bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular cloning of the genome of the carlavirus potato virus S: biotinylated RNA transcripts for virus detection in crude potato extracts
Authors: EWEIDA M. , SIT T. L. , ABOUHAIDAR M. G.
Published: February 2008

A cDNA library of potato virus S (PVS) in plasmid pBS+was produced. Insert sizes of two selected overlapping cDNA clones were 1.6 and 4.0 kbp which represent about 75% of the genomic length. Restriction enzyme mapping, hybridisation and in vitro transcription were used to determine the sense and orientation of the inserts in relation to native PVS RNA. The 4.0 kbp insert was used to produce biotinylated DNA or RNA probes for the detection of PVS and its RNA in infected potato plants. In dot‐blot hybridisation biotinylated probes were highly specific with virtually no background coloration. As little as 20 femtograms of PVS RNA could be easily detected in crude plant extracts.
A field cage method for assessing resistance to turnip root fly in brassicas
Authors: BIRCH A. N. E.
Published: February 2008

A field cage method was evaluated as an alternative to field trials for identifying sources of resistance to turnip root fly in brassicas. This involved the controlled release of adult flies and the use of egg traps to quantify egg‐laying on potted plants. Overall levels of resistance to Delia floralis, and its components, were assessed for 15 swede genotypes. Significant levels of antixenosis and antibiosis type resistance were identified in several cultivars and breeding lines. There was a close agreement between the field cage results and those from previous field trials, using comparable susceptible and resistance control cultivars. Compared with field selection, the field cage method reduced by c. 40% the time required to quantify resistance and each of its components.
Effectiveness of assessment of vigour and productivity in young vs old bushes and mature clones of tea (Camellia sinensis)
Authors: NYIRENDA H. E.
Published: February 2008

The effectiveness and validity of assessment of bush vigour as expressed by bush area, shoot number and yield in selecting for high yielding clones in tea was tested by comparing the field performance of 50 source bushes when they were 4 yr old in 1977/78 with that of the same bushes when they were 13 yr old in 1986/87 and also with that of the 8 yr old vegetatively propagated plants (clones) derived from them and transplanted to the field in December 1979.

Apparently vigorous bushes produced the highest yield. The three characters measured in mature source bushes and, to a lesser extent, clonal derivatives were positively correlated with measurements in young source bushes. Seven of the best yielding source bushes and five of the best clones in 1986/87 were present in the 10 highest yielding source bushes identified in the 1977/78 season.

Assessment of bush area and shoot number was confirmed as an effective and valid method of identifying a small, highest yielding group of source bushes from a large population of seedling tea which should go for rooting assessment and further more thorough screening of yield.
The setting of rates of development of wheat plants at crop emergence: Influence of the environment on rates of leaf appearance
Authors: HAY R. K. M. , DELÉCOLLE R.
Published: February 2008

Examination of the time courses, expressed in terms of accumulated temperature over 0°C, of leaf appearance of fifteen sowings of winter wheat, including five cultivars, over three seasons at Auchincruive, revealed several examples of bi‐linear rather than linear responses. Stepwise linear regression analysis, varying the temperature threshold by intervals of 1°C, showed that a linear relationship could be obtained for each sowing, but the appropriateness of this analysis is questioned. An alternative interpretation, that such changes in rate do have biological rather than purely statistical significance, is supported by the fact that, when they occurred, they coincided with the change in rate of spikelet initiation by the stem apex. Furthermore, similar relationships between leaf appearance and reproductive development have been demonstrated for perennial ryegrasses. Analysis of each sowing also revealed the existence of sub‐populations of plants with different rates of leaf appearance and final leaf numbers, but with synchronous phenologies. These findings are discussed in relation to the coordination of the development of apex and leaves, and the environmental cues required to ensure this coordination.
Comparison of scales used for categorising the development of wheat, barley, rye and oats
Authors: LANDES A. , PORTER J. R.
Published: February 2008

A review of the scales used to assess the development of cereals is presented. Twenty‐three scales are identified and they are separated into those that codify the external development of plants and those that describe events at the apical meristem. Comparison of the scales is made for wheat, barley, rye and oats, where this is possible. Attention is drawn to the divergence in the descriptions of similar plants on different scales. Theoretical aspects of the general usage of developmental scales are also discussed.
Effect of manganese toxicity on growth and N2 fixation in groundnut, Arachis hypogaea
Authors: NAMBIAR P. T. C. , ANJAIAH V.
Published: February 2008

The development of manganese (Mn) toxicity symptoms and its effects on the growth, nodulation, and nitrogen fixation of groundnut genotypes were examined using a quartz‐sand/solution culture system. The 11 genotypes tested all accumulated considerable concentrations of manganese (1.04–3.07 mg g‐1dry matter) when supplied with 15 μg Mn ml‐1of nutrient solution daily. Toxicity symptoms differed between genotypes: some showed no visual effects, some produced marginal leaf spots, and others developed marginal leaf spots coupled with an inward rolling of the margins of the younger leaves. The growth of one genotype (ICG 5394) grown with inorganic nitrogen as its source of N was more severely affected by Mn toxicity than when dependent on symbiotic fixation for its nitrogen.
Stimulation of sugar‐beet hypocotyl extension with potassium nitrate
Authors: DURRANT M. J. , MASH S. J.
Published: February 2008

