bluuebunny/crossref_metadata_2025 huggingface dataset:
Time‐resolved fluoroimmunoassay of potato virus M with monoclonal antibodies
Authors: JÄRVEKÜLG LILIAN , SõBER JÜRI , SINIJÄRV RIIVO , TOOTS INDREK , SAARMA MART
Published: February 2008

Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double‐antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots.

MAbs against PVM were used as capture antibodies and europium‐labelled MAbs as conjugates in time‐resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10‐‐4 with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double‐label TRFIA using europium‐labelled MAbs to PVM and samarium‐labelled MAbs to PVX.
A severe citrus tristeza virus isolate causing the collapse of trees of sour orange before virus is detectable throughout the canopy§
Authors: BEN‐ZE'EV I. S. , BAR‐JOSEPH M. , NITZAN Y. , MARCUS RUTH
Published: February 2008

A rapidly spreading decline of ‘Minneola’ tangelos, ‘Shamouti’ and ‘Valencia’ sweet oranges grafted on sour orange rootstock in the Morasha area, in the coastal plain of Israel, was found to be caused by a severe ‘seedling yellows’ strain of the citrus tristeza virus (CTV). Repeated ELISA tests revealed great variation in distribution of CTV throughout the canopies, even in declining trees. In a substantial number of the declining trees, samples of up to 10 twigs per tree were not always sufficient for CTV detection. The ELISA values (O.D. 405 nm) in the parts found infected were high, whereas in most of the twigs showing negative ELISA results the virus was absent as indicated by biological indexing. The Morasha strain of CTV was also characterised by rapid annual spread rates. The ratio D/E (the proportion of Declining trees found among ELISA‐positive ones) is proposed as a simple index of strain severity. The epidemiological consequences of the uneven distribution of CTV and rapid decline are discussed.
The occurrence of maize mosaic virus on sorghum in India1
Authors: NAIDU R. A. , HARIKRISHNAN R. , MANOHAR S. K. , REDDY D. V. R. , RATNA A. S. , KING S. B. , BANDYOPADHYAY R.
Published: February 2008

A leaf disease of sorghum (Sorghum bicolor) characterised by fine discontinuous chlorotic streaks between the veins, was observed on sorghum grown during the 1987/88 post‐rainy season in peninsular India. Early‐infected plants were stunted, had shortened internodes, and produced poorly developed panicles. The virus was transmitted by the delphacid planthopper, Peregrinus maidis. Negatively stained leaf dip preparations contained bullet‐shaped virus particles (208 ± 4.4 × 66 ± 1.0 nm) resembling those of rhabdoviruses. In ultrathin sections, the particles budded through the inner nuclear membrane and were present in the cytoplasm within membrane‐bound vesicles that were apparently contiguous with the distended outer nuclear membrane. A method for purifying the virus was developed utilising polyethylene glycol (PEG) precipitation, Celite filtration and sucrose densitygradient centrifugation. An antiserum was produced in rabbits with a titre of 1/2650 in the precipitin ring interphase test. The virus could be detected in infected sorghum leaf tissues using a direct antigen coating form of enzyme‐linked immunosorbent assay (DAC‐ELISA). In immuno‐double diffusion tests, the virus reacted positively with antisera to maize mosaic virus (MMV) from Reunion (MMV‐RN) and Hawaii (MMV‐HI), but not with antisera to barley yellow striate mosaic (BYSMV), cereal chlorotic mottle (CCMV), and cynodon chlorotic streak (CCSV) viruses. Thus, the virus isolated from sorghum is designated the MMV‐S isolate. In DAC‐ELISA tests, MMV‐S reacted positively with antisera to MMV‐R, MMV‐HI, MMV‐Florida isolate, CCSV, and CCMV, and weakly with antiserum to BYSMV. SDS‐polyacrylamide gel electrophoresis revealed four major proteins of relative mass Mr 70 000, 59 000, 32 000 and 28 000. In electro‐blot immunoassay, MMV and CCSV antisera detected the G and N proteins. These data suggest that MMV‐S should be placed in the sonchus yellow net virus subgroup of plant rhabdoviruses.
Incidence of pea seedborne mosaic virus pathotypes in the US National Pisum germplasm collection
Authors: ALCONERO R. , HOCH J. G.
Published: February 2008

One hundred and eighty‐nine isolates of pea seedborne mosaic virus (PSbMV) were obtained from seedlings of 435 pea (Pisum sativum) germplasm introductions originally acquired from India, Turkey, Latin America and Europe. Fifty‐eight per cent of the isolates were identified as belonging to pathotype P‐1, 22% to pathotype P‐4, and 7% to the mild form of the lentil pathotype L‐1. Some isolates could not be classified into any known pathotype and need further study. No isolate appeared to present a threat to peas beyond that already known to exist with previously described forms of the virus.
Further studies on the occurrence and inheritance of resistance in red raspberry to a resistance‐breaking strain of raspberry bushy dwarf virus
Authors: JENNINGS D. L. , JONES A. T.
Published: February 2008

