. The virus, for which the name escarole mosaic virus (EMV) is proposed, was transmissible by mechanical methods, by seeds and probably by pollen but not by Acyrthosiphon pisum, Aphis gossypii, Myzus persicae, Trialeurodes vaporariorum or Frankliniella occidentalis. The virions showed a single coat protein of about 32 kDa and eight encapsidated RNA species. Viral preparations sedimented as four components in sucrose density gradients. Electron microscopy indicated the presence of spherical particles with a diameter of 25 nm. Ultrastructural investigations on infected tissues revealed the formation of atypical inclusion bodies.
Comparison of the coat protein of groundnut rosette assistor virus with those of other luteoviruses
Authors: SCOTT K P. , FARMER M‐J , ROBINSON D J. , TORRANCE L. , MURANT A F.
Published: February 2008

The coat protein gene of groundnut rosette assistor virus (GRAV) was cloned and sequenced. The deduced amino acid sequences of the coat protein and of another protein encoded in a different, overlapping, reading frame resemble those of other luteoviruses. Four monoclonal antibodies against GRAV, prepared using denatured coat protein as immunogen, also reacted with some other luteoviruses in ELISA. Nevertheless, they will be useful as reagents for the identification of GRAV infections in groundnut.
In vitro growth and ripening of strawberry fruit in the presence of ACC, STS or propylene
Authors: PERKINS‐VEAZIE P M. , HUBER D J. , BRECHT J K.
Published: February 2008

Strawberry (Fragaria ananassa Duch.) fruit exhibit limited capacity for continued development following harvest. This problem can be circumvented by maintaining harvested strawberry fruit in solutions containing sucrose and a bactericide. In this study, we investigated the respiratory and ethylene production kinetics and ethylene responsiveness in strawberry fruit harvested immature and ripened in vitro in the presence of propylene. The effects of 1‐amino‐cyclopropane‐1‐carboxylic acid (ACC) and silver thiosulfate (STS) alone and in combination were also examined. Respiration and ethylene patterns of fruit harvested green and developed in vitro declined with maturation and ripening, as did those of field‐grown fruit harvested at different stages of ripeness. Exposure of detached green strawberry fruit to 5000 μl litre‐1 propylene failed to stimulate respiration or ethylene production, but advanced pigmentation changes and fresh‐weight gain significantly. Excised fruit provided with 1 mol‐3 ACC exhibited increased ethylene production, enhanced fresh‐weight gain, and accelerated anthocyanin accumulation, but showed no change in respiration. The developmental response of harvested strawberry fruit to propylene or ACC was dependent on fruit maturity at harvest, with white fruit exhibiting greater insensitivity compared with green fruit. Silver thiosulfate (0.5 mol‐3) applied alone or in combination with ACC failed to delay ripening in excised strawberry fruit. These experiments demonstrate that ripening in detached strawberry fruit can be modified by ethylene only in green fruit that are provided with a carbohydrate source. Ethylene, when applied exogenously as ACC or propylene to green fruit, can slightly increase fruit growth and the rate of colour development.
Effects of soil incorporation on the efficacy of the rhabditid nematode, Phasmarhabditis hermaphrodita, as a biological control agent for slugs
Authors: WILSON M J. , HUGHES L A. , HAMACHER G M. , BARAHONA L D. , GLEN D M.
Published: February 2008

The effects of soil cultivation immediately after application of the rhabditid nematode, Phasmarhabditis hermaphrodita, to the soil surface were investigated in two field experiments. The first experiment was done in mini‐plots separated by barriers, with an artificially introduced population of slugs (Deroceras reticulatum). Nematodes were applied as a drench at a rate of 3 times 109 ha‐1 in one of two application volumes and then left undisturbed or incorporated into the soil by cultivation to 2 cm or 10 cm depth. Moist soil conditions were maintained by irrigation throughout the experiment. Nematode application significantly reduced slug damage to Chinese cabbage seedlings throughout the 7 wk duration of the experiment and the population of D. reticulatum in soil 7 wk after treatment. However, soil cultivation had no effect and did not interact with the effect of nematodes. In the second experiment, in a crop of winter wheat, nematodes were applied to soil by hand‐lance at a rate of 3 times 109 ha‐1 and left undisturbed on the soil surface or incorporated by spring‐tine cultivation to a depth of 2, 5 or 10 cm. In this experiment, nematodes were applied to dry soil. Cultivation alone had no effect. Nematode application reduced slug damage to wheat plants in plots where nematodes were incorporated into the soil, but not where they were left on the surface. There was no detectable impact of nematodes on slug populations in the wheat experiment.
Molecular ecology of some Cecidophyopsis mites (Acari: Eriophyidae) on Ribes species and evidence for their natural cross colonisation of blackcurrant (R. nigrum)
Authors: FENTON B. , JONES A T. , MALLOCH G. , THOMAS W P.
Published: February 2008

