bluuebunny/crossref_metadata_2025 huggingface dataset:
The uptake of calcium prior to the hatching of the second‐stage juvenile of Globodera rostochiensis
Authors: ATKINSON H. J. , TAYLOR JILL D. , BALLANTYNE A. J.
Published: February 2008

Energy dispersive X‐ray microanalysis of 83 eggs of G. rostochiensis for calcium content showed that juveniles from eggs exposed to active hatching factor in potato root diffusate for 48 h contained significantly more calcium than those exposed for this time to the same diffusate inactivated by autoclaving, or to water. This occurred despite a slightly greater calcium concentration in the autoclaved than in the untreated diffusate; both contained more calcium than the water. Eggshells removed from stimulated eggs also contained more calcium than those from unstimulated eggs. The calcium content of juveniles and eggshells exposed to inactivated diffusate was similar to their corresponding values for eggs soaked in water.

A similar analysis was made of freeze‐dried samples of fluid taken from the matrix surrounding the eggs in cysts exposed to water or to active root diffusate. This showed a significantly greater calcium concentration in the stimulated cysts after 48 h exposure. The concentration subsequently decreased over the succeeding 72 h however, suggesting that the rate of calcium uptake by the stimulated eggs exceeded that of diffusion into the cyst.

This uptake of calcium by eggs of G. rostochiensis exposed to a hatching stimulus seems pertinent to recent evidence that the active factor in potato root diffusate may initiate hatching through a calcium‐mediated process.
Dispersive movement of carrot fly (Psila rosae) larvae and factors affecting it
Authors: JONES O. T. , COAKER T. H.
Published: February 2008

The movements ofPsila rosaelarvae were studied under field and laboratory conditions. In the field, larvae moved up to 60 cm along and between carrot rows, although more larvae moved during the first generation than the second. Sudden increases in soil moisture, and not its prevailing level, stimulated the larvae to move from carrots into the soil surrounding the roots. Up to 50% of the larvae that left their mines in carrots following a sudden increase in soil moisture did not return to the same mine. Evacuation of mines by larvae appears to be a reflex response to the flooding of their mine and might be connected with the production of toxic conditions within the mine following flooding.
The effects of rainfall and soil type on the population dynamics of cereal cyst nematode (Heterodera avenae) on spring barley (Hordeum vulgare) and spring oats (Avena sativa)
Authors: GRAHAM C. W.
Published: February 2008

In experiments applying water regimes ranging from one eighth to twice the recorded average rainfall to six soils (two light sands and four silty clay loams) consistent positive correlations were found between rainfall and (a) the growth of foliage and roots of spring barley and spring oats, (b) the number of larvae which invaded the root system, (c) the number of immature females in July, and (d) the incidence of the fungus Verticillium chlamydosporium, an egg parasite of H. avenae. Final cyst numbers were sometimes lower than the number of immature females, probably because the latter were destroyed by the ‘Entomophthora‐like’ fungus (Kerry & Crump 1977). Final populations of cysts and eggs were not always proportional to the number of larvae in root systems (even when the proportion of males was constant) but appeared more likely to be so in light sandy soils.
Effects of soil water level on the development of adult plant resistance to powdery mildew in barley
Authors: AYRES P. G. , WOOLACOTT B.
Published: February 2008

Barley grown in dry soil developed greater adult plant resistance (APR) to powdery mildew (Erysiphe graminis DC. f. sp. hordei Mérat) than barley grown in wet soil. Conidial germination and appressorium formation were less, and fungal development between formation of appressoria and elongating secondary hyphae on upper leaves was inhibited, when adult plants were grown in dry soil. Mildew colonies expanded more slowly on leaves of adult plants than on leaves of seedlings, especially if adult plants had grown in dry soil. APR was reduced if plants, previously grown in dry soil, were well watered more than 32 h before inoculation. Conidia originating from plants grown in dry soil had a lower solute potential and greater ability to infect plants grown in dry but not wet soil than conidia originating from plants grown in wet soil.

APR could not be attributed simply to increased cell wall or cuticle thickness, nor to lowered leaf solute potentials, as has sometimes been suggested for powdery mildew diseases. Increasing plant age and water stress induced increases in cell wall and cuticle thickness, but these changes did not always coincide with changes in disease resistance. Increasing plant age and water stress also lowered leaf solute potentials but fungal solute potentials were lower than leaf solute potentials and, more importantly, were lower than leaf water potentials. Thus, fungal growth was not limited by the availability of water from the host during penetration and hyphal establishment. It is suggested that resistance levels may be determined not by the thickness of epidermal structures, nor by lowering of solute potential per se, but by specific substances harmful to the fungus which accumulate in either cell wall, cuticle or sap, and whose concentration is dependent on the age and water stress of leaves.
A simple technique for vegetative propagation of sugar beet
Authors: SCHWABE W. W.
Published: February 2008

Experiments with annual and biennial beet cultivars showed that considerable stem extension accompanied by axillary bud development was induced by gibberellic acid treatment at a rate of 0·4 mg/wk. These plants did not flower. Such axillary buds were excised and rooted readily, making possible clonal propagation. On the termination of hormone application plants re‐rosetted and thick swollen stems with multiple cambium development formed below the new crown on both terminal and axillary growing points. This suggests that secondary cambium formation and swelling is controlled by the shoot and may possibly be due to some factor antagonistic to gibberellin, emanating from the crown.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: Pathogenic variation in Verticillium albo‐atrum isolates from hop (Humulus lupulus)
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