A strain of raspberry bushy dwarf virus (RBDV‐RB), discovered in England in 1981, readily infects by grafting many raspberry cvs that have gene Bu, which confers strong resistance or immunity to isolates of the common strain. Haida is one of two cultivars that are highly resistant or immune from RBDV‐RB, but both its parents, cvs Creston and Malling Promise, are infectible. Studies of the segregation of resistance to both RBDV‐RB and a common strain of RBDV (D200) in four progenies related to cv. Haida or its two parents, showed that resistance to RBDV‐RB was heritable and occurred when gene Bu was present with a second resistance component whose inheritance is probably multigenic. There was some indication that the second component might be a form of partial resistance to graft inoculation of varying expression, and that cv. Haida possesses this resistance at a high level that has not been distinguished from immunity in the graft inoculations used. Cultivars Creston and Malling Promise possibly have this resistance to a lesser degree, while resistance in cv. Heritage has been distinguished from immunity only by extensive graft tests. Some possible implications for breeding RBDV‐RB resistant cultivars are discussed.
Histochemical localisation of carboxylesterases in roots of Lycopersicon esculentum in response to Meloidogyne incognita infection
Authors: MELILLO M. T. , BLEVE‐ZACHEO T. , ZACHEO G. , GAHAN P. B.
Published: February 2008

A cytochemical study of esterase activity of tomato cultivars resistant (VFN8) and susceptible (Roma) to the root‐knot nematode Meloidogyne incognita has shown activity present in root tissue of both cultivars.

Inhibitor studies indicated the likely involvement of carboxy‐ and acetyl‐esterases as components in the prostele and cortical cells of cv. Roma 1, 2, and 3 days after nematode infestation. In contrast, necrotic cells immediately adjacent to the nematode in roots of VFN8 were seen to contain high levels of phenolics by 3 days after infection with the adjacent cells having high levels of carboxylesterase activity. The possible role of the enzyme in the hypersensitive response of tomato plants during nematode infection is discussed.
Effects of triazole growth retardants on oilseed rape; photosynthesis of single leaves
Authors: BUTLER D. R. , PEARS E. , CHILD R. D. , BRAIN P.
Published: February 2008

Rates of CO2 exchange were measured for single leaves on oilseed rape plants after application of triapenthenol and BAS111. For leaves which expanded after treatment, there was no detectable change in the rate of photosynthesis per unit leaf area compared with the control for either chemical about 3 wk after application. For fully expanded leaves at the time of application a reduction in the rate of photosynthesis per unit leaf area occurred and was sustained for at least 2 wk. The reduction in the rate of photosynthesis is explained by decreased stomatal conductance.
The effects of different external nitrate concentrations on growth of Avena sativa cv. Amuri treated with diclofop‐methyl
Authors: ANDREWS M. , DICKSON R. L. , FOREMAN M. H. , DASTGHEIB F. , FIELD R. J.
Published: February 2008

Avena sativa cv. Amuri fed either low or high nitrate was sprayed with diclofop‐methyl (1 kg a.i. ha‐1) at the three leaf stage. The short term effects of the herbicide on chlorophyll concentration of leaves (laminae) and short and long term effects on d.wt of the component plant parts were determined by comparison with unsprayed plants.

For unsprayed and sprayed plants, total leaf d.wt approximately doubled during the first twelve days after commencing treatments. Growth was substantially greater at high nitrate than low nitrate. For unsprayed plants, the increase in total leaf d.wt was due primarily to growth of leaf 3 but for sprayed plants it was due to growth of leaves 1 and 2. Twelve days after commencing treatments, d.wt of leaves 1 and 2 was substantially greater for sprayed plants than for unsprayed plants given similar nitrate, while chlorophyll concentration was substantially less. Leaf 3 d.wt and chlorophyll concentration were substantially greater in unsprayed plants than in sprayed plants given similar nitrate. For unsprayed plants, values were greater at high nitrate than low nitrate, for sprayed plants the converse was the case.

Forty nine days after commencing treatments, unsprayed plants had a greater total plant d.wt than sprayed plants given similar nitrate. Total plant d.wt for unsprayed plants was greater at high nitrate than low nitrate, the opposite was the case for sprayed plants. Unsprayed plants at both nitrate levels and sprayed plants given low nitrate produced seed heads but sprayed plants given high nitrate did not. Diclofop‐methyl at a rate of 0.3 kg a.i. ha‐' stopped seed head production at high nitrate. Retention and uptake of diclofop‐methyl were not significantly different at low and high nitrate. At 1 kg a.i. ha‐l diclofop‐methyl, plants switched from low to high nitrate at spraying showed damage similar to that shown by plants given high nitrate throughout. Addition of 200 μg GA into the leaf sheaths two days prior to spraying increased the efficacy of diclofop‐methyl at low nitrate.

It is proposed that increased efficiency of diclofop‐methyl at high nitrate is due to increased leaf damage caused by a greater rate of leaf expansion.
The response of determinate and semi‐determinate faba bean varieties to different sowing dates in the spring
Authors: PILBEAM C. J. , HEBBLETHWAITE P. D. , RICKETTS HELEN E.
Published: February 2008

Field trials conducted during 1986 and 1987 at the University of Nottingham compared the growth and development of two varieties of faba bean, Alfred and Ticol, in response to three different dates of sowing in the spring.

Grain yields were greater the earlier the crop was sown. This difference was attributed to the larger canopy size, especially at the pod‐filling stage of the earlier sown crops. This probably reflected the influence of temperature on the expansion and senescence of leaves during development.

