bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of a wilt disease of the potato plant in Israel caused by Erwinia chrysanthemi
Authors: LUMB V. M. , PÉROMBELON M. C. M. , ZUTRA D.
Published: April 2007

In Israel field infections of potato plants by Erwinia chrysanthemi are characterized by wilting of the leaves followed by total desiccation of the plants. These symptoms are indistinguishable from those caused by Verticillium dahliae or those that develop during the normal process of plant senescence. Diagnosis of E. chrysanthemi in the spring‐sown (February) crop in Israel is difficult because all three conditions often appear at approximately the same time, late in the growing season in May when the air temperature exceeds 25°C. The symptoms of E. chrysanthemi infection were reproduced in the field when potato seed tubers, tested and found to be contaminated at a low level with E. carotovora pv. carotovora, were inoculated with a strain of E. chrysanthemi isolated from a diseased potato plant. When plants in a growth cabinet at 30°C were stem‐inoculated with E. chrysanthemi, similar symptoms developed when the relative humidity was low (c. 80%). Presence of the disease only on plants grown from seed contaminated with E. chrysanthemi and not from uncontaminated seed suggests that the bacterium is seed borne, as is E. carotovora pv. atroseptica, the blackleg pathogen.
Histology of infection by Erysiphe graminis f.sp. hordei in spring barley lines with various levels of partial resistance
Authors: CARVER T. L. W.
Published: April 2007

The histology of resistance to infection by conidia of Erysiphe graminis f.sp. hordei has been studied in barley lines with various levels of partial resistance. Resistance reduced the proportion of conidia which formed haustoria and was expressed more strongly in fifth than in first formed leaves. Where attempted penetration from the first appressorial lobe failed, a second and sometimes a third lobe could be formed. Most penetrations were from first lobes, a few from second lobes and a negligible number from third lobes. Adult plant resistance decreased penetration success from both first and second lobes. An unidentified component of resistance appeared to impede the development of less vigorous conidia before they stimulated a host cell response. However, in all hosts the majority of failed penetration attempts stimulated a localized host response implicating this response in resistance. Some attempts caused hypersensitive death of epidermal cells in both resistant and susceptible hosts; the proportion of dead cells was higher in fifth than first leaves. Stomatal subsidiary cells were more susceptible to penetration than interstomatal cells and in resistant leaves the majority of successful penetrations were into subsidiary cells. The pathogen was also able to avoid resistance to penetration by establishing endophytic infection following entry of germ tubes through stomates.
Effects of fungicides on long‐term cropping and fruit quality of apple
Authors: HUTCHEON J. A. , COYLE J. , HOLGATE M. E. , BYRDE R. J. W.
Published: April 2007

The effects on cropping of 24 applications, over a 3‐year period, of each of five fungicidal programmes to control powdery mildew (Podosphaera leucotricha) were examined on the apple cultivar Cox's Orange Pippin. Trees receiving programmes based on ergosterol biosynthesis inhibitors (EBIs)‐fenarimol, a triadimefon/bitertanol mixture and an experimental compound coded PP 347‐each applied at 2‐week intervals during the growing season had significantly (c. 40%) less yield than those receiving the standard programme of binapacryl (not an EBI), applied weekly. Yield with a fourth EBI programme‐based on penconazole‐was also less than with binapacryl, but not significantly so. Both binapacryl and penconazole were used mixed with captan.

The lower yields were due to fewer apples harvested rather than to lower individual fruit weight. Possible reasons underlying these effects are discussed: the anti‐gibberellin action of EBI compounds may be involved.
Inhibition by bacterial lipopolysaccharide of wilt induced by phytopathogenic bacteria in cut cherry shoots, and of cherry canker disease
Authors: HIGNETT R. C. , ZAMZE S. E. , MUNRO S. M. , SMITH A. R. W.
Published: April 2007

Virulent phytopathogenic bacteria and their less virulent mutants induced wilt in cut cherry shoots treated with cell suspensions. Both heterologous and homologous bacteria induced the will reaction. The wilt‐inducing isolates also caused the hypersensitive response in tobacco. An avirulent capsulaled mutant of Erwinia amylovora did not elicit either response. Non‐phytopathogens did not cause wilting to occur. All the tested isolates aggregated after entry into plant tissues whether wilting occurred or not, but did not aggregate in suspensions in contact with cut shoots. Bacterial lipopolysaccharide or sidechain carbohydrate derived from lipopolysaccharide of Pseudomonas syringae pv. morsprunorum protected shoots against wilt when administered with the same bacterial isolate. These substances also inhibited cherry canker disease in susceptible mature trees when applied before inoculation to leaf‐scar inoculation sites. Inhibition of bacterial adhesion to mature plant tissues treated with lipopolysaccharide or sidechain is suggested as a cause of disease inhibition. The wilt reaction may provide a rapid test of phytopathogenicity.
Transmission of double‐stranded RNA and a disease factor in Ophiostoma ulmi
Authors: ROGERS H J , BUCK K W , BRASIER C. M.
Published: April 2007

