bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conidial concentration as an important factor determining the type of prepenetration structures formed by Botrytis cinerea on leaves of French bean (Phaseolus vulgaris)
Authors: VAN DEN HEUVEL J. , WATERREUS LYDIA P. 
Published: April 2007

inoculations of primary leaves of French bean (Phaseolus vulgaris) with conidia of Botrytis cinerea, suspended in 0.11 or 0.28 M glucose supplemented with 0.067 M KH2PO4 or 1 mM Na‐ATP as infection stimulants, yielded mostly spreading lesions. Light microscopy revealed that the fungus could develop three types of prepenetration structures from which penetration started: germ tube apices (GA) either non‐swollen or appearing as an appressorium‐like swelling; appressoria (HA) of different forms produced on branched germ tubes or superficial liyphae; and infection cushions (IC). These structures were also formed on leaves of cucumber and tomato.Penetration from the prepenetration structures was not markedly influenced by the glucose concentration in the inoculum or by host plant species, and varied only slightly with the isolate of B. cinerea. Penetration occurring from GA was greatly enhanced at high conidial concentrations. Low conidial concentrations, however, enhanced penetration starting from HA or IC, penetration from these structures also being dependent on the nature of the stimulant added to the glucose in the inoculum. The high proportion of GA in inocula with a high conidial concentration was associated with a rapid penetration and a rapid formation of spreading lesions.
Effects of fungicide movement between plots in field experiments
Authors: JENKYN J. F. , DYKE G. V. , TODD A. D. 
Published: April 2007

Interactions between plots of spring barley which were either unsprayed, or sprayed with triadi mefon or tridemorph to control powdery mildew (Erysiphe graminis f.sp. hordei) were measured in experiments of balanced design in 1978 and 1979. The average amounts of mildew in untreated plots with triadimefon‐reated neighbours on the predominaotly up‐wind side were usually less than half those in untreated plots with tridemorph‐treated neighbours on the up‐wind side. Triadiniefon‐treated plots had most effect on the adjacent sides of their untreated neighbours but there was evidence that their influence extended across the whole widths of these neighbouring plots. Amounts of mildew in tridemorph‐treated plots were increased by untreated neighbours.Differences in amounts of disease between these plots of spring barley with differently treated neighbours had no significant effects on grain yield. However, in a rando'mized block experiment with spring wheat in 1975 there was evidence that similar inter‐plot interactions caused consider able bias in the yield data. Possible causes of the observed effects are discussed.
The effect of temperature before or after inoculation with Phoma exigua var. foveata on the development of gangrene in potato tubers
Authors: ADAMS M. J. , GRIFFITH R. L. 
Published: April 2007

Potato tubers of five cultivais were incubated at five temperatures between 2 and 20°C for 1 month and then inoculated with Phoma exigua var. foveata and stored at 5°C. Larger rots usually developed on tubers previously incubated at the higher temperatures but cultivar differences were greatest where tubers had been incubated at 2°C. In another experiment, rot size was related to the duration of incubation at 20°C before inoculation.In a series of experiments, tubers were stored at different temperatures after inoculation; other factors (e.g. wound type or r.h.) were also investigated in some of these. Combining the results of all experiments a linear decrease of % wounds infected (logit transformation) with storage temperature was demonstrated. The size of rots was not simply related to temperature, but tended to increase over the range 2–10°C and then stabilized or declined at higher temperatures. Relative humidity treatments of 75% v. 95% did not consistently affect either the incidence of rotting or rot size. The other factors investigated did not usually interact significantly with temperature.The relevance of the results for resistance testing is discussed and a simple equation relating disease incidence to inoculum levels, type of damage and temperature is proposed.
Biological control of Pythium ultimum–induced damping‐off by treating cress seed with the mycoparasite Pythium oligandrum
Authors: AL‐HAMDANI A. M. , LUTCHMEAH R. S. , COOKE R. C. 
Published: April 2007