A semi‐determinate variety of faba bean, Alfred, yielded 31% more than a determinate variety, Ticol. This difference was not attributable to any particular yield component. In 1986, it was correlated with pods per podding node and in 1987 with the number of seeds per pod. Three reasons can be advanced to explain this greater yield. Firstly, Ticol branched more than Alfred and so a greater proportion of its total reproductive nodes were borne on the branches rather than the mainstem. Branches were shown to be inferior in terms of yield production. Secondly, it was demonstrated that Ticol was probably less able to transfer stored assimilates from the stem to the developing pod than Alfred. Thirdly, Alfred had a larger canopy during pod development than Ticol.
Effects of ethylene on the susceptibility to Botrytis cinerea infection of different tomato genotypes
Authors: BARKAI‐GOLAN RIVKA , LAVY‐MEIR GILA , KOPELIOVITCH E.
Published: February 2008

Ethylene at 10 and 100 μl/litre stimulated germ‐tube elongation of Botrytis cinerea spores incubated within normal and non‐ripening nor tomato fruits, but had little influence on the total percent of germination. Values of germ‐tube length within the mature‐green normal fruits and the mature‐green or mature nor fruits were similar to those recorded within the normal mature fruits when held in air. Exposure of the normal and the mutant fruits to 100 μl/litre ethylene immediately after inoculation with B. cinerea insignificantly increased lesion development, but resulted in increased sporulation. When tomato fruits were exposed to ethylene for 3 days before inoculation a marked stimulatory effect on rot development was exhibited on the mature‐green normal fruits but not on the nor mutant fruits. The results indicate that exogenous ethylene may directly stimulate germ tube growth of B. cinerea in both normal and mutant fruit, but that it may affect subsequent fungal growth indirectly, via stimulation of the ripening process, only in preclimacteric normal tomato fruit.
Colonisation of maize by aphid vectors of barley yellow dwarf virus*
Authors: COCEANO P. G. , PERESSINI S.
Published: February 2008

With the present research we tried to evaluate the contribution by maize (corn) to the spread of aphid vectors and in the maintenance of barley yellow dwarf virus (BYDV) in Friuli ‐ Venezia Giulia (North East Italy). We also wanted to examine differences between two corn genotypes in relation to aphid colonisation. Some aspects of plant colonisation and the frequency of BYDV infected colonies in the two cultivars are discussed.
The effect of satellite RNA on cross‐protection among cucumber mosaic virus strains*
Authors: WU GUSUI , KANG LIANGYI , TIEN PO
Published: February 2008

Tobacco and pepper plants were inoculated with a mild strain of cucumber mosaic virus (CMV) with or without satellite RNA, then challenged by a virulent CMV strain devoid of satellite RNA and protection effects detected by assessment of symptoms and protein A sandwich ELISA for the challenge CMV strain. Protection was obtained both in the presence and the absence of satellite RNA in the preinoculating strain but was greater when it was present.
Selection of nematodes for zero cyst phenotypes with soybean
Authors: LUEDDERS VIRGIL D.
Published: February 2008

Definitive genetic studies of the soybean cyst nematode (Heterodera glycines)‐soybean (Glycine max) relationship are complicated by the use of soybean lines with many genes for resistance to heterogeneous, amphimictic nematode populations. Inbreeding and artificial selection of cyst nematodes decreased their ability to form cysts on specific soybean lines assumed to have few genes for resistance. In the initial sib selection, single cysts were used to inoculate two‐seedling units consisting of a seedling of one soybean line to evaluate the nematodes' ability to form cysts on it and a seedling of another line for comparison and maintenance of the nematode inbreds being developed. This method permitted some selection but was slow and labour‐intensive. A better method of artificial selection for fewer cysts on specific soybean lines was to inbreed nematodes for about four generations, then to evaluate the inbreds for ability to form cysts on the soybean lines before selecting particular inbreds with poor ability to form cysts for the development of more inbreds. This increased the frequencies of specific nematode genes for avirulence or alleles for incompatibility with soybean lines containing the interacting [gene‐for‐gene] alleles for incompatibility (genes for resistance). The artificial selection apparently was for at least two nematode alleles for incompatibility since at least two soybean alleles were indicated in the segregation from crosses of soybean lines.
A testing sequence for reducing rejection of potential biological control agents for weeds
Authors: WAPSHERE A. J.
Published: February 2008

Many insect agents, selected for the biological control of weeds and tested under restricted cage conditions, have been rejected as unsafe for introduction because of an apparent increase in host range compared with that observed under natural conditions. These aberrant results appear to be due to the insects' inability to follow the normal behavioural sequence based on appropriate cues which lead to correct host selection. It is suggested here that a reverse sequence of testing which progressively reduces the degree of restriction and deletes unattacked plants at each stage, until only a few remain to be tested under conditions as near natural as possible, would allow previously rejected insects to be used as biological control agents.
Effects of the plant growth regulator chlormequat on plant form and yield of triticale
Authors: NAYLOR ROBERT E.L.
Published: February 2008