Non‐lethal (M strain) ‘fluctuating’ wilt was first identified in hops in 1924. Lethal (V strain) ‘progressive’ wilt appeared in the 1930s and spread rapidly through Kent, destroying all commercial varieties. By 1965 the disease was largely controlled by use of new resistant cultivars, accompanied by restricted nitrogen fertilisers, non‐cultivation (with weed control by overall herbicides), and high standards of field hygiene. Between 1968 and 1971 severe wilt developed in previously highly resistant clones, used as ‘controls’ in routine field resistance tests. Verticillium isolates from the two farms supplying the natural inoculum for these tests during 1968–71 were more virulent than previously encountered V strains, some causing severe wilt in all resistant cultivars. Subsequent surveys supported by pathogenicity tests against resistant cultivars indicated the existence of two ‘super virulent’ strains on eight farms in Kent.

The appearance of mild (M) strains in the 1920s, virulent (VI) strains in the 1930s, and ‘super‐virulent’ (V2 and V3) strains in the 1960s follow 400 years of apparent freedom from wilt. This suggests that the initial breakage of resistance barriers was critical and subsequent variations in an apparently complex, polygenically controlled resistance system are rapidly being matched by the pathogen.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: Variation in Pseudomonas morsprunorum and the selection of cherry cultivars resistant to bacterial canker
Authors: CROSSE J. E.
Published: February 2008

During 1971 and 1972 leaf spot infection caused by Pseudomonas morsprunorum was far more severe on the cv. Roundel than on the normally more susceptible cv. Napoleon, and Roundel supported higher leaf surface populations of the pathogen. This unprecedented reversal in the established field performance of the two cultivars was associated with the presence on the trees of a colony variant (race 2) of P. morsprunorum that differed from the forms of the organism previously described (race 1) in physiological, pathological and phage sensitivity characteristics. In inoculation experiments race 2 isolates showed some specificity for Roundel and race 1 isolates for Napoleon. This difference was reflected in the distribution of the races on trees of the two cultivars growing in experimental plots and commercial orchards. Similar interactions between race and host genotype were observed amongst progeny from breeding programmes and material originally selected for resistance to bacterial canker after inoculation with race 1 proved susceptible to race 2.

Three distinct groups of isolates with the colony characteristics of race 2 have been identified and one of these has affinities with Pseudomonas syringae. Group 1 isolates, corresponding to P. morsprunorum and comprising non‐fluorescent forms, were the most virulent in pathogenicity tests and accounted for the majority of race 2 infections in the field.
II. Cereal disease: the interplay between resistance and pathogenicity: Studies of host specificity of indigenous isolates of Pseudocercosporella herpotrichoides
Authors: CUNNINGHAM P. C.
Published: February 2008

Variation in host response of isolates of the eyespot pathogen from different sources was examined over a number of years. Pathogen types were found in intensively‐cropped couch‐infested cereal sites that were almost as virulent on Agropyron repens (couch) as on wheat or barley. The commonly occurring wheat (W) type isolates from couch‐free cereal crops were virulent on wheat and barley but avirulent on couch. Couch (C) types were isolated not only from couch but also from wheat, barley and oat crops with couch infestation. In pathogenicity tests on rye, C. types did not differ in virulence from the more commonly occurring W types. Aegilops ventricosa was equally resistant to both types.

W type isolates from wheat and barley were examined to assess differential pathogenicity on wheat and barley. Sequential cropping with single cereal crops was used to separate out possible specific types. Isolates from fourth wheat and fourth barley crops were more pathogenic on the original than on the alternative host. When comparisons were made between isolates from third and fifth consecutive wheat and barley crops only those from barley showed a preference for the original host. An experiment comparing isolates from third and seventh consecutive wheat and barley crops showed a decline in virulence from the short to the longer sequences on the alternative but not on the original host.
III. Variation in plant viruses: The distribution of Prunus necrotic ringspot virus serotypes
Authors: BARBARA D. J. , CLARK M. F. , THRESH J. M.
Published: February 2008

Prunus necrotic ringspot and apple mosaic viruses have been described separately but they are distantly related serologically and intermediate strains occur in hop and rose. They may therefore be regarded as type strains of two serotypic groups of a single virus (Prunus necrotic ringspot virus which was the first to be described).

The host range of both serotypes is wide, mostly amongst woody plants and there have long been recurring difficulties of diagnosis based on symptoms produced in woody or herbaceous indicator plants. These problems have been overcome by the application of enzyme‐linked immunosorbent assay which provides a rapid and convenient means of detecting and serotyping the various strains encountered.
IV. Variation in fungicide tolerance: Variation in the response of plant pathogens to fungicides
Authors: SHEPHARD M. C.
Published: February 2008

The response of a fungal population to a fungicide is normally highly variable. Individual lethal doses usually form a normal distribution when plotted against log dose. The shape of this distribution varies with chemical and organism. Spore germination, haustorial formation, etc. vary independently. Variation in disease control is the product of the variation at each stage. Variation is both genotypic and phenotypic.

