bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of white rot in dry bulb onions with artificial onion oil
Authors: MERRIMAN P. R. , ISAACS S. , MACGREGOR R. R. , TOWERS G. B.
Published: February 2008

Artificial onion oil was evaluated as a soil treatment for control of white rot in onions caused by Sclerotium cepivorum. The treatment was tested at Werribee South in a red brown earth with a sclerotial population of c. 40–100/kg soil; and at Colac in a black clay loam with c. 180/kg soil. Treatments were applied before sowing and their effect on numbers of sclerotia, disease incidence and yield of dry bulb onions determined.

At Werribee South onion oil reduced numbers of sclerotia at the 0–10 and 10–20 cm depths in soil, reduced disease incidence and increased yield in comparison with the controls. Onion oil at a concentration of 5% in water and injected (440 litredha) at 10 cm was most effective. The treatment reduced sclerotial numbers at 0–10 and 10–20 cm by 77 and 91% respectively, reduced disease from 57 to 13% and increased yield by 103%. Onion oil at 25% in water had no significant effect on populations of sclerotia or on incidence of disease.

In an experiment at Colac, the application of onion oil at 5% in water reduced sclerotial numbers from 187 to 87/kg, but not incidence of white rot.
Detection of six nepoviruses in their nematode vectors by immunosorbent electron microscopy
Authors: ROBERTS I. M. , BROWN D. J. F.
Published: February 2008

Particles of six nepoviruses were detected by immunosorbent electron microscopy (ISEM) in extracts of their respective vector nematodes. This technique was at least a thousand times more sensitive than conventional electron microscopy. It was also more rapid, reliable and sensitive than infectivity tests in which extracts of nematodes were inoculated to indicator plants. The viruses were detected in extracts of single nematodes, and in the roots and leaves of infector and bait plants.
A possible mechanism of action of asulam involving folk acid biosynthesis
Authors: STEPHEN N. H. , COOK G. T. , DUNCAN H. J.
Published: February 2008

A range of plant species was sown in beakers containing vermiculite and treated with solutions of asulam. This resulted principally in stunting of the root system which could be reversed by the simultaneous addition of either p‐aminobenzoic acid or folic acid. Compounds related to p‐aminobenzoic acid had no such activity. It is proposed that a possible mechanism of action of asulam is the inhibition of folic acid synthesis resulting in impairment of biological methylations and hence inhibition of protein and nucleic acid synthesis.
Effects of 3,5–diiodo‐4–hydroxybenzonitrile (ioxynil) on barley root growth and uptake of phosphate from culture solutions
Authors: WAIN R. L. , WHITFORD P. N.
Published: February 2008

Low concentrations (c. 10‐6 m) of 3,5–diiodo‐4–hydroxybenzonitrile (ioxynil) supplied to barley seedlings in culture solution promote a marked increase in root length and uptake of phosphate is also increased by this treatment. When [125I]ioxynil was supplied to barley seedlings through the roots for 7 days, the presence of 3,5–diiodo‐4–hydroxybenzoic acid (DIHB) was detected in the root tissue.
Protection of radish from cabbage root fly damage by seed treatments with organophosphorus and carbamate insecticides
Authors: THOMPSON A. R. , SUETT D. L. , PERCIVALL A. L.
Published: February 2008

Ten seed treatment formulations were assessed in the laboratory and glasshouse for their phytotoxicity to radish and effectiveness in preventing cabbage root fly damage. Bendiocarb, dimethoate, mecarphon and chlorfenvinphos were phytotoxic; carbophenothion, diazinon, iodofenphos and pirimiphos‐ethyl gave negligible protection. Chlorpyrifos and isofenphos performed adequately and so were compared at 14 and 20 g a.i./kg of seed in four field experiments with chlorfenvinphos soil treatments. With less than one‐third of the a.i. needed for soil treatments, the seed treatments gave similar or, in one experiment, better protection than 2·2 kg chlorfenvinphos/ha incorporated in the soil before sowing.

Insecticide residues in mature radish from soil treated at 2·2 kg a.i./ha with a chlorfenvinphos e.c. were 0·04–0·06 μg/g, within the current Codex tolerance of 0·1 μg/g; the same dose of a granular formulation of chlorfenvinphos produced residues of 0·06‐0·21 μg/g. Chlorpyrifos residues in mature radish grown from seed treated at 20 g a.i./kg were 0·12‐0·65 μg/g, mostly less than the most relevant Codex tolerance, for carrots, of 0·5 μg/g. Seed treatment with the same dose of isofenphos, for which there are no Codex tolerances, produced residues of 0·17‐0·27μg/g.

No insecticide treatments are currently approved in the U.K. to protect radish from damage by cabbage root fly larvae. Soil treatment with a chlorfenvinphos e.c. seems to be suitable for protecting single radish crops. If suitable formulations of chlorpyrifos or isofenphos were made available commercially, seed treatment with these insecticides would lessen the risk of residues accumulating in soil and contaminating successive radish crops grown in the same soil. Seed treatment would also provide an alternative to applying smaller doses to the soil for second or subsequent crops.
Differential host preference in Pseudocercosporella herpotrichoides with spring‐sown wheat and barley monoculture
Authors: CUNNINGHAM P. C.
Published: February 2008

Incidence of eyespot was assessed in different‐length sequences of spring‐sown wheat and barley in field experiments. Disease levels in the fourth crop were greater with single cereal systems than when the alternative crop was grown in the fourth year. The existence of host specificity as a possible cause of this phenomenon was examined in comparative pathogenicity studies of isolate collections obtained from differentially‐cropped plots from the same field.

