bluuebunny/crossref_metadata_2025 huggingface dataset:
The detection and estimation of Verticillium dahliae in naturally infested soil
Authors: HARRIS D. C. , YANG J. R. , RIDOUT M. S.
Published: April 2007

The effects of several factors on the estimation of Verticillium dahliae in soil by the wet‐sieving method were studied. The following factors were important for maximising recovery: the removal of soil particles of < 20 μm size from suspensions before plating; the medium used for plating; the amount of sieved soil inoculated to plates; the length of time of incubating plates; and the method of incubating soil on plates. There was no short‐term effect of air‐drying soil before analysis. Using sodium hexametaphos‐phate to aid soil dispersion, treating soil suspensions with sodium hypochlorite, or making suspensions from different amounts of soil had no consistent effect on recovery. Excessive sample‐to‐sample variability in the results of some experiments was attributed to non‐random distribution of fungus propagules in soil, or to the difficulty of standardizing the sieving part of the analysis, or both. Wet‐sieving was generally more effective in detecting V. dahliae and gave higher counts than a sucrose‐flotation method. Bait methods with eggplants or antirrhinums proved ineffective for estimating V. dahliae in naturally infested soil.
Effects of impacting rain drops on the growth and development of powdery mildew fungi
Authors: SIVAPALAN A.
Published: April 2007

The effects of rain on different stages of powdery mildew development were investigated quantitatively for Erysiphe graminis on barley, Erysiphe pisi on pea and Sphaerotheca pannosa on rose. Water drops 4 mm in diameter released from a height of 2·5 m onto target leaves reduced the numbers of conidia on the impacted surfaces and inhibited subsequent mildew development, the effects declining as the interval between inoculation and impaction increased. Simulated rainfall applied after inoculation reduced the numbers of conidia on leaves and inhibited mildew development, the effect declining as the interval between inoculation and treatment lengthened. Simulated rainfall applied to infected plants reduced their capacity to inoculate other plants, the effect declining as the interval between treatment and use as inoculum lengthened. Controlled exposure of infected peas and roses to natural rain reduced the numbers of conidia on leaves and inhibited subsequent mildew development, especially on upper leaf surfaces.
Biocontrol of Botrytis cinerea and Alternaria brassicicola on Dutch white cabbage by bacterial antagonists at cold‐store temperatures
Authors: LEIFERT C. , SIGEE D. C. , STANLEY R. , KNIGHT C. , EPTON H. A. S.
Published: April 2007

Bacterial antagonists against Botrytis cinerea were isolated from different Brassica spp. and identified. All isolates showing in vitro antagonism at 4°C were shown to be either fluorescent pseudomonads or Serratia spp. In vitro antagonism against B. cinerea and Alternaria brassicicola was found to depend on the temperature and concentration of nutrients in the medium.

Bacterial strains which showed in vitro antagonism were tested for in vivo antagonism at 4°C against B. cinerea and A. brassicicola using a leaf disc bioassay. Pseudomonas fluorescens isolates CL42, CL66, CL82 and Serratia plymuthica strain CL43 showed inhibition of Botrytis growth on leaf discs; P. fluorescens isolate CL74 and all Serratia liquefaciens isolates exhibited intermediate control. All other fluorescent pseudomonad isolates showed poor control or caused rotting of the cabbage tissue.
Aerodynamic diameter of conidia of Alternaria species
Authors: MCCARTNEY H. A. , SCHMECHEL D. , LACEY M. E.
Published: April 2007

The aerodynamic diameters of conidia of five species of Alternaria and Stemphylium botryosum were estimated using an inertial impaction method based on a May Ultimate Impactor. The same technique was used to estimate the aerodynamic diameter of unidentified Alternaria species collected from an oilseed rape crop. Aerodynamic diameters tended to increase with spore length or diameter and ranged from about 10 to 40 μm, although spore length ranged from about 10 to 220 μm. It was also found that the aerodynamic diameter, and therefore the fall speed of Alternaria‐like spores, can be estimated from cylinders of unit density and the same length and mean diameter of the spores.
Effects of ozone exposure and leaf age of wheat on infection processes of Septoria nodorum Berk.
Authors: TIEDEMANN A. v. , FIRSCHING K. H.
Published: April 2007

The infection process of Septoria nodorum was studied on the flag and second leaves of wheat plants at the flag‐leaf emergence growth stage (GS 39), after pre‐inoculative fumigation with different doses of ozone (0, 80, 180 or 240 μg/m3) for 7 h daily over 7 days. On ozone‐treated plants, formation of appressoria occurred earlier, leading to a greater number and density of appressoria and faster growth of superficial infection hyphae than on plants grown without ozone amendment. Additionally, on leaves treated with 180 and 240 μg/m3 ozone, the percentage of papillae per appressorium was only half that on control plants. The number of germ tubes per conidium was not significantly affected by any treatment. Effects of increasing leaf age on the infection process were similar to those obtained with ozone. These results provide further evidence for similarities in the physiological effects of ozone and leaf ageing, which support the hypothesis that disease alterations due to ozone are strongly determined by the senescing effects of the pollutant.
Comparison of sampling procedures for two rice diseases: leaf blast and tungro
Authors: DISTHAPORN S. , HAU B. , KRANZ J.
Published: April 2007