The successful use of a fungicide should, theoretically, result in a shift in the dose‐response of the survivors. The shift ought to be greatest where the original spread of the lethal dose was widest.

The effect of ethirimol on barley powdery mildew supports these theoretical conclusions. Good control of mildew following the use of ethirimol resulted in residual populations which were less sensitive to the fungicide than those in nearby untreated fields. Within treated fields the most sensitive members of the population were absent and the overall variation decreased. The progressive shift in sensitivity which might have been expected did not occur. Successive sampling of the same fields revealed rapid changes in sensitivity, but in either direction. The proportion of less sensitive individuals declined toward the end of the season and much of the original variability returned.
Survival of inoculum of the leaf blight fungus Phytophthora colocasiae infecting taro, Colocasia esculenta in the Solomon Islands
Authors: GOLLIFER D. E. , JACKSON G. V. H. , NEWHOOK F. J.
Published: February 2008

Phytophthora colocasiae was successfully isolated by baiting with detergent‐treated taro leaf discs 8 cm diameter placed on water slurries of soil, on suspensions of macerated infected leaf lesions or on the washings from petioles of harvested plants. Taro root tips, detached or left on corms, were not susceptible to zoospores of P. colocasiae nor were detached root tips of Lupinus angustifolius. Cubes of taro corm used as baits, and agar selective for Phycomycetes which was inoculated directly with soil, both became too heavily overrun by Phythium splendens to allow detection of P. colocasiae. Investigations indicated that inoculum on lesions of detached leaves and in soil remains viable for only a few days. Petiole bases which comprise the bulk of the ‘tops’ used for vegetative propagation, lost detectable natural inoculum rapidly (2 days) if stored dry, but less rapidly (14 days) if planted immediately in the field. Artifically augmenting surface inoculum with naturally produced sporangia considerably extended the periods of detectability, probably by increasing the chances that a few propagules would survive, especially during dry storage. Incubation of inoculated tops in high humidity led to active infection and sporulation on petioles, especially on cut ends, a situation that might be paralleled under suitable moisture conditions in the field. Of several aroid species tested by artificial inoculation only Alocasia macrorrhiza was susceptible. Natural infection of this plant has not been seen, making it an unlikely alternate host of P. colocasiae under field conditions. Thus perennation between taro crops is effected by shortlived surface propagules and possibly also by mycelium within lesions on petioles. Reduction of the former and prevention of the latter might be achieved by dry storage of tops for 2 to 3 wk.
The effects of temperature on leaf growth of sugar beet varieties
Authors: MILFORD G. F. J. , RILEY JANET
Published: February 2008

Leaf growth of nine varieties of sugar beet (Beta vulgaris L.) was studied at constant temperatures of 7, 11, 15 and 20·C, using generalised logistic curves fitted to the data to estimate the parameters of growth. The rate of leaf appearance increased linearly with temperature and was the same in all varieties. There were differences between varieties in the weighted mean rates of expansion of leaf area per plant (Ā), the temperature coefficient of Ā and the leaf area duration (D); these differences were caused more by differences in rates of expansion and final sizes of individual leaves than by differences in rates of leaf production. The growth of the first six leaves produced by each plant was examined in detail. The greater size of successive leaves of plants and genotypic differences between comparable leaves were more attributable to differences in the rate than differences in the duration of leaf expansion. Increasing temperatures increased leaf size because they accelerated the rate of expansion more than they shortened the duration of the expansion phase. It is inferred that all effects arose through differences in the initial sizes of leaves before they unrolled from the shoot apex. Dry matter production was proportional to D but was partitioned more to the storage root at the colder temperatures. This may have been related to the differential effects of temperature on cell division and expansion and the relative contribution of these two processes to the final sizes of the leaves and storage root.
The inter‐relationship between the age of carrot roots at harvest and infection by Mycocentrospora acerina in storage
Authors: VIES W. P. DA , LEWIS B. G.
Published: February 2008

Infection of carrot roots by Mycocenlrospora acerina in chill storage (3.5 °C) following inoculation with chlamydospores was studied in 1973–74 and 1974–75.

AREAS of intact periderm were only rarely infected, and the high level of periderm resistance predominated over other variables. However, wound infection tended to increase with depth of wound and with increasing age of the plants at harvest. Irrespective of age of root or depth of wound, roots were comparatively resistant to infection at harvest and early in storage, resistance being expressed as a restriction of mycelial growth on the wound surface or localisation of the lesion. Increasing susceptibility with time in storage, depth of wounds, or age at harvest, resulted in larger numbers of inoculated sites becoming infected and a more rapid development from localised to progressive lesions.
The significance of tuber damage and inoculum concentration of Phoma exigua var. foveata in the development of gangrene in stored potato tubers
Authors: ADAMS M. J.
Published: February 2008

The susceptibility to gangrene infection of wounds of various shapes and depths on potato tubers was studied by inflicting wounds using differently‐shaped brass teeth and rods of different diameters. Inoculating wounds with spore suspensions or damaging tubers which had been previously contaminated with Phoma exigua var. foveata or which had been recently lifted from plots of field experiments showed that wounds in which tissue was crushed were most susceptible to infection. Over a wide range of inoculum concentrations and in experiments using several different cultivars the incidence of infection of any wound type was compared to that of the standard severe cut and crush wound. Using a probit transformation a linear relationship was established, the slope of the line indicating the relative susceptibility of the wound.