In two experiments, isolates from the third, fourth or fifth consecutive barley crops produced more disease on barley than on wheat and isolates from wheat caused more disease on wheat than did isolates from barley. Isolates from 4‐yr wheat and barley sequences showed significant specificity of isolates for their original hosts but in another experiment such specificity was not detected in isolates from 3‐ and 7‐yr sequences of wheat and barley. However, there was a significant reduction in virulence of isolates in the seventh compared with the third crop, when comparisons were done on the alternative rather than on the original host species. This suggests that extreme selection pressure for pathogen virulence on a particular host species may lead to impairment of pathogenic range.
Studies on double strain occupancy of nodules and the competitive ability of Rhizobium trifolii on red and white clover grown in soil and agar
Authors: BROMFIELD E. S. P. , JONES D. GARETH
Published: February 2008

An investigation concerning double strain occupancy of nodules and the competitive ability for nodulation of Rhizobium trifolii strains 7A strr and 32 spcr was carried out using red and white clover varieties grown in agar and soil.

Only two nodules of the 498 typed from plants grown in soil contained both inoculated strains and none of those analysed by the replica plating technique were formed by both 32 spcr and an indigenous strain. In contrast, plants grown on agar produced between 17% and 25% doubly infected nodules. Strain 32 spcr was more competitive for nodulation than 7A strr both in soil and agar. Indigenous rhizobia in soil were highly competitive for nodulation with the introduced strains; increasing the density of the inoculum resulted in an increase in the proportion of nodules occupied by the inoculated strains. The strains used as mixed inocula in soil were less successful in nodulation than the same strains used as pure inocula. The results also indicate that there was a host effect on the nodulation success of 7A strr.
Pepino mosaic virus, a new potexvirus from pepino (Solanum muricatum)
Authors: JONES R. A. C. , KOENIG RENATE , LESEMANN D. E.
Published: February 2008

Pepino mosaic virus (PepMV), a previously undescribed virus, was found in fields of pepino (Solanum muricatum) in the Canete valley in coastal Peru. PepMV was transmitted by inoculation of sap to 32 species from three families out of 47 species from nine families tested. It caused a yellow mosaic in young leaves of pepino and either a mild mosaic or symptomless infection in 12 wild potato species, five potato cultivars and potato clone USDA 41956 but S. stoloniferum and potato cultivars Merpata and Revolucion reacted with severe systemic necrotic symptoms. The virus was transmitted by plant contact but not by Myzus persicae. It was best propagated and assayed in Nicotiana glutinosa. Sap from infected N. glutinosa was infective after dilution to 10‐1 but not 10‐6, after 10 min at 65°C but not 70°C and after 3 months at 20°C.

PepMV had filamentous particles with a normal length of 508 nm; the ends of some seemed damaged. Ultra‐thin sections of infected leaves of N. glutinosa revealed many inclusions containing arrays of virus‐like particles some of which were banded or whorled; small aggregates of virus‐like particles were also common. The virus was purified by extracting sap from infected leaves in a solution containing 0·065 M disodium tetraborate, 0·435 M boric acid, 0·2% ascorbic acid and 0·2% sodium sulphite at pH 7·8, adding silver nitrate solution to the extract, and precipitating the virus with polyethylene glycol followed by two cycles of differential centrifugation. Particles of PepMV normally yielded two proteins with molecular weights of 26 600 and 23 200, but virus obtained from infective sap aged overnight yielded only the smaller protein suggesting that it was a product of degradation of the larger one. The virus is serologically related to two potexviruses, narcissus mosaic and cactus X and its properties are typical of the potexvirus group.
The effect of increasing dosage of barley yellow dwarf virus on some resistant and susceptible barleys
Authors: BOULTON R. E. , CATHERALL P. L.
Published: February 2008

Five spring barleys, grown either in pots out of doors or in the field, were inoculated with barley yellow dwarf virus (BYDV) using 5, 10, 20 or 50 infective aphids (Rhopalosiphum padi) per plant. Control plants of each variety received no aphids. Infection with all aphid numbers had highly significant adverse effects on all varieties except Cb 1029, an early maturing BYDV‐resistant barley of Ethiopian origin. 12583 Co, a locally bred, late maturing barley possessing the same resistance gene as Cb 1029 suffered more in a pot experiment, but less than three susceptible varieties all of which were severely damaged even when few infective aphids were used. Progressive effects with increasing aphid numbers, indicative of dosage response, occurred in some varieties. These effects included delay in heading and increased stunting, but not less yield. In Cb 1029, BYDV infection caused a reduction in the number of heads per plant, but this was partly compensated for by an increase in the number of grains per head. Conversely, BYDV infection in 12583 Co caused an increase in the number of heads, partly offset by a decrease in the number of Brains tier head.
Leaf mottling of Spartina species caused by a newly recognised virus, spartina mottle virus
Authors: JONES PHILIP
Published: February 2008

The cause of a previously undocumented leaf mottling of Spartina species was investigated. Negatively stained preparations of sap from mottled leaves revealed flexuous particles 725 × 12 nm. Pinwheels with associated laminar inclusion bodies were observed in thin sections of affected mesophyll cells. The virus was purified from infected Spartina anglica plants and had a sedimentation coefficient in 0·015 m borate of 150S. The virus was transmitted by inoculation of sap to healthy Spartina anglica, but not to a range of other graminaceous or dicotyledonous species tested. It was distantly serologically related to agropyron mosaic virus, but not to other viruses with similar morphology; the name spartina mottle virus is proposed.
Seed survival and periodicity of seedling emergence in some species of Atriplex, Chenopodium, Polygonum and Rumex
Authors: ROBERTS H. A. , NEILSON JUNE E.
Published: February 2008