Steeping sugar‐beet seeds in an aqueous thiram suspension, as now used commercially in the UK, makes seedling emergence more rapid and increases the number of plants established. This study investigated whether the potassium and nitrate, removed by steeping, were needed to stimulate subsequent hypocotyl growth. Experiments under controlled conditions showed that re‐incorporation of KNO3 by adding the salt to the steeping solution or, less wastefully during pelleting, slightly slowed root protrusion but made hypocotyl extension more rapid, particularly under dry conditions. There were indications that placement of KNO3 under the seed would be better. Nevertheless, in the field where recommended amounts of fertiliser were applied, incorporation of about 5 g KNO3/kg seed during pelleting was consistently beneficial following the four sowings. This amount decreased the time to half‐final emergence by 0.3 days, gave 3% more established plants and, with the later sowings, increased dry weight in mid‐May by 10%.
Tolerance of cotton to Meloidogyne incognita as influenced by phosphorus fertiliser and a vesicular arbuscular mycorrhizal fungus
Authors: PRICE N. S. , HUSSEY R. S. , RONCADORI R. W.
Published: February 2008

Cotton was grown in soils of differing phosphorus levels with and without a mycorrhizal fungus and with a range (0 to 3200 eggs/ 100 c‐3 soil) of Meloidogyne incognita eggs added. Tolerance of cotton to M. incognita did not differ between plants grown in different soils with or without the mycorrhizal fungus, though plant size could differ markedly. Plant tolerance was increased by a delay in adding nematodes.
A rapid technique to predict malting quality in barley prior to harvest
Authors: SWANSTON J. S. , WE I. A. CO
Published: February 2008

Samples of grain from three spring barley cultivars of differing malting quality were collected at regular intervals during four weeks prior to harvest. The samples were dried, then assessed for relative grain hardness using the “Milling Energy” test. Ranking order of the cultivars for this character, which relates strongly to malting quality, was unaltered throughout. In a further experiment, it was demonstrated that selection for milling energy could be successfully practised on oven‐dried grain collected six weeks after ear emergence.
Nitrate accumulation in vegetables and its relationship to quality
Authors: BLOM‐ZANDSTRA MARGARETHA
Published: February 2008

Many plants, especially leafy vegetables, accumulate nitrate under low light conditions as uptake of nitrate exceeds reduction. Nitrate may harm the health of the consumer as it can be converted to nitrite causing methaemoglobinaemia or carcinogenic nitrosamines. To take directional measures during the growth of vegetables which will decrease the nitrate content, physiological knowledge about the nitrogen economy of the plant is needed. In this review the physiological role of nitrate as osmoticum and its relationship with carbon utilisation will be described; some practical implications for growers and the consequence for quality of the product will be discussed.
Transpuparial transmission of Kashmir bee virus and sacbrood virus in the honey bee (Apis mellifera)
Authors: ANDERSON DENIS L. , GIBBS ADRIAN J.
Published: February 2008

When particles of Kashmir bee virus (KBV) and sacbrood virus (SBV) were fed to larvae of the honey bee, Apis mellifera, in Australian colonies, the resulting pupae became in apparently infected. There was no statistically significant difference in the susceptibility of 1, 2, 3 or 4‐day‐old larvae for either virus, but 5‐day‐old larvae were significantly less susceptible to SBV than younger larvae. There was no significant difference in the proportions of pupae that became in apparently infected when, as larvae, they were fed various concentrations of each virus, but significantly more larvae were removed from their cells when fed concentrated preparations of each virus than when fed diluted preparations. Susceptible larvae that became in apparently infected with KBV and SBV developed normally into in apparently infected pupae and later, emerged as in apparently infected worker bees.
Epidemiological studies of Colletotrichum gloeosporioides disease of cocoa
Authors: MOHANAN R. CHANDRA , KAVERIAPPA K. M. , NAMBIAR K. K. N.
Published: February 2008

The intensities of foliar infection (leaf blight and shot hole) and pod rot, caused by Colletotrichum gloeosporioides, were recorded from a cocoa‐areca mixed garden and a cocoa‐monocrop garden during 2 years. The intensity of pod rot was recorded from both the gardens. The intensities of leaf blight and shot hole gradually increased from July, reached a peak during September‐November, decreased thereafter and reached the lowest level during April‐June. Increase in leaf infection was associated in both plantings and in both years with the period of rain (June‐November). The phylloplane population of C. gloeosporioides also increased during June‐November when the temperature tended to be low and constant with high rainfall and relative humidity. During this period there were few susceptible stages of pods (cherelles and young pods) and pod infection was very low. Nearly mature pods were free from infection. I n both years, pod infection was more in the cocoaareca mixed garden than' in the cocoa‐monocrop; it was observed during January‐May, when the susceptible stages were mostly prevalent but when the C. gloeosporioides population was low and the climatic factors appeared to be relatively unfavourable. This may be one reason for the lesser incidence of pod rot when compared to foliar disease.
The histology of lesion development in raspberry canes infected by Elsinoe veneta
Authors: WILLIAMSON B. , McNICOL. R. J.
Published: February 2008

A histological survey was made of the canes of several raspberry genotypes inoculated in the field and glasshouse with Elsinoe veneta. Acervuli bearing conidia developed on all genotypes and hyphae penetrated the cortex, polyderm and phloem inducing extensive cell divisions, utilisation of starch reserves and deposition of suberin and lignin‐like materials in these tissues.