A diseased isolate of Ophiostoma ulmi was found to contain 10 segments of double‐stranded RNA (dsRNA) with molecular weights ranging from 2.40 x 106 to 0.23 x 106. In contrast seven other healthy isolates in the same vegetative compatibility group contained either no dsRNA or up to four dsRNA segments. Transmission of the disease to healthy isolates by hyphal anastomosis was accompanied by‐transmission of the 10 dsRNA segments. In a genetic cross in which the diseased isolate acted as the female parent single‐ascospore progeny were healthy and either contained no dsRNA or only one segment of dsRNA. When elm trees were inoculated with diseased isolates, subsequent reisolations were healthy and retained only two to seven of the dsRNA segments or were diseased and retained all 10 dsRNA segments. Following conidiogenesis a diseased isolate gave rise to single‐conidial progeny which were either slow growing and diseased, like their parent, with all 10 dsRNA segments, or faster growing like healthy isolates. Some of the faster growing conidial isolates retained only two to seven of the dsRNA segments and were disease‐free. However a majority of the faster growing conidial isolates retained all 10 dsRN A segments and were shown to carry the disease in a latent form. The possibility that the disease of O. ulmi is conferred by specific segments of dsRNA and the potential of d‐factors for the control of Dutch elm disease are discussed.
Further studies of the inheritance of benomyl resistance in Venturia pirina isolated from pear orchards in Israel
Authors: SHABI E. , KOENRAADT H. , KATAN TALMA
Published: April 2007

Fourteen single‐spore cultures of benomyl‐resistant Venturia pirina were isolated from pear scab lesions at four sites in Israel. According to the ability of the isolates to germinate and grow at varying benomyl concentrations, four levels of resistance were determined in vitro: three isolates with low resistance (LR) grew at 0.5 but not at 5 μg/ml benomyl: five moderately resistant (MR) isolates grew at 5 but not at 50 μg/ml benomyl: five highly resistant (HR) isolates grew at 50 μg/ml but their hyphae were curled: and one isolate with very high resistance (VHR) grew unaffected at 50 μg/ml benomyl. The difference between the HR and the VHR phenotypes was clearly shown on medium amended with N‐(3.5‐dichlorophenyl) carbamate (MDPC): only the VHR isolate showed negative cross‐resistance to 1 μg/ml MDPC. whereas HR isolates grew unaffected. Crosses between resistant isolates and sensitive wild types, as well as between different resistant isolates, showed that the various levels of resistance are conferred by four allelic mutations that constitute a polymorphic series at a single locus.
Assessment of partial resistance to Pyricularia oryzae in six rice cultivars
Authors: YEH W. H. , BONMAN J. M.
Published: April 2007

The partial resistance to blast of six rice cultivars was assessed in greenhouse experiments and in an upland nursery experiment. IR36. Milyang30 and Milyang42, which have shown relatively little disease in farmers' fields for several years, had lower relative disease efficiency and smaller lesions with lower sporulation capacity than did IR50. Milyang 57 and Suweon 264. Latent period was the least important component of partial resistance. Using the area under disease progress curves as a measure of relative disease progress in the nursery, disease development on IR36 and Milyang 42 was slight and on Milyang 30 intermediate. By comparison, the three susceptible cultivars showed rapid increases in disease. Partial resistance may be associated with more durable blast resistance in certain cultivars.
Serological detection of Fiji disease virus antigens in the planthopper Perkinsiella saccharicida and its inefficient ability to transmit the virus
Authors: FRANCKI R. I. B. , RYAN C. C. , HATTA T. , ROHOZINSKI J. , GRIVELL C. J.
Published: April 2007

Individual adult Perkinsiella saccharicida reared on sugarcane infected with Fiji disease virus (FDV) were confined on healthy plants for 7 days to test for virus transmission and were then sacrificed and assayed for the presence of FDV‐specific structures by immunoelectron microscopy. Only 15% of the insects contained FDV antigens and 6% transmitted the virus. FDV‐specific antigens were detected in individual planthoppers by immuno‐osmophoretic and enzyme‐linked immunosorbent assays about as efficiently as by immunoelectron microscopy. The possible reasons for the inefficient acquisition and transmission of FDV by P. saccharicida are discussed.
Bacteria associated with internal breakdown of onion bulbs and their possible role in disease expression
Authors: COTHER E. J. , DOWLING VIVIENNE
Published: April 2007

Bacteria of the genera Pseudomonas. Erwinia. Klebsiella, Enterobacter and Escherichia were isolated from internal swollen leaf bases of naturally infected onion bulbs and were pathogenic to onion tissue on reinoculation. In pathogenicity tests, inoculation of slices from symptomless bulbs with one bacterium or with a sterile needle often resulted in isolation of P. aeruginosa, Serratia marcesvens and Bacillus cereus. It is postulated that the bacteria isolated form part of the endophytic microflora of an onion bulb, and that they may become opportunistic pathogens when changes in host physiology are triggered by high temperatures at bulb maturity.
Pear blossom blast in South Africa caused by Pseudomonas syringae pv. syringae*
Authors: MANSVELT E. LUCIENNE , HATTINGH M. J.
Published: April 2007