Seeds or fruits of 10 weed species were collected in each of 3 years and mixed with the top 7·5 cm of sterilised soil which was confined in cylinders sunk in the ground outdoors and cultivated three times yearly. The numbers of seedlings emerging were recorded for 5 yr and the numbers of viable seeds remaining then determined. Few, if any, seedlings of Atriplex, Chenopodium or Polygonum spp. emerged in the autumn of sowing; the main emergence was consistently in March–May (A. hastata, A. patula), April–May (P. lapathifolium, P. persicaria), April–June (C. polyspermum), May–June (C. rubrum) or June–August (C. hybridum). When sown before November, some seedlings of Rumex crispus, R. obtusifolius and R. sanguineus appeared immediately. Most emerged in April in subsequent years. Seedling emergence was usually greatest in the first year; thereafter, with all species, seedling numbers decreased approximately exponentially from year to year. The mean numbers of seeds found to be viable after 5 yr ranged from 2·5% (R. sanguineus) to 16·6% (C. rubrum) of those sown.
Studies on the biology of Botrytis species on overwintered salad onions
Authors: MAUDE R. B. , PRESLY A. H.
Published: February 2008

In the years 1973/4–1974/5, Botrytis cinerea was responsible for losses of 26% and 37% respectively in overwintered salad (green) onion crops grown at Wellesbourne. The fungus invaded the tips of cotyledonary and young true leaves and then grew downwards and inwards through the leaf axils to colonise the internal tissues and produce a collar rot which caused plants to collapse and die. More direct infection of the junction between an older and younger leaf produced a similar effect. Symptoms were rarely noticeable (except occasionally in the later stages of the disease) and affected plants disappeared unobtrusively. The incidence of collar rot increased as the rate of leaf production fell with the drop in temperatures in winter months but decreased as leaf growth resumed with increases in temperature in the spring. The fungus grew and sporulated well at low temperatures (5°C) and more inoculated seedlings developed collar rot when maintained at simulated winter temperatures (7°C) than when kept at simulated spring temperatures (15°C).

B. squamosa occurred spasmodically producing white leaf lesions but caused no loss of plants. B. allii although present at a low incidence did not increase in the crops but in common with B. cinerea caused some damage to the bases of plants at harvest.
The effect of seed, furrow and stem base spray treatment with iprodione on white rot disease (Sclerotium cepivorum) in spring‐sown salad onions
Authors: ENTWISTLE A. R. , MUNASINGHE H. L.
Published: February 2008

Seed treatment with iprodione at 125 and 150 g a.i./kg was superior to calomel seed treatment at 500 g a.i./kg in reducing disease losses and increasing yields in field experiments with salad onions infected with white rot; iprodione at 50, 62·5 and 100 g a.i./kg and thiophanate‐methyl at 150 g a.i./kg were as effective as calomel.

Furrow treatment with iprodione or thiophanate‐methyl at 0·05 and 0·15 g a.i./m row or calomel at 0·5 g a.i./m row gave similar control as equivalent rates of seed treatment. Neither seed nor furrow treatments gave adequate control with prolonged exposure of the crop to the disease.

A single stem base spray of iprodione at 0·0625 g a.i./m row applied 5 wk after drilling, reduced losses from 46% with a standard calomel seed treatment to 20%; increasing the stem base spray concentration to 0·25 g a.i./m row did not improve the control but resulted in a doubling of yields. The most effective control was obtained with iprodione applied as a seed treatment at 62·5 g a.i./kg combined with a single stem base spray at 0·0625 g a.i./m row 5 wk after drilling and this reduced losses to 6% compared with losses of 46% with calomel treated seed and 88% with untreated seed; increasing the stem base spray concentration did not improve control but resulted in higher yields.
The relationship between glycoalkaloids and resistance to the white potato cyst nematode, Globodera pallida in potato clones derived from Solanum vernei
Authors: FORREST J. M. S. , COXON D. T.
Published: February 2008

No relationship was found between the degree of resistance to Globodera pallida and total glycoalkaloid content of the roots or tubers of a number of potato clones derived from Solanum vernei × S. tuberosum. Nematode infestation of the roots did not lead to increases in the glycoalkaloid content of susceptible or resistant potatoes.
Cabbage stem weevil (Ceutorhynchus quadridens) on spring oilseed rape in Southern England and its control
Authors: GRAHAM C. W. , GOULD And H. J.
Published: February 2008

Surveys in 1974–75 in which 20 plants were examined in each of 105 fields showed that cabbage stem weevil was widespread on spring oilseed rape in the south of England, the larvae sometimes infesting a large percentage of plants and reducing vigour and yield. In replicated field trials during 1974–77, infestations were reduced by seed treatments of gamma‐HCH or sprays of gamma‐HCH, azinphos‐methyl, azinphos‐methyl + demeton‐S‐methyl sulphone, chlorpyrifos or triazophos. In some experiments treatments significantly improved plant growth or yield, or both. Granules of carbofuran or phorate also reduced larval infestations and damage, but both thiofanox granules and dimethoate sprays were ineffective. Sprays of gamma‐HCH or azinphos‐methyl + demeton‐S‐methyl sulphone which were effective against stem weevil could also in some years give improved control of blossom beetles (Meligethes spp.)
Epidemiology of eyespot (Pseudocercosporella herpotrichoides) on winter wheat, with particular reference to the period of infection
Authors: HOLLINS T. W. , SCOTT P. R.
Published: February 2008