Three field experiments were conducted in order to evaluate the effect of application of the plant growth regulator chlormequat on growth and yield of the cereal triticale. Application of chlormequat resulted in shorter triticale plants as a result of restricted elongation of the upper internodes of the stem. These shorter plants produced a lower weight of straw and were more resistant to lodging. In two experiments chlormequat application led to no statistically significant increase in triticale grain yield; in a third yield was increased. Chlormequat consistently increased the number of grains per ear but this was offset to some extent by a lower mean grain weight. Yield was closely correlated with the number of grains per m2. Leaf senescence was delayed by chlormequat. The results are consistent with the hypothesis that chlormequat can increase yield potential.
Effects of acidic fog on productivity of celery and lettuce and impact on incidence and severity of diseases
Authors: MUSSELMAN ROBERT C. , McCOOL PATRICK M.
Published: February 2008

The effects of acidic fog on productivity of celery and lettuce were examined using a portable fogging apparatus to expose field plots to simulated fog episodes. Acidic solutions were formulated to simulate fog reported for southern California. Celery (Apium graveolens var. dulec cv. Bishop) and lettuce (Lactuca sativa cv. Mesa 659) were exposed in separate experiments once or twice each week during crop growth and maturation to 1 ‐ to 2‐h of fog at specific acidity levels between pH 1.6 and 3.8. Necrosis occurred as small, irregularly shaped white (celery) or brown (lettuce) lesions on the most exposed portions of the plants. Fog necrosis sufficient to reduce marketability of celery was evident after single exposures at pH 2.4. Although injury occurred on wrapper leaves of lettuce at acidity levels as high as pH 3.4, marketability was reduced from foliar necrosis only after exposure to acidity levels of pH 2.6 or lower. Repeated exposure of lettuce to acidity below pH 2.0 was necessary to reduce yield. The field experiments demonstrated that acidic fog influenced natural incidence of disease. At low pH fog exposure, celery had increased occurrence of basal stalk rot and lettuce exhibited increased bacterial soft rot. Indirect effects of acidic fog on host‐pathogen relationships and subsequent crop marketability may be more important than the direct effects of acidic fog exposure on plant tissue.
The growth, yield and nutrient uptake of winter wheat following root‐pruning
Authors: AYLING SARAH M.
Published: February 2008

The effect of root‐pruning on shoot growth was investigated in winter wheat growing in lysimeters. Removal of half of the root axes at the beginning of stem elongation reduced shoot dry matter, determined 1 month after pruning, by 13% and grain yield by 8%. Removal of either the seminal or nodal root system during tillering reduced shoot dry weight, measured during the growing season, by 7% and grain yield by 25%. Root‐pruning had negligible, or only transient, effects on the concentration of nitrogen, phosphorus, potassium, magnesium and manganese in the shoots. The harvest index was not affected by root‐pruning.
An experimental design and procedures for testing putative controls against naturally‐occurring take‐all in the field
Authors: HORNBY D. , BATEMAN G. L. , PAYNE R. W. , BROWN M. E. , HENDEN D. R.
Published: February 2008

In experiments during 1983–86 take‐all was more severe and eyespot and sharp eyespot less frequent in 2nd‐4th crops of winter wheat at Woburn (Beds.) than at Rothamsted (Herts.). Third crops had most take‐all and yielded least grain. Against this background, small plots, 37 cm × 31 cm, in which all plants were sampled, were tried as a means of increasing experimental precision. They were arranged in fours in incomplete blocks and blocks with complementary treatments (putative controls of take‐all) were paired. Thirty of these block‐pairs were distributed throughout each experimental site in each year to provide one replicate of the design for each of three sampling times: April, June and August. Unattributed variation in disease and plant growth for plots within blocks was compared to that in other strata (block‐pairs and blocks within block‐pairs) of the experiment. The variability amongst block‐pairs scattered throughout the site was nearly always greater than that for blocks within block‐pairs (98% of take‐all assessments, 71% of soil infectivity estimates, 94% of eyespot and sharp eyespot assessments and 86% of all plant measurements). The variability of blocks within block‐pairs exceeded that of plots much less frequently (56% and 69% of take‐all assessments, 33% and 25% of soil infectivity measurements, 63% and 56% of eyespot and sharp eyespot assessments and 50% and 63% of plant measurements; Rothamsted and Woburn, respectively). Small plots were judged mostly on this last comparison, where a variance ratio in excess of 1 indicated that the small plots had decreased variability and increased precision.

Variance ratios for different assessments of take‐all indicates that small plots: i) most consistently decreased disease variability during the years of maximum disease, ii) were slightly less effective at Rothamsted than at Woburn, and iii) were usually less effective in fourth crops than in previous crops.

Soil infectivity was most uniform after crops with most disease and blocks were rarely more variable than plots. hxcept when disease was severe, soil infectivity in August tended to be positively associated with the yield of the crop just harvested.