Oxidase‐negative. fluorescent pseudomonads were isolated from cankers, necrotic buds, spots and lesions on leaves and fruit, blasted blossoms and blossoms with lesions on the inside of the calyx cup. as well as from symptomless buds, leaves, blossoms and fruit of pear trees (Pyrus communis). The isolates (431) were characterized by biochemical tests as Pseudomonas syringae pv. syringae and as forms intermediate between this pathovar and P.s. pv. morsprunorum. A resident phase of pv. syringae was found on leaves, fruits and blossoms, and in buds. Typical symptoms appeared on healthy pear trees inoculated with 18 lest isolates of P.s. pv. syringae and two intermediate isolates. A heterogeneous group of strains of P. syringae seems to cause pear blossom blast in South Africa.
Virulence and aggressiveness of single‐zoospore isolates of Phytophthora fragariae
Authors: KENNEDY DIANA M. , DUNCAN JAMES M. , DUGARD PATRICIA I. , TOPHAM PAULINE H.
Published: April 2007

A system for scoring the virulence of isolates of Phytophthora fragariae based on a scale of root rot from 0(no symptoms) to 5 (76‐100% roots roiled) on a series of strawberry cultivars is described. Thirty‐two single‐zoospore isolates from one field site were compared by subjecting their root rot scores to cluster analysis and this grouped them into two major clusters equivalent to physiologic races B66–3 and B66‐11, Different sub‐clusters of isolates of race B66‐11 produced different degrees of rotting on the same hosts. Apart from differences in virulence between the sub‐clusters there was some evidence for differences in aggressiveness between isolates within sub‐clusters.

Increasing inoculum concentration by over 300‐fold increased rotting by c. 25% but did not alter the rankings of different isolate/host combinations. Repeated passage of isolates through cultivars of differing susceptibilities did not affect their pathogenicity.
Interactions between Sclerotium cepivorum and cultivars of onion, leek, garlic and Allium fistulosum
Authors: COLEY‐SMITH J. R.
Published: April 2007

Laboratory and field experiments showed that germination of sclerotia of Sclerotium cepivorum was slower in the presence of cultivars of leek than in the presence of those of onion, garlic and Allium fistulosum. Spread of infection amongst closely spaced plants was also less in leeks than in the other three species. No evidence was found for any differences in the resistance of root tissues of the four Allium species. It is considered that differential stimulation of sclerotium germination is likely to have been the principal reason for the low incidence of white rot infection in leeks which was reported previously.
A comparison of flavour and odour compounds of onion, leek, garlic and Allium fistulosum in relation to germination of sclerotia of Sclerotium cepivorum
Authors: COLEY‐SMITH J. R.
Published: April 2007

The low ability of cullivars of leek to stimulate germination of sclerotia of Sclerotium cepivorum compared with those of onion, garlic and Allium fistulosum appears to be associated with their relative iv small seeds, the lower levels of flavour and odour precursors in their roots and the relatively high proportion of the inactive methyl radical in their flavour and odour profiles.
The dynamics of homologous and heterologous interactions between rice and strains of Xanthomonas campestris
Authors: PARRY R W. H. , CALLOW J. A.
Published: April 2007

Lesion development, bacterial multiplication and spread were measured in leaves of cultivars of rice containing different Xa (resistance) genes, following inoculation with different races of the bacterial leaf blight pathogen. Xanthomonas campestris pv. oryzae. Both compatible and incompatible races possessed the ability to colonize rice plants. The difference between compatible and incompatible host pathogen combinations appeared to be mainly in symptom production since multiplication rates and spread were very similar until after the onset of symptoms. No form of HR (hypersensitive response) was observed. The ability of incompatible races to modify host reaction in dual‐inoculation was dependent on the genotype of the host plant. The heterologous non‐pathogen of rice X. campestris pv. campestris produced few symptoms, failed either to multiply or spread within rice leaves and was unable to induce any marked cross‐protection against homologous pv. oryzae strains in dual‐inoculation experiments.
Fireblight at Long Ashton: a case history, 1971–1983
Authors: BYRDE R. J. W. , HUTCHEON J. A. , WILLIAMS R. R. , BILLING EVE , GWYNNE C.
Published: April 2007

At Long Ashton Research Station serious outbreaks of fireblight (caused by Erwinia amylovora) occurred on apples in 1978, 1980 and 1982. and on pears in 1979, Mid‐season and late‐flowering cider apple cultivars were particularly affected. On cider apple, outbreaks were associated with years of profuse blossom coinciding with unusually warm temperatures during bloom. Spread of infection between hosts, including hawthorn and cotoneaster, was undoubtedly important. These and other factors underlying the outbreaks are discussed.
Witches' broom disease on cocoa in Rondonia, Brazil: basidiocarp production on detached brooms in the field
Authors: RUDGARD S. A.
Published: April 2007

Fruiting of Crinipellis perniciosa was assessed in relation to various climatic factors using dead witches' brooms detached from cocoa, either suspended in the canopy or laid on leaf litter under cocoa. Induction of basidiocarp production occurred over approximately 60 days with rain. Basidiocarps were finally observed on about 85% of brooms in all samples examined and induction of fruiting required at least 17 rainy days, although brooms with a minimum age of 2 years produced basidiocarps about 25 days before brooms with a minimum age of 1 year. Groups of brooms showed distinct cycles of basidiocarp production, and up to 50% of fruiting occurred on dead, attached leaves, Fruiting was reduced on brooms on leaf litter and basidiocarps survived for less time than when brooms were suspended in canopy. Brooms were most productive with moderate amounts of wetness per day, and less than 4 h or more than 20h was inhibitory. No fruiting occurred at mean air temperatures higher than 30°C or lower than 20°C. The microclimate of the litter layer is discussed in relation to reduction of fruiting caused by pruning of brooms.
Infection of resistant and susceptible cultivars of wheat by Pyrenophora tritici‐repentis
Authors: LOUGHMAN R , DEVERALL B. J.
Published: April 2007

Conidial germination, appressorial formation. penetration of epidermal walls, formation of intracellular vesicles and growth of intracellular hyphae in epidermal cells occurred within 12 h of inoculation. Hyphae then grew slowly between mesophyll cells for the next 12 h. Some papillae formed beneath appressoria and most infected epidermal cells retained stain by 24 h after inoculation, indicating major changes in cellular physiology. Slight differences between cultivars in some of these events were not related to resistance.