Ribosomal DNA from Cecidophyopsis mites from different Ribes species was amplified using the polymerase chain reaction and the products digested using restriction enzymes. After separating the DNA fragments on gels, it was possible to identify specimens of mites obtained from field samples by comparing the profiles of their DNA banding patterns with those of known Cecidophyopsis species. Using this analysis, a non‐gall forming mite found infesting blackcurrant buds in New Zealand was identified as the gooseberry mite (C. grossulariae). On wild red currant (Ribes spicatum) from Finland showing two sizes of galled buds, the red currant gall mite (C. selachodon) was identified in the larger galls located at the tips of branches and a distinct mite in the smaller galls located on the lower parts of the branches. A mite with a DNA banding profile indistinguishable from this latter mite from R. spicatum was also identified in galled buds of blackcurrant genotypes growing in Finland, including those containing the blackcurrant gall mite (C. n'ftw)‐resistance genes P or Ce. The DNA banding profile of this mite resembled most closely that of C. ribis, but was distinct from it. The occurrence of C. grossulariae and this distinct Cecidophyopsis mite on blackcurrant has implications for the genetic control of Cecidophyopsis mites and possibly for the spread of the reversion disease agent in this crop.
The effects of organic and conventional farming methods on plant bug densities (Hemiptera: Heteroptera) within winter wheat fields
Authors: MOREBY S J.
Published: February 2008

An understanding of the mechanisms responsible for direct and indirect effects of pesticides on Heteroptera were studied by comparing densities within fields of winter wheat on organically and conventionally managed farms. Weed and insect densities were estimated in 56 fields in 1990 and 62 in 1991. Four out of five of the heteropteran groups studied were more numerous within organic fields in both years, however differences were statistically significant in only one out of 10 comparisons. Differences in agricultural practices between the two farming regimes are given as possible reasons for the densities observed.
Genetic variation in Drechslera teres populations as indicated by RAPD markers
Authors: PELTONEN S. , JALLI M. , KAMMIOVIRTA K. , KARJALAINEN R.
Published: February 2008

Random amplified polymorphic DNA (RAPD) was used to assess genetic variation among 48 isolates of Drechslera teres originating from different sites in Finland. RAPD profiles were generated with five arbitrary 10‐mer primers and revealed polymorphisms suitable for screening differentiation in this fungal population. Using UPGMA clustering analysis, a similarity coefficient of approximately 63% was observed between all D. teres isolates studied. The variation was, however, distributed on a small scale as different genotypes were found from the same plant. The isolates could not be grouped according to geographic origin, aggressiveness, growth rate or morphological features, indicating that the primers used in this study were neutral markers for these characters. The primers were, however, able to differentiate between isolates of Helminthosporium species (D. teres, Drechslera graminea and Bipolaris sorokiniana).
Unusually severe symptoms are a characteristic of the current epidemic of mosaic virus disease of cassava in Uganda
Authors: GIBSON R W. , LEGG J P. , OTIM‐NAPE G W.
Published: February 2008

Mosaic disease (MD) is more severe in cassava plants infected within the area of the current epidemic in northern and central Uganda than to the south of the affected area. This difference in severity was recorded within a single cultivar as well as amongst the mixtures of cultivars found commonly in farmers' fields. An increase in severity also occurred as the epidemic passed through localities. Varietal or agroecological factors coincident with the area of the epidemic are therefore unlikely to cause the increased severity. The severe disease could also be graft and cutting transmitted and could super‐infect mildly diseased plants. Both mildly and severely diseased plants gave positive reactions in ELISA tests to antisera prepared against African cassava mosaic virus (ACMV) and an unusually severe form of ACMV or a closely related geminivirus is likely to be the cause of the severe mosaic disease. The epidemic also involves increased populations of the whitefly vector of ACMV, Bemisia tabaci, and possible hypotheses are presented as to how these phenomena may be related.
A novel luteovirus from sweet potato, sweet potato leaf speckling virus
Authors: FUENTES S. , MAYO M A. , JOLLY C A. , NAKANO M. , QUERCI M. , SALAZAR L F.
Published: February 2008

