bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic variation in tolerance of host monoterpenes in a population of the ascomycete canker pathogen Crumenulopsis sororia
Authors: ENNOS R. A. , SWALES K. W.
Published: April 2007

Twenty families of single‐ascospore isolates of the canker pathogen Crumenulopsis sororia were collected from eight trees of Pinus sylvestris in a native pinewood. Measurements were made of growth rate of each isolate in the presence and absence of a saturating atmosphere of the five principal monoterpenes of P. sylvestris cortical oleoresin (α‐pinene, β‐pinene, 3‐carene, β‐myrcene and limonene).

All monoterpenes significantly reduced the mean linear growth rate of the C. sororia population. However, there was highly significant genetic variation among isolates in their tolerance of all five monoterpenes. The extent of genetic variation was greatest for β‐myrcene and limonene tolerance, and least for α‐pinene and 3‐carene tolerance. Significant positive correlations between tolerance of different monoterpenes were found, implying the presence of tolerance mechanisms common to a range of compounds.
Development of the teleomorph of non‐self‐anastomosing isolates of Rhizoctonia solani by a buried‐slide method
Authors: HYAKUMACHI M. , UI T.
Published: April 2007

A buried‐slide method of inducing teleomorph development was compared with a soil method for isolates of Rhizoctonia solani in anastomosis group 2. The teleomorph (Thanatephorus cucumeris) developed frequently in the buried‐slide method. For non‐self‐anastomosing isolates, which cannot grow through soil, the teleomorph was observed only in the buried‐slide method. One of the five soils tested was particularly favourable. The buried‐slide method allows easy examination of the teleomorph with minimum disturbance to the hymenium. It has demonstrated the identity of non‐self‐anastomosing isolates with T. cucumeris.
Pathogenic variability amongst isolates of Crinipellis perniciosa from cocoa (Theobroma cacao)
Authors: WHEELER B. E. J. , MEPSTED R.
Published: April 2007

Dry witches' brooms from cocoa were imported from various areas within Bolivia, Brazil, Colombia, Ecuador, Trinidad and Venezuela. Basidiocarps of Crinipellis perniciosa were induced to form on these brooms and seedlings of different types of cocoa were inoculated with basidiospores either on the hypocotyl or cotyledon bud. Host reactions were assessed mainly by recording stem base swelling and broom development at the cotyledon node (hypocotyl inoculations) or the extent of swelling and branching of shoots (cotyledon bud inoculations).

Results from 30 experiments indicated considerable diversity amongst isolates in inducing disease symptoms, but suggested that two groups or populations of C. perniciosa exist on cultivated cocoa. One group (A), comprising isolates from Bolivia and Pichilingue (Ecuador) and most isolates tested from Colombia, induced severe symptoms on cocoa with Scavina 6 as one parent; the other group (B), comprising isolates from Brazil, Trinidad and Venezuela, did not. Within these groupings variants could be further distinguished by particular host reactions. Isolates from Ecuador, especially from the Oriente, a centre of diversity for Theobroma cacao, showed a range of pathogenicity comparable to that found amongst isolates from cultivated cocoa over a much wider area.
Growth rates of, and mycelial interactions between, isolates of Crinipellis perniciosa from cocoa
Authors: McGEARY F. M. , WHEELER B. E. J.
Published: April 2007

Growth of 87 single‐basidiospore isolates of Crinipellis perniciosa, derived from witches' brooms on cocoa in 10 localities throughout South America and the Caribbean, was examined at 25°C on five agar media (Czapek‐Dox, prune extract, potato‐dextrose, V8 and carboxymethylcellulose). Interactions (designated intermingling or mutually antagonistic) between paired mycelia of 64 isolates were determined on V8 plates.

Six somatic‐compatibility groups were identified comprising isolates from; (1) Pichilingue and Rio Palenque in Ecuador, Chigorodo and Manizales in Colombia; (2) Sucua (Ecuador); (3) Manaus (Brazil); (4) Ouro Preto (Brazil); (5) Castanhal (Brazil); (6) Trinidad and Tobago. This geographical separation of isolates was supported by results of the growth tests; growth of isolates within each compatibility group differed from other groups on at least one of the five media.

Separation of isolates by these methods did not conflict with previous results from tests of pathogenicity and could be useful in selecting isolates for screening cocoa lines for resistance to C. perniciosa.
Long‐term effect of soil solarization in controlling verticillium wilt of globe artichokes in Greece
Authors: TJAMOS E. C. , PAPLOMATAS E. J.
Published: April 2007

Soil solarization, either singly or in combination with a reduced dosage (34 g/m2) of methyl bromide, was effective in controlling verticillium wilt of globe artichokes for three successive cropping seasons. Both treatments resulted in greatly reduced natural populations of Verticillium dahliae microsclerotia, which were positively correlated with significant reductions in diseased plants as well as with the early formation of primary artichoke heads and increased yield. Propagules of Talaromyces flavus increased and survived better in solarized than in solarized and fumigated soils and could be partially involved in the effectiveness of solarization. Propagules of Aspergillus terreus invariably increased in treated plots but their involvement in the longevity of the treatment is questionable.
Effect of potato physiology on the interpretation of ELISA results for potato leafroll virus
Authors: GUNN L. V. , PARES R. D.
Published: April 2007