The results indicated that the polyderm was invaded via the passage cells at an early stage in its development. Phloem fibre cells surrounded by lignified middle lamellae were rarely infected, but since the fibre bundles did not form a complete sheath around the vascular tissues, hyphae spread between the bundles to invade the phloem in all genotypes. The deposition of suberin and lignin‐like materials in host cells in the cortex, phelloid cells of the polyderm and phloem partially restricted the spread of mycelium.
Production of cloned cDNA from a Swedish barley yellow dwarf virus isolate
Authors: EWEIDA MOHAMED , OXELFELT PER
Published: February 2008

A cDNA library was produced from the RNA of a Swedish MAV‐like isolate of barley yellow dwarf virus (BYDV). The procedure involved random priming and the ds cDNA was cloned into the EcoRl site of the plasmid pUC19. Among the clones obtained some hybridised specifically with MAV‐like isolates whereas others also hybridised with PAV‐like isolates. Only very weak hybridisation was observed with an RPV‐like isolate. An Australian cDNA clone, reported to be PAV‐specific (pBY82, Waterhouse, Gerlach & Miller, 1986), hybridised with Swedish MAV‐like but not with PAV‐like isolates. Probes prepared from the clones detected virus in plant extracts by dot‐blot hybridisation with sensitivity greater than that of ELISA. Virus was also readily detected in extracts of viruliferous aphids.
Particle properties of parsnip yellow fleck virus
Authors: HEMIDA S. K. , MURANT A. F.
Published: February 2008

Particle preparations of parsnip yellow fleck virus (PYFV) isolates A‐421 and P‐121, representing the two major serotypes, were made by clarifying leal extracts with ether or butan‐1‐ol and concentrating the virus particles by precipitation with polyethylene glycol and differential centrifugation. The preparations contained c. 31 nm‐diameter particles comprising two sedimenting components. Top component (T) consisted of stain‐penetrable protein shells with A260/A280= 0.8–0.9, sedimentation coefficient (S20) = 56 S (A‐421) or 60 S (P‐121), and buoyant density = 1.297 g/cm3. Bottom component (B) consisted of nucleoprotein particles, not penetrable by negative stain, with A260/A280= 1.9, sedimentation coefficient (S020.w) = 148 S (A‐421) or 153 S (P‐121), and buoyant density = 1.520 g/cm3 (A‐421) or 1.490 g/cm3 (P‐121). Yields of B component particles were up to c. 1 mg/100 g leaf tissue (both isolates); yields of T component particles were up to c. 0.6 mg (A‐421) or 5.5 mg (P‐121) per 100 g leaf tissue. PYFV particles were found to contain a single RNA species (mol. wt c. 3.4 × 106, c. 9800 nucleotides), constituting 40% of the particle weight, and three polypeptide species, of mol. wt (× 10 3)30, 26 and 24 (A‐421) or31, 26 and 23 (P‐121).
Preparation of mycoplasma immunogens from plants and a comparison of polyclonal and monoclonal antibodies made against primula yellows MLO‐associated antigens
Authors: CLARK M. F. , MORTON ANNE , BUSS SANDRA L.
Published: February 2008

A method is described for obtaining from plants partially purified preparations of mycoplasma‐like organisms (MLO) which are suitable for use as immunogens for polyclonal or monoclonal antibody production, and as antigens for directly coating ELISA plates. Using this method a mouse monoclonal antibody to primula yellows MLO was prepared, and its characteristics compared with those of primula yellows polyclonal antibodies from rabbits and also against polyclonal antibodies made to similar preparations of European aster yellows MLO. No serological distinction was obtained between any of the homologous or heterologous combinations of antibody and MLO preparation using ELISA, fluorescence microscopy with FITC‐labelled antibodies, or immunoprobes of western blots of partially purified MLO preparations. By contrast, there were no cross‐reactions between the primula or aster yellows antibodies or MLO preparations and preparations of clover phyllody or tomato big bud MLOs or their respective polyclonal antibodies. The primula yellows MLO monoclonal and polyclonal antibodies, and also the European aster yellows MLO polyclonal antibodies, all appeared to recognize only a single major antigen of approximate M, = 22 400 daltons. Some possible explanations for the apparent specificity of the polyclinic antisera for a single antigen, and the relevance to MLO preparation procedures are discussed.
The phosphorus budget of a field‐grown strawberry (Fragaria x ananassa cv. Hapil) crop: evidence for a mycorrhizal contribution
Authors: DUNNE M. J. , FITTER A. H.
Published: February 2008

The phosphorus content of a field‐grown strawberry crop was monitored over one growing season and the allocation of P to different plant parts determined. In the early part of the season, leaves were the major sink for P and this was partly supplied by redistribution from rhizomes. Once flowers were initiated, these became the major sink and their P requirement was satisfied by new uptake. The calculated rates of P inflow to the roots in this phase of growth were so large that it was necessary to postulate not only that P uptake was assisted by mycorrhizas, but that the whole root system, including the old, brown roots, was active. The implications of this conclusion for concepts of vesicular‐arbuscular mycorrhizal function under field conditions are discussed.
The influence of cypermethrin and oxydemeton‐methyl treatment on Lygus damage in young Scots pine seedlings
Authors: HOLOPAINEN J. K.
Published: February 2008