On the second day. intercellular hyphae emerged more extensively from the infection sites into the mesophyll of the susceptible cultivar Banks, and formed significantly larger mycelia than in the resistant cultivar BH1146 by 3‐5 days from inoculation. Rapid intercellular growth then continued in the susceptible cultivar but not in the resistant cultivar. Necrotic lesions expanded faster in the susceptible cultivar from day 3. By day 10. most lesions in this cultivar were large and light brown with a conspicuous chlorotic margin but those in the resistant cultivar were small and dark brown with inconspicuous chlorosis.
Factors affecting expression of resistance in pepper (Capsicum annuum) to blight caused by Phytophthora capsici in screening trials
Authors: REIFSCHNEIDBR FRANCISCO J. B. , CAFÉ‐FILHO ADALBERTO C. , REGO ARILDO M.
Published: April 2007

The effects of plant age, fungus isolate, zoospore concentration and inoculation method on the resistance of pepper (Capsicum annuum) to blight (Phytophthora capsici) were studied under controlled conditions. Each of the factors studied produced differing responses in the pepper lines tested hut line CNPH 286 proved to be a reliable source of resistance and is now being used in a breeding programme. An inoculation method for screening pepper lines for blight resistance is proposed, using a standardized zoospore suspension applied to the base of plants 45 days from sowing.
Effects of disease and plant competition on yield in monocultures and mixtures of two wheat cultivars
Authors: ALEXANDER HELEN MILLER , ROELFS A. P. , COBBS GARY
Published: April 2007

Disease seventy and crop yield were compared in monocultures and mixtures of two wheat cultivars. one susceptible and one resistant to Puccinia graminis f. sp. tritici. Part of each plot was inoculated and part treated with fungicide. Rust seventy was inversely related to the proportion of resistant plants present. Weight of grain in 100 heads of the susceptible cultivar increased as the amount of rust decreased. The susceptible cultivar yielded less than the resistant cultivar in monoculture, but was a stronger competitor in mixtures. Competitive abilities of the cultivars were independent of severity of rust in the mixtures studied.
Patterns of development of Septoria nodorum and S. tritici in some winter wheat crops in Western Europe, 1981‐83
Authors: ROVLE D.J. , SHAW M W. , COOK R. J.
Published: April 2007

In data collected at 19 sites in Western Europe during 1981‐83. two patterns of development of Septoria nodorum and S. tritici on foliage of winter wheal were distinguished. In sudden outbreaks, lesions appeared simultaneously on the upper leaf layers of crops, usually after the end of stem extension; these outbreaks were ascribed to short, heavy rain storms in which pycnidiospore inoculum in basal leaves was elevated up to 60 cm through the crop canopy. Gradual epidemics were characterized by disease arising on successive leaf layers as they appeared during sustained periods of weather suitable for inoculum transport and infection.

The data indicate incubation periods of 2‐4 weeks for S. nodorum and 3‐5 weeks for S. tritici. it is suggested that a leaf layer cannot normally sustain more than one pathogen generation and that its infection arises from inoculum borne on leaves older than in the layer situated immediately below it. The potential level of disease in a crop may relate to the amount of inoculum present in spring. The proportions of disease caused by the two Septoria species varied greatly between sites and years, but the data provided no explanation.

It is concluded that a septoria forecast scheme needs to recognise the importance of sudden disease outbreaks and to include not only weather but also host growth and inoculum factors.
Components of resistance of apple to powdery mildew (Podosphaera leucotricha)
Authors: JEGER M. J. , BUTT D. J. , SWAIT A. A. J.
Published: April 2007

Components of resistance of apple to Podosphaera leucotricha were assessed in the glasshouse by spraying shoot tips of cultivars with conidia. Disease incidence (proportion of leaf surfaces with mildew) and colony numbers were higher and incubation periods correspondingly shorter on the older leaves. unrolled at the time of inoculation. Numbers of colonies were higher on the lower surface. Spore production per colony was higher on the younger leaves. In general, a short incubation period on a cultivar was associated with a high disease incidence, many colonies and high spore production. For some cultivars the association between these components permitted resistance to be classified as very high (cv. Discovery), very low (cv. Golden Delicious), or intermediate(cvs Bramley's Seedling. Suntan). The effects of inoculum concentration and post‐inoculation environment (glasshouse or outdoors) on components of resistance were assessed in a further study. No interactions between cultivar and inoculum concentration were detected. There was generally an associated variation in components between cultivars within an environment, but inconsistencies in cultivar rankings were noted between the two environments and the two studies. Mean incubation period was shorter and colony area larger in the glasshouse than outdoors. There were significant differences in conidia/cm2 colony between cultivars only in the glasshouse. Components conferring high resistance in cv. Discovery and low resistance in cv. Golden Delicious were confirmed in both environments and in both studies.
Components of spore production in apple powdery mildew (Podosphaera leucotricha)
Authors: BUTT D.J. , JEGER M. J.
Published: April 2007