A virus obtained from accession DLP 1541 of the International Potato Center (CIP) sweet potato germplasm collection was shown to induce a curling and a white speckling of the leaves of infected plants. We propose to name it sweet potato leaf speckling virus (SPLSV). It was found in samples from 15 of 77 accessions tested and also in samples from farms at Chiclayo and Trujillo in northern Peru. SPLSV was transmissible by grafting, but not mechanically, and was transmitted in a persistent manner by Macrosiphum euphorbiae but not by Myzus persicae, Aphis gossypii or whiteflies. Isometric particles were purified from infected plants by procedures designed to purify luteoviruses. Reverse transcription and polymerase chain reaction amplification of RNA from SPLSV‐infected plants using degenerate primers designed to amplify sequences either in luteovirus RNA or in potato leafroll virus (PLRV) RNA yielded c. 500 bp and c. 600 bp DNA fragments respectively. The nucleotide sequence of these fragments encoded two polypeptides characteristic in sequence of luteovirus proteins, which suggests that SPLSV should be classified in the genus Luteovirus. The amino acid sequence of the putative coat protein was 70% identical to that of PLRV. On the basis of the coat protein sequences, SPLSV is more similar to PLRV than is any other luteovirus. However, SPLSV particles did not react with antibodies to PLRV in ISEM or ELISA tests.
Weed performance in crop rotations with and without leys and at different nitrogen levels
Authors: ANDERSSON TORSTEN N. , MILBERG PER
Published: February 2008

Weed populations were studied from a 26‐year‐old field experiment in southern Sweden with three different 6‐year crop rotations, each with four rates of nitrogen application. The rotations differed in that one had a two‐year legume‐grass ley, another had a two‐year grass ley, and that the third had spring wheat followed by a repeatedly harrowed fallow. The leys and the fallow were followed by turnip rape, winter wheat, oats and barley which was undersown in the two ley rotations. Data on weed biomass, collected in one season, were subjected to multivariate analysis.

Winter turnip rape had the highest weed biomass. However, of the several weed species, only Matricaria perforata Merat was important in wheat (the crop following turnip rape in the rotation). The weed flora did not differ consistently between rotations. We conclude that none of the three rotations had developed any major weed problems under the past weed management regime (herbicides applied to cereal crops).

There was no consistent effect of nitrogen fertilisation on total weed biomass in any of the three rotations. However, when comparing the weed floras in winter wheat, turnip rape and oats, the unfertilised plots differed from the plots receiving nitrogen. In the two latter crops, the abundant, low‐growing annual Stellaria media (L.) Vil. performed best in fertilised plots with dense stands. Equisetum arvense L., the most abundant perennial weed, was important only in unfertilised plots.
The influence of R:FR ratio on the growth, photosynthesis and rooting ability of Terminalia spinosa Engl. and Triplochiton scleroxylon K. Schum
Authors: NEWTON A C. , DICK J McP , McBEATH C. , LEAKEY R R B.
Published: February 2008

Stockplants of the tropical hardwoods Terminalia spinosa Engl, and Triplochiton scleroxylon K. Schum were grown in a controlled environment under red:far‐red (R:FR) ratios ranging from 0.5‐3.1. In both species, rates of shoot height increment were higher (P < 0.05) under the low R:FR ratios as a result of increased internode elongation. In Terminalia spinosa, specific leaf area (SLA) was also significantly higher under lower R:FR ratios, values ranging from 175 to 210 cm2 g‐1 in the 3.1 and 0.9 treatments respectively. No effect of R:FR ratio on SLA was recorded in Triplochiton scleroxylon. Pre‐severance photo‐synthetic rate, stomatal conductance and water‐use efficiency were increased under the higher R:FR ratios in Terminalia spinosa, rates of photosynthesis ranging between 2.68‐4.59 μmol m‐2 s‐1 in the 0.5 and 3.1 R:FR treatments respectively. Gas exchange rates of Triplochiton scleroxylon were unaffected by R:FR treatment. These contrasting responses to variation in R:FR ratio were associated with differences in rooting ability. In Terminalia spinosa, significantly higher percentage rooting was recorded in the cuttings from the 3.1 R:FR treatment than from 0.5, with values of 93.7% and 77.5% recorded respectively. R:FR ratio also affected rooting percentages of Triplochiton scleroxylon, but in this case, higher rooting percentages were recorded in the lower R:FR ratios, values ranging from 31.1–54.1% in the 3.0 and 0.5 R.FR treatments respectively. This difference in rooting response is attributed to the contrasting effects of R:FR ratio on the leaf and stem morphology of the two species. The implications of these results for stockplant management are discussed.
Identification of phytoplasmas associated with a decline of European hackberry (Celtis australis)
Authors: BERTACCINI A. , MITTEMPERGHER L. , VIBIO M.
Published: February 2008