This paper records the occurrence of an antigen produced in plants infected by potato leafroll virus (PLRV), which is copurified with the virus and induces an immune response in rabbits used for virus antiserum production. The antigen also appeared to be produced in uninfected but physiologically stressed potato plants. These plants reacted with antisera to PLRV in ELISA tests, thereby giving false positive results. We refer to the compound as virus‐stress antigen (VSA). The importance of this finding, not only to serological testing for PLRV, but also as a possible explanation for some false‐positive reactions that occur with other host‐virus combinations, is discussed. The necessity of having detailed information on plants from which samples are taken for testing is emphasized.
Application of alginate gel for protection of wounds against crown gall (Agrobacterium tumefaciens)
Authors: DEACON J. W. , MacDONALD R K. W. , FOX F. M. , LASCARIS D.
Published: April 2007

In glasshouse and laboratory experiments, calcium alginate gel, produced in situ on wounds by successive dipping in solutions of sodium alginate and CaCl2 gave significant protection against infection by pathogenic isolates of Agrobacterium tumefaciens on carrot discs, tomato cuttings and chrysanthemum cuttings. Gel protection was sometimes equal to that given by strain K84 of A. radiobacter and also operated against a pathogenic isolate insensitive to control by strain K84. Sodium alginate or CaCl2 alone gave little or no protection, suggesting that calcium alginate acted by physically excluding the pathogen from wound surfaces. The use of the method described is discussed for delivery of biological or chemical control agents to plant surfaces whilst also providing protection in its own right.
Quantitatively expressed resistance to anthracnose (Colletotrichum gloeosporioides) in Stylosanthes scabra
Authors: CHAKRABORTY S. , CAMERON D. F. , IRWIN J. A. G. , EDYE L. A.
Published: April 2007

Nineteen accessions of Stylosanthes scabra that had low terminal severities of anthracnose in the field were evaluated for their response in the glasshouse using four isolates representing three different races of Colletotrichum gloeosporioides. Accessions could be allocated to one of three groups: one showed a higher disease severity after inoculation with isolate UQ14 compared to the other isolates; the second showed a higher severity after inoculation with isolates WRS32 and/or WRS20 compared to isolates SR4 and UQ14, and the third group showed moderate to low disease severities following inoculation with all four isolates. Based on reduced disease severity and compatible infection types, a set of six accessions was selected from the three groups for further testing, two of which showed no significant difference in their response to the four isolates. Two components of resistance, incubation period and infection efficiency were studied in the selected accessions. Of these, incubation period appeared unrelated to the expression of resistance. Criteria for identifying this form of quantitatively expressed resistance are discussed.
The identification of a gene for race‐specific resistance to Peronospora parasitica (downy mildew) in Brassica napus var. oleifera (oilseed rape)
Authors: LUCAS J. A. , CRUTE I. R. , SHERRIFF CHRISTINE , GORDON PAMELA L.
Published: April 2007

The oilseed rape cultivar Cresor was resistant to 14 isolates of Peronospora parasitica derived from crops of Brassica napus in the UK. Segregation for resistance to one isolate among F2 plants and F3 progeny of crosses between Cresor and the susceptible cultivars Victor and Jet Neuf indicated that resistance was controlled by a single gene. There was evidence that genetic background and environment could influence the phenotypic expression of this resistance. Two sexual progeny isolates derived from a homothallic isolate of P. parasitica avirulent on Cresor were completely virulent on this cultivar. This suggested that the parental isolate was heterozygous at a matching locus or loci for avirulence and demonstrated the race‐specific nature of the resistance.
Survival and dispersal of a marked strain of Pseudomonas syringae in a maple nursery
Authors: MALVICK D. K. , MOORE L. W.
Published: April 2007

A pathogenic Pseudomonas syringae strain resistant to rifampicin and nalidixic acid was sprayed upon and colonized maple twigs and perennial ryegrass. The inoculated twigs were sampled at intervals of 2‐3 weeks from July 1985 to September 1986, and epiphytic populations of the marked strain recovered during this time ranged from undetectable to 104 colony‐forming units/g. The results showed that this strain of P. syringae could overwinter on maple twigs and potentially serve as a source of inoculum in the spring. Aerial dispersal was also investigated. The marked strain inoculated onto grass growing in pots was detected on medium in inverted petri plates, on maple leaves and with an Andersen sampler positioned from 12 to 100 cm above the grass. The number of detectable cells that dispersed vertically upwards was low even in the presence of wind, rain, or irrigation water. The marked strain inoculated onto maple branches was isolated from grasses under the inoculated trees, showing that P. syringae was dispersed downward. Lateral dispersal of the marked strain from inoculated to uninoculated trees was not detected. The identity of the antibiotic‐resistant strain isolated from the trees and grasses was confirmed by DNA restriction‐fragment profile analysis.
Monilinia laxa associated with blossom wilt of apricot and almond in Himachal Pradesh, India
Authors: GUPTA G. K. , BYRDE R. J. W.
Published: April 2007

Blossom wilt, an important phase of the brown rot disease, resulting in crop losses in apricot and almond, is reported for the first time from North India. Based on general morphology, cultural and sporulation characteristics, and isoelectric focusing profiles, the causal fungus was identified as Monilinia laxa.
Occurrence of a strain of eggplant mottled crinkle virus in Solanum capsicastrum in India
Authors: RAJ S. K. , SRIVASTAVA K. M. , ASLAM M , SINGH B P
Published: April 2007

Leaf crinkle symptoms, stem necrosis and stunting were observed in Solanum capsicastrum plants in India. A virus was isolated from these plants and identified as a strain of eggplant mottled crinkle virus based on host reactions, in vitro properties, icosahedral particle morphology, buoyant density (1.39 g cm3), molecular weight (41 ± 0.5 kDa) of coat protein subunits and serological relationships
NEW HONORARY MEMBER OF THE BRITISH SOCIETY FOR PLANT PATHOLOGY
Authors: Wood R. K. S.
Published: April 2007