The period of infection by Pseudocercosporella herpotrichoides was investigated by transplanting winter wheat from uninfested to infested sites at Cambridge. Maximum infection was found on plants moved between November and March; most conidia were trapped during winter but infection was not closely related to the numbers of conidia. Plants exposed at intervals on infested land and incubated in a standard environment became infected throughout the period from October to July; infection was not closely related to the numbers of conidia trapped or plant age, but was positively correlated with the number of wet days/wk. Thus, while enough P. herpotrichoides conidia were dispersed throughout the life of winter wheat crops to cause substantial infection, environmental factors limited the development of new infections from April onwards. Practical implications of these results for the choice of sowing date, the development of resistant varieties, and fungicide use, are discussed.
Predisposition to Septoria nodorum as a result of take‐all (Gaeumannomyces graminis) infection of wheat
Authors: JENKINS P. D. , JONES D. GARETH
Published: February 2008

In a series of experiments excised leaves from take‐all infected wheat plants and from control plants were inoculated with Septoria nodorum. Larger lesions, more lesions/leaf and more pycnidia/unit area of lesion were produced from take‐all plants. Significant effects of predisposition were demonstrated when only 3% of the area of the total root system was infected by take‐all.

Microscopical investigations revealed that germ‐tubes of S. nodorum grew more rapidly on leaves from take‐all plants, but the time of penetration was not affected. It is proposed that the observed effects of predisposition arose because more germ‐tubes produced successful infections and host tissue was more rapidly colonised.

The importance of these results for the epidemiology of glume blotch is discussed.
Vector relationships and other characteristics of barley yellow striate mosaic virus (BYSMV)
Authors: CONTI MAURIZIO
Published: February 2008

Barley yellow striate mosaic virus (BYSMV) was inoculated by its planthopper vector Laodelphax striatellus (Homoptera, Delphacidae) to 44 species of Gramineae, 26 of which in eight tribes were infected. The virus was not transmitted through wheat seed nor did it infect five dicotyledonous hosts of other rhabdoviruses. The most susceptible species were in the tribes Festuceae and Hordeae. Barley, Bromus spp., oats, Phalaris canariensis, Setaria italica, Sorghum spp., and sweet corn cv. Golden were diagnostic hosts. Electron microscopy of crude sap was also a sensitive diagnostic method. Properties of BYSMV were determined by injecting L. striatellus with crude sap from infected barley. Sap was infectious after 10 min at 50–55 °C but not after 10 min at 60 °C, when diluted with buffer to 10‐‐2 but not to 10‐‐3, when stored for 2 but not 4 days at 5 °C or when kept for 1 but not 2 days at 22 °C.

The planthopper Javesella pellucida was an experimental vector of BYSMV but the virus was not transmitted by the leafhoppers Macrosteles sexnotatus or Psammotettix striatus (Homoptera, Cicadellidae). The latent period of BYSMV in L. striatellus was most commonly 15 or 16 days (minimum, 9 days; maximum, 29 days). The minimum acquisition access period for transmission was between 1 h and 5 h, and the minimum inoculation feeding time was 15 min. After 24 h and 8 day acquisition feeds, 30.4% and 42.8% respectively of L. striatellus transmitted BYSMV. When transferred daily, infective hoppers transmitted virus intermittently. The maximum retention of infectivity by L. striatellus was 36 days.

Two of five infective females transmitted BYSMV transovarially. Larvae became infective in the second wk after hatching and transmitted for up to 3 wk.
Properties of a resistance‐breaking strain of potato virus X
Authors: MOREIRA A. , JONES R. A. C. , FRIBOURG C. E.
Published: February 2008

During indexing of a potato germplasm collection from Bolivia, a strain of potato virus X (PVX), XHB, which failed to cause local lesions in inoculated leaves of Gomphrena globosa was found in 7% of the clones. XHB was transmitted by inoculation of sap to 56 species from 11 families out of 64 species from 12 families tested. It was best propagated in Nicotiana glutinosa or N. debneyi; Montia perfolia and Petunia hybrida were useful as local lesion hosts. Inoculated leaves of G. globosa plants kept at 10°, 14°, 18°, 22°, or 26 °C after inoculation were always infected symptomlessly. XHB caused a mild mosaic, systemic chlorotic blotching or symptomless infection in 16 wild potato species and eight Andean potato cultivars, systemic necrotic symptoms in clone A6 and cultivar Mi Peru, and bright yellow leaf markings in cultivar Renacimiento. It caused necrotic local lesions in inoculated leaves of British potato cultivars with the PVX hypersensitivity gene Nb but then invaded the plants systemically without causing further necrosis; with gene Nx systemic invasion occurred but no necrotic symptoms developed. These reactions resemble those of PVX strain group four. XHB differed from other known strains of PVX in readily infecting PVX‐immune clones 44/1016/10, G. 4298.69 and USDA 41956, cultivars Saphir and Saco, and Solanum acaule PI 230554.