In 1977 and 1978, crops of cv. Pentland Dell were surveyed for damage incidence, inoculum and inoculum potential on arrival at a commercial bulk store. Nets of tubers buried among the tuber bulk were recovered after storage and gangrene incidence compared with damage and inoculum assessments. Inoculum potential and incidence of severe damage both influenced disease development but damage incidence was of greater importance, showing that priority should be given to decreasing damage and to curing to promote rapid wound healing in endeavours to control the disease.
Observations on the prevalence and incidence of ergot disease in Great Britain with special reference to open‐flowering male‐sterile cereals
Authors: WOOD G. , COLEY‐SMITH J. R.
Published: February 2008

Ergot (Claviceps purpurea) of grasses is prevalent throughout Britain. The disease also occurs regularly in most cereal varieties but generally is of low incidence. Incidence is much greater in open‐flowering and male‐sterile cereals, with the infection seeming to come, initially, from the large reservoir of inoculum amongst grasses. The production of F1‐hybrid cereal seed, which necessitates the use of male‐sterile lines, could therefore be jeopardised.
Effects of environmental factors on growth of lesions on field bean leaves infected by Botrytis fabae
Authors: HARRISON J. G.
Published: February 2008

Chocolate spot lesions increased in size only slowly when the relative humidity of the air was below 66%. Following a lag phase immediately after infection the rate of increase was linear and proportional to humidity between c. 70% and 100% r.h. Lesions on leaflets kept at 70% r.h. for 8 h and at 100% r.h. for 16 h/day increased in size at only 27% of the rate of those at continuous 100% r.h. The optimum temperature for lesion growth was between 15 and 22 °C, the minimum <4 °C and the maximum c. 30 °C. Humidity did not interact with temperature between 10 and 20 °C. Neither light intensity nor a film of water over the leaves affected lesion growth. These findings are discussed in relation to meteorological data and field observations.

The possible mechanisms whereby humidity affects lesion growth did not appear to be related to CO2 and O2 concentrations nor to the overall water potential of the leaf.

Preliminary evidence is presented for the production of phytotoxins within lesions.
Effects of aldicarb persistence on field populations of Heterodera schachtii
Authors: BATTERBY S. , PATOUREL G. N. J. LE , WRIGHT D. J.
Published: February 2008

In field trials in 1976 and 1977 various granular formulations of aldicarb (2–8 to 12.8 kg a.i. ha‐1) were applied to sugar‐beet fields infested with Heterodera schachtii. The levels of toxic residues of aldicarb and of H. schachtii populations in the soil were monitored at intervals throughout the sugar‐beet season.

A severe drought in 1976 seriously affected the field trials and although aldicarb levels were maintained in the soil no aldicarb treatment proved effective in controlling H. schachtii; this was probably due to lack of mobility of the pesticide in the soil. In 1977, the final nematode populations in plots treated with 2.8 or 11.2 kg a.i. ha‐1 added incrementally through the growing season to simulate the effect of a controlled release formulation were not significantly different from those of untreated plots. In contrast treatment at drilling with fast‐releasing formulations at all application rates did promote control of H. schachtii populations. No significant increase in yield was found on any trial after treatment with aldicarb.

The value of controlled release formulations of aldicarb for the control of H. schachtii populations over the growing season has not been proven.
Resistance to aphids in immature wheat and barley*
Authors: LOWE H. J. B.
Published: February 2008

Resistance to Sitobion avenue and Metopolophium dirhodum was assessed in the glasshouse by releasing immature aphids on uncovered wheat and barley plants at the tillering stage. Six cultivars of winter wheat were tested with S. avenue and of these cv. Kador was resistant and cv. Maris Huntsman susceptible. Among seven cultivars of barley, cv. CI16145 was more resistant to S. avenue than any other whilst cvs Tyra and Nirakei 10 were the most susceptible, but the cultivars did not differ significantly in the numbers of M. dirhodum on them, although there were ranking differences similar to those observed with S. avenue.
Observations on the production and dispersal of spores, and infection by Rhynchosporium secalis
Authors: STEDMAN O. J.
Published: February 2008

The numbers of spores of Rhynchosporium secalis washed from samples of barley plants taken weekly, varied markedly. No consistent association with amount of previous rainfall or length of the preceding dry period was detected. On potted seedlings exposed within a crop most infection occurred during long rain periods or when rain fell late in the evening; fewest lesions usually developed on seedlings prevented from touching adjacent plants.