Council of the British Society for Plant Pathology has much pleasure in announcing that it has conferred Honorary Membership of the Society on Emeritus Professor R. K. S, Wood, FRS
Comparison of resistance‐inducing abilities of virulent and avirulent races of Erysiphe graminis f.sp. hordei and a race of Erysiphe graminis f.sp. tritici in barley
Authors: THORDAL‐CHRISTENSEN H. , SMEDEGÅRD‐PETERSEN V.
Published: April 2007

Resistance to powdery mildew was induced in barley by preinoculation with virulent and avirulent races of barley powdery mildew (Erysiphe graminis f.sp. hordei), and with a race of wheat powdery mildew (E. graminis f.sp. tritici). Four inducer densities were tested in 13 different induction periods between 1 and 24 h. Generally, the resistance induced by barley powdery mildew increased up to 10‐12 h of induction and was maintained in longer induction periods. The inducing abilities of virulent and avirulent races could not be distinguished up to 10‐12 h of induction, after which the inducing ability of avirulent races increased significantly in relation to virulent races. Wheat powdery mildew was able to induce more resistance than barley powdery mildew in induction periods up to 8 h. In a single inoculation procedure the number of haustoria developing from virulent barley powdery mildew decreased as inoculum density increased. The effect was ascribed to induction of resistance. This reduction of infection efficiency in the compatible interaction was compared to induced resistance. However, the inoculum density needed for 50% resistance induction in the double inoculation procedure was approximately 40 times higher than the inoculum density needed for 50% reduction in infection efficiency in the single inoculation procedure.
Sporulation on infected tissues, and presence of airborne Verticillium albo‐atrum in alfalfa fields in New York
Authors: JIMÉNEZ DÍAZ R. M. , MILLAR R. L.
Published: April 2007

The phenology of Verticillium albo‐atrum (Vaa) sporulation on infected tissues and the presence of Vaa in the air were investigated in alfalfa fields affected by verticillium wilt (VW) during the 1983/84 growing season. Few and scattered Verticillium conidiophores developed on stubble by the end of May, but abundant Verticillium sporulation was found on necrotic leaflets and petioles by the beginning of June at the first appearance of symptoms. Abundant conidiophores developed also on necrotic stems and leaf tissues sampled later. Sporulation was never found on entirely green stems. Concentration of airborne colony‐forming units (cfu) of Vaa ranged from 0.0 to 15.3 cfu/m3 above fields with a VW incidence of 2.2‐33.0% in June and August, and from 5.9‐25.9 cfu/m3 during mowing of the crop in August. The ratio of Vaa to other airborne fungi above sampled fields was less than 5 x 10‐3, Airborne fungi were even more abundant at the time of mowing. Our results suggest that airborne V. albo‐atrum may not play an important role in the epidemiology of VW of alfalfa.
Quantitative histological studies of compatible and incompatible interactions between accessions of Macroptilium atropurpureum and Uromyces appendiculatus
Authors: OGLE H. J. , IRWIN J. A. G. , BRAY R. A.
Published: April 2007

Quantitative histological studies of pre‐penetration, penetration and post‐penetration events were made for one compatible interaction and five interactions showing varying degrees of incompatibility between Uromyces appendiculatus and Macroptilium atropurpureum. Four histologically different resistant responses to infection were observed, CPI 91348 exhibited a response, characterized by significantly fewer pustules per unit area and a longer generation time than the susceptible cultivar Siratro. Significantly fewer urediniospores produced appressoria on 91348 than on Siratro. Resistance in CPI 84997 was associated with the development of large areas of necrotic tissue; 99.8% of colonies showed an indeterminant hypersensitive response. Colony areas for the above three host genotypes were not significantly different at 144 h after inoculation.

The remaining lines developed varying degrees of chlorosis only. Colonies in CQ 1382 and (CPI 92643 grew only slowly, but were still growing 144 h after inoculation and, as with CPI 84997, this growth continued after necrotic tissue appeared (indeterminant hypersensitivity), In CQ 1398, colony growth ceased by 96 144 h after inoculation, coinciding with the appearance of necrotic tissue (determinant hypersensitivity).
Mechanisms of inhibition of Gaeumannomyces graminis var. tritici by fluorescent pseudomonads
Authors: BRISBANE P. G. , ROVIRA A. D.
Published: April 2007

The take‐all fungus Gaeumannomyces graminis var. tritici reduced the weight of wheat plants grown in tubes containing sterilized sand and plant nutrient solution. Fluorescent pseudomonads, when added to the tubes, inhibited the take‐all fungus and increased plant weight. Iron (as FeNaEDTA) had no effect on the inhibition of the fungus by the pseudomonads. Some of the pseudomonads produced a compound in the wheat rhizosphere with a UV absorption peak at 365 nm, but the inhibition of G. graminis by pseudomonads was not proportional to the UV absorbance of rhizosphere extracts. A yellow crystalline compound, absorbing at 365 nm, was extracted from broth cultures and shown to be toxic to G. graminis under acid conditions. This compound is considered to be phenazine‐I‐carboxylic acid.
Effects of treatments to perennial ryegrass on the development of Septoria spp. in a subsequent crop of winter wheat
Authors: JENKYN J F. , KING J. E.
Published: April 2007

An experiment started in spring 1979 tested the effects of different treatments to perennial ryegrass, established as pure stands or undersown in spring wheat, on the severity of septoria diseases on the grass and in a following crop of winter wheat, sown in autumn 1980. Other plots were fallowed in 1979 and 1980 before sowing to winter wheat, also in autumn 1980.