XHB had slightly flexuous filamentous particles with a normal length of 516 nm. It was transmitted readily by plant contact and it partially protected G. globosa leaves from infection with XCP, a group two strain of PVX. Sap from infected N. glutinosa was infective after dilution to 10‐‐6 but not 10‐‐7 after 10 min at 75° but not 80 °C and after 1 yr at 20 °C. XHB was readily purified from infected N. debneyi leaves by precipitation with polyethylene glycol followed by differential centrifugation. Microprecipitin tests showed that XHB and XCP are closely related serologically.
The effects of nematode resistant and susceptible spring oat cultivars and aldicarb on the cereal cyst nematode Heterodera avenae and yields in contrasting soil types
Authors: WILLIAMS T. D. , BEANE J.
Published: February 2008

The effects of the cereal cyst‐nematode, Heterodera auenae Woll. on resistant and susceptible oat cultivars, with and without aldicarb treatment, were compared on a clay‐with‐flints soil at Rothamsted and a loamy sand at Woburn. At both sites, when H. auenae was extremely scarce, yields were not further enhanced by aldicarb. At Rothamsted aldicarb increased yields by 48–72% when H. auenae averaged 10 eggs/g soil. At Woburn, aldicarb increased yields of both susceptible and resistant varieties by 80–90% with 20 eggs/g. The resistant varieties conferred yield benefits in the following oat crop equal to the residual effects of aldicarb applied before the previous crop, demonstrating that H. auenae was wholly responsible for the yield losses. Nematode resistant oats suffered as much or more damage from root invasion by H. auenae juveniles as the susceptible varieties but the resulting decrease in nematode numbers led to considerable yield improvements in the following year. At Woburn in 1977, when formalin was an added treatment, fewer females were infected by parasitic fungi and post‐crop egg numbers were greater.
Nematodes associated with peas and beans in Scotland
Authors: BOAG B.
Published: February 2008

Six hundred and sixty‐four soil samples from farms growing peas and beans in eastern Scotland were examined for plant parasitic and predatory nematodes. Neither pea cyst‐nematode, Heterodera goettingiana nor pea early‐browning virus disease were found. Stem nematode, Ditylenchus dipsaci was recorded in broad beans once. The most frequently occurring plant parasitic nematodes were Tylenchorhynchus dubius, Longidorus elongatus, Rotylenchus goodeyi and Helicotylenchus vulgaris but numbers were generally too small to cause damage. It is concluded that although potentially damaging plant parasitic nematodes occur in Scotland, nematode‐related diseases occur infrequently and are of little significance to the crop.
Insect feeding on different sorghum cultivars in relation to cyanide and phenolic acid content
Authors: WOODHEAD S. , PADGHAM D. E. , BERNAYS E. A.
Published: February 2008

Insect feeding on sorghum was studied in the field and in the laboratory. Quantitative differences in cyanogenesis and phenolic acid content were also measured on the same or simillar plants. High concentrations of cyanide were correlated with a reduction in feeding by grasshoppers and by first‐instar larvae of Chilo partellus; high concentrations of phenolic acids were correlated with reduced feeding by various grasshoppers and by the planthopper Peregrinus maidis. Mythimna separata larvae, and adults and nymphs of Rhopalosiphum maidis, were apparently unaffected by these chemicals. Some sorghum cvs which were relatively unpalatable to grasshoppers and to P. maidis had low levels of the test chemicals, so that here some other factor or factors must be involved.
An evaluation of the sampling variation when estimating the population of Verticillium dahliae in field soil
Authors: EVANS G. , GLEESON A. C.
Published: February 2008

This paper describes a study designed to find a reliable sampling procedure for estimating the population of Verticillium duhliue in field plots that would not be too demanding in terms of the time required to assay soil samples. In the soil under study, the amount of time needed to obtain reliable estimates of the inoculum density was reduced by taking the larger plot sizes in the range considered, generally taking more plots with fewer samples per plot, and mixing the samples within a plot before redividing for assaying.
Tolerance trials with young cocoa trees infected with cocoa swollen‐shoot virus
Authors: LEGG J. T. , KENTEN R. H. , LOCKWOOD G.
Published: February 2008

In three short‐term field trials, 24 cocoa progenies were assessed for sensitivity to infection with a severe Ghanaian strain of cocoa swollen‐shoot virus. Some of the progenies were derived from tolerant parents, others had themselves shown mild symptoms as young seedlings. Stem diameters, diameter increments, canopy scores and latent periods (time between inoculation and expression of symptoms) of plants infected when 12 to 22 months old were compared with similar measurements of healthy plants.

During the period between 6 and 18 months after inoculation, infection reduced the stem diameter increment of the least sensitive progeny in each trial by 52, 25 and 7%, the last value increasing to 38% during the period between 24 and 30 months after inoculation. Within trials, the effects of virus infection on stem diameter increments and canopy scores were well correlated but latent periods were not significantly correlated with any other variate.

In one trial, pod yield was more closely related to canopy condition at the time of cropping than to stem diameter increment 2 yr earlier. Weak correlations between pre‐ and post‐bearing increases in diameters in these trials indicated that tolerance was not directly related to vigour. None of the progenies is considered suitable for direct use as tolerant varieties in Ghana.
Factors affecting the detection of potato leafroll virus in potato foliage by enzyme‐linked immunosorbent assay
Authors: TAMADA T. , HARRISON B. D.
Published: February 2008

Using antiserum globulins that reacted only weakly with plant materials, potato leafroll virus (PLRV) at 10 ng/ml was detected consistently by enzyme‐linked immunosorbent assay (ELISA). The reaction with PLRV particles was slightly impaired in potato leaf extracts that were diluted less than 10‐1 but not at greater dilutions. Antiserum globulins that reacted more strongly with plant materials could be used satisfactorily for coating microtitre plates but were unsuitable for conjugating with enzyme.