These findings reveal changes in the scale of disease patterns, both during the crop sequence and within individual crops, and suggest more than one scale of pattern in take‐all‐infested fields. This is discussed in relation to field experimentation and take‐all decline.
Characterisation of watermelon curly mottle virus, a geminivirus distinct from squash leaf curl virus
Authors: BROWN JUDITH K. , NELSON MERRITT R.
Published: February 2008

Purified preparations of watermelon curly mottle virus (WCMoV), a whitefly‐transmitted geminivirus, contained dimeric or geminate particles of 20 times 30 nm and the virus was transmissible by mechanical means. Virus yields ranged from 100–150 μg/100 g leaf tissue. Purified preparations exhibited a typical nucleoprotein absorbance profile with a maximum absorbance at 258 nm, and A280 / A260 ratio of 0.61–0.64. Infectivity was associated with two light‐scattering, virus‐containing bands following sucrose density gradient centrifugation. The viral capsid protein was resolved as a doublet by SDS‐PAGE. The estimated mol. wts of the two bands within the doublet were 29 100 (±1550) and 27 733 (±1550), respectively. DNA isolated from virus particles was resolved by gel electrophoresis into two circular single‐stranded DNA bands of approximately 2.6 to 2.7 kb. The two bands are believed to represent the individual components of a bipartite genome, characteristic of previously described whitefly‐transmitted geminiviruses.
Distribution and dynamics of mycophagous and microbivorous nematodes in potato fields and their relationship to some food sources
Authors: HOFMAN T. W. , S'JACOB J. J.
Published: February 2008

Nematodes are not uniformly distributed in soil. The aim of this study was to investigate the distribution pattern of mycophagous and microbivorous nematodes and to develop sampling methods to detect them at different sites in the soil. Sampling of nematodes was carried out by three methods: using an auger, by collecting soil which was shaken from the roots (root shaking sample) and by collecting roots with the adhering rhizosphere soil (rhizosphere sample). Distribution patterns and population dynamics of mycophagous nematodes were similar to other microbivorous nematodes in three potato fields. Population densities in the rhizosphere samples were 4–50 times higher than those in auger samples. Samples obtained with the auger and root‐shaking methods yielded more or less equal population densities.

Numbers of the mycophagous nematodes Aphelenchus avenae, Aphelenchoides sp. and unidentified microbivorous nematodes increased several fold within a few days on suitable substrates in soil. These substrates could be the dying roots of plants of which the haulms were killed or flax straws that were previously colonised by the fungus Rhizoctonia solani.
Effects of leaf‐matter incorporation on Aphelenchoides composticola (Nematoda), mycofloral composition, mushroom compost quality and yield of Agaricus bisporus
Authors: GREWAL P. S.
Published: February 2008

Incorporation of dried leaves of Azadirachta indica, Cannabis sativa, Eucalyptus tereticornis and Ricinus communis at 3 kg per 100 kg of dry wheat straw prior to composting had several effects. When compared with controls, treated composts exhibited a higher temperature during composting, a higher nitrogen content and a neutral pH. The treatments resulted in enhanced populations of thermophilic fungi and mesophilic antibiotic‐producing fungi, but reduced numbers of mesophilic competitor/pathogenic moulds. Populations of the mycophagous nematode, Aphelenchoides composticola were reduced below economic injury level in dried leaf treated composts.

Compost obtained from C. sativa and R. communis treatments were more rapidly colonised by the mushroom mycelium (Agaricus bisporus) than that from any other treatment. When compared with compost treated with carbofuran R. communis, C. sativa and A. indica treatments significantly increased mushroom yield by 19.4, 8.1 and 6.5% and by 108.5, 88.7 and 85.9% when compared with the control. Yield from the E. tereticornis treatment was also higher than the control but lower than that of the nematicide treatment.
The use of foliage assessment to improve the identification of tolerance to damage by nematodes (Globodera pallida) in potatoes
Authors: DALE M. F. B. , BROWN J.
Published: February 2008

Six potato trials, two in each of three years, were conducted in collaboration with the Agricultural Development and Advisory Service (ADAS) at sites infested with potato cyst nematodes (G. pallida Pa 2/3). The trials were part of a selective screen to identify PCN tolerant and intolerant clones with each trial consisting of four blocks divided into nematicide treated and untreated sub‐blocks. A range of partially resistant and susceptible material was assessed for yield losses due to PCN damage to the roots and for the effect on the foliage by comparison between the nematicide treated and untreated areas. The relationships between the foliage symptoms, untreated yields, treated yields, proportional yield loss, initial PCN population and the post‐harvest PCN population levels are examined. Significant correlation coefficients were obtained between foliage symptoms and yield of clones in PCN infected soil and also between foliage symptoms with percentage yield loss due to PCN infestation. The conclusions were that the assessment of PCN damage to foliage vigour/development can contribute positively to a more accurate identification of tolerant or intolerant potato genotypes.
Separation of three Rubus‐feeding species of aphid — Sitobion fragariae (Wlk.), Macrosiphum funestum (Macch.) and Amphorophora rubi (Kalt.) (Hemiptera: Aphididae) — by electrophoresis
Authors: LOXDALE H. D. , BROOKES C. P.
Published: February 2008

Four species of aphid infest wild and cultivated blackberry (Rubus fruticosus agg., R. lachiatus, etc) and other Rubus species in Britain and Continental Europe, ‐ Sitobion fragariae (Walker), Macrosiphum funestum (Macchiati), Amphorophora rubi (Kaltenbach) and Aphis ruborurn (Bösrner). The nymphs, especially the early instars, of the first three species are fairly difficult to differentiate morphologically. However, they can clearly be separated using electrophoresis. The present paper describes diagnostic enzyme/isoenzyme banding patterns which allow differentiation of the first three species as apterous and alate adults and their instars using two enzymes ‐ carboxylesterase (EST) and phosphatase (PHOS).
Field dissipation of the pyrethroid insecticide/acaricide biphenthrin on the foliage of peach trees, in the peel and pulp of peaches, and in tomatoes
Authors: PAPADOPOULOU‐MOURKIDOU E. , KOTOPOULOU A. , STYLIANIDISM D.
Published: February 2008

Biphenthrin was applied in the field to peach trees and tomato plants at rates of 2 and 4 g of biphenthrin a.i., 100 e.c. Talstar (Anon., 1983; FMC, USA)/100 litres of water. During the experimental period, three to four applications were made to peach trees and four to tomato plants at 14‐day intervals. Samples from peach foliage, peaches and tomatoes were collected at set post‐application dates and analysed for biphenthrin residues by GLC.