Septoria tritici was most severe in winter wheat after fallow and least severe in wheat that had been direct‐drilled after ryegrass. These effects were attributed to differences in amounts of available nitrogen, and consequent differences in crop growth, rather than to any differences in primary inoculum.

Symptoms attributed to S. nodorum on the ryegrass were more common where the grass had been established under spring wheat than where it had been sown as a pure stand. They also tended to be more common where ryegrass had been inoculated with spores of S. nodorum than where it had been sprayed with captafol. Similar effects on symptoms attributed to Septoria spp. (mostly S. tritici) on the wheat were apparent in July. The results support the conclusion that the greater severity of septoria diseases that often occurs on wheat after grass than after non‐graminaceous breaks, is probably due in part to survival of the pathogens on grass and, in some circumstances, on debris remaining from a previous wheat crop. However, other factors are also likely to be involved.
Agglutination response of the conidia of eight Fusarium species to lectins having different sugar‐binding specificities
Authors: CRISTINZIO G. , MARZIANO F. , GIANNATTASIO M.
Published: April 2007

The agglutinating effect of five lectins having different sugar‐binding specificities on the conidia of a variety of strains from eight Fusarium species was examined. Conidia of all the strains of F. solani and F. oxysporum were strongly agglutinated by concanavalin A and Helix pomatia agglutinin; D‐mannose (and D‐glucose) and N‐acetyl‐D‐galactosamine inhibited the agglutination induced by concanavalin A and Helix pomatia agglutinin, respectively. Conidia of the other species of Fusarlum examined (F. culmorum, F. sambucinum, F. graminearum, F. avenaceum, F. moniliforme and F. xylarioides) were not agglutinated by either lectin. No conidia from the Fusarium species were agglutinated by wheat‐germ agglutinin, potato lectin and Ulex europaeus agglutinin‐I. These results have provided some insight into the chemical nature of the outermost layer of Fusarium conidia and this information may be of taxonomic significance.
Inhibition of germination of sporangia of Peronospora hyoscyami by cation deprivation: the effects of substrate and chelating agents
Authors: JOHNSON G. I.
Published: April 2007

Germination of sporangia of Peronospora hyoscyami de Bary (tobacco blue mould) was affected by the germination substrate. Washed sporangia germinated freely in water on glass slides, but failed to germinate on agarose. Germination was reduced on detached tobacco leaves, being lower on cv. Hicks Q46 than on cv. ZZ100. Inhibition of germination by agarose was reversed by the addition to the inoculum of an extract obtained by centrifuging a suspension of non‐living, powdered torula yeast Candida utilis (Hennenberg) Lodder & van Rij. Yeast extract also improved germination in vivo. The siderophore rhodotorulic acid, the chelating agents ferric and sodium citrate, and riboflavin combined with calcium and magnesium salts, also stimulated germination of sporangia on agarose. The chelating agent ethylenediaminetetraacetic acid (EDTA) inhibited germination on glass slides. Inhibition by EDTA was partially reversed by the addition of ferric salts. The inhibition of germination by agarose and stimulation by additives may have been due to effects on the availability of cations to sporangia ofP. hyoscyami. The reduction in germination on tobacco leaves may have involved a similar mechanism.
Host responses to fungal penetration in Evysiphe graminis f.sp. hordei infections in barley
Authors: WRIGHT ALISON J. , HEALE J. B.
Published: April 2007

Resistance mechanisms restricting penetration and establishment were investigated in an incompatible interaction using an avirulent race CC/3 (BMV 1 + 4) of Erysiphe graminis f.sp hordei on barley cv. Athos (BMR 2 + 5) and a compatible interaction using the universal susceptible cv. Golden Promise (BMR 0). In both interactions: (i) auto‐fluorescence of the host cell wall occurred adjacent to the primary germ tube tip after 4 h, and by 10 h near to the appressorial germ tube; (ii) strongly fluorescing papillae developed after 12 h, being frequently associated with failed penetrations; and (iii) only 30% of the attempted penetrations from appressorial lobes resulted in an incipient haustorium at 16 h. Hypersensitive reactions occurred in cells with an incipient haustorium in 30% of appressorial penetrations on Athos, but only in 4% of those on Golden Promise. Twenty per cent of hypersensitively reacting cells in Athos appeared dead by 14 h using trypan blue (membrane exclusion test), compared with 5% for neutral red, suggesting that plasma membrane damage is an early event in the hypersensitive response. Haustorial death was associated with host cell death, but did not precede it; appressorial death occurred 2‐4 h after that of the host cell.
Botryodiplodia theobromae causing fruit rot of Annona muricata in Mauritius
Authors: LUTCHMEAH R. S.
Published: April 2007

Botryodiplodia theobromae is reported for the first time as a pathogen of Annona muricata. The fungus was isolated from severely rotted fruits in Mauritius and was shown to be pathogenic by inoculation of wounded fruits under controlled conditions.
Fungicide and nitrogen applications in relation to the improvement of disease control and yield in winter barley
Authors: JORDAN V. W. L. , STINCHCOMBE G. R. , HUTCHEON J. A.
Published: April 2007

In crops of winter barley, cvs Igri and Halcyon, crop structure and intensity of foliar diseases were altered by delaying the main top dressing of nitrogen until mid‐April. A single application of fungicide then was sufficient to decrease substantially the severity of fungal disease and improve grain yield at harvest.