The morphology of powdery mildew (Podosphaera leucotricha) colonies of known age was studied on six apple cultivars inoculated in a glasshouse. Colonies were observed first on the older leaves. Mean disease incidence ranged from about 20% for cv. Laxton's Superb to about 45% for cv. Crispin. Conidiophore density (number of conidiophores/mm2 colony) was higher on younger than on older leaves, higher on the upper than on the lower leaf surface, and decreased with the age of the colony. The number of hyphal interceptions on a line transect was higher on the upper surface but the ratio of conidiophore density to hyphal interceptions was greater on the lower surface and did not differ with colony age or cultivar. The number of conidia/conidiophore was higher on the younger leaves and on the upper surfaces and was at a maximum 7‐12 days after the first sign of the colony. The number of conidia/mm2 colony was higher on lower surfaces, especially of the younger leaves. There was generally an associated variation between cultivars in components of spore production.
Influence of spray programmes on development of fungicide resistance in the eyespot pathogen of wheat, Pseudocercospovella herpotrichoides
Authors: HOARE F. A. , HUNTER T. , JORDAN V. W. L.
Published: April 2007

A site with no known history of cereal growing or carbendazim fungicide use was inoculated in 1983 with an equal mixture of spores of R‐type and W‐type isolates of Pseudocercosporella herpotrichoides. all sensitive to carbendazim. Following three consecutive years of carbendazim sprays, more than 90% of isolates recovered were carbendazim‐resistant. A majority of R‐type isolates was recovered after 3 years and resistance was found to be more frequent in R‐type than in W‐type isolates. A mixture of carbendazim with prochloraz initially delayed the development of carbendazim resistance, but after 3 years the incidence of resistance was similar to that where carbendazim alone was applied. The best control of eyespot was given by the mixture and by a split application of prochloraz in the first year, by the mixture in the second year, and by the split prochloraz application in the final year. A greater proportion of R‐type isolates was recovered from prochloraz‐treated plots than from unsprayed plots; the proportion of these that were resistant to carbendazim was lower than that from carbendazim treatments. Throughout this study isolates resistant to prochloraz were not detected.
Etiology of a newly described root rot of guar (Cyamopsis tetragonoloba) in Australia caused by Phytophthora cryptogea
Authors: STIRLING A. M. , IRWIN J. A. G.
Published: April 2007

An isolate of Phytophthora obtained from diseased roots and stems of guar (Cyamopsis tetragonoloba) growing in waterlogged soil from Dalby. Queensland. was identified as Phytophothora cryptogea (P. drechsleri). Sex organs were not observed, Pathogenicity to guar seedlings was established under glasshouse conditions either by using a hypocotyl‐wound inoculation technique, or adding motile zoospores to seedlings growing under saturated conditions. This appears to be the first report of this disease. Seven isolates of P. drechsleri from hosts other than guar were shown to be pathogenic to guar following hypocotyls‐wound inoculation.

The host range of the guar isolate was studied using both hypocotyl‐wound inoculation and zoospores. After hypocotyl inoculation, the following species were found to be susceptible: cantaloupe. cowpea, cucumber, mungbean, pea. pigeon‐pea, safflower. sunflower, tomato and watermelon. Slight symptoms were observed on bean and chickpea. When zoospores were used as the inoculum, only pea. pigeon‐pea, sunflower and safflower were highly susceptible. A range of guar cultivars and breeding lines were screened for resistance using zoospore inoculum, and although no genotypes were highly resistant, there were significant differences between disease reactions.
Effects of virus infection of faba bean on subsequent infection by Uromyces viciae‐fabae
Authors: OMAR S. A. M. , BAILISS K. W. , CHAPMAN G. P. , MANSFIELD J. W.
Published: April 2007

Prior infection of faba bean with bean yellow mosaic virus (BYMV) and bean leaf roll virus decreased pustule density on leaves subsequently infected by Uromyces viciae‐fabae. Changes were most marked on young leaves showing conspicuous symptoms of systemic virus infection and in plants virus‐infected for at least 2‐4 weeks. Pustule density progressively decreased when inoculations were made with uredospore generations successively produced on and inoculated to BYMV‐infected leaves.

Uredospore germination and germ tube length were similar on virus‐free and BYMV‐infected leaves and on agar seeded with spores produced for one or several generations on BYMV‐infected or virus‐free plants. Formation of appressoria was slightly reduced on BYMV‐infected leaves but changes in the post‐penetration development of the rust probably accounted for much of the decreased pustule production encountered.
The timing and sequence of events leading to stem canker disease in populations of Brassica napus var. oleifera in the field
Authors: HAMMOND KIM E. , LEWIS B. G.
Published: April 2007