Laboratory experiments were carried out to evaluate the efficiency of two insecticides, cypermethrin and oxydemeton‐methyl, in controlling the nymphs and adults of Lygus bugs and the resulting damage caused by these bugs to small pine seedlings. Both insecticides significantly increased the mortality of bugs on the seedlings compared with bug mortality on untreated controls. Mortality of bugs was higher in the oxydemeton‐methyl treatment than in the cypermethrin treatment. The occurrence of seedlings with multiple leaders and the number of leader shoots per seedling were significantly decreased in insecticide‐treated seedlings. Mean number of leader shoots was significantly higher in seedlings treated with oxydemeton‐methyl than in seedlings treated with cypermethrin after a 24‐h exposure to nymphal instars of Lygus. The mortality of the pine seedlings was very low but significantly decreased in insecticidal treatments. Factors affecting the effects of different insecticides on bug mortality and their efficiency in controlling the multiple‐leadering phenomenon are discussed.
The effects of desiccation and root diffusates from potato and mustard on eggs of the white potato cyst nematode Globodera pallida
Authors: FORREST J. M. S.
Published: February 2008

Following exposures to potato root diftusate of between 6 and 12 h, desiccation killed a proportion of juveniles in eggs of G. pallida and affected the hatching behaviour of survivors. In hatching tests of 9 wk duration, more juveniles hatched in the final wk from cysts, which were soahed and dried alternately for 9 wk than from cysts soaked in tap water for the final 2 wk only. Mustard root diffusate prevented eggs previously stimulated by potato root diffusate from hatching, but it did not alleviate the effects of desiccation.
Non‐propagative translocation of velvet tobacco mottle virus in the mirid, Cyrtopeltis nicotianae
Authors: GIBB KAREN S. , RANDLES J. W.
Published: February 2008

Nymphs of the mirid, Cyrtopeltis nicotianae became infective when injected with velvet tobacco mottle virus (VTMoV). Injections of amounts between 1 and 154 ng into the haemocoele induced 2/60 to infect test plants and these two nymphs contained 50 and 63 ng of virus respectively. Injection of amounts between 15 and 2400 ng rendered 11/47 nymphs infective. This observation is characteristic of a circulative association. However, there is no evidence that the salivary glands are involved in transmission and the virus is therefore defined as translocating, rather than circulating, in the mirid vector.

Mirids which acquired infectivity by feeding lost it between 5 and 9 days after completion of acquisition, and the most rapid loss of infectivity occurred within 2 days. Nine days after acquisition none contained antigen detectable by ELISA, but detectable antigen decreased less rapidly than infectivity, and at all times more mirids contained antigen than were able to transmit. Mirids containing antigen carried between 150 and 3340 ng each. Thus, although VTMoV can be transmitted by its mirid vector following introduction of virus into the body cavity by injection, VTMoV is not propagative. Nor does the presence of virus within the mirid guarantee an ability to transmit.
Deterrent effect of carboxylic acids on cabbage root fly oviposition
Authors: COLE ROSEMARY A. , JONES T. H. , FINCH S.
Published: February 2008

In laboratory experiments, 11 selected carboxylic acids were tested to determine which part of the sinapic acid molecule is responsible for deterring cabbage root fly from laying its eggs on otherwise‐acceptable cauliflower host‐plants. The deterrent effect was only obtained with compounds containing at least one carboxylic group in the molecule. Hence, the aliphatic acids were as deterrent as the aromatic acids to the fly and all the carboxylic acids were as deterrent as sinapic acid, reducing oviposition by > 50%. The inclusion of two carboxylic groups in the molecule, (e.g. phthalic acid and oxalic acid) did not increase the deterrent effect observed with sinapic acid. Some of the long chain fatty acids, with low volatility, low water solubility and thus greater persistence, offer practical opportunities for deterring Delia radicurn from laying its eggs on plants in the field.
Infectibility of some new raspberry cultivars with arabismosaic and raspberry ringspot viruses and further evidence for variation in British isolates of these two nepoviruses
Authors: JONES A. T. , MITCHELL M. J. , BROWN D. J. F.
Published: February 2008

In field trials at sites of an outbreak of arabis mosaic nepovirus (AMV) in England and of raspberry ringspot nepovirus (RRV) in Scotland, the results of exposure of some new raspberry cultivars to natural infection with these viruses showed discrepancies from those obtained in graft inoculation tests using AMV‐Lib and RRV‐S, the Scottish type isolates. In particular, cv. Glen Prosen, which is immune to AMV‐Lib and RRV‐S, was infected with AMV and RRV in the field trials. Studies on these and other field isolates of AMV and RRV showed that they differed from the type isolates in Rubus host range and in symptomatology in herbaceous hosts. However, whereas four isolates of RRV found infecting Rubus were distinguishable by spur formation in gel double‐diffusion serological tests, six AMV isolates were indistinguishable by this method. Immunoelectrophoresis of virus particles did not distinguish the six AMV isolates, but isolates RRV‐MX and RRV‐T were distinguishable from RRV‐S and the English type isolate, RRV‐E. Like the two RRV type isolates, RRV‐MX contained a single electrophoretic component, but it migrated must faster whereas RRV‐T contained two components, one with a migration rate similar to that of RRV‐MX and the other similar to that of the type isolates. Polyacrylamide gel electrophoresis of protein preparations from highly purified virus particles of RRV isolates E, S and MX detected a single polypeptide of estimated mol. wt 54 × 103, 54 × 103 and 50 × 103 respectively but that of isolate T contained two polypeptides of estimated mol. wt 54 × 103 and 50 × 103. These data suggest that RRV‐T is a mixture of two isolates. In laboratory tests the nematode Xiphinema diversicaudatum transmitted four isolates of AMV efficiently whereas two populations of the nematode Longidorus elongatus were less efficient vectors of four RRV isolates. Neither vector species transmitted virus to any of nine raspberry cultivars. The results are discussed in relation to the control of nepoviruses in raspberry and to the biology of these viruses.
Specificity of the effect of sap‐transmissible viruses in increasing the accumulation of luteoviruses in co‐infected plants
Authors: BARKER H.
Published: February 2008