The presence of phytoplasmas in declining trees of European hackberry was demonstrated for the first time using polymerase chain reaction assays with primers amplifying phytoplasma 16S rDNA regions. Restriction fragment length polymorphism analysis of these DNA fragments together with PCR, employing primers specific for particular phylogenetic groups of phytoplasmas, made it possible to detect the presence of aster yellows group (16SrI) related phytoplasmas. These were classified into two different subgroups (I‐B and I‐C) and were present in both symptomatic and asymptomatic hackberry plants. Aster yellows‐related phytoplasmas were found in all the root samples collected during the winter. In addition, phytoplasmas from the peach X disease group (16SrIH) were found in four out of 10 root samples; in five root samples phytoplasmas of the elm yellows group (16SrV) were also present.
Monoclonal antibodies for the detection and differentiation of faba bean necrotic yellows virus isolates
Authors: FRANZ A. , MAKKOUK K M , KATUL L. , VETTEN H J
Published: February 2008

Murine monoclonal antibodies (MAbs) were produced for the detection of faba bean necrotic yellows virus (FBNYV), an isometric ssDNA virus belonging to a new, yet unnamed genus of plant viruses. A total of 19 FBNYV‐specific MAbs were obtained from three fusion experiments and characterised by determining their immunoglobulin types and titres as well as their corresponding epitopes. At least six distinct epitopes were revealed on FBNYV particles of different virus isolates. Only two MAbs reacted with SDS‐dissociated FBNYV virions in triple antibody sandwich (TAS)‐ELISA and with viral capsid protein in Western blots. Almost all MAbs were more sensitive in detecting FBNYV in viruliferous aphids by TAS‐ELISA than polyclonal anti‐FBNYV IgG by double antibody sandwich ELISA and permitted virus detection in individual aphids even following short acquisition access feeding periods.

Coat protein variation among FBNYV isolates and serological relatedness to taxonomically similar viruses was studied by determining the cross reactivity of these MAbs with several field isolates of FBNYV as well as with milk vetch dwarf (MDV), banana bunchy top (BBTV), and subterranean clover stunt (SCSV) viruses. Whereas none of the MAbs reacted with BBTV, only one reacted with SCSV, indicating that FBNYV and SCSV share a common epitope. By contrast, 16 of the 19 MAbs reacted with MDV, suggesting that FBNYV and MDV are serologically closely related and strains of the same virus. When all 19 MAbs produced were tested against a total of 107 samples of FBNYV collected during virus surveys in Egypt, Ethiopia, Jordan, Morocco and Syria, five MAbs showed differential reactions. While the majority of the samples reacted with all 19 MAbs, about 20% of the 107 FBNYV samples did not react with one and/or other of these five MAbs, permitting the differentiation of seven serotypes of FBNYV and suggesting a considerable coat protein variation in FBNYV isolates from the countries surveyed. The MDV isolate from Japan and five FBNYV samples from Ethiopia appeared to be the least closely related to typical FBNYV isolates by not reacting with three and four, respectively, of the five differentiating Mabs.
Distribution and incidence of yellowing viruses in sugar beet crops in Spain from 1990 to 1993
Authors: ROMAN C PEREZ DE SAN , ORTIZ A. , AYALA J.
Published: February 2008

Surveys of the principal yellowing viruses of sugar beet, beet yellows virus (BYV) and beet mild yellowing virus (BMYV) in Spain were carried out from 1990–1993. Beet yellowing viruses were detected in all provinces, although the mean percentages of plants infected with BYV and BMYV were practically zero in the southern zone. Within the northern zone high variations from one province to another could be observed. The mean percentages of plants infected with BYV were higher in the Ebro Valley than in the Duero Valley. Areas infected with BYV were very restricted, while BMYV could be found to a variable extent all over Spain, although the infection levels were lower. The incidence and distribution of these viruses in the Spanish sugar beet crop makes the study and application of control measures for beet yellowing viruses necessary.
Viral twig necrosis of sweet cherry. Modes of transmission and spread of petunia asteroid mosaic virus (PeAMV)
Authors: PFEILSTETTER E. , KUNZE L. , ZINKERNAGEL V.
Published: February 2008

Grafting symptomless scions, derived from petunia asteroid mosaic virus (PeAMV)‐infected trees, to healthy rootstocks resulted in only 3.3% infection in the resulting trees. Up to 90% of seeds from infected sweet cherries contained high quantities of PeAMV, but the virus was not transmitted to the seedlings apparently because of low virus content in the embryo and loss of infectivity during seed maturation and storage. Replanting healthy cherry trees cv. Sam, grafted to different rootstocks, into contaminated soils resulted in new infections. Eight of 13 trees on rootstocks derived from Prunus avium (F 12/1 and cv. Sam on its own roots) were infected with PeAMV within a period of four years but only one of 16 trees on Weiroot‐rootstocks (selections from Prunus cerasus) became infected. The detection of PeAMV in naturally contaminated soil samples by the bait plant procedure, using Nicotiana clevelandii, was superior to testing soil eluates by enzyme‐linked immunosorbent assay (ELISA) and immuno electron microscopy (IEM). Wild plants may contribute to virus propagation and maintenance of virus contamination of the soil as 25 of 310 samples from 712 herbaceous plants growing in the vicinity of infected trees contained PeAMV; the contaminated samples represented 12 species. The perpetuation of PeAMV by infected scion wood is probably of minor significance, and infection via the soil probably represents the most important means of spread of viral twig necrosis in northern Bavaria.
Determining the effectiveness of resistance to subterranean clover mottle sobemovirus in different genotypes of subterranean clover in the field using the grazing animal as virus vector
Authors: FERRIS D G , JONES R A C , WROTH J M
Published: February 2008

