bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field studies on the effects of ryegrass mosaic virus on the yield of Italian ryegrass cv. S 22
Authors: HOLMES S. J. I. 
Published: February 2008

SUMMARYA simple and effective technique for the large scale inoculation of field plots with ryegrass inosaic (RMV) was used in 1977 and 1979 to study the effects of RMV on the yield of Italian ryegrass cv. S 22.In 1977, symptoms of RMV developed rapidly in inoculated plants following the first cut. At the second and third cuts necrosis was recorded in many plants, particularly in plots receiving high levels of nitrogen. At the fourth cut the incidence of symptoms was 72% in plots which received 189 kg ha‐1 N during the growing season and 83.5% in the plots which received 378 kg ha‐1 N. RMV infection reduced total dry matter yield by the equivalent of 3.03 t ha‐1 and 3.57 t ha‐1 in the low and high nitrogen plots respectively.In 1979 in both the high (360 kg ha‐1 N) and the low (120 kg ha‐1 N) nitrogen plots, symptom development was slower than in 1977 and never reached either the incidence or severity in the earlier trial. The low incidence of plants with symptoms was reflected in the relatively small loss in total dry matter yield due to RMV infection recorded in the low (4.4%) and high (6.3%) nitrogen plots.Possible reasons for these differences in symptom development and yield loss in the two trials are discussed.
Physiological responses of apple fruits to oxygen concentrations
Authors: KNEE MICHAEL 
Published: February 2008

SUMMARYThe effects of oxygen concentration on respiration and ripening processes in apple fruits at storage temperatures have been investigated. The response of carbon dioxide production to a change in O2 concentration occurred after a delay of 1–4 days, depending upon the time and direction of change. When apples were stored in flowing streams of oxygen/nitrogen mixtures the time of onset of ethylene production was inversely related to oxygen concentration and the maximum rate of production was directly related to oxygen. However when apples were stored in product‐generated atmospheres low ventilation caused rapid accumulation of ethylene. The retardation of ripening processes by low oxygen concentrations observed under these conditions was not, therefore, a result of inhibition of ethylene synthesis. When permanganate was present in the storage container the build up of ethylene was delayed, especially at low oxygen concentrations. In these conditions there was sometimes a further retardation of softening and soluble polyuronide formation. Rates of chlorophyll degradation in peel and cortex, flesh softening and soluble polyuronide formation were all half maximal at 2.5–4.0% O2.
Field control of take‐all of wheat by avirulent fungi
Authors: WONG P. T. W. , SOUTHWELL R. J. 
Published: February 2008

SUMMARYIn field experiments in New South Wales, wheat inoculated with Gaeumannomyces graminis var. tritici had less take‐all and yielded significantly more grain (P≤ 0·05) when simultaneously inoculated with G. graminis var. graminis and a lobed hypho‐podiate Phialophora sp. synonymous with Phialophora radicicola Cain var. radicicola sensu Deacon than when unprotected with these fungi. An isolate of P. radicicola var. graminicola did not confer any protection. The yields of cross‐protected wheat approached those of healthy wheat where take‐all incidence was slight to moderate while control was less economically significant where disease was severe. If this form of control proved similarly effective against natural inoculum it might be best employed at the beginning of a wheat monoculture after a break crop and serve to delay the onset of severe take‐all.A preliminary survey of 28 wheat fields in New South Wales using a bait technique and examining for characteristic fungal structures showed that G. g. graminis was rarely present in the soil and the lobed hyphopodiate Phialophora sp. and P. r. graminicola were absent. Significant populations of G. g. graminis only occurred in first wheat crops after a long period of native pasture. In New South Wales, at least, these avirulent fungi would have to be introduced to wheat fields for take‐all control.
The detection by serological methods of viruses infecting the rose
Authors: THOMAS B. J. 
Published: February 2008

SUMMARYHomogenates of herbaceous test plants infected with arabis mosaic virus (AMV), prunus necrotic ringspot virus (PNRSV), or strawberry latent ringspot virus (SLRV), and purified virus preparations were used to assess the sensitivities of four serological methods (the enzyme‐linked immunosorbent assay ‐ ELISA, immunodiffusion in gels, the latex flocculation assay, and serologically specific electron microscopy ‐SSEM) for the detection of these viruses. The latex test was up to 250 times more sensitive than gel immunodiffusion, but SSEM and ELISA were respectively up to 1000 and 200 times more sensitive than the latex test.Gel immunodiffusion and latex tests failed to detect any of the viruses in infected roses. Although ELISA reliably detected PNRSV and SLRV when leaves from infected roses were homogenised in a leaf: buffer ratio of 1 g:10 ml, AMV was occasionally undetected. However, when a modified ELISA technique, which reduced non‐specific reactions, was used some PNRSV‐infected roses were also not detected. Detection by SSEM was c. twice as sensitive as ELISA for all three viruses in rose extracts. The relative advantages of ELISA and SSEM for the detection of plant viruses are discussed.
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

SUMMARYEnergy 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

SUMMARYThe 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

SUMMARYIn 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

SUMMARYBarley 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

SUMMARYExperiments 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

ABSTRACTNon‐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

ABSTRACTDuring 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

ABSTRACTVariation 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

ABSTRACT 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

ABSTRACTThe 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

SUMMARY 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

SUMMARYLeaf 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

SUMMARYInfection 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.