The concentration of potato leafroll luteovirus (PLRV) (c. 1300 ng/g leaf) in singly infected Nicotiana clevelandii plants was increased up to 10‐fold in plants co‐infected with each of several potyviruses, or with narcissus mosaic potexvirus, carrot mottle virus or each of three tobravirus isolates. With the tobraviruses, PLRV concentration was increased equally by co‐infection with either NM‐type isolates (coat protein‐free cultures containing RNA‐1) or M‐type isolates (particle‐producing cultures containing RNA‐1 and RNA‐2). In contrast, the accumulation of PLRV was not substantially affected by co‐infection with either of two nepoviruses, cucumber mosaic cucumovirus, broad bean mottle bromovirus, alfalfa mosaic virus, pea enation mosaic virus or parsnip yellow fleck virus. The specificity of these interactions between PLRV and sap‐transmissible viruses was retained in tests made in Nicotiana benthamiana and when beet western yellows luteovirus was used instead of PLRV.
A model of the effect of codling moth granulosis virus on Cydia pomonella
Authors: BRAIN P. , GLEN D. M.
Published: February 2008

A model was developed based on an initial ingestion phase, followed by a period of virus multiplication and host death, to describe the effects of codling moth granulosis virus (CpGV) concentration and time from initial infection on the percentage of codling moth larvae (Cydia pornonella) dying from virus infection in the laboratory. With modification, this model also described the effect of CpGV concentration on the reduction of damage to fruit by C. pomonella larvae in the field. In both cases, the effect of CpGV increased with the l/10th power of virus concentration.

LT50 (time to death of 50% of larvae) was inversely related to virus concentration in the laboratory.

The model predicts the threshold concentration for death of larvae, as well as LD50(C50 and LD90(C 90,) for all ages of larvae.

The model also predicts that if the majority of larvae entered through the sides of apple fruits, rather than through the calyx or near the stalk (as they probably did in the field), then the efficacy of CpGV in reducing fruit damage would be lowered. This effect of site of entry is especially marked at low virus concentrations.
Evaluation of three techniques used to determine surfactant phytotoxicity
Authors: COUPLAND D. , ZABKIEWICZ J. A. , EDE F. J.
Published: February 2008

Three techniques were used to measure and compare the phytotoxicities of Triton X‐45 and Agral 90 (two organic surfactants) with two organosilicone surfactants (Silwet L‐77 and L‐7607), and to compare these four non‐ionic compounds with a cationic tallow amine surfactant (Hyspray). Total ion efflux and ethylene response methods were used in vivo and in vitro, while a betacyanin efflux method was an in vitro system only. The first two methods, using intact leaves, were considered to be more closely related to normal spraying conditions than the betacyanin efflux test which used explant material. However, the use of intact leaves was thought to bias the results in favour of the leaf penetration properties of the surfactants rather than their phytotoxicities. The in vitro pigment efflux method provided a simple way of ranking the surfactants in order of their potential phytotoxicities, especially with regard to effects on membrane permeability. This ranking, in increasing order of toxicity, was: Silwet L‐7607, Silwet L‐77, Agral 90, Triton X‐45 and Hyspray.
Resistance of cereals to aphids: Interaction between hydroxamic acids and the aphid Sitobion avenae (Homoptera: Aphididae)
Authors: LESZCZYNSKI B. , DIXON A. F. G.
Published: February 2008

The hydroxamic acids in the seedlings of four varieties of winter wheat were extracted initially in boiling methanol in order to avoid enzymatic hydrolysis. The increase in numbers of aphids on these varieties of wheat were recorded. HPLC analysis of hydroxamic acids in the extracts showed the presence of DIMBOA‐glucoside, DIMBOA‐aglucone and its benzoxazolinone (MBOA). There was a highly significant negative correlation between the concentration of DIMBOA‐aglucone in the seedlings and aphid performance. However, the association between aphid performance and DIMBOA‐aglucone in the tips of the seedlings was weaker. In general aphid infestation of wheat seedlings slightly increased the concentration of all the hydroxamic acid derivatives. Moreover, aphids ingested hydroxamic acids and were able to detoxify some of the DIMBOA‐aglucone they ingested.
The effects of sowing date and choice of insecticide on cereal aphids and barley yellow dwarf virus epidemiology in northern England
Authors: McGRATH P. F. , BALE J. S.
Published: February 2008

During the mid‐1980s, Sitobion avenae became recognised as an important vector of barley yellow dwarf virus (BYDV) in the Vale of York. A field trial at the University of Leeds Farm, North Yorkshire, was carried out during the autumn/winter of 1984‐85 to evaluate different control procedures against S. avenae‐transmitted BYDV and to investigate its epidemiology. Winter barley was sown on three dates in September, and plots were sprayed with either deltamethrin, demeton‐S‐methyl or pirimicarb on one of three dates between mid‐October and mid‐November, making a factorial design.