The detection end‐point of PLRV, in leaf sap of potato cv. Cara plants grown from infected tubers in the glasshouse, was about 10‐2 and the virus was reliably detected in extracts of composite samples of one infected and 15 virus‐free leaves. PLRV concentration was much less in extracts of roots or stolons than in leaf extracts. The virus was detected in infected leaves of all 27 cultivars tested.

PLRV was readily detectable 2 wk before symptoms of secondary infection developed in field‐grown plants of cv. Cara and Maris Piper and remained so for at least 5 wk. Its concentration was slightly greater in old than in young leaves and was similar to that in glasshouse‐grown plants. In field‐grown plants of cv. Maris Piper with primary infection, PLRV was detected in tip leaves 21–42 days after lower leaves were inoculated by aphids; in some shoots it later reached a concentration, in tip leaves, similar to that in leaves with secondary infection. Symptoms of primary infection developed in the young leaves of some infected shoots but were inconspicuous and were not observed until at least a week after PLRV was detected by ELISA.
The effect of different periods of dehydrationhehydration upon the ability of second stage larvae of Anguina tritici to survive desiccation at 0% relative humidity
Authors: WOMERSLEY CHRISTOPHER
Published: February 2008

The effect of various desiccation regimes on the ability of second stage larvae of Anguina tritici (Steinbuch, 1799) to survive drying at 0% relative humidity has been studied. It was found that both repeated dehydrationhehydration cycles and the length of the desiccation period itself decreased viability of the larvae. The results are discussed in relation to the mechanisms which may facilitate anhydrobiosis.
A method of measuring differences between bean varieties in tolerance to sub‐optimal temperatures
Authors: HARDWICK R. C. , ‘ANDREWS D. J.
Published: February 2008

Bean (Phaseolus vulgaris and P. coccineus) plants were grown in controlled environments at (day/night) temperatures of either 25°/20 °C or 20°/15 °C. The lower temperatures tended to reduce the weight of stem relative to the weight of leaf. An interpolation procedure was devised for estimating the magnitude of this effect, which varied between cultivars. It is suggested that the interpolation parameter can be used as an indication of varietal cold tolerance. Thus estimated values of the parameter (h), normalised so that 1 unit = 1 S.E.D, were large and positive in a cv. Seafarer previously characterised as cold intolerant (h = 4–19), large and negative in the relatively cold tolerant P. coccineus cv. Hammond's Dwarf Scarlet (h = ‐3.03), and near to zero (h = 1–11) in the standard commercial variety of P. vulgaris cv. Prelude.

The experiment with cvs Seafarer and Prelude was repeated three times and similar values of h were obtained on each occasion. There was only a small variation of h with harvest date; over a period in which plant weight increased at least 3.5 and up to 9 times. In the third experiment a modification of the harvesting procedure was adopted so that plants could be tested for cold tolerance and then grown on for seed production. This semi‐destructive test was applied to, and the results are reported for, nine cultivars which are of interest as potential dry‐bean cultivars for the United Kingdom.
Fireblight in Kent, England in relation to weather (1955–1976)
Authors: BILLING EVE
Published: February 2008

A system for the assessment of potential for fireblight Erwinia amylovora activity (PFA), based on standard temperature and rainfall records, has previously been outlined. Here some recent modifications are described and the system is discussed more fully and tested for its ability to explain outbreaks of fireblight in different hosts in Kent, south‐east England for the years 1955–76.

In most cases, there was a satisfactory match between PFA patterns and recorded field outbreaks and incidents and it is concluded that warnings based on the system could have lessened risk of disease in some hosts in past years. In the short term (depending on the accuracy of weather forecasts) the system can be used predictively. Its use in this way is discussed together with underlying principles of some of the criteria used and possible ways in which the precision of the system might be improved.
Fireblight Erwinia amylovora and weather: a comparison of warning systems
Authors: BILLING EVE
Published: February 2008

Warning systems for fireblight Erwinia amylovora developed in New York, Illinois and California, USA, and in south‐east England are compared. General principles which might be applicable in the different climates were sought. The consequences of applying threshold temperature values chosen for one area in a different climatic area were examined using Sacramento, California; Rochester, New York; Vlissingen, The Netherlands; Kent, England as examples. A graded system for assessing fireblight risks, derived from all the systems, is suggested. It takes into account both risks of infection and risks of high insect activity and it is best used in conjunction with Billing's incubation period assessment system.
The resistance of the perennial ryegrass cultivar Endura to ryegrass mosaic virus
Authors: GIBSON R. W. , WOODS R. D. , PICKERING S. PETA
Published: February 2008

The perennial ryegrass cv. Endura is particularly resistant to infection with two ryegrass mosaic virus isolates, RMV‐Roth and RMV‐Sax. A few plants appeared immune to RMV‐Roth but were infected by RMV‐Sax. Two plants that developed only mild symptoms after infection with RMV‐Roth contained few virus particles, but passage through these resistant plants caused no detectable change in the virulence of RMV‐Roth towards S 22 Italian ryegrass. In offsets derived from one of these resistant plants, RMV‐Sax caused severe symptoms and attained a high virus concentration but it was unable to infect if the plant was already infected with RMV‐Roth.
Hibiscus latent ringspot virus, a newly recognised virus from Hibiscus rosa‐sinensis (Malvaceae) in western Nigeria
Authors: BRUNT A. A. , BARTON R. J. , PHILLIPS SUE , LANA A. O.
Published: February 2008