The effectiveness of resistance to subterranean clover mottle sobemovirus (SCMoV) previously identified in different genotypes of subterranean clover (Trifolium subterraneum) inoculated with infective sap in the glasshouse, was tested in two field experiments which used the grazing animal as virus vector. Replicated plots each consisting of paired test rows of 20 different genotypes were used. Clover plants infected with SCMoV were transplanted in between the paired test rows and these acted as sources of the virus for spread by grazing sheep. Although used in different years at different sites with different virus isolates, the field exposure methodology employed produced consistent results. The genotypes each behaved similarly in both experiments as regards the relative extents of SCMoV infection that developed, levels ranging from 0–98%. The previously identified resistance in six ‘highly resistant’ and three ‘partially resistant’ cultivars was effective under field conditions. However, the ‘partial resistance’ in three others was overcome, cvs Green Range and Mt Barker developing levels of infection approaching those in ‘susceptible’ cultivars, while an intermediate infection level developed in cv. Karridale. The three cultivars in which partial resistance was not effective all belonged to ssp. subterraneum. In subterranean clover breeding programmes, field screening using the grazing animal as a vector is advisable to determine whether SCMoV resistance found by sap inoculation is still effective under field conditions.
Environmental assessment of veterinary avermectins in temperate pastoral ecosystems
Authors: WRATTEN S D , FORBES A B
Published: February 2008

Avermectins and their metabolites are excreted mainly in the faeces; they do not readily move from the site of dung deposition because of their low solubility in water and their tight binding to organic matter. Avermectins degrade in the environment through photodegradation and aerobic breakdown by soil organisms. The dung mesofauna potentially exposed to avermectin residues includes insects, earthworms, springtails, mites and nematodes. These organisms occupy a variety of different niches within the ecosystem and the faunal composition changes as the pats age. Some members of this fauna act in concert with soil microbial flora and assist in the breakdown of dung and consequent nutrient re‐cycling on pasture. There are marked seasonal patterns of faunal abundance and behaviour which affect their relative importance in the decomposer community. Some species of the coprophagous insect fauna, particularly in the larval stages, can be adversely affected by the presence of avermectin residues in the faeces. Veterinary use patterns of avermectins in temperate regions indicate that peak periods of insect activity and peak times of avermectin use are often asynchronous. When avermectin usage and insect activity do coincide, the heterogeneous patterns of administration to livestock and the focus of treatment on young animals result in the deposition on pasture of faeces which are predominantly free of avermectin residues. Results of large scale, long term studies indicate that, even under conditions of relatively high levels of avermectin use in cattle, the impact on non‐target insect populations and their function is limited.
Vectoring ability of aphid clones of Rhopalosiphum padi (L.) and Sitobion avenae (Fabr.) and their capacity to retain barley yellow dwarf virus
Authors: JING‐QUAN GUO , LAPIERRE HERVÉ , MOREAU JEAN‐PIERRE
Published: February 2008

Vectoring ability of four aphid clones, Rp‐M and Rp‐R26 of Rhopalosiphum padi and Sa‐R1 and Sa‐V of Sitobion avenae, to transmit barley yellow dwarf (PAV, MAV and RPV) luteoviruses (BYDV) was compared in controlled conditions. Significant differences between highly efficient vectors (HEV), Rp‐M and Sa‐Rl, and poorly efficient vectors (PEV), Rp‐R26 and Sa‐V, were found in transmission of their specific viruses with acquisition and inoculation access periods (AAP, IAP) of 5 days. BYD‐RPV was occasionally transmitted by both clones of S. avenae. None of 150 tested apterous adults of the Rp‐R26 transmitted BYD‐MAV, while 10% of transmission was observed from those of the Rp‐M in a parallel test. An improved ELISA and immuno‐PCR were adapted to test for viruses in aphids. The results obtained by the improved ELISA indicated there was a good correlation between virus detection in single aphids of HEV clones after a 5 day AAP and virus transmission by them. In contrast, the percentages of virus‐carrying aphids of PEV clones were generally higher than those of their transmission rates. BYD‐MAV and BYD‐RPV were also detected by the improved ELISA in single aphids of their PEV clones, with the exception of BYD‐RPV in those of Sa‐V. However, after a 2‐day IAP, the improved ELISA in most cases failed to detect these viruses in single aphids of PEV clones.