Disease control and yield responses were greatest when fungicides were applied during a 3‐week period after the main nitrogen application in April. No additional yield benefits were obtained by making two fungicide applications at growth stage (GS) 31 and GS 39.
Armillaria species in northern Britain
Authors: GREGORY S. C.
Published: April 2007

Five species of Armillaria, A. borealis, A. cepistipes, A. ostoyae. A. mellea and A. lutea, were identified among 145 isolates collected from sites in northern Britain. Most of the collection sites were in coniferous woodland containing dead or dying trees and A. ostoyae, a well‐known pathogen of conifers, was the most frequently isolated species. Two species believed to be weakly pathogenic, A cepistipes and A. lutea, were also commonly found; the former has only rarely been recorded in Britain before. The significance of the records is discussed.
Peronospora on Phygelius aequalis compared with Peronospora sordida and Peronospora verbasci
Authors: HALL G. , HUMPHREYS‐JONES D. R.
Published: April 2007

Leaves of Phygelius aequalis cv. Yellow Trumpets were found to be infected with a species of Peronospora closely resembling the descriptions of P. verbasci and P. sordida. Comparison with herbarium specimens showed that there was little difference between the three fungi examined, collections on different hosts most probably representing special forms. The fungus on Phygelius is described, and is referred to P. sordida until species concepts in Peronospora have been more clearly established.
Occurrence of squash mosaic virus in melons in Greece
Authors: AVGELIS A. D. , KATIS N.
Published: April 2007

Squash mosaic virus (SqMV) was isolated from melon plants raised from imported seed. Virus identification was based on host range, aphid and seed transmission tests, electron microscopy and serology. Seed testing by ELISA detected SqMV only in the cultivar Touralia imported from the USA.
Vegetative incompatibility in Pseudocercosporella herpotrichoides
Authors: HOCART M. J. , LUCAS J. A. , PEBERDY J. F.
Published: April 2007

Vegetative compatibility among 15 strains of Pseudocercosporella herpotrichoides and a strain of P. aestiva was assessed, using a range of sulphate non‐utilizing, nitrate non‐utilizing auxotrophic and morphological mutants. Selection for resistance to selenate and chlorate provided a system for the isolation of spontaneous sulphate and nitrate non‐utilizing mutants with relative ease. Other auxotrophic and morphological mutants were obtained after UV‐mutagenesis. Compatible interactions were identified by complementary growth at the interface between pairs of mutants with dissimilar phenotypes. While most strain combinations proved incompatible, compatible interactions were found in P. herpotrichoides between two unrelated W‐type strains and also between two unrelated R‐type strains. No complementation was observed between W‐type and R‐type strains or between P. herpotrichoides and P. aestiva.
Identification of W‐type and R‐type isolates of Pseudocercosporella herpotrichoides
Authors: CREIGHTON N. F.
Published: April 2007

W‐type isolates of Pseudocercosporella herpotrichoides grown on a maize‐based agar and exposed to near‐ ultra‐violet radiation at c. 13°C produced a greenish black colour, whilst R‐type isolates produced a pink or pale brown colour in the agar medium. More colonies from directly plated lesions or from spore suspensions could be recognized as P. herpotrichoides and could be more easily differentiated as W‐type or R‐type or as mixtures of both by colour production on maize agar (MA) than by colony morphology on potato dextrose agar (PDA), despite the presence of other fungi. Isolates with intermediate morphology on PDA were positively identified as W‐type or R‐type on MA; their pathogenicities to wheat and rye seedlings were usually similar to those of W‐type or R‐type isolates with typical colony morphology, confirming their identification on MA. Drops of mixed suspensions of W‐type and R‐type spores on PDA formed fast‐growing colonies with smooth margins which sometimes had slow‐growing sectors with feathery margins. Drops of the same mixtures on MA formed greenish black colonies which sometimes had pink or pale brown sectors. However, when these mixtures were spread onto MA, W‐type and R‐type colonies could easily be differentiated by colour.
Control of Glomerella cingulata f.sp. camelliae with fungicides
Authors: COOK R. T. A.
Published: April 2007

A critical test of fungicidal activity against the wound pathogen Glomerella cingulata f.sp. camelliae on camellias involved the application of a conidial suspension to scratches on detached leaves, treated with fungicide 24 h previously. In this test, prochloraz at 250–500 μg/ml a.i. in both EC and manganese WP formulations was highly effective, inhibiting leaf rotting by 90–100% compared with 55% or less in some tests with benomyl, chlorothalonil and captafol at 500–1000 μg/ml and captan at 1200 μg/ml. Prochloraz gave similar protection to leaves when applied to whole plants. Protection was less, especially on older leaves, when wounding and inoculating were delayed by 7 or more days after treatment. Prochloraz did not prevent all infection through comparatively large wounds, e.g. leaf scars, made on stems 24 h after treatment.