The precision and accuracy of eight random and systemic sampling methods, along with various sample sizes, were compared by means of a sampling simulation program with actual field data for two rice diseases, leaf blast and tungro. Three severity levels of leaf blast and two incidence levels of tungro were used. Precision depended primarily on disease intensity, followed by the sample size and the sampling method. Relative accuracy did not prove to discriminate sampling methods adequately, but simulated absolute accuracy is able to identify biases of systematic sampling paths. The results emphasize the necessity of pilot sampling at various stages of epidemics. The usefulness of simulated sample sizes and sampling methods based on real data is also demonstrated. With this approach a more practical combination of sample size and method may be found for different levels of disease intensity using precision and absolute accuracy as criteria.
Use of Trichoderma harzianum in combination or alternation with fungicides to control cucumber grey mould (Botrytis cinerea) under commercial greenhouse conditions
Authors: ELAD Y. , ZIMAND G. , ZAQS Y. , ZURIEL S. , CHET I.
Published: April 2007

A preparation of Trichoderma harzianum was sprayed on cucumber plants in greenhouses in order to control fruit and stem grey mould. Up to 90% control was achieved by the biocontrol agent (0·5–1·0 g/l) which in most experiments under commercial conditions was as effective as the dicarboximide fungicides iprodione or vinclozolin (0·5 g/l each) alone or alternated with diethofencarb + carbendazim (0·25 g/l each). However, in one experiment disease incidence in Trichoderma‐treated plots did not differ significantly from the control. A mixture of T. harzianum with a dicarboximide fungicide resulted in up to 96% control of grey mould. In this case control was always significant (P=0·05) but improvement of control compared with each treatment alone was not significant (P=0·05). The alternation of sprays with the biocontrol preparation and with a dicarboximide fungicide was tested in three out of the five experiments and was found to be effective, thus enabling a reduction in the use of chemical sprays. Populations of T. harzianum were on a level of 3 × 105‐8 × 105 c.f.u. per leaf and ten times lower on one fruit. They remained high after the second and third sprays. Conditions favouring the ability of T. harzianum to control grey mould were temperatures above 20°C and relative humidity between 80 and 97%.
Establishment of apricot and almond trees using soil mulching with transparent (solarization) and black polyethylene film: effects on Verticillium wilt and tree health
Authors: STAPLETON J. J. , PAPLOMATAS E. J. , WAKEMAN R. J. , De VAY J. E.
Published: April 2007

Apricot (Prunus armeniaca) and almond (P. dulcis) trees at the first leaf stage were planted in soil infested with Verticillium dahliae and mulched with transparent or black polyethylene film, or not mulched, in the San Joaquin Valley of California, March‐August 1990. During the 19‐week mulching treatment, summer soil temperatures reached as high as 46, 41, and 33°C at 18 cm depth; and 41, 37, and 32°C at 30 cm depth under clear film, black film, and no film, respectively. Trees mulched from the time of planting with transparent polyethylene (solarization) did not survive or grow as well as those mulched with black film or not mulched. Incidence of foliar symptoms due to Verticillium wilt was reduced by 86–100% in both apricot and almond trees by black, as well as transparent film mulch the following season. Incidence of vascular discoloration symptoms of trunks and primary scaffolds due to Verticillium wilt was similarly reduced by both mulches. Mulching with black polyethylene film gave better overall results than solarization with transparent film. The intermediate soil temperatures produced did not chronically harm trees, as judged by tree survival and annual growth of trunk diameter, yet the prolonged period of soil heating provided control of Verticillium wilt equivalent to that of solarization with transparent polyethylene. These studies provided further evidence that in‐season mulching can be used to conserve water during establishment of new orchards or replant trees in warm, arid climates.
Biological diversity of citrus ringspot isolates in Spain
Authors: NAVAS‐CASTILLO J. , MORENO P.
Published: April 2007

Eight isolates of citrus ringspot were selected by symptoms induced in field trees and compared with a citrus psorosis isolate for symptom expression on several citrus species under temperature‐controlled glasshouse conditions. Symptom expression in each host‐isolate combination was quantified by a pathogenicity index (PI) that considered symptom intensity and the number of plants showing each symptom. A general pathogenicity index (GPI) was defined for each isolate as a weighted mean of the different PI. A wide range of symptoms could be observed depending on host‐isolate combination and incubation temperature. On the basis of symptoms induced in the glasshouse, cross protecting reaction against psorosis B challenge inoculation, mechanical transmissibility to Chenopodium quinoa, and presence of a c. 48‐kDa protein associated to fractions of a sucrose gradient infective on C. quinoa (Navas‐Castillo et al, 1993), six of the ringspot isolates (RS‐ALC, RS‐SOR, RS‐GR, RS‐INV, RS‐CV and RS‐SR) could not be distinguished from the psorosis isolate used as control, whereas the other two isolates (RS‐ALM and RS‐BUR) were clearly different. Field symptoms induced by these two isolates also differed from those induced by psorosis or by the other ringspot isolates.
Windborne spread of ergot disease (Claviceps africana) in sorghum A‐lines in Zimbabwe
Authors: FREDERICKSON D. E. , MANTLE P. G. , DE MILLIANO W. A. J.
Published: April 2007

Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male‐sterile sorghum A‐lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana, on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread (r=0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici, and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa.
Effects of artichoke latent virus and broad bean wilt virus isolate FA on components of growth and yield of globe artichoke
Authors: MANZANARES M. J. , CORRE J. , LE SAINT J. P. , HERVE Y.
Published: April 2007