Detection by immuno‐PCR demonstrated that all three viruses could be acquired and retained by the aphids of both HEV and PEV clones. But, as visualised from electrophoretic bands, after the 2‐day IAP the amplified products from aphid extracts of PEV clones were reduced. The detection in a batch of nine aphids by the improved ELISA revealed that virus content in PEV clones decreased more rapidly than that in HEV clones during transmission. Thus, the difference in transmission efficiency of the aphid clones within species was not caused by an inability to acquire virus, but was determined by variation in vectoring ability between them. This was due to differences in ability to prevent the passage of virions from haemocoel to salivary duct and/or different capacities for the retention of BYDV.
Susceptibility of the summer fruit tortrix moth, Adoxophyes orana (Lepidoptera: Tortricidae), to chlorpyrifos and strategies for insecticidal control in orchards
Authors: CROSS J V
Published: February 2008

The susceptibility of populations of the summer fruit tortrix moth, Adoxophyes orana, from apple orchards in Kent, England, to chlorpyrifos was determined in 1992, 1994 and 1995, by topically dosing larvae feeding on leaves or adults adhered to pheromone trap sticky bases. LD50 values (range 6.3 to 23.2 ng chlorpyrifos per individual) for first or second generation males, second generation females or for first generation fourth instar larvae collected in the field were significantly greater (2–3 fold) for populations from orchards with a long history of treatment with broad‐spectrum organophosphorous and other insecticides than for those from untreated orchards (range 1.6 to 8.1 ng chlorpyrifos per individual), though there was considerable variation between sites and years.

Twelve replicated orchard experiments between 1993 and 1995 were used to examine a range of different strategies for insecticidal control. Applications of chlorpyrifos against overwintered larvae feeding in trusses in spring gave, at best, a 75% reduction in larval numbers, insufficient to prevent damage by the subsequent generation in summer. However, two applications of fenoxycarb (one immediately pre‐and one immediately post‐blossom of apple cv. Cox) completely prevented successful subsequent development of the pest, and a single (post‐blossom) spray nearly so.

The timing of application of chlorpyrifos against first generation larvae hatching from eggs in June was shown to be critical and currently used methods of spray‐timing were unreliable. The effective persistence of chlorpyrifos was short (< 7 days). Though good control could be achieved with a single spray, a better strategy was to apply a series of sprays at 7‐day intervals to cover the egg hatch period. Sprays of Bacillus thuringiensis at the same timing intervals gave, maximally, an 80% reduction in larval numbers, but usually less: improved control was not achieved by applying a programme of sprays compared to a single spray, though a novel, more potent, formulation was significantly more active. Triazophos was also effective as an egg hatch spray. Sprays of chlorpyrifos or tebufenozide between late September and mid‐October 1995 against second or third instar larvae migrating to overwintering sites before diapause, failed to reduce significantly the numbers of subsequent overwintering larvae or the numbers that emerged to feed on blossom trusses in spring.
Development of pea bacterial blight caused by Pseudomonas syringae pv. pisi in winter and spring cultivars of combining peas (Pisum sativum) with different sowing dates
Authors: MANSFIELD P J , WILSON D W , HEATH M C , SAUNDERS P J
Published: February 2008

Pea bacterial blight occurred by natural infection in a field trial on peas in 1995. Disease development in the winter cultivars Rafale, Frilene and Froidure was compared with that in the spring cultivars Baccara, Conquest and Bohatyr, each sown on six dates in October, November, December, mid‐March, late March and April. Disease incidence had reached 100% plants affected in all treatments by mid‐July. Disease severity was greater in winter‐sown (October, November or December) than in spring‐sown peas of each cultivar at each assessment. Significant (P < 0.05) differences in disease severity occurred between cultivars in the winter‐sown plots in May and June and the spring cultivars were affected more severely than the winter cultivars. Comparison of areas under the disease progress curves for both disease incidence and severity also showed that the winter‐sown peas were more affected by disease than spring‐sown peas and that spring cultivars were more severely affected than winter cultivars. Yield was strongly correlated with disease severity. A linear regression model suggested that, for peas sown in October, November or December, a yield loss of 0.5 tha‐1 occurred for each 10% increase in canopy area affected by pea bacterial blight.
Factors determining recovery and reversion in mosaic‐affected African cassava mosaic virus resistant cassava
Authors: GIBSON R W , OTIM‐NAPE G W
Published: February 2008