Incorporation of the aggressive mycoparasite Pythium oligandrum into a carboxymethyl cellulose‐based seed coating decreased damping‐off of cress seedlings by Pythium ultimum in both naturally infested soil and artificially infested sand. This effect is attributed to the germination of P. oligandrum oospores on the seed surface with subsequent generation of a protectant mycelium around the seedling. P. oligandrum oospores survived storage periods of 10—20 weeks at zero relative humidity both on glass slides and within seed coatings. The mycoparasite also survived an 18–month burial in natural soil, probably in the form of oospores.The implications of these observations for biocontrol of seedling diseases by P. oligandrum are discussed.
Nutritional factors affecting the behaviour of Uromyces viciae‐fabae uredospores on broad bean leaves
Authors: PARKER ANN , BLAKEMAN J. P. 
Published: April 2007

Both germination of Uromyces viciae‐fabae uredospores and growth of germ tubes were increased when spores were leached for 12 h at 0.4 ml/min water flow whereas leaching at aflow rate of 2.8 ml/min completely inhibited germination. Washing uredospores once in water caused a reduction in growth of germ tubes and in the numbers of lesions produced on detached leaves of the host, broad bean (Vicia faba).During germination uredospores from recently formed pustules leaked considerably moreendogenous nutrients on hydration than older uredospores. However, the majority of the leaked compounds were reabsorbed by young uredospores within a few hours. Concentrations ofglucose and leucine equivalents leaked from uredospores and from leaves were compared.Leaf leachates stimulated growth of uredospore germ tubes to an extent similar to that caused by low concentrations of glucose and amino acids but the addition of pollen inhibited growth of germ tubes. A variety of nutrients caused stimulation of uredospore germination and growth of germ tubes at low concentrations whereas higher concentrations of exogenous nutrients inhibited these processes. The response of uredospores was affected by their age.Utilization of exogenous 14C‐labelled nutrients by germinating uredospores was very low compared with that of cells of a leaf surface yeast, Cryptococcus sp. Cryptococcus; cells could consume over 90% of the glucose in a solution of glucose and amino acids of concentrations similar to those in leaf leachates before germinating U. viciae‐fabae uredospores had taken up 10%.
The spread oi Erysiphe graminis f. sp. hordei in mixtures of barley varieties
Authors: CHIN K.M. , WOLFE M. S. 
Published: April 2007

A model is proposed of mechanisms which might affect the progress of Erysiphe graminis f. sp. hordei in mixtures of barley varieties. Results obtained from two field trials indicate that the efffect of mixtures may be panitioned into three categoriesof the influence of the reduced density of the susceptible plants, the barrier effect of the resistant plants, and the induced resistance due to the non‐virulent pathogen biotypes. In the early stages of plant growth the lower density of susceptible plants accounted for most of the reduction in pathogen development in mixtures. As the epidemic progressed, the barrier and induced resistance effects increased in importance and the total mixture effect was at a maximum mid‐way through epidemic development. Towards the end of the trials the overall mixture effect declined though the influence of induced resistance was at its maximum. The reasons for these changes and their implications for the use of host varietal mixtures in disease control are discussed.Mixtures also protected the crop against a pathogen other than the target organism.
Studies on metalaxyl‐resistant Phytophthora infestans in potato crops in south‐west Scotland
Authors: HOLMES S. J. I. , CHANNON A. G. 
Published: April 2007

In 1981 metalaxyl‐resistant Phytophthora infestans was found in 44% of the 63 crops examined in south‐west Scotland. In 1982, when fungicides containing acylalanines (metalaxyl or ofurace) were not used in the area, it was detected in 15%. Metalaxyl‐resistant strains were found in several crops which had been sprayed only with non‐acylalanine fungicides or had received no fungicidal treatment. In neither year was resistance associated with a significant breakdown of disease control.Metalaxyl‐resistant isolates of the blight fungus were obtained from tubers from crops in which resistance was detected on the foliage.In detached leaf experiments, resistant isolates retained their ability to grow on leaves treated with 100 μg/ml of metalaxyl after 52 weekly transfers on untreated leaves, and produced sporangia on leaves treated with up to 2000 μg/ml of metalaxyl or ofurace. In mixtures with sensitive sporangia the proportions remained stable after nine weekly transfers on untreated leaves. However, at concentrations as low as 50 μg/ml, metalaxyl and ofurace reduced the extent of colonization and the numbers of sporangia produced by resistant isolates by an average of 50%.
Biological control of two‐spotted spider mite (Tetranychus urticae) by Phytoseiulus persimilis on strawberries grown in walk‐in’ plastic tunnels, and a simplified method of spider mite population assessment
Authors: CROSS J.V. 
Published: April 2007