The effects of single and mixed artificial infections by artichoke latent virus (ALV) and broad bean wilt virus isolate FA (BBWV‐FA) on components of growth and yield of three globe artichoke lines were evaluated in an aphid‐free glasshouse. Virus infections reduced plant vigour (length of leaves and height of the ramifications) and dry weight, increased dry matter percentage, lengthened harvest period, and induced significant losses in the number of harvested buds, which resulted from reduced production of ramifications. However, the magnitude of affected parameters depended on inherent line differences and the type of virus infection. The greatest reductions occurred with the ALV + BBWV‐FA infection. In single infections ALV led to the more severe effects, especially on components of yield. The level of ALV coat protein, as determined by ELISA, indicated differences in titre between plants of three lines. Can line, which exhibited greater yield reduction than Cada or CBT lines, had the higher ALV virus titre. Conversely Cari was less susceptible to BBWV‐FA infection than Cada. The detrimental effects of virus infection emphasize the need for virus control, and differences in responses among lines indicate the possibility of control by plant breeding.
The natural occurrence of Thanatephorus cucumeris leaf spot on Hevea brasiliensis in Sri Lanka
Authors: JAYASINGHE C. K.
Published: April 2007

Thanatephorus cucumeris. the causal agent of target leaf spot disease of Hevea, is recorded in Sri Lanka for the first time on Hevea brasiliensis.
Characterization of two Tospoviruses in Italy: tomato spotted wilt and impatiens necrotic spot
Authors: VAIRA A. M. , ROGGERO P. , LUISONI E. , MASENGA V. , MILNE R. G. , LISA V.
Published: April 2007

Tospovirus serogroups I and III have recently been designated as species, tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV), while the species status of serogroup II isolates remains undefined. Fifteen Tospovirus isolates from ornamental and vegetable crops in Liguria, Italy, were found to belong either to TSWV (seven isolates) or to INSV (eight isolates) on the basis of test‐plant reactions, serological techniques using DAS ELISA kits raised against the nucleoproteins of the type members of the two species, and cytopathology. None of them could be assigned to serogroup II using DAS ELISA kits raised against nucleoproteins of this serogroup. Italian isolates representative of the two species reacted in indirect ELISA using a polyclonal antiserum against the entire particle of a TSWV isolate, but with higher intensity for our TSWV isolates than for the INSV isolates. Western blots and dot immunobinding assays confirmed that the nucleoproteins of the two species are unrelated whereas the glycoproteins are related. The cytopathology was similar for two isolates representative of TSWV and INSV, except that the type of filaments encountered was different, and appeared to be characteristic of the species.
Clostero‐like particles associated with a yellows disease of melons in South‐eastern Spain
Authors: JORDÁ‐GUTIÉRREZ C. , GÓMEZ‐GUILLAMÓN M. L. , JUÁREZ M. , ALFARO‐GARCÍA A.
Published: April 2007

Melon yellows disease is a new disease of melon which has become very important in several areas of protected melon crops in the south‐east of Spain. It is spreading to other regions of the Mediterranean Coast. On first studies a viral agent was suspected; however, there were no experimental data to support such a hypothesis. In 1988 it was demonstrated that the disease was transmitted by Trialeurodes vaporariorum.

The disease was found to be associated with the presence of long flexuous viral particles typical of Closterovirus Group II. A preliminary method for purification of the virus has been developed and an antiserum has been prepared.
Development of monoclonal antibody‐based immunological assays for the detection of live propagules of Rhizoctonia solani in soil
Authors: THORNTON C. R. , DEWEY F. M. , GILLIGAN C. A.
Published: April 2007

Mouse monoclonal antibodies (mAbs) and rabbit (polyclonal) antiserum were used to develop DIAGNOSTIC‐ELISA, double‐antibody‐sandwich‐ELISA (DAS‐ELISA), DIP‐STICK and immuno‐fluorescence colony staining immunoassays for the specific detection of Rhizoctonia solani in soil. mAbs were raised against an anastomosis group 4 isolate of R. solani. Mice were immunized using either phosphate‐buffered saline (PBS) suspensions of lyophilized mycelium plus Quil A adjuvant, or with a solubilized acetone precipitate prepared from cell‐free surface washings from solid slant cultures. Polyclonal antisera were raised in rabbits using PBS suspensions of lyophilized mycelium and Quil A adjuvant. Hybridoma supernatants and rabbit antisera were screened by ELISA. Four of the cell lines raised produced mAbs that were species‐specific. They recognized antigens from R. solani by ELISA and immunofluorescence, but not other related or unrelated species of soil‐borne fungi. The remaining cell line produced mAbs that cross‐reacted slightly, by ELISA, with antigens from R. cerealis. These mAbs did not recognize R. cerealis by immunofluorescence, or other related or unrelated soil‐borne fungi, by ELISA.
Hemibiotrophic infection of Pisum sativum by Colletotrichum truncatum
Authors: O'CONNELL R. J. , URONU A. B. , WAKSMAN G. , NASH C. , KEON J. P. R. , BAILEY J. A.
Published: April 2007