Poor control of the disease in a nursery was not due to resistance of the pathogen to benomyl; in vitro tests failed to detect full resistance at this time. Under nursery conditions a statutory policy of destroying infected plants and spraying the remainder with prochloraz or prochloraz manganese (both at 500 μg/ml), alternating with benomyl (500 μg/ml) on a weekly basis apparently prevented spread of the disease to healthy plants.
Isolation and characterization of a potyvirus associated with bushy dwarf symptom in chickpea, Cicer arietinum, in India
Authors: ANJAIAH V. , REDDY D. V. R. , MANOHAR S. K. , NAIDU R. A. , NENE Y. L. , RATNA A. S.
Published: April 2007

A potyvirus that induced stunting and a characteristic bushy appearance at the apical region, due to proliferation of terminal branches with narrowed, reduced and deformed leaflets, was isolated from chickpea in India. The virus was sap‐transmissible to 14 species of Chenopodiaceae, Leguminosae, Solanaceae and Malvaceae; Chenopodium amaranticolor was a good local lesion host. Virus particles, trapped by immunosorbent electron microscopy and stained with uranyl acetate, were 710 ×10 nm long. Purified virus preparations contained a single polypeptide species of 32,500 Da and one nucleic acid species of 3.1 · 106 Da. The virus was serologically related to soybean mosaic, azuki bean mosaic and peanut mottle viruses but not to clover yellow vein, pea seed‐borne mosaic and bean yellow mosaic viruses.

On the basis of these properties, the virus was identified as a previously undescribed potyvirus in chickpea, for which the name chickpea bushy dwarf virus is proposed.
Detection of beet cryptic viruses 1 and 2 in a wide range of beet plants using cDNA probes
Authors: XIE W. , ANTONIW J. F. , WHITE R. F.
Published: April 2007

The patterns of dsRNA bands separated by gel electrophoresis were used to analyse cryptic viruses in a wide range of beet plants, but uncertainties about the identities of some bands made the method unreliable. Four cDNA clones, each specific to one of the dsRNA genomic components of the beet cryptic viruses (BCVs) in sugar beet cv. Sharpes Klein E, were used in the analysis of Northern blots of a wide range of beet plants for the presence of BCV1 and BCV2. The presence of both viruses was demonstrated in sugar beetcvs Regina, Amethyst, Salohill and Bravo, red beet cv. Boltardy, leaf beet cv. Perpetual Spinach and fodder beet cv. Monofix, but only BCV1 or a closely related virus was found in Beta maritima. Beet temperate virus (BTV) from Japanese leaf beet was shown to have nucleic acid sequences in common with BCV1 from sugar beet cv. Sharpes Klein E.
Severe mosaic caused by zucchini yellow mosaic virus in cucurbits from Jordan
Authors: AL‐MUSA A. M.
Published: April 2007

A virus disease causing severe mosaic in melon (the melon isolate) was identified as a strain of zucchini yellow mosaic virus (ZYMV). Identification was based on host range, aphid transmissibility, electron microscopy, and serological tests. The virus was recovered from all cultivated cucurbits in Jordan and from naturally infected Moluccella laevis. It was seed‐transmitted in Ranunculus sardous. Host‐range comparison showed that the melon isolate and a French isolate belong to a different biotype group from a Connecticut isolate (ZYMV‐CT); this was confirmed by indirect ELISA. During 1987–1988. ZYMV appeared to be the predominant virus affecting cucurbits.
Flowering events in relation to smut susceptibility in pearl millet
Authors: THAKUR R. P.
Published: April 2007

In field experiments at ICRISAT, selected lines of pearl millet (Pennisetum glaucum) resistant and susceptible to smut (Tolyposporium penicillariae) were evaluated for the timing of flowering events. In smut‐resistant lines, the time from the boot‐leaf stage (inoculation) to stigma emergence varied in the range 46–120 h, from boot to anther emergence 105–190 h, and from stigma emergence to anther emergence (protogyny period) 59–131 h; in smut‐susceptible lines, the corresponding periods were 62–140 h, 146–200 h and 44–120 h, respectively. There were no significant correlations between timing of events and smut severity. Three cytoplasmically male‐sterile lines showed longer protogyny periods and higher smut severity than their corresponding maintainer lines. Four lines having short protogyny periods (22–52 h) and resistance to ergot (Claviceps fusiformis) also showed high resistance to smut. Resistance to smut in most ergot‐susceptible lines was independent of the timing of flow ering events, but in ergot‐resistant lines it could be closely related to flowering events.
Suppression of Septoria tritici and Puccinia recondita of wheat by an antibiotic‐producing fluorescent pseudomonad
Authors: LEVY E. , EYAL Z. , CARMELY S. , KASHMAN Y. , CHET I.
Published: April 2007

A fluorescent Pseudomonas sp. (strain LEC 1) isolated from soil suppressed Septoria tritici by 88% and Puccinia recondita by 98% when applied to wheat seedlings 3 h prior to inoculation with the pathogens. Fractionation and analysis of two inhibitory compounds from cultures of strain LEC 1 on thin‐layer chromatography plates yielded the phenazine antibiotics 1‐hydroxyphenazine (phOH) and chlorora‐phin. 1‐hydroxyphenazine reduced the growth of Pythium aphanidermatum, Fusarium oxysporum f.sp. vasinfectum, Sclerotinia sclerotiorum and S. rolfsii on a denned medium, with greatest activity against P. aphanidermatum and least against S. rolfsii. Application of 160 mg/l phOH to wheat seedlings reduced S. tritici by 61% and P. recondita by 75%. Lower concentrations of the antibiotic were less effective. Growth of 5. tritici in liquid medium was reduced by phOH at 5–20 mg/l and prevented at 40 mg/l. When phOH was added to the medium 48 h after inoculation (logarithmic growth phase), growth was interrupted but later recovered with phOH concentrations up to 40 mg/l; there was no recovery at 60 mg/l. Chlororaphin inhibited the growth of S. tritici on malt agar medium.
Effects of humidity and air speed on sporulation of Phytophthora infestans on potato leaves
Authors: HARRISON J. G. , LOWE R.
Published: April 2007