During 1980 and 1981, a large‐scale trial of the biological control of two‐spotted spider mite (Tetranychus urticae Koch) on protected strawbenies, using the predatory'mite Phytoseiulus persimilis Athias‐Henriot, was done in 52 ‘walk‐in’ plastic tunnels on a commercial nursery in southern England. Introductions of predatory mites in March or early April at a rate of one per plant were consistently successful. In 1980, when predators had not been introduced the previous year (so enabling large numbers of spider mites to overwinter) peak mite populations were large, causing slight foliar damage in some tunnels before control was achieved. In 1981, only a small residual population of spider mites had survived from the previous year and peak numbers were small; the crop appeared healthy and there was no visible damage by mites. For jdequate control, reintroduction of predators was found to be necessary when CTops were replanted in the summer following soil cultivation and sterilization with methyl bromide.A population assessment method for two‐spotted spider mite based on counting aggregations of the mites was devised. The mean number of spider mites (all stages) per leaf was found to be approximately the same as the number of leaves with five or more mites present in a 25‐leaf sample.
Laboratory studies on the growth and reproduction ofCladosporium allii‐cepae, the cause of leaf blotch of onion
Authors: HALL K. , KAVANAGH J. A. 
Published: April 2007

Cladosporium allii‐cepaeis a slow‐growing pathogen of onion which, on malt extract agar, had a mean colony diameter of 2.7 cm after 28 days at 16°C. Growth and reproduction were greatest on malt onion leaf agar and were poor on synthetic media. The optimum and maximum temperatures for growth were 20 and 28°C, respectively. Sporulation was most abundant at 10–15°C. The fungus grew poorly in buffered Czapek Dox medium at pH 2.2–7.8 and most growth was recorded at pH 6.5. Sporulation was enhanced by exposure of colonies to near ultraviolet light.A large proportion of spores germinated in distilled water and at 100% r.h. In distilled water germination was greatest at 15–20° and in air at 100% r.h. at 20°C. Of 10 fungicides tested, fentin hydroxide, fentin acetate/maneb and iprodione were the most effective in inhibiting spore germination, growth and reproduction of the fungus.
Rose mosaic disease: symptoms induced in roses by graft inoculation with both prunus necrotic ringspot and apple mosaic viruses
Authors: THOMAS B. J. 
Published: April 2007

Symptoms induced in rose by single isolates of the cherry serotype of prunus necrotic ringspot virus (PNRSV) and an apple serotype (apple mosaic virus; ApMV) were characteristically different, and appeared at different times throughout the growing season according to the ambient temperature. These features remained discrete, even in roses infected by both viruses and were shown by immunospecific electron microscopy to be a reliable indication of infection by either virus.However, cross‐protection between the two isolates was not reciprocal; mixed infections were established only when roses were simultaneously graft‐inoculated with ApMV and PNRSV, or when PNRSV‐infected roses were supei‐infected with ApMV. The significance of these results in relation to the possible natural occurrence of mixed infections in rose or of isolates of intermediate serotype is discussed.
Host‐mediated interactions between pathogen genotypes
Authors: CHIN K. M. , WOLFE M. S. , MINCHIN P. N. 
Published: April 2007

Barley c ltivars with different resistance genes were inoculated with various sequences of virulent and non‐virulent isolates of Erysiphe graminis f.sp. hordei. The resistance induced in incompatible reactions decreased infection by virulent isolates while, conversely, the degree of susceptibility induced in compatible reactions was sufficient to increase the ability of normally non‐virulent isolates to infect a resistant host. The net effect of interactions was always overall reduction of conidial production when compared with inoculation of a virulent isolate alone.Each interaction between isolates was dependent on the host cultivar, the pathogen isolates used and on the inoculation sequence. Often, induced resistance was most obvious when a nonvirulent isolate was inoculated prior to a virulent isolate. Induced susceptibility was usually more apparent when the virulent isolate was inoculated first. However, on the cultivar Wing, induced susceptibility was more apparent following prior inoculation of a non‐virulent isolate. On the cultivar Hassan, prior inoculation with a virulent isolate sometimes induced susceptibility, but in some cases more susceptibility was induced by prior inoculation with a non‐virulent isolate. In the latter instances, although relatively little infection developed, the majority of the spores produced were those of the normally non‐virulent isolate.There was some evidence of non‐virulent isolates acquiring the ability to infect normally incompatible hosts. This effect disappeared after several generations in the absence of the virulent isolate.
Biochemical characteristics of sporelings of Puccinia graminis f. sp. tritici and protoplasts from wheat isolines of potential significance in specificity
Authors: HOLDEN D. W. , STRANGE R. N. 
Published: April 2007