Natural epidemics of Leptosphaeria maculans in cultivated populations of Brassica napus var. oleifera were predominantly monocyclic, involving a sequence of five phases; latent infection of the lamina, leaf lesion expression, symptomless systemic growth down the petiole, latent infection of the stem, and stem canker development. This sequence potentially terminated in severe stem cankers if initiated from ascospore infection of any leaf between a plastochron index of PI =n+ 0.5 and n+1.0 until plant growth stage 3.1 of the Harper & Berkenkamp scale. At PI < n+ 0.5, infection was rare and at PI > n+ 1.0, the infection sequence was usually terminated by leaf abscission. Differential effects of ambient temperature on the rates of progress of infection and leaf development determined whether abscission occurred before infection reached the stem. Based on these interrelationships, a system for predicting the incidence of severe stem cankers is proposed.
Evaluation of selective media and bait methods for estimating Phytophthora cactorum in apple orchard soils
Authors: HARRIS D. C. , BIELENIN ANNA
Published: April 2007

Soil plating, with a specially devised selective medium, gave estimates of Phytophthora cactorum in an East Mailing Research Station apple orchard soil up to three times those obtained by dilution and baiting with apple seedlings or cotyledons and using the most probable number analysis.

When the same techniques were applied to a range of soils from apple orchards in south‐east England with a history of P. cactorum diseases the plating method failed in most instances, mainly because Pythium spp. rapidly swamped the plates. The dilution/baiting method was applicable to all soils though there was a tendency to underestimate because of anomalous results at lower soil dilutions.

Oospores were the only propagules which could be confirmed as sources of P. cactorum colonies on soil isolation plates.
Wind dispersal of conidia of Botrytis spp. pathogenic to Vicia faba
Authors: HARRISON J. G. , LOWE R.
Published: April 2007

Increasing numbers of conidia were blown from sporulating cultures of Botrytis fabae and B. cinerea as windspeed increased up to 10 m/s. Partial drying of cultures increased the number of spores blown away at low and intermediate windspeeds. Release of spores at a constant windspeed was sustained over a prolonged period. Different patterns of release from colonies of the two species when windspeed was gradually increased, or at a constant windspeed. may be related to differences in spore size affecting the drying rate. Many conidia of both species were released as clumps. A higher proportion of B. cinerea than B. fabae conidia were clumped, partly because the mean number of spores per clump was greater. Individual conidia fell more slowly in still air than did clumps. The humidity in a bean crop was more favourable to development of Botrytis lesions than that above the crop. Low windspeeds measured within crops may restrict dispersal of conidia and may result in uneven distribution of chocolate spot lesions.
Transmission of Fusarium graminearum from seed to stems of winter wheat
Authors: DUTHIE J. A. , HALL R.
Published: April 2007

Infection of stem bases of winter wheat by Fusarium graminearum was directly related to the incidence of infection of seed at planting. The efficiency of transmission of the pathogen from seed to stem ranged from 55 to 94% over four sampling dates in two trials. The incidence of infection of stem bases did not increase between autumn and the following summer, indicating that all transmission occurred during the autumn. Per cent germination of seed and stand density decreased as the incidence of infected seed increased.
The occurrence of three viruses in hop (Humulus lupulus) in China
Authors: YU J , LIU Y
Published: April 2007

Forty‐two percent of leaf samples taken from hop cv. Qingdao Dahua growing in plantations in northeastern China in 1983‐1984 were infected with hop mosaic virus (HMV) and/or hop latent virus (HLV). Mosaic or line‐pattern symptoms were seen in some plants but only in spring and it is uncertain if the symptoms were caused by either virus which appeared in our studies to be similar, both serologically and in host range, to HMV and HLV described in Europe and North America. In host range studies, HMV infected Nicotiana clevelandii systemically without inducing symptoms. Occasionally it caused chlorotic spots in the inoculated leaves of Chenopodium quinoa and brown star‐point lesions in inoculated leaves of Phaseolus vulgaris cv. Topcrop, The virus was purified by PEG precipitation from extracts of N. clevelandii plants; yields were about 40‐120 mg/kg fresh leaves. The virus contained a single protein (estimated molecular weight 34 200) that was estimated to contain 272 amino acids with no methionine, and a single RNA species (estimated molecular weight 295 x 106) that represented c. 6% of the particle weight. HLV sometimes caused inconspicuous chlorotic spots in inoculated leaves of C. murale and local pinpoint lesions in P. vulgaris in winter only. A virus similar to alfalfa mosaic virus was isolated from leaves of hop cv. Golding and caused systemic necrotic symptoms in C. quinoa and C. amaranticolor, and systemic chlorotic spots in hop cv. Styrian.
Diagnosis of potato virus YN: a comparison between polyclonal and monoclonal antibodies and a biological assay
Authors: ROSE D. G. , McCARRA SUSAN , MITCHELL D. H.
Published: April 2007

In an investigation conducted over 5 years, tests of samples from the Scottish Seed Potato Classification Scheme showed that when monoclonal antibodies (McABs) were used with the enzyme‐linked immunosorbent assay (ELISA), they reliably detected the tobacco veinal necrosis strain of potato virus Y (PVYN). Polyclonal antibodies used in the first 3 years of the investigation were unreliable in differentiating PVYN from the ordinary strain (PVYN). It is suggested that ELISA and McABs be routinely used to diagnose PVYN and that all samples which give negative results be further assayed biologically to identify the virus or to indicate strains of PVYN not detectable by the McAB. Problems encountered with both assay systems are discussed.
Symptom remission in spiked sandal trees by infusion of tetracycline antibiotics
Authors: ALI M. I. MOHAMED , BALASUNDARAN M. , GHOSH S. K.
Published: April 2007