The infection of pea (Pisum sativum) by Colletotrichum truncatum was studied by light and electron microscopy. These investigations were facilitated by use of an Argenteum pea mutant, which has a readily detachable epidermis. Infection pegs emerging from appressoria penetrated epidermal cells directly. Large intracellular primary hyphae formed a dense stromatic mycelium confined within a single epidermal cell. Primary mycelia gave rise to thinner secondary hyphae which radiated into surrounding cells and caused extensive wall dissolution. Melanized sclerotia developed in the centre of chlorotic water‐soaked lesions. Acervuli were not observed. Epidermal cells survived initial penetration by primary hyphae, as shown by their ability to plasmolyse and accumulate Neutral red, but all infected cells were dead when the secondary hyphae had formed. Six cultivars of pea were susceptible, but seven other legumes were resistant. A single isoform of polygalacturonase with a pI of 8·3 and apparent Mr of 40000 was purified from culture filtrates and the TV‐terminal amino acid sequence determined. The relevance of the results to the taxonomy of C. truncatum and the relationships between infection process and host range are discussed.
Studies on the resistance of grapevine to powdery mildew
Authors: LI H.
Published: April 2007

Studies of 68 cultivars of Vitis vinifera and two interspecific hybrids inoculated with four naturally occurring isolates of Uncinula necator demonstrated variation for pathogenicity between isolates and variation in resistance between cultivars. There was no specific interaction between the cultivars and the isolates. The progenies produced either by selling or hybridization of cultivars of V. vinifera always contained some resistant individuals regardless of the parental resistance ratings. However, the proportion of resistant plants was positively correlated to the level of resistance of the parent(s). The results indicate that ‘minor’ resistance genes exist in the cultivars of V. vinifera, and that resistance to U. necator could be improved by recurrent selection.
Gummosis and wilt of Acacia mearnsii in South Africa caused by Ceratocystis fimbriata
Authors: MORRIS M. J. , WINGFIELD M. J. , de BEER C.
Published: April 2007

A dieback of Acacia mearnsii trees was observed in the Mkomasi river valley, Natal Province, South Africa. A fungus, tentatively identified as Ceratocystis fimbriata, was consistently isolated from affected twigs and branches. Reinoculation of the pathogen resulted in the development of typical wilt and dieback of A. mearnsii seedlings and saplings and in a dieback of Protea cynaroides plants. This is the first report of this disease in South Africa.
The effects of soil solarization and soil fumigation on Fusarium wilt of watermelon grown in plastic house in south‐eastern Spain
Authors: GONZALEZ‐TORRES R. , MELÉRO‐VARA J. M. , GÓMEZ‐VÁZQUEZ J. , DÍAZ R. M. JIMÉNEZ
Published: April 2007

The effects of pre‐planting solarization or fumigation with metham‐sodium of sand‐mulched soil on fusarium wilt of watermelon in plastic house culture were investigated at Almeria, south‐eastern Spain. In two trials, 2 months' solarization increased the average maximum soil temperature by c. 5°C to 44‐48° C at 10 cm depth and by 4‐5° C to 40‐42° C at 20‐30 cm. The amount of Fusarium oxysporum in the upper 15 cm of a naturally infested soil was reduced by solarization and by fumigation. During the 9 months following treatment, the F. oxysporum population stabilized at a low level in soil solarized for 2 months, but fluctuated in soil solarized for 1 month and increased in fumigated soil. The amount of wilt in watermelon sown into this soil after treatment was generally low; plants growing in solarized or fumigated soil suffered less wilt than plants in untreated soil but the differences were not significant. In a soil artificially infested with the highly pathogenic race 2 of F. oxysporum f. sp. niveum, F. oxysporum populations were greatly reduced following solarization or fumigation, and fluctuated erratically thereafter. Solarization for 2 months completely controlled wilt in watermelon and gave a fruit yield almost five times that of plants in untreated soil. Solarization for 1 month only slowed disease development slightly but gave a yield more than twice that in untreated soil. Fumigation with metham‐sodium retarded disease development considerably and tripled fruit yield. Plant performance was significantly better in soil solarized for 2 months than in uninfested control soil, suggesting beneficial effects of this treatment additional to wilt control.
Molecular characterization of Pseudocercosporella herpotrichoides isolates by amplification of ribosomal DNA internal transcribed spacers
Authors: POUPARD P. , SIMONET P. , CAVELIER N. , BARDIN R.
Published: April 2007

In order to determine whether a given isolate of Pseudocercosporella herpotrichoides. the cause of eyespot disease of cereals, belongs to the W‐type or the R‐type, we have developed a test based on the polymerase chain reaction (PCR). Sequences of the internal transcribed spacer (ITS) region of the ribosomal genes were determined for three different isolates of each pathotype. Primers complementary to variable sequences were specifically chosen to amplify differentially DNA from W‐ and R‐types. Specific reaction conditions of the PCR assay were experimentally determined by testing four isolates of each type that exhibit a wide range of sensitivity to fungicides.
Stipe necrosis of cultivated mushrooms (Agaricus bisporus) associated with a fluorescent pseudomonad
Authors: RICHARDSON P. N.
Published: April 2007

Pseudomonad bacteria (Pseudomonas fluorescens) causing necrosis of the central stipe tissue of Agaricus bisporus are reported for the first time.
Resistance to Peronospora viciae expressed as differential colony growth in two cultivars of Pisum sativum
Authors: CLARK J. S. C. , SPENCER‐PHILLIPS P. T. N.
Published: April 2007