An apparatus is described for the control of humidity, air speed and temperature around detached potato leaflets and whole plants. Leaflets and plants inoculated with Phytophthora infestans were incubated in air at 15°C. Abundant sporangia were formed in an air speed of 0.3 × 10−3 m/s when the ambient humidity was 90–100% RH, but not at 85 or 80% RH. At air speeds of 5.5 × 10−3 and 13.7 × 10−3 m/s there were numerous sporangia at 100% RH, but not at 95–80% RH. The number of sporangia formed on leaflets kept in air flowing at 5.5 × 10−3 m/s with alternating humidities of 80 and 100% RH each for 12 h per day was intermediate between numbers formed on leaflets incubated at each humidity continuously, and higher than numbers formed at a constant 90% RH. Removing leaflets from plants before inoculation did not affect the number of sporangia produced.
Occurrence of Tapesia yallundae, teleomorph of Pseudocercosporella herpotrichoides, on unharvested wheat culms in England
Authors: HUNTER T.
Published: April 2007

Apothecia of Tapesia yallundae are reported for the first time in the UK. They were observed on decaying stems and leaf sheaths of unharvested wheat near Bristol in January 1989. Isolates from single ascospores produced cultures typical of the W‐type form of the anamorph, Pseudocercosporella herpotrichoides. Pathogenicity on wheat was confirmed by inoculation and re‐isolation from glasshouse‐grown wheat seedlings.
Watermelon necrosis caused by a strain of melon necrotic spot virus
Authors: AVGELIS A. D.
Published: April 2007

A severe disease of watermelon (Citrullus vulgaris) grown in plastic houses in Crete, was characterized by leaf and stem necrosis followed by death of the plants. A strain of melon necrotic spot virus (MNSV) was identified as the causal agent of the disease on the basis of biological, morphological and serological properties. The watermelon strain of MNSV induced only local necrotic lesions in melon and cucumber plants and was serologically distinct from MNSV Cretan isolate. Gomphrena globosa was found a useful herbaceous host for differentiating it from common isolates of MNSV.
Phytophthora katsurae from cocoa
Authors: LIYANAGE N. I. S. , WHEELER B. E J.
Published: April 2007

Phytophthora katsurae is reported for the first time from cocoa.
Races of rust (Puccinia antirrhini) of Antirrhinum majus and the inheritance of host resistance
Authors: AITKEN E. A. B. , NEWBURY H. J. , CALLOW J. A.
Published: April 2007

Fifty‐five isolates of P. antirrhini urediospores were collected from around the world. These isolates were used to inoculate the leaves of 10 cultivars of Antirrhinum majus. Two races of P. antirrhini were identified (α and β). None of the cultivars challenged exhibited resistance to isolates of Race β. Some cultivars were resistant to Race a. Resistance was inherited in a manner consistent with the existence of a dominant, nuclear allele at a single locus.
Histopathology of compatibility and incompatibility between oilseed rape and Albugo Candida
Authors: LIU Q. , RIMMER S. R. , SCARTH R.
Published: April 2007

Cotyledons of one resistant and three susceptible rape lines/cultivars were inoculated with zoospores of Albugo Candida race 7. Samples of whole cotyledons were examined by differential interference contrast microscopy. The time course of the infection process was followed histologically. Germination of zoospore cysts occurred 2‐3 h after inoculation. Infection was initiated with germ‐tubes penetrating through stomata. Haustorium formation was first observed in the palisade mesophyll cells adjacent to the substomatal chambers 8 h after inoculation.

Only after the establishment of the first haustorium did compatible and incompatible interactions begin to differentiate. In the resistant cultivar, most primary hyphae produced single haustoria. Necrosis of the invaded host cell was first observed 12 h after inoculation followed by cessation of fungal growth. The death of host cells was largely restricted to the penetration site; the adjacent non‐penetrated cells remained apparently unaffected. In the susceptible hosts, necrosis of infected cells occurred only infrequently, and hyphal growth continued unabated, resulting in mycelial ramification into the mesophyll. Numerous haustoria were produced.

Histological studies showed that the earliest event distinguishing a compatible from an incompatible interaction occurred after formation of the first haustorium and that resistance was not manifested until the host mesophyll cell had come into contact with the first haustorium. The distinction between compatibility and incompatibility was substantiated by quantitative analysis of white rust development on both resistant and susceptible lines/cultivars.
Serological and molecular evidence for the complexity of the leafroll disease of grapevine
Authors: TANNE EDNA , NAVEH LEA , SELA ILAN
Published: April 2007

Samples of leafroll‐infected grapevines from various countries, as well as local sources, were tested by ELISA with antisera against two closteroviruses (GVA and NY‐1) and a potyvirus (GPV) thought to be associated with leafroll. Many of the samples reacted positively with more than one antiserum, and often with all three. Positive reactions with GPV antiserum were corroborated by molecular dot‐blot hybridization. One of the closteroviruses, grapevine virus A (GVA) was originally isolated from a grapevine affected by stem‐pitting; furthermore, a grapevine with stem‐pitting reacted positively with all three antisera, and with a potyvirus probe by dot‐blot hybridization. All the leafroll‐diseased vines reacted, at least in some tests, with one or more of the antisera. Hence, in spite of the complexity of this syndrome, healthy and diseased grapevines could be distinguished.
Histological studies of the expression of the Lr9, Lr20 and Lr28 alleles for resistance to leaf rust in wheat
Authors: SOUTHERTON S. G. , DEVERALL B. J.
Published: April 2007