The foliar residues of biphenthrin ranged from 65±1 (maximum to 25± 1 (minimum) ng/cm2 and from 101±52 (maximum) to 35±7 (minimum) ng/cm2 at the low and high rates of application, respectively. The residues of biphenthrin in the peach fruit peel ranged from 1016±367 (maximum) to 247±44 (minimum) ng/g for the low rate and from 2845 (maximum) to 368±15 (minimum) ng/g for the high rate of application. The maximum amount of biphenthrin residues measured in the peach pulp was 47±10 ng/g while at 21‐day after the third application and at 7‐day after the fourth application the residues present were at levels lower than the detection limit (1 ng/g) for the method applied. In whole tomatoes the residues of biphenthrin ranged from 119±14 (maximum) to 31±2 (minimum) ng/g. Plots of 1nC versus t, where C is the amount of biphenthrin ng/cm2 of peach leaf surface or per gram of fruit tissues and t is the post‐application time in days, were constructed and the persistence half‐lives of biphenthrin were calculated.
A cotyledon screen for resistance to scab (Cladosporium cucumerinum) in cucumber (Cucumis sativus) seedlings
Authors: VAKALOUNAKIS D. J. , WILLIAMS P. H.
Published: February 2008

An efficient protocol for differentiating cucumber (Cucumis sativus) seedlings resistant and susceptible to scab (Cladosporium cucumerinum) has been developed by examining the interacting factors of spore density and cotyledon growth stage. The procedure permitted both resistant and susceptible plants to be recovered. Seedlings were grown at 20°C and inoculated 1 day after emergence by placing a 5 μl inoculum droplet (2 × 106 spores/ml) on the newly expanded cotyledons. Seedlings were incubated in a darkened dew chamber for 48 h at 20°C and 100% r.h., and then grown for 6 days at 20°C. Plants could be rated as resistant or susceptible 8 days after inoculation.
Fungitoxic effects of extracts from some West African plants
Authors: AWUAH R. T.
Published: February 2008

Extracts from five West African plants were evaluated in vitro for fungitoxicity against Ustilago maydis, Ustilaginoidea virens, Curvularia lunata and Rhizopus sp. Steam distillate from leaves of Cymbopogon citratus completely inhibited the growth of all four fungi, and hot water extracts from fresh leaves of Ocimum gratissimum and Chromoleana odorata, and dry fruits of Xylopia aethiopica, reduced radial growth by 10–60%. A hot water extract from dry fruits of Monodera myrstica was ineffective as a fungitoxicant.
Susceptibility of four hedgerow shrubs to a range of herbicides and plant growth regulators
Authors: MARSHALL E. J. P.
Published: February 2008

Crataegus monogyna, Prunus spinosa, Fraxinus excelsior and Sambucus nigra, common woody species of hedgerows, were grown in pots and treated in June with half and full recommended rates of 15 herbicides and three plant growth regulators. C. monogyna was affected by fewest compounds, while the other three species showed differing tolerances. The wild‐oat herbicides, diclofop‐methyl, flamprop‐m‐isopropyl and difenzoquat did not adversely affect the shrubs. Plant growth regulators used at rates recommended for cereals and grassland had only minor effects. Clopyralid killed only S. nigra, while mecoprop, fluroxypyr, chlorsulfuron, metsulfuron‐methyl and glyphosate caused significant damage to most species. Height of C. monogyna was increased after treatment with diclofop‐methyl, difenzoquat, ethofumesate, mefluidide and chlormequat.
Further studies on resistance to Leptosphaeria coniothyrium in the red raspberry and related species
Authors: JENNINGS D. L. , BRYDON E.
Published: February 2008

Rubus pileatus and its F1 hybrids with raspberry (R. idaeus) were resistant to cane blight (Leptosphaeriu conioth‐yriurn), but little resistance was obtained in subsequent backcross generations apart from a hybrid identified in the second backcross. Two hybrids from backcrossing R. coreanus to raspberry also showed resistance. R. pileatus and its F, hybrids produced hard growth, unlike that of raspberries, which may have been associated with a form of resistance that could not easily be transferred to commercial raspberry cultivars. Some of the genotypes used as parents showed intermediate levels of resistance and it is possible that the highly resistant genotype identified in the second backcross arose from a recombination of genes for resistance. Plants with pubescent canes (gene H) were up to 20% more resistant to mycelial inoculation than those with non‐pubescent canes (gene h), and the percentage of machine‐harvester inflicted wounds with disease symptoms that resulted from natural infection was also less in genotypes with pubescent canes. Many genotypes with intermediate levels of resistance suffered only limited damage from mycelial inoculation and so there are good prospects for breeding cultivars with an effective resistance, despite the limited value of R. pileatus as a donor species.
Leaf and root degeneration in early maturing onions: A physiological disorder
Authors: RABINOWITCH HAIM D. , ZIG URI
Published: February 2008