Peronospora viciae sporulated frequently following localized inoculation of leaflets of Pisum sativum cv. Krupp Pelushka but rarely on cv. Early Onward (60 and < 1% of plants respectively). Similar results were obtained following inoculation of seedling shoot apices. The proportions of sporangia that germinated, formed appressoria, invaded via stomata or cuticle, and established colonies, were similar on leaflets of both cultivars. After 2 days, total hyphal lengths of most colonies were greater than 100 μm (94% in Krupp Pelushka, 64% in Early Onward), but in Krupp Pelushka there were five times as many haustoria per unit length of hypha. Subsequently, only occasional colonies in Early Onward grew to the same extent as in Krupp Pelushka, with 8% and 88% respectively attaining lengths > 800 μm after 4 days. Reduced growth of hyphae in Early Onward was associated with increased frequency of host cells stained by trypan blue.
Thresholds for control of Septoria spp. in winter wheat based on precipitation and growth stage
Authors: HANSEN J. G. , SECHER B. J. M. , JØRGENSEN L. N. , WELLING B.
Published: April 2007

A simple forecasting model for Septoria spp. in winter wheat was developed based on historical data (1980–89) including precipitation, growth stage, disease severity and yield response to fungicide treatments. The number of days with precipitation ≥ 1 mm, calculated during a 30‐day period starting at the beginning of stem elongation (GS 32), correlated well with attacks of Septoria spp. later in the season and with the yield response in trials with fungicide treatments. Seven or 8 days with rainfall ≥ 1 mm was suggested as a threshold for Septoria treatment. Model development and possible further improvements are discussed.
Immunosorbent electron microscopy and gold label antibody decoration of MLOs from crude preparations of infected plants and vector insects
Authors: VERA C. , MILNE R. G.
Published: April 2007

A simple method is given for immunotrapping, gold labelling and electron microscopy of mycoplasmalike organisms (MLOs) from crude preparations of infected plants or insects, enabling MLOs to be confidently distinguished from host materials in negative stain preparations. The appearance of the MLOs is described. MLOs were trapped from extracts of infected periwinkle plants (Catharanthus roseus) and infected vector leaf hoppers (Macrosteles quadripunctulatus), using electron microscope grids coated with the F(ab)2 portion of specific rabbit IgGs. The MLOs were then decorated with the intact igG and labelled with goat anti‐rabbit IgG conjugated to gold particles 5 or 15 nm in diameter. Preparations were negatively stained in 0.5% ammonium molybdate or left unstained. The MLOs used were European aster yellows (EAY) from plant and vector, and Australian tomato big bud (TBB) from the plant. Preparation time was 4 h; large numbers of MLOs and MLO fragments could be trapped and identified, and EAY could be confidently distinguished from the serologically unrelated TBB. Morphologically, EAY and TBB were indistinguishable, both presenting spheroidal bodies, tubular forms and apparently budding chains of cocci. Bacilliform virus‐like particles were sometimes associated with EAY MLOs, especially those from the vector.
Fusarium stem and fruit rot of sweet peppers in the glasshouse
Authors: FLETCHER J. T.
Published: April 2007

A stem and fruit rot of sweet peppers (Capsicum annuum) occurred in 1992 in West Sussex affecting a large proportion of plants of cv. Tasty and to a lesser extent cv. Mazurka. Fusarium solani was isolated from the stem lesions and also from a short distance above and below them. The disease was largely nodal. Distinctive fruit symptoms also occurred. Symptoms were reproduced by inoculation of wounds on the stem. On agar and in a small in vivo test the pathogen was sensitise to benomyl at 2 μg ml. The disinfectants, commercial sodium hypochlorite, Purogene and Tego 51 effectively killed macrospores following exposure for 15 min.
Characterization of isolates of Phytophthora infestans collected in northwestern France from 1988 to 1992
Authors: ANDRIVON D. , BÉASSE C. , LAURENT C.
Published: April 2007

Isolates of the potato late‐blight pathogen Phytophthora infestans, collected in several French regions from 1988 to 1992, were characterized in order to determine the structure and pathogenicity of French populations and to compare them with other European samples. All 254 French isolates tested were of the Al mating type, as were two Sicilian, five Portuguese and one Spanish isolate. Metalaxyl sensitivity of 157 isolates was investigated. The frequency of resistance to this chemical decreased in western France from 1989 to 1992. Two glucose phosphate isomerase phenotypes (90/100 and 90/90) were detected among the 46 isolates tested; the former largerly predominated (75–80%) in the samples investigated. Both phenotypes corresponded to the population recently introduced into Europe. A third genotype (86/100), typical of the former European population, was found in one isolate from Picardy, originating from an artificially infected field trial. Five isolates from Portugal and Italy were of the 100/100 phenotype. Race patterns among 26 isolates from western France were very similar, and could not be explained by local selection. The unusual composition of the Brittany population, consisting of ‘new’ genotypes but all belonging to the Al mating type, is possibly related to the metapopulation type of structure of P. infestans in Europe.
Phage sensitivity in relation to pathogenicity and virulence of the cotton bacterial blight pathogen of Sudan
Authors: FREIGOUN S. O. , EL FAKI H. I. , GELIE B. , SCHIRMER M. , LEMATTRE M.
Published: April 2007

At least two pathotypes of Xanthomonas campestris pv. malvacearum are now known to exist in Sudan. The pre‐Barakat (race 1) and post‐Barakat (race 2) pathogens have been shown to exhibit different host specificity. The former is pathogenic and highly aggressive on only cultivars with no resistance genes or with the B2 and/or B3 resistance factors, while the latter can infect the B6 cultivars also. Race 2 in Sudan, which was previously reported to infect all the standard differentials, produced milder angular leaf spot symptoms and occasionally restricted vein infection. Moreover, it exhibited reduced growth in planta compared with race 1.