Hibiscus latent ringspot virus (HLRV) was prevalent in Hibiscus rosa‐sinensis in Ibadan, Nigeria. It was readily transmitted mechanically to 22 of 73 species from seven of 20 families, but was best propagated in Nicotiana clevelandii or Hibiscus cannabinus and assayed in Chenopodium murale. HLRV was readily purified from systemically infected hosts by differential centrifugation of leaf extracts clarified with 8.0% n‐butanol, followed by molecular permeation chromatography on controlled‐pore glass beads (700 Å, 120–200 mesh). The virus has isometric particles c. 28 nm in diameter which sedimented as three components (T, M and B), with sedimentation coefficients (s°20, w) of 51; 114 and 132 S and buoyant densities in caesium chloride of 1.32, 1.49 and 1.52 g/cm3, respectively. All three components contained a single polypeptide of rnol. wt 53.6 × 103. T component particles contained only protein but M and B components also contained single‐stranded RNA of rnol. wt 2.2 × 106 and 2.5 × 106, respectively. The properties of HLRV suggest affinities with nepoviruses but no serological relationship was detected between HLRV and 15 recognised or possible members of the nepovirus group.
Water stress in field‐grown perennial ryegrass.
Authors: JONES M. B. , LEAFE E. L. , STILES W.
Published: February 2008

Swards of perennial ryegrass (Lolium perenne) were grown in the field and in boxes with low water‐holding capacity (simulated swards). Water stress was allowed to build up in half the swards by using rain covers and withholding irrigation. Stress developed slowly in the field swards (over a period of 4 wk) but rapidly in the simulated swards (over a period of 5 days). Comparisons of leaf water potential, osmotic potential and stomatal resistance were made between these stressed swards and field and simulated swards whose soil water content were kept within 20 mm of field capacity. Measurements were made on the youngest fully expanded leaves. In the field swards the leaves on which measurements were made had grown during the development of stress, whereas in the simulated swards they were fully developed before the imposition of stress.

Daily minimum values of leaf water potential fell to —12 bars (‐1.2 M Fa) in both field and simulated irrigated swards, to —16 bars in the stressed field swards and to —20 bars in the stressed simulated swards. Osmotic potential declined in the stressed leaves; in the field swards this ensured that turgor was maintained under stress but in the rapidly stressed simulated swards turgor fell to zero for a significant part of the day.

In all swards, leaf resistance measurements indicated that stomata began to close at leaf water potentials below —13 bars. There was no clear difference between slowly and rapidly stressed swards in the sensitivity of stomata to the decrease in leaf water potential.

Leaves which grew under slowly developing stress were morphologically different from leaves from non‐stressed swards. The leaves were smaller, had a higher stomatal density, smaller epidermal cells and showed deeper ridging on their adaxial surface.
Effect of simulated rain on retention, distribution, uptake, movement and activity of difenzoquat applied to Avena fatua
Authors: CASELEY J. C. , COUPLAND D.
Published: February 2008

In glasshouse studies the degree of control of A vena fatua increased as the period between application of difenzoquat and the onset of simulated rain was prolonged. 0.5 mm of ‘rain’ removed 29% of the herbicide deposit without adversely affecting performance at the recommended dose of 1 kg/ha. A further 30% was removed by 2.0 mm of ‘rain’, resulting in a marked reduction in acrivity. With lower amounts of ‘rain’ (0.16 mm), some of the spray deposit was redistributed from the leaf lamina to the leaf base/ligule area. The rate of penetration of 14C‐difenzoquat was much greater when applied to the inner surface of the leaf sheath than when the leaf blade and outer sheath areas were treated. Translocation from the ‘inner sheath’ to other parts of the plant was up to 100 times greater than from other areas. It is suggested that the performance of difenzoquat is not reduced by low amounts of rain because: (1) the spray deposit is removed principally from the leaf blade, whilst in the more responsive ligule/leaf sheath area the herbicide remains in solution, (2) the recommended dose of 1 kg/ha allows for some loss of active ingredient without reduction in performance. The practical implications of the work are discussed and further topics for research are outlined.
Evidence for a calcium‐binding site on the eggshell of Globodera rostochiensis with a role in hatching
Authors: ATKINSON H. J. , TAYLOR JILL D.
Published: February 2008

Two inhibitors of hatching in Globodera rostochiensis, ruthenium red and lanthanum, have been shown to bind to the eggshell using the techniques of microdensitometry for ruthenium red and X‐ray microanalysis for lanthanum. Neither inhibitor penetrated or adhered to unhatched or hatched viable juveniles. Scatchard analysis for binding of lanthanum and ruthenium red to eggshells gave dissociation constants (K) of KLa 32.5 ± 14.0 μM and KRured 33.5 ± 5.0 μM respectively. Both values are within the 95% fiducial limits of those shown to cause 50% inhibition of hatch in previous work. Pretreatment with sodium hypochlorite separated an outer part of the eggshell from an inner region which exclusively bound ruthenium red. It is the inner lipoprotein layer that is believed to include the membranes controlling the permeability of the tylenchid eggshell. The rate of binding of ruthenium red was similar for intact and isolated eggshells with 50% binding occurring after 6.11 ± 0.91 min and 4.95 ± 2.38 min but the latter gave a significantly higher maximum binding suggesting that rupture of the eggshells made available additional binding sites on their inner surface. The binding of ruthenium red to the eggshells was pH dependant over most of the range pH 2.8–8.5 with 50% binding, given with its standard deviation, occurring at pH 5.75 ± 0.85.