Rhopalosiphum padi, the main vector of BYDV in southern England, were rarely found during the experiment, but the numbers of S. avenae were much higher, reaching a peak of 21% of plants infested in the unsprayed plots of the first sowing date. Single applications of each insecticide reduced populations of S. avenae to zero. Some treatments, particularly in the early sown plots and those treated with pirimicarb, however, did allow some recolonisation, and thus led to increased virus incidence and decreased yields. Sprays applied before the end of the migration of S. avenae were more efficient at controlling BYDV if the insecticide was persistent, otherwise a spray after this period, in November, was more effective.

Virus incidence, although reduced by sprays, was generally low in plots sown on 18 and 27 September. In contrast, about 11% of plants were infected in unsprayed plots sown on 6 September and a small yield benefit was obtained with insecticidal treatments.

Enzyme‐linked immunosorbent assay (ELISA) of plants taken from the plots indicated that MAV‐ and PAV‐like strains were present, and were most likely to have been transmitted by S. avenae.
Carabid populations in field beans and their effect on the population dynamics of Sitona lineatus (L.)
Authors: HAMON N. , BARDNER R. , ALLEN‐WILLIAMS L. , LEE J. B.
Published: February 2008

The abundance and diversity of potential carabid predators of Sitona lineatus (L.) in field beans were monitored between 1980 and 1983. The absolute abundance of the large predatory species was determined in mark‐recapture experiments and a radio‐labelling technique was used to estimate the level of predation in the field. Using previously published population data for S. lineatus, the importance of predation in the population dynamics of the weevil was estimated. The mortality of weevil larvae due to predation varied from 0.6%– 10.5% while that of adult weevils varied from 2.6%– 23.8%. It appeared that carabids played a significant role in the population dynamics of S. lineatus and, in years when abundant, could reduce the population of larvae and overwintering adults by more than 30%.
Feeding behaviour of the staphylinid beetle Tachyporus hypnorum in relation to its potential for reducing aphid numbers in wheat
Authors: DENNIS P. , WRATTEN S. D. , SOTHERTON N. W.
Published: February 2008

Aphid consumption by larval and adult Tachyporus hypnorum (Coleoptera: Staphylinidae) in different reproductive states was compared under laboratory conditions. Post‐overwintering (spring/summer) adults had a higher consumption rate of first/second instar Sitobion avenae (Hemiptera: Aphididae) than did overwintering adults. Choice experiments incorporating Isotoma viridis (Collembola: Isotomidae) and Sciara thomae (Diptera: Mycetophilidae) as alternative prey items showed that T. hypnorum had a strong preference for aphids at a range of prey frequencies. Numbers of aphids consumed were reduced when leaves infected with Erysiphe graminis f.sp. tritici (powdery mildew of wheat) were offered to beetles with aphids in choice experiments. Behavioural studies of adult T. hypnorum showed that foraging rates on wheat plants increased with increasing amounts of both mildew and aphids on plants. Feeding upon only the conidia of E. graminis was observed. Results are discussed in relation to previous data derived from gut dissection, to a field survey of alternative foods and to the phenology of T. hypnorum in relation to that of aphids in the wheat crop.
Genetic structure and relationships of four populations of the stalk boring moth, Eldana saccharina
Authors: BANK F. H. VAN DER , LESLIE G. W. , ALLISON J. C. S.
Published: February 2008

Twenty‐seven protein coding loci were examined by means of horizontal starch gel electrophoresis in samples of larvae from four populations of the stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in Natal, South Africa. The populations were collected in two localities approximately 250 km apart. In each locality a sample was obtained from sugarcane and also from the locally most abundant indigenous host plant of this insect (Cyperuspapyrus L. in one locality and C. dives Delile ‐ synonomous with C. immensus CB CI. ‐ in the other).

More than one allele was detected at eight of the loci in all four populations and at a further locus in three of the populations; the other 18 loci were monomorphic for the same allele in all populations. Average expected heterozygosity over the 27 loci was approximately 0.12 in all populations. Genetic distances among the populations were small, but were greater between the two populations from the indigenous hosts and the two from sugarcane than within either of these pairs of populations. Possible explanations of these results are discussed.
Effects of alien cytoplasm substitution on the response of wheat cultivars to Septoria nodorum
Authors: KEANE E. M. , JONES P. W.
Published: February 2008

The effects of alien cytoplasm substitution on the response of wheat to Septoria nodorum were studied, using alloplasmic series of two cultivars, Chris and Selkirk. In general, cytoplasmic substitution caused unidirectional effects on Septoria‐response, alloplasmic lines of both cultivars expressing lower levels of partial resistance (in leaf and head tissue) but higher levels of yield tolerance than the corresponding euplasmic line. The reduced resistance in alloplasmics was closely associated with reduced incubation periods of Septoria infection in both leaf and head tissue. Cytoplasmic substitution resulted in increased yield tolerance to Septoria‐infection in both the non‐tolerant Selkirk and the relatively tolerant Chris. Unlike their effects on partial resistance, specific cytoplasms exerted similar effects on tolerance in the two parental cultivars, several cytoplasms of the D plasmatype being particularly effective in increasing Septoria‐tolevance. The potential for the development of Septoria‐toterant cultivars by the incorporation of alien cytoplasms is discussed, in view of the observed neutral effects of D plasmatype cytoplasms on other agronomic traits.
Epidemiology of Cladosporium allii and Cladosporium allii‐cepae, leaf blotch pathogens of leek and onion.
Authors: JORDAN MARY M. , BURCHILL R. T. , MAUDE R. B.
Published: February 2008