Spike disease of sandal has recently been recorded in Kerala. For chemotherapy of the diseased trees a gravity‐flow infusion technique was used to compare tetracycline compounds. All the compounds, including doxycycline and oxytetracycline, were effective when 500 mg per tree was infused in 500 ml water, but disease remission lasted for 4 months only. Repeated infusions failed to give complete remission. Increasing the concentration of tetracycline to 4–8 g per tree gave remission for 7–8 months; at 12 g per tree, phototoxicity was observed.
The establishment of systemic infection in leaves of oilseed rape by Leptosphaeria maculans
Authors: HAMMOND KIM E. , LEWIS B. G.
Published: April 2007

In a series of growth room experiments in which leaves of Brassica napus var. oleifera were inoculated with ascospores or pycnidiospores of Leptosphaeria maculans successful infections progressed through three consecutive phases. Initial establishment in the mesophyll was succeeded by a phase of intercellular exploration, when hyphal proliferation was highly variable and host cell necrosis always ensued, and then by a systemic phase when hyphae were consistently sparse. Host cells associated with the hyphal front were capable of autofluorescence, accumulation of vital stains and plasmolysis, indicating that they were viable and that the pathogen was biotrophic throughout this sequence. During either of the first two phases permanent fungistatic containment, involving the formation of vesicles by disintegration of the hyphae, often occurred. Localization at the first phase was symptomless; at the second it was signified by a lesion with a clearly defined margin.

There was a negative correlation between biotrophic potential and necrotrophic potential of three pathogenic isolates, on both the moderately susceptible cultivar Primor and the resistant cultivar Jet Neuf. As leaves aged, a progressively larger proportion of infections failed to become systemic. With increasing inoculum load, symptomless localization of infection diminished, the phase of necrosis extended, and the probability of irreversible systemic development increased.
Effects of barley yellow dwarf virus on some varieties of Italian, hybrid and perennial ryegrasses and their implication for grass breeders
Authors: CATHERALI P. L. , PARRY ANNE L.
Published: April 2007

With the exception of chlorotic streaks in a few plants, a severe strain of barley yellow dwarf virus (BYDV) transmitted by Rhopalosiplum padi caused no obvious foliar symptoms in 54 varieties of ryegrass when they were defoliated monthly. When defoliation ceased and yellow or red discoloration of the leaf tips was allowed to develop, it was a poor indicator of the seventy of disease effect on yield. Thus, some varieties which developed marked discoloration were less severely damaged than some with little or none While BYDV induced yield significant in some varieties of ryegrass, it increased it significantly in others. In some varieties these BYDV‐induced yield increases occurred throughout the year, but in others they occurred in 1 month and were offset by a yield decrease in another. BYDV infection caused a greater yield reduction in roots than in shoots. Even varieties giving increased shoot yield gave decreased root yield. The possible disadvantages of the resulting increase in shoot to root ratio are discussed. It is concluded that breeding ryegrass for BYDV‐induced yield increases may be easier and more rewarding than breeding for resistance or tolerance.
Sumatra disease in cloves induced by a xylem‐limited bacterium following mechanical inoculation
Authors: HUNT PETER , BENNETT CHRIS P. A. , SYAMSU HILMA , NURWENDA ENDANG
Published: April 2007

Suspensions of a Gram negative, non motile nutritionally fastidious bacterium, cultured from clove trees affected by Sumatra disease and inoculated by needle puncture into the xylem of seedling cloves and young trees, caused the death of over 60% of the plants withing 2 year. Bacteria, confined to zylem vesssels, occurred throughout the vascular systems of dying plants and were also still active in some of the plants which survived for 3 years after inoculation. Bactria resembling those used as inoculum were readily reisolated form dying plants but not from any water‐treated controls. Symptoms in experimental plants and the appearance and distribution of vessels occluded by bacteria were indistinguishable from those resulting from natural infection. All clove types tested were susceptible, including progeny from trees which had survived past disease attack. Result suggest the importance of using vigorously growing plants and providing protection against full sunlight during incubation for the successful establishment of beacterial infection in juvenile clove plants follwing mechanical inoculation.
Detection of a mycoplasma‐like organism in peanut plants with witches' broom using indirect enzyme‐linked immunosorbent assay (ELISA)
Authors: HOBBS H. A. , RKDDY D. V. R. , REDDY A. S.
Published: April 2007

The mycoplasma‐like organism (MLO) associated with peanut (groundnut) witches’ broom (PWB) from India was partially purified and an antiserum produced against it. Using a protein A indirect enzyme‐linked immunosorbent assay (ELISA) procedure, PWB MLO was detected in crude extracts of leaves. stems and pegs of infected peanut plants, although stems were a better source than leaves and pegs. Extracts of infected tissues of three diseases of assumed MLO etiology in India, little leaf of brinjal (eggplant). I med rosed witches “broom, and Daturd sp. witches’ broom, failed to react with the PWB MLO antiserum.
Programming applications of dicarboximides to control bunch rot of grapes caused by Botrytis cinerea
Authors: NAIR N. G. , EMMETT R. W. , PARKER F. E.
Published: April 2007