The development of the leaf rust fungus (Puccinia recondita f.sp. tritici) in a susceptible cultivar and three other cultivars possessing the Lr9, Lr20 and Lr28 alleles for resistance was studied by light and fluorescence microscopy. Formation of the substomatal vesicle, intercellular hypha and the first haustorial mother cell was unaffected by resistance. Lr9 and Lr28 expression was rapid, first seen as early initiation of hyphal branching at 16 h after inoculation, then reduced haustorial diameters at 19 h. Limited host cell necrosis was seen immediately afterwards. Elongation of intercellular hyphae was reduced between 20 and 24 h, and virtually ceased by about 30 h. Numbers of infection sites with a second haustorial mother cell were briefly higher at 24 h. Reduced hyphal branching and haustorial mother cell numbers were seen at 20–24 h and 36 h respectively. Lr20 expression was not seen until 36 h when reduced hyphal branching was observed, accompanied by extensive host cell necrosis. Reduced haustorial mother cell numbers were detected at 48 h. Findings suggested a secondary role for host cell necrosis in the expression of the Lr9 and Lr28 alleles. Host necrosis may play a determinant role in Lr20‐based expression.
The assessment of partial resistance to powdery mildew disease in hops
Authors: DARBY P. , MANSFIELD J. W. , GODWIN J. R.
Published: April 2007

Progeny comprising 1643 hop seedlings from crosses between eight partially resistant parents were screened under glasshouse conditions for resistance to a single pathotype of Sphaerotheca humuli. Results indicated polygenic inheritance of resistance. Genotypes representative of seedlings with ‘light’, ‘moderate’ and ‘severe’ infection from each family were transplanted to a hop garden where a natural epidemic of an introduced pathotype of powdery mildew developed. There was a significant positive association between amounts of disease on seedlings and on leaves of adult male plants, but no corresponding agreement between amounts of disease on female plants. A weak positive association was found between infection of seedlings in the glasshouse and subsequent cone infection in the field. Estimates of infection on leaves of adult plants and on cones were very closely associated. Partial resistance to powdery mildew was not associated with any deleterious agronomic or brewing quality characters.
The effect of calcium cyanamide on the reaction of swede cultivars to populations of Plasmodiophora brassicae
Authors: WILLIAMSON CYNTHIA J. , DYCE PATRICIA E.
Published: April 2007

The effect of using calcium cyanamide to control clubroot in four swede cultivars was examined in a field trial and two pot trials. Three populations of Plasmodiophora brassicae were used which differed in pathogenicity. The four swede cultivars showed a similar ranking for disease severity with all three pathogen populations; in intermediate environments which were neither very conducive nor unfavourable to disease development, resistance was expressed differentially.

Increasing the concentration of calcium cyanamide increased the yield of uninoculated plants, probably due to a response to nitrogen, but at the highest concentration (2.55 g/kg soil), yields were reduced due to phytotoxicity. In inoculated plants, disease severity was progressively reduced with increasing concentrations of calcium cyanamide. A higher inoculum density was required to initiate disease symptom development in the more resistant cultivars. Similarly, higher concentrations of inoculum were required to cause disease when increasing concentrations of calcium cyanamide were used. The effect of the chemical appeared to be to reduce the inoculum density. These data could be interpreted in terms of a disease threshold effect related to the number of viable pathogen propagules required to cause disease on particular host genotypes. The ways in which the breakdown products of calcium cyanamide may interact with host and pathogen are discussed in relation to disease development.
Occurrence of bacterial wilt of peanut (Arachis hypogaea) caused by Pseudomonas solanacearum and opportunistic infection of aibika (Abelmoschus manihot) in Papua New Guinea
Authors: TOMLINSON D. L. , MOGISTEIN M.
Published: April 2007

Pseudomonas solanacearum, the cause of bacterial wilt was isolated from stems, roots and developing cotyledons of peanut and the stem of a single aibika plant growing in a subsistence garden in Port Moresby. The garden had been cleared and planted to peanut after a fallow of at least 2 years. The bacterium could not be isolated from roots or rhizosphere soil of locally growing grasses and weeds, nor could seed transmission be demonstrated in peanut.
Twig and stem blight of cotton caused by Botryodiplodia theobromae
Authors: LAKSHMANAN P. , MOHAN S.
Published: April 2007

A twig and stem blight of cotton (Gossypium hirsutum) was observed in Tamil Nadu, India in 1977. The causal organism was isolated in pure culture and identified as Botryodiplodia theobromae, a first record of this species causing twig and stem blight on cotton. Typical fruit rot symptoms were produced on several inoculated fruits but not Citrus sp., Punica granatum or Achras sapota.
Shoot apex fasciation in Sesamum indicum associated with mycoplasma‐like organisms
Authors: TAMIMI K. M. , FATTAH F. A. , AL‐HAMDANY M. A.
Published: April 2007

Shoot apex fasciation was observed in sesame crops in central Iraq. The symptoms included flattening of the shoot apex, shortened internodes, and intense proliferation of leaf and flower buds. Mycoplasma‐like organisms were detected by electron microscopy in sieve elements of fasciated plants but not in normal plants. Plants sown in July showed less fasciation than plants sown in June or May. Almost no fasciation occurred on plants grown inside insect‐proof cages, irrespective of their origin from seed of fasciated or normal plants. Insect‐borne and not seed‐borne transmission is therefore suggested.