Three onion cvs., four sowing dates, two plant densities and two photoperiod regimes were employed to elucidate the factor(s) responsible for leaf and root degeneration which occur frequently in crops of early maturing onions in the Arava valley, Israel, causing heavy economic losses. It was found that the symptoms developed in early maturing genotypes which showed the abnormal sequence of early bulbing in the autumn, followed by the reversal of bulbing later in the season. At this time of season root regrowth is restrained due to low soil temperatures and therefore mineral and water supply to the sprouting foliage is likely to be limited. These interpretations appear to be correct for the problem has been avoided in several seasons by the prevention of early bulbing by sowing later, by keeping population density at standard rates, and by the prevention of mineral deficiency by application of extra nitrogen.
Phytotoxicity of methyl bromide on chrysanthemum cuttings
Authors: HELYER N. L. , LEDIEU M. S.
Published: February 2008

The phytotoxicity of methyl bromide gas on chrysanthemum cuttings was investigated in relation to gas concentration, length of exposure, temperature, and variety and age of cuttings. Concentrations of 10.5 to 13.5 g/m3 for 4 to 5 h produced a concentration time product (CTP) of 54 g h/m3 which is suitable for safe fumigation of most varieties of chrysanthemum. Length of exposure was not critical up to 5 h. However, fumigations of cuttings which were more than 3 wk old generally caused excessive phytotoxicity and therefore cannot be recommended. There was less damage at temperatures of between 14 and 16°C than at higher temperatures. A table of predictions from a fitted regression equation is included to demonstrate the increased susceptibility of chrysanthemums at higher temperatures and ages of cuttings.
A method for in vitro production of conidia of Elsinoe veneta and the inoculation of raspberry cultivars
Authors: WILLIAMSON B. , HOF LYSBETH , McNICOL R. J.
Published: February 2008

Conidia of two isolates of Elsinoe veneta were consistently produced in vitro by a 3‐stage culture system in which sparsely sporulating microcolonies produced on corn meal agar were used to ‘seed’ Czapek‐Dox V8 juice agar. E. veneta then sporulated on this medium if dises were floated mycelium uppermost on sterile distilled water for 24 h at 25°C. Both isolates also produced microconidia in vitro.

Only the growing apices of raspberry canes were susceptible to infection. Of 12 genotypes inoculated in the glasshouse, a red raspberry derivative of Rubus coreanus, EMRS 2769/9, was the most resistant and the black raspberry selection SCRI 815286 and cv. Malling Delight were the most susceptible. Of four red raspberry cultivars inoculated in the field cv. Malling Orion was the most susceptible. Inoculated flowers and developing fruits produced malformed fruits because infected drupelets were smaller or slower to ripen than uninfected ones.
Purification and some particle properties of anthriscus yellows virus, a phloem‐limited semi‐persistent aphid‐borne virus
Authors: HEMIDA S. K. , MURANT A. F. , DUNCAN G. H.
Published: February 2008

Anthriscus yellows virus (AYV), a phloem‐limited virus transmitted in the semi‐persistent manner by the aphid Cavariella aegopodii, was purified by treatment of leaf extracts with cellulasc, followed by differential and sucrose density gradient centrifugation. ‘The preparations contained isometric particles c. 29 nm in diameter which were unstable unless stored in buffer at pH 8.0 containing 1 mM CaCl2,. The particles sedimented as two components, ’full‘ nucleoprotein particles with A260/A280= 1.83 containing about 42% nucleic acid, and ’empty‘ protein shells with A260,/A280= 0.73; their buoyant densities in CsCl solutions were 1.52 and 1.27 g/cm3. Respectively. Yields of ihe nircleoprotein particles were c. 1.75 mg/kg leaf tissue. The particles contained a single species of RNA, of mol. wt 3.6 × 10 “(10 000 nucleotides). Particle protein preparations contained four electrophoretic species, of mol. wt (× 103) 35.0, 28.3, 23.3 and 22.3.C. aegopodii did not transmit AYV from purified preparations. A rabbit injected with AYV preparations produced antibodies that coated AYV particles in electron microscope tests, but gave variable reactions in immunosorbent electron microscopy (ISEM), depending on the composition of the medium. No reactions were obtained in enzyme‐linked inimunosorbent asjay (ELISA). No serological relationship was detected in ISEM between AYV and any of 10 viruses that resembled it in one or more properties.
Host ranges and serological properties of eight isolates of parsnip yellow fleck virus belonging to the two major serotypes
Authors: HEMIDA S. K. , MURANT A. F.
Published: February 2008