The severity and persistence of symptoms of mosaic virus disease were monitored during the first six months of two growing seasons in cassava of the African cassava mosaic virus (ACMV)‐resistant cv. TMS 30572 either inoculated by grafting with a mild or severe strain or infected from the planted cutting. Symptomless shoots developed between January and March 1995 in two field trials differing in age by c. 6 months; this recovery occurred during particularly hot weather. Recovery was often only temporary in the plants inoculated with the severe strain and occurred later compared with those inoculated with the mild. In 1996, the weather was cooler and recovery that year was delayed until flowering, c. 7 months after planting, when recovered shoots were often produced from buds in the axils of symptomless leaves produced amongst diseased leaves. Most cuttings taken from the upper parts of diseased plants produced symptomless (reverted) progenies whereas most cuttings taken from the base of diseased plants produced diseased progenies. Reversion seemed to be associated with the recovery that had already occurred in the upper stems of the parent plants.
Determining the relative roles of different aphid species as vectors of cucumber mosaic and bean yellow mosaic viruses in lupins
Authors: BERLANDIER F A , THACKRAY D J , JONES R A C , LATHAM L J , CARTWRIGHT L.
Published: February 2008

Glasshouse and field studies were done to determine the relative roles of different colonising and non‐colonising aphid species as vectors of two non‐persistently transmitted viruses, cucumber mosaic cucumovirus (CMV) and bean yellow mosaic potyvirus (BYMV) in narrow‐leafed lupin (Lupinus angustifolius) crops in Australia. The abilities of nine different aphid species in transmitting CMV from infected to healthy lupins and BYMV from infected subterranean clover to healthy lupins were compared in the glasshouse using 5–10 min acquisition access feeds. The percentage transmission efficiencies found with lupin‐colonising aphid species were (CMV/BYMV): Acyrthosiphon kondoi (6/15), Aphis craccivora (10/14) and Myzus persicae (11/77). With non‐colonising species the respective efficiencies were: Brachycaudus rumexicolens (0.9/0), Lipaphis erysimi (4/8), Rhopalosiphum maidis (9/6), R. padi (5/5), Sitobion miscanthi (2/11) and Therioaphis trifolii (4/5). When flying aphids were trapped in the field in four successive years (1993–1996) on vertical nets downwind of virus‐infected lupins, 13 different species were caught at a “wheatbelt” site and 18 at an urban irrigated site. Of 2833 aphids caught at the “wheatbelt” site, 64 transmitted CMV to lupin test plants. At the irrigated site, numbers of aphids transmitting CMV/numbers caught were 12/186 while the corresponding numbers for BYMV were 11/727. M. persicae, A. kondoi and R. padi transmitted both viruses, while additional vectors of CMV found were A. craccivora, Acyrthosiphon pisum, B. rumexicolens, L erysimi, R. insertum, T. trifolii and Toxoptera citricidus. Averaged over four years, A. kondoi accounted for 50% of CMV transmissions at the “wheatbelt” site, M. persicae for 16% and R. padi for 22%, and these three species were caught in the greatest numbers, comprising 28%, 13% and 37% respectively of the total catch. At the irrigated site R. padi accounted for half the CMV transmissions, while R. padi and A. kondoi together accounted for most of the BYMV transmissions. R. padi, A. kondoi, M. persicae and T. citridus were the most common aphid species at this site. These findings suggest that M. persicae, A. kondoi and R. padi are the aphid species likely to be most important as vectors of CMV and BYMV in narrow‐leafed lupins grown in mediterranean‐type climatic zones of southern Australia.
Effect of specific leaf nitrogen content on photosynthesis of sugarcane
Authors: ALLISON J C S , WILLIAMS H T , PAMMENTER N W
Published: February 2008

In the laboratory, rate of photosynthesis (P) of the youngest fully emerged leaf lamina on a shoot, whether taken from a 4 or 8 month old sugarcane plant, increased approximately linearly with specific leaf nitrogen content (SLN) from < 1.0 to c. 1.7 g m‐2; the rate of increase was greater the higher the incident photosynthetically active radiation (PAR) flux density, over the range 80 to 1600 μmol m‐2s‐1. In a field crop receiving standard fertiliser, including 150 kg N ha‐1, SLN of the green leaf canopy decreased more or less linearly with depth, from > 1.7 g m‐2at the top to c. 1.0 g m‐2at the bottom at 15 wk of age, and progressively with time to 1.2 to 0.85 g m‐2from top to bottom of the canopy by week 45. Where an extra 300 N ha‐1were applied in top‐dressings, the decrease in SLN with time was somewhat smaller, to 1.3 to 0.9 g m‐2from top to bottom of the canopy by week 45. Calculations with a model, using the data from laboratory and field, suggest a decrease of about 25% in canopy gross P and about 30% in canopy net P from wk 15 to wk 45 in the crop receiving standard fertiliser only; the calculated decreases where the crop received additional nitrogen were about 17% and 20% respectively. There would seem to be a need for a change in type of cultivar to make profitable use of augmented nitrogen fertiliser.
Observations on feeding and population structure of five New Zealand terrestrial planarians which prey on lumbricid earthworms
Authors: YEATES G W , BOAG B. , JOHNS P M
Published: February 2008