Bacteriophage studies revealed that the two races are quite distinct in their phage sensitivity. Race 1 can be lysed by only three, or rarely four, of the six phages used for typing, while race 2 is sensitive to all of them. The present study suggests that phage 7 may be the type‐determining phage for race 2. Race 2 strain mutants resistant to phage 3 or 4 were found to be sensitive to phage 7 and pathogenic to both Acala and Barakat, although showing marked attenuation of virulence. However, mutants resistant to phage 2 or 7 were insensitive to all the phages and although they retained their pathogenicity to Acala, they either lost the ability to infect Barakat or produced a hypersensitive reaction. The resistance of all mutants was found to be due to failure to adsorb the homologous phage, indicating a change in the cell wall. The association of this with the attenuation of virulence suggests that bacterial wall components may function as virulence determinants in Xanthomonas campestris pv. malvacearum.
Controlled environment studies on the infection of Emex australis by Phomopsis emicis
Authors: SHIVAS R. G.
Published: April 2007

The effect of temperature, dew period, inoculum concentration and host maturity on the growth and development of Emex australis after inoculation with Phomopsis emicis was studied in controlled environments. Disease was assessed by recording changes in the length of stems, number of fully expanded leaves, dry weights, number of fruits and disease severity index. Disease was as severe at 18°C as it was at 28°C. There was a trend of increased disease with longer dew period. Inoculum concentrations of 1·106 and 1·107 conidia per ml resulted in a significant net reduction in stem growth compared with lower concentrations. Progressively higher disease ratings occurred as the inoculum concentration increased to 1·107 conidia per ml. There were no significant effects of inoculation with P. emicis on either seedlings, rosettes or flowering rosettes, but 10‐week‐old plants were highly susceptible to infection and stem collapse. The implications of these results for the potential development of P. emicis as a mycoherbicide are discussed.
Studies on the biology of black mould (Aspergillus niger) on temperate and tropical onions. 2. The effect of treatments on the control of seedborne A. niger
Authors: HAYDEN N. J. , MAUDE R. B. , EL HASSAN H. S. , AL MAGID A. A.
Published: April 2007

Treatment of A. niger‐inoculated onion seed with benomyl dust (1 g a.i./kg), or a foliar spray of thiram (0·4% a.i./ha) applied to plants grown from inoculated seed under temperate (UK) conditions reduced the incidence of A. niger in harvested crops. Treatment of naturally contaminated Sudanese onion seed with a benomyl + thiram mixture at a rate of 2·5 + 2·5 g a.i./kg or soaking the seed in hot water (15 min at 60°C) reduced the incidence of black mould on bulbs grown in the Sudan in field soil that had not previously been used for onion production. The seed treatments were less effective in crops produced in fields regularly used for onion production. However, incubation of harvested bulbs in moist chambers showed that damage to the internal storage tissue of onion bulbs caused by A. niger was reduced by seed treatment.
The host range of beet yellowing viruses among common arable weed species
Authors: STEVENS M. , SMITH H. G. , HALLSWORTH P. B.
Published: April 2007

Twenty common arable weed species were inoculated using Myzus persicae to transmit beet yellows virus (BYV), beet mild yellowing virus (BMYV), and an isolate of beet western yellows viruses (BWYV) that did not infect beet. The viruses were detected by enzyme‐linked immunosorbent assay (ELISA), in which monoclonal antibodies distinguished between BMYV and BWYV, and by aphid transmissions to indicator host plants. Spergula arvensis, Stellaria media, Lamium purpureum and Papaver rhoeas were susceptible to all three viruses whereas Senecio vulgaris, Capsella bursa‐pastoris, Anagallis arvensis and Chrysanthemum segetum were susceptible to both BMYV and BWYV, and Matricaria perforata, Raphanus raphanistrum, Veronica persica, Urtica urens and Viola arvensis were susceptible to BWYV only. Atriplex patula, Chenopodium album and Portulaca oleracea were susceptible to BYV only. Myosotis arvensis, Silene alba, Poa annua and Solanum nigrum were not susceptible to any of the viruses. Portulaca oleracea was shown for the first time to be a host of BYV, and C. segetum a host of BMYV and BWYV. In spring 1991, 8% of weeds sampled in a field of autumn‐sown oilseed rape contained BWYV. Tests on weeds collected from an area of ‘set‐side’ adjacent to sugar beet showed that 3% contained BMYV and 3% BWYV. No sampled weeds were infected with BYV. The role of weeds in the epidemiology of sugar beet virus yellows is discussed.
Occurrence of bacterial brown spot of dry beans in the Transvaal province of South Africa
Authors: SERFONTEIN J. J.
Published: April 2007

Bacterial brown spot, caused by Pseudomonas syringae pv. syringae, caused epidemics on dry beans (Phaseolus vulgaris) on the Transvaal Highveld in South Africa during 1992. Crop losses of up to 55% were reported in plantings of the dry bean cultivar Bonus. The pathogen was detected in commercial seed stocks.
The role of Poa annua in the epidemiology of barley yellow dwarf virus in autumn‐sown cereals
Authors: MASTERMAN A. J. , HOLMES S. J. , FOSTER G. N.
Published: April 2007

Studies of cereal aphids and barley yellow dwarf virus (BYDV) from 1989 to 1992 revealed that Poa annua is an abundant weed of commercial winter barley crops during the summer months. P. annua was frequently infected with BYDV, and there were usually similarities with the BYDV infection of the surrounding barley crop. These P. annua weeds were often infested by cereal aphids both in July (pre‐harvest) and in September (in cereal stubble fields). Poa‐infested cereal stubbles may be major local sources of viruliferous aphids, increasing the risk of BYDV in nearby winter cereals. P. annua plays an important role in the epidemiology of S. avenae‐transmitted BYDV.
Long‐term development of Heterobasidion annosum in basidiospore‐infected Sitka spruce stumps
Authors: MORRISON D. J. , REDFERN D. B.
Published: April 2007