Rotorod traps fitted with a 13 mm diameter disc at the apex of each arm were operated under 24 cm diameter covers. Spores were collected on circular cover slips fixed to each disc with glycerine jelly. At all stages of crop growth more spores were trapped at ground level than at other heights tested up to 1 m. The number of spores trapped was not related to the quantity of or duration of rainfall but was related to the mean rate of fall during brief showers only. Efficiency of droplet retention was assessed in a wind tunnel. It declined rapidly when more than c. 5 pl was presented to the disc surface and was less at a wind speed of 1.0 than 0.5 m s‐l. Spore distribution on discs indicated that spores were washed from the surface during long rain periods.
Characterisation of rhizobia isolated from nodules on locally‐adapted Glycine max grown in Nigeria
Authors: BROMFIELD E. S. P. , ROUGHLEY R. J.
Published: February 2008

Strains of Rhizobium spp. (cowpea miscellany) and R. japonicum are characterised by their symbiotic performance on two hosts, Vigna unguiculata cv. Ife Brown and Glycine rnax cv. Bossier. The results indicate that isolates from G. max cv. Malayan, a promiscuously nodulating cultivar adapted to Nigerian conditions, form a group intermediate between R. japonicum and R. spp. but are more closely related to the latter. We tentatively suggest on the evidence of symbiotic performance that R. japonicum is a specialised group within R. spp.
Some effects of differently‐acting nematicides on the cereal cyst‐nematode (Heterodera avenae) and on the appearance of ‘scorch’ in spring wheat on light loamy sand
Authors: WILLIAMS T. D. , BEANE J.
Published: February 2008

In a field trial on light loamy sand, aldicarb was more effective than formalin or dazomet in controlling cereal cyst‐nematode on spring wheat.

In the second year of the trial severe ‘scorch’ symptoms appeared and yield losses were greatest in aldicarb treated plots that received most nitrogen even though invasion of plants by juveniles of Heterodera avenae was greatly reduced. Before a dry spell in early summer, crop growth was best in those plots which had received most nitrogen but which finally yielded least; crop growth‐stage and the timing of dry periods are critical in the development of ‘scorch’ symptoms (early shrivelling, browning, and failure of ear emergence) on a light soil given a high rate of nitrogen. ‘Scorch’ occurred at the very luwest H. avenae population levels; the effects of fungal pathogens and NO3 nitrogen content of the crop remain uncertain. The rôle of copper in the ‘scorch’ condition could not be assessed since it was applied in a wetter year, in which ‘scorch’ failed to appear.
Selection for cold tolerance in Phaseolus vulgaris— yields of selected lines grown in warm and cool environments
Authors: HARDWICK R. C. , ANDREWS D. J.
Published: February 2008

Forty‐eight F4 families of a cross between two cultivars of Phaseolus vulgaris were grown in ‘warm’ and ‘cool’ environments in the field. The F2 and F3 generations had been assessed for cold tolerance using the test described by Hardwick & Andrews (1980). The mean seed yields of the F4's were 333 and 167 g m‐2 in the ‘warm’ environment (blackened soil surface, clear polyethylene mulch, windbreaks) and ‘cool’ environment (whitened soil surface, no mulch or windbreaks) respectively. The ratio of yields in the two environments was larger in families selected for cold sensitivity than in those selected for cold tolerance (values of ratio 2.28 to 1 and 1.76 to 1 respectively).

The ‘warm’ treatment decreased the number of days between sowing and emergence from 15.6 to 8.6, increased the estimated weight per seedling axis at emergence from 544 to 904 mg/plant, and increased the weight/plant at flowering from 3.75 to 4.7 g. Plants from the ‘warm’ treatment had bigger leaf weights, smaller stem weights, more branches and bigger specific leaf areas than plants of the same weight from the ‘cool’ treatment. Differences in yield were due mainly to differences in the number of seeds produced/plant.

Eleven F, families were grown in a simple yield trial the following year. The season was cooler and yields were reduced. The reduction in yield was greater in the cold sensitive than in the cold tolerant families.
Influence of host plant Brassica species) and temperature on population increase of the cabbage whitefly Aleyrodes brassicae
Authors: IHEAGWAM EMMANUEL UCHE
Published: February 2008

Laboratory studies on the influence of host plant species on population growth of the cabbage whitefly Aleyrodes brassicae Walk. showed that greatest longevity occurred on mustard and lowest on turnip. Leaf age did not affect survival. At 20 or 25 °C the survival curves from mustard plants were shortened Slobodkin's type I whereas those from purple sprouts and turnip were typical of Slobodkin's type II. At 15 °C the survival curves from young leaves of all host plants were of Slobodkin's type I but those from mature leaves were of Slobodkin's type III except that of mustard which was of type I. Young leaves induced higher fecundities than mature leaves. Fecundity was highest on mustard followed by purple sprouts and turnip. This affected population rate such that, for example, daily rm values on young leaves of mustard, purple sprouts, and turnip at 25 °C were 0.206, O.172, and 0.147, respectively.
A comparison of a corer and a shovel for sampling populations of wheat bulb fly Delia coarctata eggs
Authors: McKINLAY R. G. , FRANKLINT M. F.
Published: February 2008

The most commonly used tool for sampling soil for eggs of the wheat bulb fly Delia coarctata Fall.) is a corer, but in Scotland samples are taken with a modified shovel. The sampling properties of a corer and shovel were compared in two exercises in which soil samples were taken from the ridge, sides and furrow of drills of maincrop potatoes at several sites in east Scotland. Although each tool sampled approximately the same surface area of soil, the corer sampled three times as much soil as the shovel. The numbers of wheat bulb fly eggs estimated by the corer and shovel were similar in both sampling exercises and there were no indications that the comparison of the two tools was affected by the sampling position on the potato ridge. The results of the two exercises gave no reason to believe that in similar conditions the shovel is an inferior sampling tool or that population estimates obtained with a shovel in Scotland are not comparable with those obtained with a corer. Evidence from some sites suggested that wheat bulb flies lay more eggs on the potato ridge than in the furrow.
The relationship between cabbage root fly egg laying and volatile hydrolysis products of radish
Authors: ELLIS P. R. , COLE ROSEMARY A. , CRISP P. , HARDMAN J. A.
Published: February 2008