The affinity of various lectins for protoplasts from isolines of wheat differing in their reaction to Puccinia graminis Pers. f. sp. tritici, Ericks and E. Henn. race 21 and for infection structures of the fungus was studied. Protoplasts of both isolines were agglutinated by concanavalin A and soybean lectin and lysed by wheat germ agglutinin. Pokeweed mitogen and wheat germ agglutinin bound to fungal germ tubes and appressoria but not to uredospore walls, substomatal vesicles or infection hyphae.Viability of protoplasts from either isoline was not affected when they were incubated with uredospores, germlings with and without infection structures or with an extract of the susceptible line, heavily infected by the fungus. No differences between polypeptide fractions prepared from protoplasts of the isolines were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis.
The effects of direct harvesting and drying systems on the incidence and control of neck rot (Botrytis allii) in onions
Authors: MAUDE R. B. , SHIPWAY M. R. , PRESLY A. H. , O'CONNOR D. 
Published: April 2007

Direct harvesting, with mechanical removal of the foliage (topping), of onion crops followed by post‐harvest drying at ambient temperatures (c. 18°C) resulted in an increase in the incidence of onion neck rot (Botrytis allii).The disease was substantially reduced if topped onions were dried at 30°C with an airflow of 425 m3 air/h/tonne. The treatment was most effective if the crop was removed from the field for drying within 48 h of topping thus avoiding severe infection of the damaged green tissues of the necks of onions.
The occurrence and effects of barley yellow dwarf virus in maize in SW England
Authors: PEARSON M. N. , ROBB SHEILA M. 
Published: April 2007

During 1975 and 1976 barley yellow dwarf virus was isolated, using the aphid Rhopalosiphum padi (L.) from five maize cultivars in the Exeter area. The isolates produced interveinal flecking, often accompanied by leaf reddening, in the maize cultivar Anjou 210 and several other susceptible cultivars. ln 1976 visual assessment of six commercial maize plantings indicated natural infections ranging from 11 to 14% of plants, whilst infection in a disease observation plot ranged from 0.8 to 27.5%. Population counts for the three aphid vectors Sitobion avenae (F.), Metopolophium dirhodum (W.) and Rhopalosiphum padi (L.), associated with the crop, corresponded closely with the Rothamsted Insect Survey results from Starcross, Devon.The maize cultivars Anjou 210 and De Kalb 202 were grown in experimental plots with individual rows containing 0, 25, 50, or 100% barley yellow dwarf‐infected plants. Infection caused severe stunting of Anjou 210 but had less effect on De Kalb 202. Dry matter yield losses of 50% for Anjou 210 and 27% for De Kalb 202 were recorded; there were also significant changes (p<0.05) in dry matter content, metabolisable energy, digestible crude protein and water soluble carbohydrate.
Mapping rhizoctonia patch in consecutive cereal crops in Western Australia
Authors: MACNISH G. C. 
Published: April 2007

Rhizoctonia patches in a field were mapped during consecutive seasons of cropping with wheat, oats or barley sown directly without tillage into the previous season's stubble. Distribution, size, shape and number of patches varied considerably between seasons. Less than a quarter of patches were circular and the others tended to be elongated parallel to seed‐rows. Barley was most severely affected, followed by wheat and then oats.It is proposed that changes in patch distribution, configuration and number between seasons is due to shifts in a balance of suppressive or conducive soil factors interacting with Rhizoctonia solani inoculum.
Effect of fungal pathogens on digestibility and chemical composition of Italian ryegrass (Lolium multiflorum) and tall fescue (Festuca arundinacea)
Authors: LAM A. 
Published: April 2007