The extent of colonization by Heterobasidion annosum was measured in 1989 in Sitka spruce stumps that had been inoculated with basidiospores in 1981 and assessed for infection in 1983. Only stumps that had infection in the sapwood in 1983 contained the fungus in 1989. There was a significant positive correlation between the sapwood area colonized in 1983 and the total area colonized in 1989. Between 1983 and 1989, H. annosum spread within the body of stumps and into most primary roots. There were significant correlations between the stump area colonized in 1983 and 1989 and the percentage of stump and root volume colonized in 1989. Roots of 26 excavated stumps were in contact with an average of two roots on each of two living trees. Fourteen roots on eight living trees became infected, and H. annosum spread proximally an average of 126 cm into trees. We believe that this is the first report of the transfer of H. annosum from spruce stumps inoculated with basidiospores to adjacent live trees.
Bacterial sudden yellow death and soft rot of Coriandrum sativum
Authors: ROMEIRO R. S. , SIMOES A. R. , MUCHOVEJ J. J. , OLIVEIRA J. R. , SOUZA R. M.
Published: April 2007

Parsley (Coriandrum sativum) plants exhibited a sudden yellowing and death that included a soft rot of the roots and the basal parts of the petioles. A rod shaped, facultatively anaerobic, Gram negative bacterium was isolated that infected healthy parsley plants, reproducing the original symptoms. Biochemical, biological, staining and morphological studies suggested that the bacterium was most closely related to Erwinia carotovora subsp. betavasculorum. As E. carotovora has not been reported from parsley (in Brazil) (Robbs et al., 1981), this appears to be a new disease in Brazil.
The occurrence of thiabendazole‐resistant isolates of Polyscytalum pustulans and Helminthosporium solani on seed potato tubers in relation to fungicide treatment and storage
Authors: CARNEGIE S. F. , CAMERON A. M. , HIDE G. A. , HALL S. M.
Published: April 2007

Tubers infected with thiabendazole‐sensitive isolates of Polyscytalum pustulans and Helminthosporium solani were treated annually for 4 years with benomyl, thiabendazole or a formulated mixture of thiabendazole and imazalil, and grown at three farms in Scotland. The proportion of thiabendazole‐resistant isolates of H. solani increased, and isolates producing black colonies became more common with successive annual applications of thiabendazole or benomyl. Silver scurf was not reduced after three annual applications. When these fungicides were applied once to untreated seed the incidence of resistant isolates of H. solani was much less in 1988 than in 1991 when tubers had been grown on farms for 3 years from untreated seed.

The proportion of resistant isolates of P. pustulans increased with the number of successive applications of thiabendazole or benomyl but at differing rates on each farm. At one farm, skin spot was not reduced by three annual applications of these fungicides whereas at the other farms it was reduced by 90–100% by four annual applications.

A smaller proportion of resistant isolates of P. pustulans and H. solani was obtained after applying the mixture of thiabendazole and imazalil than after benomyl or thiabendazole alone. Their occurrence was not related to the number of fungicide applications. The mixture also reduced both diseases by more than 75% over the 4 years.

At one farm where resistant isolates of H. solani were present, tubers were infected when stored on trays but not when stored in bags.
Virulence for faba bean and production of ascochitine by Ascochyta fabae
Authors: BEED F. D. , STRANGE R. N. , ONFROY C. , TIVOLI B.
Published: April 2007

The production of ascochitine by seven isolates of Ascochyta fabae accounted for the toxicity of culture filtrates of the fungus to cells isolated from leaves of Vicia faba. The LD50 value for cells from cultivars that were susceptible, tolerant or resistant to the fungus was similar i.e. 3·0 × 10−5m, 3·8 × 10−5m and 2·9 × 10−5 M, respectively. Ascochitine affected neither the germination of seeds nor the growth of mature plants at 5·17 × 10−4m but caused necrosis and wilting of plant cuttings at 2·5 × 10−4m and 5·10−4m. There was no association between virulence of 16 isolates of A. fabae for three cultivars of V.faba and the production of ascochitine in vitro. One isolate produced no ascochitine in vitro and yet was the most virulent for two of three cultivars. The toxin could not be extracted from infected plants.
First report of bacterial canker of kiwifruit in Iran
Authors: MAZAREI M. , MOSTOFIPOUR P.
Published: April 2007

Symptoms of bacterial canker of kiwifruit consisting of darkening and shrivelling along the bark were observed in kiwifruit orchards in Tonkabon, Iran. Longidutinal sections showed darkening of cortical and woody tissues. A fluorescent pseudomonad was consistently isolated from canker tissues. According to biochemical, physiological and pathogenicity tests the causal agent was identified as Pseudomonas syringae pv. syringae. This is the first report of the disease in Iran.
Foliar spray of phosphates induces growth increase and systemic resistance to Puccinia sorghi in maize
Authors: REUVENI R. , AGAPOV V. , REUVENI M.
Published: April 2007