Competitive binding of lanthanum influenced the binding of ruthenium red to the eggshells from which Scatchard analysis gave Kla of 176 ± 79 μM. Similarly, calcium influenced the binding but this caused a biphasic plot with high and low affinity binding sites of K“ca of 0.423 ± 1.16 μm and K‘ca of 1078 ± 462 μM. The existence of a high affinity site for calcium that also binds ruthenium red, suggests that the eggshell membrane includes a calcium binding glycoprotein as found in some other receptor mechanisms.
Screening for resistance to potato cyst nematode using closed containers
Authors: PHILLIPS M. S. , FORREST J. M. S. , WILSON LINDA A.
Published: February 2008

A screening method is described whereby potato plants are grown in soil in closed plastic containers in the dark, producing root systems upon which potato cyst nematodes can reproduce. Tubers are planted in John Innes No. 2 compost at 30% moisture and inoculated with an egg suspension. The canisters are held at 20°C for 7 wk after which, visible developing females are counted. This method of screening is more rapid, economical and produces data as reproducible as those from conventional pot tests. The value of the test for detecting resistance early in a potato breeding programme is discussed.
The herbicidal activity of bromoxyside (3,5–dibromo‐4–hydroxyphenyl methyl sulphide), its esters and related compounds
Authors: WILCOX E. J. , WAIN R. L. , WAIN ROSEMARY J.
Published: February 2008

Studies on the herbicidal activity of 3,5–dibromo‐4–hydroxybenzonitrile (bromoxynil) and 3,5–dibromo‐4‐hydroxyphenyl methyl sulphone (bromoxysone) have been extended to include 3,5–dibromo‐4‐hydroxyphenyl methyl sulphide (bromoxyside), its esters and other related compounds.

Bromoxyside produced chlorotic effects in barley and wild oat seedlings, the herbicidal activity being similar to that of bromoxysone but quite different to that of bromoxynil. A range of aliphatic and aromatic esters of bromoxyside were prepared and examined as herbicides using barley and wild oat seedlings as test plants. The acetate and propionate were the most active against both species. No compound tested was more herbicidal to wild oat than to barley. Introduction of a further bromo or methyl ring‐substituent into bromoxyside removed herbicidal activity.

Spraying plants of differing age showed that the herbicidal effect was greater when the plants were small.
Methods for detection of resistance to woolly aphid (Eriosoma lanigerum) in apple
Authors: LYTH M. , WATKINS R.
Published: February 2008

Two ways of examining resistance in apple to Eriosoma lanigerum were assessed. The first method involved a single mass inoculation of young seedlings with first‐instar nymphs. This failed to identify many susceptible seedlings and also produced inconsistent results which strongly suggested an uneven distribution of aphids at inoculation. Repeated inoculations were far more efficient in identifying known susceptibles than single inoculations, but they did not discriminate between susceptible and some resistant seedlings. However, the technique would be very useful where the major objective was the identification of higher levels of resistance. To overcome the destructive nature of mass inoculation and the inefficiency in classifying individual seedlings, a second method was devised using clonal material which allowed replication of genotypes. Calibrated inoculations made direct comparisons with controls possible and aphid numbers could be estimated with acceptable accuracy with a volumetric technique. However, comparisons based on approximate colony lengths were adequate, and faster, for routine screening.
Effects of pesticide treatments on the yield of swedes
Authors: FRENCH N. , COLLINGWOOD C. A. , SAYNOR M. , BROCK A. MURIEL
Published: February 2008

The effects of insecticide and fungicide applications to swedes (Brassica napus var. napobrassica) were examined at 15 sites in England from 1974 to 1978. Several different pesticide combinations were applied including carbofuran granules at drilling (63 mg a. i./m of row), demeton‐S‐methyl sprays (0·24 kg a. i./ha) and fluotrimazole sprays (0·18 kg a. i./ha). The best treatments, which varied in different years, gave significantly higher yields than no treatment in 12 out of a total of 15 trials, with varying levels of damage attributable to cabbage root fly (Delia brassicae), aphids (Myzus persicae) and powdery mildew (Erysiphe cruciferarum) in each of the 4 years. In 10 of 12 trials, plots receiving a complete insecticide and fungicide programme yielded on average 40% (range 21–61%) more than untreated plots, mainly through control of root fly and aphids in 1975 and of aphids and mildew in 1976. Aphid damage to swedes was exceptionally severe in both years. Granular formulations of aldicarb, carbofuran, chlorfenvinphos or fonofos used alone to prevent cabbage root fly damage gave significant yield benefits in only 8 of the 15 trials, with least effect in 1977 and 1978 when growing conditions for swedes were good and damage relatively light.
Control by imazalil of fruit storage rots caused by Alternaria alternata
Authors: PRUSKY D. , BEN‐ARIE RUTH
Published: February 2008

The fungicide imazalil has potential value for controlling post‐harvest diseases caused by Alternaria alternata in pears, apples and persimmons. Imazalil was active in vitro on germination and hyphal growth (ED50) at 1.4 and 0.5 μg/ml, respectively. Protectant action of the fungicide lasted only 1 day after treatment. At 1000 μg/ml the fungicide inhibited development of Alternaria rot in inoculated apples at 0 °C and in naturally infected pears and persimmons at–1 °C.