Radish populations selected from the cvs Asmer Tip Top and Sparkler on the basis of high or low preference by the cabbage root fly for egg laying were tested at different ages by exposing them to the pest in a laboratory test chamber. Results confirmed the existence of a cycle of changing attractiveness of radish for egg laying, the peak occurring as plants reached a marketable age. Selection within radish cvs for different levels of preference resulted in a shift in the cycle of attraction such that ‘high‐preference’ plants reached a peak in attractiveness earlier than ‘low‐preference’ ones. Egg laying was correlated with the total amounts of two volatile glucosinolate hydrolysis products (4–methylthio‐3–butenyl isothiocyanate and 1–cyano‐4–methyl‐thio‐3–butene) detected in ether extracts of macerated radishes. The relationship between chemicals and egg laying suggested a possible chemical assay to complement biological techniques for identifying cabbage root fly‐resistant radish for breeding work.
Development of potato blight Phytophthora infestans after planting infected seed tubers
Authors: BOYD A. E. W.
Published: February 2008

About 1000 blight‐infected seed potato tubers, usually of the cultivar King Edward, were planted for 9 yr and the subsequent plants examined until the disease had developed in the plots. Haulm infection originated each year from the seed tubers and occurred first on basal leaves. When tubers were inoculated with a complex race of P. infestans this race was recovered from the leaves and from the soil near the seed tuber.

Transmission of infection from soil to leaves was demonstrated by splash of artificially contaminated soil to leaves suspended above the soil.

In 4 yr, plants were grown on flat rows as well as on ridges. In 2 yr, when emergence was almost complete, infected stems were observed on otherwise normal plants. In the first year 0.6% grew on ridges and 3.0% on the flat and in the second all grew on the flat (5.3%). Only seven of the 43 plants had more than one infected stem. Flat plots had a significantly higher number of stemdplant than ridge plots, but this bore no relation to numbers of infected stems. When flat plots which had developed affected plants had soil replaced as ridge plots, no further infected stems were observed. Such stems continued to develop on flat plots.

No prematurely dead stems were observed below soil level when all plants were dug.

Underground portions of most infected stems showed little evidence of P. infestans which was found only at about soil level. Infection appeared to occur first in this area.
Studies on the seed‐borne phases of dark leaf spot Alternaria brassicicola and grey leaf spot Alternaria brassicaeof brassicas
Authors: MAUDE R. B. , HUMPHERSON‐JONES F. M.
Published: February 2008

Tests in Britain on samples of basic and commercial Brassica oleracea seed between 1976 and 1978 showed that many lots were infected with Alternaria brassicicola. A. brassicae was uncommon in basic seed in these years and in commercial seed harvested in 1976 and 1977 but was frequent in seed harvested in 1978. Most affected seeds were contaminated by surface‐borne spores and mycelium of A. brassicicola but many were internally infected by the fungus situated within the seed‐coat and in some seeds in the embryo tissues. Superficial contamination by the fungus declined rapidly after 2 yr in cabbage seeds stored at 10 °C, 50% r.h. but internal infection persisted for up to 12 yr. In some samples, internal infection was commonly associated with small shrivelled seeds. Surface contaminated and internally infected seeds transmitted the disease but seedling infection was more closely correlated with the latter.
The effect of iprodione on the seed‐borne phase of Alternaria brassicicola
Authors: MAUDE R. B. , HUMPHERSON‐JONES F. M.
Published: February 2008

Alternaria brassicicola infection of Brassica oleracea seeds was effectively controlled by a dust application of iprodione (Rovral 50% w.P.). At 2.5 g a.i./kg the seed‐borne fungus was usually eliminated from samples with up to 61.5% affected seeds (35.5% internally diseased) but higher levels of infection required increased doses for complete eradication of the fungus. The germination of healthy seeds, including samples from 7–yr‐old stocks, on filter paper was unaffected by the treatment. However, the germination of diseased samples, particularly those internally infected with A. brassicicola, was improved. More seedlings emerged from iprodione treated than from untreated seeds in glasshouse soil but the differences were not significant. The application of gamma‐hexachlorocyclohexane to iprodione treated seeds sown in soil did not adversely affect subsequent emergence or disease control. Disease control was maintained and germination was not affected by the treatment when treated infected seeds were stored for 2 yr at 10 °C, 50% r.h. In a field trial iprodione seed treatment reduced seedling infection in a cabbage crop grown from naturally diseased seeds (100% contaminated, 45.5% internally infected) from 5.6 to 0.04%.
The relative importance of some yield components in East of Scotland strawberry plantations
Authors: MASON D. T. , RATH N.
Published: February 2008

Yield components were measured in 69 plantations of the strawberry cv. Cambridge Favourite located in eastern Scotland. Yield of fruit/ha was positively correlated with number of crowndha. Number of berries/truss (inflorescence), mean berry weight and weight of fruithuss were negatively correlated with number of emerged trusses/crown. Weight of fruit/truss was positively correlated with both number of berries/truss and mean berry weight.