Isolates of Cladosporium allii and Cladosporium allii‐cepae grew at 20°C and 15–20°C respectively on 2.5% malt extract agar and both species tolerated a wide pH range with maximum sporulation of C. allii‐cepae between 5–8.5. C. allii did not sporulate in the light in culture and grew more rapidly in darkness. At least 8 h darkness was necessary for optimum conidiation of both fungi on lesions of leek and onion but conidiophores were produced in light and dark conditions after 2–12 h incubation at > 90% relative humidity (r.h.). Radiation of 2 W/m23 W/m2(the approximate equivalent to strong moonlight) prevented conidiation of C. allii and C. allii‐cepae respectively. Relative humidities of 95–100% increased sporulation of both fungi on leaf lesions.

Laboratory and field experiments to measure the effects of temperature, light and relative humidity'on sporulation showed that maximum sporulation of both pathogens on leaf lesions occurred in the late autumn (November‐December) with a secondary peak in the early spring (March‐April). Conidia of Cladosporium allii and C. allii‐cepae were intermittently detected in the air over diseased leek and onion crops during the years 1982–1985. The simultaneous occurrence of 8 h darkness, r.h. > 95% and temperatures of 9–12°C resulted in the presence of high concentrations of conidia of C. allii in the atmosphere above leek crops in the subsequent 24 h.

The pattern of spore release for both fungi was similar with maximum and minimum concentrations of conidia recorded during late‐morning early afternoon (10.00–14.00 h) and during the night respectively. There was little correlation between declining relative humidity and spore release but there was a significant correlation between concentrations of conidia trapped and increasing light intensity and to a lesser extent with temperature. Mechanical disturbance of the crops by rain, wind and human activity resulted in isolated increases in spore concentrations.
Quantitative assay of resting spores of Polymyxa graminis on barley roots
Authors: YILI RUAN , WANHE ZOU , JIANPING CHEN
Published: February 2008

A procedure was developed to examine amounts of Polymyxa graminis on eleven barley cultivars from a field experiment on a site infested with barley yellow mosaic virus (BaYMV) and which differed in field response to the virus. Powder produced from dried barley roots infected with P. graminis was soaked overnight at 4°C in a solution of 1 % sodium metaphosphate and 0.25% Tween 20. This was followed by high speed homogenisation, filtering, ultrasonic treatment of the residue and differential centrifugation. A suspension of individual resting spores free from other recognisable fungi was obtained, which ranged in concentration from 0.4 to 7.3 × 107spores per g root. Repeated extraction of the residues suggested that most spores were liberated by the first cycle of treatment. The cultivar with the greatest incidence of BaYMV also had the most P. graminis; some cultivars resistant to BaYMV had less P. graminis but there was no general correlation between the incidences of virus and vector.
The impact of pests and diseases on the herbage yield of permanent grassland at eight sites in England and Wales
Authors: CLEMENTS R. O. , MURRAY P. J. , BENTLEY B. R. , LEWIS G. C. , FRENCH N.
Published: February 2008

Plots at each of eight widespread permanent pasture sites below 300 m and representative of large areas of long established grassland in England and Wales, were treated with an insecticide plus molluscicide, a fungicide or nematicide treatment. Populations of various invertebrates and the occurrence of foliar fungal diseases were assessed.

Leaf blotch (Drechslera) was the most common disease, but neither this nor other foliar fungal diseases were prevalent until late in the growing season. The fungicide treatment did not control diseases satisfactorily. The fungicide and nematicide treatment had little effect on total annual herbage yield. Leatherjackets, crambids, slugs and frit fly larvae were present, usually in low numbers, at most sites. The insecticide and molluscicide treatment increased yield by 11% on average across all sites and years. Losses caused by pests to UK grasslands were estimated to be over £500 million per year.
Migratory plant‐parasitic nematodes associated with cereals in Scotland
Authors: BOAG B. , BOWEN S. , SPAULL A. M. , WRIGHT G. , SMITH B. F. L.
Published: February 2008

Ninety‐eight soil samples were collected from cereal farms on mainland Scotland and examined for migratory plant‐parasitic and predatory nematodes. Soil analysis was also carried out on each sample. Of the 25 parasitic nematode species identified Longidorus elongatus was the most frequently found and while populations were generally low, populations great enough to cause damage were detected. Populations of other plant‐parasites were usually low. Individual species were unlikely to cause economic losses but their combined effect could possibly reduce yields. Analysis of the relationships between nematode species suggested that neither competition nor predation were important factors limiting population size. With few exceptions, none of the soil factors measured influenced the occurrence or abundance of the nematodes identified.
Breeding for increased nitrogen fixing ability among wild and cultivated species of chickpea
Authors: JAISWAL H. K. , SINGH R. K.
Published: February 2008

Two chickpea species, one wild (Cicer reticulatum JM2106) and one cultivated (C. arietinum ICC8923) were selected as the parents for this study. C. reticulatum showed high nodule number, nodule dry weight and nitrogen content/plant as compared to C. arietinum. In lines derived from the crosses H208 × (ICC8923 × JM2106) and BG274 × (ICC8923 × JM2106), increase in nodule dry weight, nitrogen content/plant, plant dry weight and grain yield was observed over the parent ICC8923. Similarly F6 lines also showed improvement in these traits over the cultivated parent. It is concluded that the increase in grain yield and dry matter is the result of improvement in nitrogen utilisation together with an increase in the available fixed nitrogen.
Thermal insulation of the winter cauliflower curd by wrapper‐leaves
Authors: TAPSELL C. R. , GROUT B. W. W. , FULLER M. P.
Published: February 2008