Isolates of parsnip yellow fleck virus (PYFV) from parsnip (P‐121), celery (CV506 and CV065) and Heracleum sphondylium (Hs2) were serologically close to each other but distant from isolates from carrot (Dc2 and Dc5) and Anthriscus sylvestris (A‐421 and As2), which were in turn close to each other serologically. The two groups of isolates also differed from each other in host range. Minor differences in immunological reactions and in host range and symptomatology were observed between isolates in each group. Particles of all eight isolates had similar RNA and protein compositions. The data confirm that PYFV isolates fall into two major serotypes, those from parsnip, celery and H. sphondylium belonging to the P‐121 serotype and those from carrot and A. sylvestris belonging to the A‐421 serotype.
The comparison of isolation techniques for nematophagous fungi from soil
Authors: BAILEY F. , GRAY N. F.
Published: February 2008

Using a single soil, a comparison was made of six well‐known techniques for the isolation of nematophagous fungi. Each technique was tested for its ability to isolate the fungi present with regard to the number of species recovered, the number of plates needed to be 95% sure of isolating all the species possible and the amount of soil required. The advantages and disadvantages of each method are discussed. The results show that specific techniques are required for the isolation of endoparasites and predators respectively. The soil sprinkling technique and the Baermann funnel technique are shown to be the most efficient methods overall, with six and seven replicates required for 95% probability of isolating all the predator and endoparasite species respectively.
On insect‐plant associations in agriculture and the selection of agents for weed biocontrol*
Authors: DENNILL G. B. , MORAN V. C.
Published: February 2008

Hokkanen & Pimentel (1984) proposed a novel approach for the selection of biocontrol agents. They advocated the selection of agents from a relative of the weed plant rather than from the target weed species itself. The new relationship that such agents would have with the weed would be characterised by a relative lack of homeostasis compared with the old herbivore‐plant associations traditionally used in weed biocontrol, and would consequently be more effective. There are few examples to support these contentions because of the traditional use of old herbivore‐plant associations in weed biocontrol.

In the present study, herbivore‐plant associations in agricultural situations, which are analogous to agent‐weed associations, are examined to assess the potential of new associations for weed biocontrol. The herbivores on 14 introduced crop plants which have salient similarities to the major weeds in the south‐western Cape were surveyed: (a) 68% of the 188 insect and mite herbivores are indigenous species in new associations with these host plants, and (b) of the five most damaging pests on each of 13 of the crop plants, 53% are in new associations with the plants. Of the 40 most important agricultural pests in South Africa, 58% are in new associations, confirming these results. About 50% of the insect and mite herbivores in new associations with their host plants are oligophagous, indicating that new associations are not necessarily characterised by polyphagy and hence unsafe for use in weed biocontrol.

We conclude that new associations between herbivore species and host plants have strong potential in weed biocontrol because (a) their frequency in agriculture indicates that they can easily be established in weed biocontrol situations, (b) they are as damaging as old associations and (c) they are not necessarily unsafe as regards host specificity. We therefore advocate the use of both the classical approach and that of Hokkanen & Pimentel (1984). Our support for Hokkanen & Pimentel (1984) is, however, based on evidence and rationale clearly different to theirs, and we provide novel guidelines, which can be routinely and practically applied in the selection of agents for weed biocontrol.
Lipid profile of Pleurotus sajor caju
Authors: NAIR N. G. , SONG C. H. , JIANG J. Y. , VINE J. H. , TATTUM B. , CHO K. Y.
Published: February 2008

The lipid profile of Pleurotus sajor caju was studied in relation to mycelial and sporophore growth and different cultural factors. The growth was characterised by lipid synthesis during mycelial growth and utilisation during sporophore growth. The degree of instauration increased during mycelial growth and decreased during sporophore formation. The fatty acid composition of mycelium and sporophore was similar, linoleic acid (C18:2) being the most dominant acid in both. C:N ratio had a significant (P<0.05) positive effect on mycelial dry weight; however, per cent total lipids was similar. Non‐polar lipids became more unsaturated as the temperature was raised from 10° to 25°C and pH from 3.0 to 6.0, but declined when the cultures were aerated. Mycelial dry weight increased significantly (P<0.05) when the liquid medium was supplemented with lipids. In general, fatty acids with carbon chain length C16 and C18 stimulated the growth of mycelium. Supplementation of solid substrate (cotton seed hulls) with safflower oil, soybean oil or rice bran significantly (P<0.05) increased the yield of sporophores. Total lipids and ratio of non‐polar to polar lipids were not affected by lipid supplementation.
Relationships between indices of seed maturity and carrot seed quality
Authors: STECKEL JOYCE R. A. , GRAY D. , ROWSE H. R.
Published: February 2008

Carrot seeds cvs Chantenay and Amsterdam were harvested on several occasions from crops grown in 1985 and 1986, from the time they had reached or were close to their maximum dry weight and were starting to turn brown.

Maximum seed dry weight occurred approximately 40–45 days after flowering (DAF) in both cultivars. Maximum germination (International Seed Testing Association 14‐day count) occurred 40 and 55 DAF in cvs Chantenay and Amsterdam, respectively, but the maximum 7‐day count and the minimum coefficient of variation of embryo length did not occur until 60 DAF in cv. Chantenay and 55 to 65 DAF in cv. Amsterdam. Percentage germination was negatively and linearly related to seed moisture content, chlorophyll a + b content in the seed coat and seed distortion, measured on a modified tensile‐testing machine, the relationships accounting for 77, 71 and 64% of the variance in the 7‐day germination count, respectively. The corresponding values for the 14‐day count were 63, 61 and 50%. A simple field test for monitoring seed maturity is proposed.