When grapevine plants in a glasshouse were artificially inoculated with Botrytis cinerea and then treated with dicarboximides at different stages of bunch development, treatment at 80% cap‐fall, with or without treatment before bunch closure, gave significantly better control than treatment at 3 weeks before harvest. In field trials, early applications of procymidone reduced natural infection by B. cinerea better than late applications. Spray application at pre‐bloom followed by a second application during bloom is recommended. Procymidone, vmclozolin and iprodione at 1 g/l were significantly more effective in controlling natural infection than dichlozolinate, benomyl, captan, chlorothalonil and copper oxychloride.
Pepper yellow vein, a new disease of sweet peppers
Authors: FLETCHER J T , WALLIS W. A. , DAVENPORT F.
Published: April 2007

A new disease of peppers (Capsicum annuum) is described. The most characteristic symptom is vein yellowing of the youngest leaves. Some streaking occurs on the first‐formed fruits. The symptoms were reproduced in pepper plants cv. Bellboy by graft and Olpidium transmission. Most pepper cultivars tested were susceptible but some appeared to he resistant. The disease had no effect on fruit weight.
Interactions between Globodera pallida juveniles, Verticillium dahliae and three potato cultivars, with descriptions of associated histopathologies
Authors: STOREY G. W. , EVANS K.
Published: April 2007

Experiments carried out in agar culture showed that the potato cultivar Pentland Javelin is relatively resistant to infection by Verticillium dahliae because it has a multilayered cortex of thick‐walled cells, each producing lignituber appositions to invading hyphae. Its thick‐walled xylem vessels are difficult to penetrate, its large vessel lumens difficult to obstruct, and its ability to produce tyloses limits the spread of the fungus, By comparison. Maris Anchor roots have fewer cortical layers and very small xylem vessels which are more easily blocked by hyphae. Maris Peer is intermediate in both the number of cortical cell layers and the size of xylem vessels. Globodera pallida juveniles assist V. dahliae to evade the natural defences of the root by opening an invasion channel for the fungus. In Maris Anchor and Maris Peer, but not in Pentland Javelin, the nematode provokes a widespread hypersensitive response; the resulting cell wall lignification impedes the growth of those hyphae which invade several days after the nematode. Hyphae grow well in syncytia and this enhances the probability of their penetrating xylem vessels. Although V. dahliae is generally held to induce symptoms through xylem blockage, the phloem colonization which was noted may affect the growth of both plant and nematode through its effect on assimilate movement towards root lips and into syncytia.
Assessment of upward movement of rain splash using a fluorescent tracer method and its application to the epidemiology of cereal pathogens
Authors: SHAW M. W.
Published: April 2007

To help understand inoculum transport in splash‐dispersed cereal pathogens, the pattern and extent of upward movement of splash droplets produced by rain was measured using a ‘splashmeter’. This comprised a cylinder of chromatography paper arranged vertically at the centre of an annular reservoir containing UV‐fluorescent cellulose‐binding dye. Natural rainfall from April to August 1985 was examined over grass and, latterly, in a wheat crop; artificial rain generated in a rain tower was used for controlled experiments. The decay in proportion of droplets reaching a given height corrected to equivalent receptor areas was exponential above 5–10 cm. The height at which equivalent areas of receptor were covered with dye was strongly dependent on the drop size spectrum of the incident rainfall, rising when larger drops were present. Presumably because of this, the results show that splash height could not be predicted from data on rainfall volume rate alone. Field observations suggested that a sudden outbreak of Septoria tritici lesions in a wheat crop could be related to unusually great upward transport of rain splash detected 3 weeks earlier by the splashmeter.
The effect of film‐forming anti‐transpirants on leaf rust and powdery mildew incidence on wheat
Authors: ZIV O. , FREDERIKSEN R. A.
Published: April 2007

Various film‐forming anti‐transpirants effectively controlled leaf rust and powdery mildew on wheat in the field. Two applications of anti‐transpirant emulsions applied after flag leaf emergence were sufficient to suppress leaf rust and powdery mildew on wheat leaves. When applied before, but not after, inoculation anti‐transpirant polymers also reduced leaf rust on seedling plants in a growth room experiment.
Effect of fosetyl aluminium and captafol* on red core disease and fruit yield of established strawberries
Authors: O'NEILLWG T. M. , GRIFFIN W.
Published: April 2007

Fosetyl‐Al applied once, as a spray in the autumn after fruit picking, gave very good disease control and significantly increased the number of healthy roots and marketable fruit yield in 2‐year‐old strawberry plants. ev. Redgauntlet. Fosetyl‐AI applied twice, after fruit picking and in spring, further increased the number of healthy roots, but yields were not significantly better than the single treatment. A half‐rate spray of fosetyl‐Al plus a half‐rate drench of captafol applied after picking and in spring gave good disease control and a yield significantly better than all other treatments. In the same crop the following year, both of the twice‐yearly treatments gave a significant reduction in red core recorded in September and the two‐fungicides treatment gave a significant increase in fruit yield. In a second trial, a half‐rate spray of fosetyl‐Al plus a half‐rate drench of captafol applied after picking and in spring again gave good disease control and significantly increased fruit yield. Timing fungicide application, both after fruit picking and in spring according to root development (5 mm or 15–20 mm), had no effect on the level of red core control and little effect on fruit yield. The half‐rate fosetyl‐Al plus half‐rate captafol treatment was significantly less effective when captafol was applied as a spray rather than as a drench.