The role of leaves as insulation for mature curds during exposure to frost has been investigated for winter‐harvested cauliflower. The inner, wrapper‐leaves and their enclosed air spaces provided significant protection for the curd tissues in mild frost, but under more severe conditions (below – 2.5°C) were ineffective. A relationship between higher wrapper‐leaf number and increased insulation was described. The increase in insulation however, was small even with much higher wrapper‐leaf numbers. Exposure of the curd surface at maturity was found to prevent the insulating effect of wrapper‐leaves, particularly if the diameter of the exposed area was greater than 6 cm. The data also suggested a possible role for the exposed stem of the cauliflower as a site of heat loss that may adversely affect curd temperature.

It is postulated that breeding for improved frost resistance by greatly increasing wrapper‐leaf number would not be effective, although any reduction in wrapper‐leaf number and the presence of tightly wrapped curds should be avoided. Furthermore, exposure of the curd surface at maturity should be kept to a minimum.
The effect of an experimental growth retardant (WL83801) on leaf growth and development in Lolium perenne L.
Authors: FOREMAN M. H. , MARSHALL C.
Published: February 2008

The experimental growth retardant WL83801, applied as a root drench, had a rapid and persistent effect in retarding the growth and development of leaves in L. perenne. Leaves of the main shoot were greatly reduced in length, were broader, and appeared faster than in control plants. The rate of extension of individual leaves was greatly reduced in retarded plants but still followed a diurnal pattern that closely corresponded with temperature. There was evidence that leaf extension was far less responsive to temperature in treated plants. At the cellular level WL83801 had no significant effect on leaf blade cell number, thus reductions in leaf length were associated with the retardation of cell elongation. Changes in leaf structure were also observed.

These changes in the pattern of leaf growth and development are discussed in relation to the primary mode of action of the growth retardant in interfering with gibberellin biosynthesis.
Feeding behaviour and mortality of the slug, Deroceras reticulatum in relation to control with molluscicidal baits containing various combinations of metaldehyde with methiocarb
Authors: BOURNE N. B. , JONES G. W. , BOWEN I. D.
Published: February 2008

In terms of control of slug pests, the differing modes of action of the two molluscicides metaldehyde and methiocarb appear to provide some advantages for the former during warm, dry weather and for the latter during cool, wet weather. With a view to exploiting these different modes of action, the feeding behaviour of Deroceras reticulatum (Müller) presented with molluscicidal baits containing various combinations of metaldehyde with methiocarb was investigated. Voluntary feeding trials conducted in the laboratory with both candidate and standard treatments (containing metaldehyde or methiocarb alone) are described. By combining the two active ingredients in certain ratios the total concentration of active ingredients may be reduced without adversely affecting the efficacy of a bait formulation in terms of slug mortality.
An improved test for evaluating the pathogenicity of isolates of Fusarium solani f.sp. pisi on pea
Authors: DYER P. S. , INGRAM D. S.
Published: February 2008

An improved in vitro test is described for determining the pathogenicity of Fusarium solani f.sp. pisi isolates on pea. This technique involves the use of polypropylene fibre Milcap plugs to suspend peas in boiling tubes containing spore suspensions in 0.1% water agar. Results were available after 14 days of incubation at 25°C. Four levels of pathogenicity were detected on pea cultivars Little Marvel and Dark Skinned Perfection using a total of eight isolates and strains of F. solani f.sp. pisi.
Further investigations of the host range of the carrot fly, Psila rosae (F.)
Authors: HARDMAN J. A. , ELLIS P. R. , SAW PAMELA L.
Published: February 2008

Techniques were developed for testing umbelliferous species against naturally‐occurring populations of carrot fly in the field. The most efficient technique involved exposure of plants to either first or second generations of the insect in the field, followed by caging of infested plots and trapping of emerged flies in water in yellow water dishes.

In a series of field experiments between 1981 and 1989 inclusive, a total of 132 umbelliferous species and sub‐species were tested against carrot fly. Seventy‐eight of these proved to be new hosts, 27 were confirmed as hosts and 27 failed to support any carrot flies. Six non‐umbelliferous plant species failed to be colonised by carrot fly. Sources of variability in investigations of the host range of insects are discussed.
Alternaria alternata f.sp. cucurbitae, the cause of a new leaf spot disease of melon (Cucumis melo)
Authors: VAKALOUNAKIS D. J.
Published: February 2008

A leaf spot disease of melon caused by Alternaria alternata f.sp. cucurbitae was recorded for the first time in Crete. Necrotic flecks surrounded by chlorotic halos developed on the cotyledons and the leaves of the middle and the upper part of the plants; the flecks enlarged and coalesced to form lesions of 2 cm or more in diameter with brown fructifications of the pathogen on their surface. Severely affected cotyledons and leaves became chlorotic and died. Of 16 species from eight botanical families that were inoculated, only those of the Cucurbitaceae were susceptible. Of four isolates of A. alternata from tomato, sunflower, pear and cucumber, only the cucumber isolate was pathogenic to melon foliage.