Slight infection by Drechslera siccans or Rhynchosporium spp. significantly reduced in vitro dry matter digestibility, water‐soluble carbohydrate and the total amino acid content of Italian ryegrass (Lolium multiflorum) foliage. The concentration of all 15 amino acids detected was reduced, with arginine reduced significantly more than the others. Total nitrogen was either increased or not changed, and the amino acid composition was not altered. Limited work with Drechslera festucae on tall fescue (Festuca arundinacea) gave similar results. Small samples of healthy and diseased grass leaves at three different physiological stages were used to detect these changes.Limited leaf spotting by D. siccans caused metabolic changes of the same magnitude as extensive leaf blotching by Rhynchosporium. Impaired photosynthesis and growth of the fungi within the leaf tissues are possible causes of these changes. Decreased digestibility and increased dry matter content of diseased grass foliage could be of great practical importance.
A study of populations of Pseudomonas syringae pv. syringae on stonefruits in Victoria
Authors: WIMALAJEEWA D. L. S. , FLETT J. D. 
Published: April 2007

In a survey of the major stonefruit nurseries in Victoria during winter 1978 and 1979, Pseudomonas syringae pv. syringae, the causal organism of bacterial canker, was found to be present on most of the stonefruit material in all nurseries but was detected most frequently on apricot.The epiphytic populations of P.s. pv. syringae on leaves, buds and shoots of apricot and cherry were assessed periodically between 1979 and 1983 by determining the proportion of trees bearing the bacterium or by counting numbers of bacteria. Populations consistently reached peak levels during spring and late autumn, with highest levels in spring. Populations were lowest during mid‐ to late summer. High proportions of tree contamination and high populations coincided with periods when maximum temperatures ranged from 19° to 25°C, and when rainfall was moderately high. The significance of these findings in the light of information from other studies on the seasonal variability of host susceptibility, and in relation to chemical control, is discussed.There was no evidence of occurrence of P.s. pv. morsprunorum in Victoria.
Methods for visualizing hyaline fungi for the detection of antifungal compounds on thin‐layer chromatograms
Authors: WOODWARD S. , PEARCE R. B. 
Published: April 2007

Two methods facilitating the use of hyaline fungi for the detection of antifungal compounds on thin‐layer chromatograms are described. Fungal growth was visualized under ultraviolet light either by the metabolic release of fluorescein from the esterase substrate fluorescein diacetate, or by the binding of a fluorescent brightener (Calcofluor White M2R New, or Tinopal‐CBS) to the mycelium on the TLC plate.These methods were used to demonstrate compounds inhibitory to the wood‐decay fungus Heterobasidion annosum in bark extracts of Sitka spruce (Picea sitchensis).
The relationship between brown and corky root rot caused by Pyrenochaeta lycopersici and yield loss in tomatoes established by the use of artificially infested soils
Authors: POLLEY R. W. 
Published: April 2007

In an experiment conducted in a commercial glasshouse, tomato plants were grown in pots containing soils infested with a range of levels of Pyrenochaeta lycopersici in a randomized block design. There was found to be a negative correlation (r= ‐0.93) between total yield in kg per plant (y) and % disease severity (x) recorded 8 weeks after planting when the disease data were exponentiated; the best fit was obtained by the equation v = 45.7–42.3x0.006 Fruit number was reduced by 0.2% for each 1% increase in the disease, but a stronger correlation was obtained by the equation y (fruit number) = 417–368x 0.006In a separate trial, the relationship between disease severity 8 weeks after planting and yield loss was shown to be affected by soil type. Early‐season loss of potential yield was found to be lower in sandy soil than in peat and clay. By the end of the season, loss in total potential yield was greater in peat soil than in clay. The effect that soil conditions can have in modifying the relationship between disease severity and yield loss is discussed.
Pelleting of seed with the antagonist Pythium oligandrum for biological control of damping‐off
Authors: LUTCHMEAH R. S. , COOKE R. C. 
Published: April 2007

Pythium oligandrum oospores, incorporated in clay carrier, survived a commercial seed‐pelleting process to give protection against damping‐off in sugar beet and cress induced by Pythium ultimum, together with damping‐off in carrot caused by Mycocentrospora acerina.It is suggested that field scale evaluation of P. oligandrum as a biocontrol of fungally incited seedling diseases is now both feasible and desirable.