The feeding of five terrestrial planarians found in New Zealand on European lumbricid earthworms was studied. Under laboratory conditions between 60–83% ofArtioposthiaspp. fed in the first 24 h compared with 21–40% ofAustraloplanaspp. The mean percentage weight gain varied from 31% forAustraloplana sanguineavar.albato 113% forArtioposthiasp. 1. Analysis of the weights of the planarian species showed a mean 11‐fold difference betweenAustraloplana sanguineaandArtioposthia triangulataand that these body weights were not related to mean percentage weight gains after feeding. The relationship between the weights of egg capsules and pregnant female planarians was similar forAustraloplana sanguineavar.alba(11%),Artioposthia triangulata(12%) andArtioposthia testacea(13%). This study confirms that there are terrestrial planarians in New Zealand which have the potential to prey upon European lumbricid earthworms but which have not been detected in Europe. Greater knowledge of their biology is necessary to control the spread and impact of these organisms around the world.
Application of the most probable number method to estimations of entomopathogenic nematode populations in soil
Authors: HASS B. , GRIFFIN C T , KEATING J G , DOWNES M J
Published: February 2008

The calculation of most probable numbers (mpn) was used for the estimation of numbers of infective entomopathogenic nematodes in soil. The mpn concept was first introduced in bacteriology as a means of estimating numbers of organisms in a substrate without a direct count, in cases where direct enumeration could not be applied. In the work reported here, soil samples infested with infective juveniles (IJs) ofHeterorhabditis megidis(isolate HF85) were diluted with uninfested soil and the diluted soils were baited with mealworm larvae (Tenebrio molitor). The mpn of infective units of IJs in the undiluted soil was calculated. The mpn calculation was found to be applicable to entomopathogenic nematodes in soil under particular conditions. It could be successfully applied to data for the response of soil units but not to the data based on the response of individual insects, as the latter did not confirm to a Poisson series. The calculated mpn represented between 2.9 and 7.1% of the initial inoculum of IJs. It was suggested that IJs might act as a group in infecting an insect host. Using the data forTenebriomortality on parasitisation, the mpn based on quantal response of the mealworms would therefore not give the true density of IJs in the soil sample but the effective density, or the quantity of infective units. Although the biological significance of the infective unit needs further clarification, mpn was found to be a useful parameter for use in comparative experiments.
Evaluation of groundnut genotypes for heat tolerance1
Authors: CHAUHAN YASHVIR S , SENBOKU T.
Published: February 2008

Heat tolerance of groundnut (Arachis hypogaea L.) genotypes was evaluated by solute leakage and chlorophyll fluorescence techniques in heat‐hardened and non‐hardened plants. To determine the appropriate hardening treatment, 1‐month‐old plants of two groundnut genotypes, ICGV 86707 and Chico were conditioned at five combinations of hardening (37°C) and non‐hardening (30°C) air temperatures over a 5‐day period. Heat injury, was assessed through measurements of electrolyte leakage after stressing leaf discs to 55°C for 15 min. The relative injury was significantly influenced by the conditioning temperatures and by the temperature during 24 h prior to measurement if those involved non‐hardening conditions. Relative injury and chlorophyll fluorescence were measured after stressing leaves of six genotypes at a range of temperatures between 49°C and 55°C. Significant genotype × hardening treatment interactions were observed in relative injury and chlorophyll fluorescence. Chico was susceptible to heat stress, the relative injury test identified ICGV 86707 as tolerant, and the chlorophyll fluorescence test identified ICGV 86707 as tolerant under hardened conditions and ICGV 87358 as tolerant when non‐hardened. When expressed as percentage of control values, the relative injury and chlorophyll fluorescence measurements over the 49–53°C stress temperature range were strongly correlated. Chlorophyll concentrations were increased by hardening in all genotypes except Chico. In Chico, chlb concentration was decreased and the chla/b ratio increased by hardening, and chlorophyll concentrations were correlated with chlorophyll fluorescence parameters. Chlorophyll concentration may therefore provide an alternative means of screening for heat tolerance.