Since crown number accounted for more than 50% of the yield variance it is suggested that the potential yields of strawberry plantations can be predicted from crown counts made during the dormant period.
Effect of abscisic and gibberellic acid on grain set in wheat
Authors: RADLEY MARGARET
Published: February 2008

When abscisic acid was applied to wheat ears at or just before anthesis, it prevented grain set in the third floret of each spikelet but not in the lower florets. It had no effect on semi‐dwarf cultivars in pot experiments, but there was a small response in a field experiment. Gibberellic acid inhibited anthesis in all florets of all cultivars.
Use of protein A to improve sensitisation of latex particles with antibodies to plant viruses
Authors: TORRANCE L.
Published: February 2008

Protein A‐coated latex (PAL) was compared with uncoated latex (L) for sensitisation with antibodies to five plant viruses: apple mosaic virus (ApMV), arabis mosaic virus (AMV), plum pox virus (PPV), potato virus Y ordinary strain (PVY°) and prunus necrotic ringspot virus (NRS V). A range of globulin concentrations was used with each antiserum and detection end points determined in serial dilutions of infective sap. When sensitised with antibodies to ApMV, PAL detected ApMV readily, whereas L did not. When sensitized with antibodies to PVY° and AMV, PAL gave higher detection end points than L. However, PAL gave little increase in sensitivity with the antisera to PPV and NRSV. Non‐specific aggregation of latex, which sometimes occurred in very dilute sap with PAL, could be dispersed by adding 0.02% Tween‐20 to the extraction buffer. Globulins of PVY° and AMV could be used at higher dilutions with PAL than with L, giving a saving in antiserum. Both types of latex sensitised with PVY° antibody globulins readily detected the tobacco veinal necrosis and C strains of this virus.
Barley yellow dwarf virus infectivity of alate aphid vectors in west Wales
Authors: A'BROOK JOHN , DEWAR A. M.
Published: February 2008

Live trapping at 0.9 m of alate aphid vectors of barley yellow dwarf virus (BYDV) at Aberystwyth from 1970 to 1979 showed that ten species transmitted the virus to oat test plants. Conversion of percentage infective at 0.9 m to numbers infective based on continuous trapping at 1.2 m showed Rhopalosiphum padi and R. insertum to be the main vector species in most years, whilst Metopolophium dirhodum and Sitobion auenae were normally of minor importance. The data obtained suggest that epiphytotics of BYDV in autumn‐sown cereals were caused by numerous infective vectors flying late in the year and transmitting severe strains of the virus. Evidence is presented that gynoparae and males of R. padi are involved in the autumn spread of BYDV and that three further aphid species, Anoecia corni, Metopolophium albidum and M. frisicum are BYDV vectors. The use of live and continuous trapping techniques in forecasting BYDV epiphytotics is discussed.
Genetic control of the reactions of raspberry to black raspberry necrosis, raspberry leaf mottle and raspberry leaf spot viruses
Authors: JONES A. T. , JENNINGS D.L.
Published: February 2008

Black raspberry necrosis virus (BRNV) induces a severe apical necrosis in black raspberry (Rubus occidentalis) but fails to induce diagnostic symptoms in red raspberry. However, BRNV infection of F1, F2 and F3 hybrids from the cross black raspberry × red raspberry induced mosaic symptoms of varying intensity but no typical apical necrosis.

In a survey of 28 red raspberry cultivars, a few developed severe angular chlorotic leaf spots when infected with raspberry leaf mottle virus and a few others did so when infected with raspberry leaf spot virus. These reactions were determined by single dominant genes designated Lm and Ls respectively.

The value of the different host reactions for controlling the effects and spread of these viruses is discussed.
Application of enzyme‐linked immunosorbent assay to the detection of potato leafroll virus in potato tubers
Authors: TAMADA T. , HARRISON B. D.
Published: February 2008

Factors affecting the detection of potato leafroll virus (PLRV) by enzyme‐linked immunosorbent assay (ELISA) in tubers of field‐grown potato plants with primary or secondary infection were studied. The reactions of extracts of virus‐free potato tubers were minimised by pre‐incubating the extracts at room temperature and by careful choice of the dilution of enzyme‐conjugated globulin. PLRV was reliably detected in tubers produced by secondarily infected plants of all six cultivars tested. PLRV concentration was greater in heel‐end than in rose‐end vascular tissue of recently harvested tubers but increased in rose‐end tissue when tubers stored at 4°C for at least 5 months were placed at 15–24°C for 2 wk.

PLRV occurred at greater concentration in tubers from plants of cv. Maris Piper with natural or experimentally induced primary infection than in tubers from secondarily infected plants; again PLRV concentration was greater in heel‐end than in rose‐end vascular tissue. Plants whose shoots were infected earliest in the growing season were invaded systemically and produced the greatest proportion of infected tubers; plants infected late in the season also produced infected tubers but PLRV was not detected in their shoot tops. PLRV concentration in tubers from the earliest‐infected plants was less than in tubers from later‐infected plants. PLRV was detected reliably by ELISA in tubers from progenies that were totally infected but was not detected in all infected tubers from partially infected progenies.

ELISA is suitable as a routine method of indexing tubers for PLRV, although the virus will not be detected in all infected tubers produced by plants to which it is transmitted late in the growing season.
Water stress in field‐grown perennial ryegrass.
Authors: JONES M. B. , LEAFE E. L. , STILES W.
Published: February 2008

Two sets of irrigated and water‐stressed swards of perennial ryegrass (Lolium perenne) growing in the field were compared. One set of swards was grown normally (field swards) and the other was established in boxes of low water‐holding capacity (simulated swards). Rain covers were used to exclude rain from half of both sets of swards: the others were kept within 20 mm of field capacity.

Daily minimum values of leaf water potential fell to —12 bars (—1.2 MPa) in the irrigated swards, —16 bars in the stressed field swards and —20 bars in the stressed simulated swards. Dry‐matter production was reduced in the stressed field swards and leaf extension declined markedly in both the field and simulated swards.

Canopy photosynthesis at saturating light intensity was reduced by about half in the stressed field swards and by more than 80% in the stressed simulated swards. In the former case a proportion of this reduction was due to the lower leaf area but the mean rate of leaf photosynthesis at saturating light intensity (Pmax/LAI) was reduced by about 40% and this was attributable to increased stomatal resistance calculated from canopy transpiration rates or measured with a porometer. The more marked decline in photosynthesis in the stressed simulated swards was not only the consequence of more complete stomatal closure but also a decrease in the quantum efficiency of photosynthesis.

When water stress occurs naturally in the field it appears that changes in the leaves take place as stress is developing and these changes result in a less severe effect of water stress on leaf photosynthesis. When stress is imposed with unnatural rapidity, as in the simulated swards, there is no opportunity for these changes in the leaf to occur and stress leads to a rapid and severe decline in leaf photosynthesis.

The importance of these findings for the grass sward under water stress is discussed.
Prospects for fungicidal control of take‐all of wheat
Authors: BATEMAN G. L.
Published: February 2008

A range of fungicides and herbicides was tested against Gaeumannomyces graminis (causal agent of take‐all) on agar plates, and on wheat seedlings in pots and in liquid culture. Benomyl, the standard in all tests, was consistently most effective: like iprodione, nuarimol and KWG 0599, it diminished infection from inoculum placed just below the seeds more effectively when applied as a drench than as a soil‐mix. Benomyl as a soil‐mix was most effective in soils with least organic matter. Some compounds toxic to the pathogen on agar plates and in plants grown in liquid culture were ineffective as soil treatments. The practical limitations of soil treatment with conventional fungicides and application methods are discussed.
Fluxes and accumulation of ethirimol in haustoria of Erysiphe pisi and protoplasts of Pisum sativum
Authors: MANNERS J. M. , GAY J. L.
Published: February 2008

Isolated purified fractions containing haustorial complexes and mesophyll protoplasts were used to investigate the relative affinities in vitro of the host‐parasite interface and host for the mildew specific fungicide, ethirimol. Compounds labelled with [14C] were used throughout this study.

Isolated haustorial complexes accumulated fungicide against a concentration gradient and, in 15 min, to much higher concentrations than they accumulated glucose, sucrose, uracil, glycine, ethanolamine hydrochloride, inulin carboxylic acid, thiocyanate ions or uridine diphosphate glucose. Accumulation of ethirimol ceased after 30 min when the internal concentration was over twenty times greater than in the ambient medium. Similar quantities were absorbed in 15 min at pH 4.2 and 6–2. The quantities absorbed during 1 h incubation were directly related to the ambient concentration (4–400 μm). Ethirimol introduced into haustorial complexes was easily removed by washing; one third was removed in the first 5 min and only one sixth of the original remained after 3 h. Analysis of the kinetics of ethirimol efflux showed that it was located in two compartments within the complexes; thus it most probably entered the fungal cytoplasam.

Ethirimol entered pea mesophyll protoplasts showing biphasic kinetics with considerable uptake in the first 30 min and a more gradual influx during the following 18 h. It was not accumulated against a concentration gradient until 6 h and after 18 h the internal concentration exceeded that of the ambient by only 1.74 fold.

Extraction and chromatography showed that only small proportions of the ethirimol were degraded by haustorial complexes and protoplasts during the experimental periods.

These in vitro experiments indicate competitive accumulation of ethirimol by the host‐parasite interface in vivo.
Behaviour of the systemic nematicide oxamyl in plants in relation to control of invasion and development of Meloidogyne incognita
Authors: WRIGHT D. J. , BLYTH A. R. K. , PEARSON P. E.
Published: February 2008

A single foliar application of oxamyl (12.5 μg) in acetone significantly reduced invasion of cucumber seedlings by Meloidogyne incognita juveniles for at least 21 days but did not affect the early stages of development of juveniles which had already invaded the roots. In contrast, application of oxamyl to the roots significantly reduced both invasion and development of juveniles. Concurrent studies using radiolabelled oxamyl showed that the amount of toxicant in the roots after 3 days was 13 times greater following root application than after foliar treatment.

It is probable that oxamyl concentrates at the sites of nematode attack as an overall concentration of only 3 ng oxamyl g‐1 root was sufficient to prevent invasion. Much greater concentrations than this were required to affect the nematode in vitro. Oxamyl appeared to be lost from the roots into the soil principally in the form of its non‐toxic oxime and it is suggested that the site of action following foliar application is at the root surface or outer cortex. Studies on the invasion behaviour of M. incognita juveniles on agar showed that the action of oxamyl had a sensory component.