A single foliar spray of 0‐1 M phosphate salts solution was applied to the upper side of maize (cv. Jubilee) leaves 1,2 and 3 at the five‐to six‐leaf stage, 2‐4 h before inoculation with Puccinia sorghi. This treatment induced systemic resistance against common rust as expressed by 98% reduction in the number of pustules of P. sorghi developed on leaves 5, 6 and 7, There was no damage or chlorotic stippling on the induced leaves (1, 2 and 3) as a result of the phosphate spray, A less effective, but still significant. reduction (90%) in the number of pustules was obtained when the foliar spray was applied 6 days before inoculation. One foliar spray of K2HPO4 on leaves 1,2 and 3,6 days before inoculation, stimulated plant growth regardless of inoculation. The foliar spray on the day of inoculation was less effective in stimulating growth. Appropriate mixtures of phosphate solutions revealed that the level of protection was not necessarily dependent on the gradual changes in the pH of the solution. The possible dual use of phosphate salts as foliar fertilizers and as agents for induced resistance is discussed.
Contamination and subsequent multiplication of soft rot erwinias on healthy potato leaves and debris after haulm destruction
Authors: BURGESS P. J. , BLAKEMAN J. P. , PEROMBELON M. C. M.
Published: April 2007

Small plots of potatoes were inoculated with a mixture of Erwinia carotovora (E. c.) subsp. carotovora and E. carotovora subsp, atroseptica strains resistant to rifampicin. Subsequently the population off, c. subsp, carotovora and E. c. subsp, atroseptica (rifampicin‐resistant and wild types) present as epiphytes on the surface of potato leaves was assessed using three methods, qualitative, semi‐quantitative and quantitative, during 1986 and 1987. The population was generally low (< 102 colony forming units (> 104cfu/g leaves) but reached higher levels (> 104 cfu/g) on occasions later in the growing season, Rifampicin‐resistant erwinias were reisolated only infrequently throughout this study. Different methods of haulm destruction (herbicide, pulverization, sulphuric acid treatment and natural senescence) greatly influenced the number of erwinias present in the resulting plant debris. Pulverization resulted in the highest population (106‐107 wild‐type cfu/g) in both seasons. In 1987. the wettest of the two seasons of this study, herbicide treatment resulted in similarly high populations. The results suggest that the high numbers of erwinias found in the haulm debris were probably derived from the generally low populations of epiphytic bacteria previously present on healthy leaves, E. c. subsp, carotovora was the most frequent subspecies in the rotting plant debris; E. c. subsp, atroseptica was more commonly found on healthy leaves. The implications of the results are discussed in relation to the production of seed potatoes with a low risk of blackleg.
Serological variability in Xanthomonas albilineans, causal agent of leaf scald disease of sugarcane
Authors: ROTT P , DAVIS M. J. , BAUDIN P
Published: April 2007

The serological characteristics of 215 strains of Xanthomonas albilineans from 28 locations throughout the world were investigated. Three serovars were identified by using three sera prepared against strains from different locations. The same variation among strains was observed with different serological assays: immunofluorescence. dot‐blot enzyme immunoassay and agglutination. Serovar I is the largest group and consists of strains from various geographic locations such as Australia. USA (Florida), Guadeloupe. India. Mauritius. Réunion and including South Africa. Serovar II contains only strains from Africa: Burkina Faso. Cameroon. Kenya. Ivory Coast. Serovar III is the smallest group and contains strains from Caribbean islands (Guadeloupe. Saint Kitts. Martinique). Oceania (Fiji) and Asia (Sri Lanka). This serological variability should be considered when serological techniques are applied for the diagnosis of leaf‐scald disease of sugarcane.
Evaluation of fungal antagonists for control of onion white rot in soil box trials
Authors: KAY S. J. , STEWART A.
Published: April 2007

Four fungi (Chaetomium globosum, Trichoderma viride, T. harzianum, Trichoderma sp.) were capable of reducing the incidence of onion white rot relative to the untreated control in two soil‐box trials. When applied as a soil additive (sand: bran: fungal homogenate, 1:1:2) at the rate of 0‐1% wheat bran/g dry soil, all fungal isolates provided levels of disease control equivalent to the fungicide (procymidone 0‐5 g a.i./100g seed) treatment. The best results were achieved with the Chaetomium globosum and Trichoderma (C62) isolates which gave 78% and 73% control of white rot. respectively, in trial 1 and 67% and 73% control, respectively, in trial 2. Reduced control was observed when the test fungi were applied as seed coatings or incorporated into alginate pellets.
The relationship between wheat yield and stripe rust as affected by length of epidemic and temperature at the grain development stage of crop growth
Authors: MURRAY G. M. , ELLISON P. J. , WATSON A. , CULLIS B. R.
Published: April 2007

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici. was associated with mean losses of up to 84% in the yield of wheat in southern New South Wales, Australia, between 1984 and 1987. Yield loss became smaller in cultivars with increasing levels of resistance in adult plant reaction and did not appear in cultivars with seedling susceptibility and moderate or better adult plant reaction levels in the 3 years when epidemics began after emergence of the flag leaf. However, in 1984 the stripe rust epidemic began during stem elongation, and yield losses of up to 21% occurred in cultivars with seedling susceptibility and a moderate or better adult plant reaction.

Yield was significantly negatively correlated with the proportion of leaf area affected by stripe rust at stages of crop development from the end of heading to late milk. The correlation was greatest at the early milk stage of growth where the relationship was logarithmic. Two factors significantly influenced this relationship. Yield loss increased as the length of the epidemic increased, and decreased as temperature increased during grain development. The relationship that was developed for predicting yield loss accounted for 80‐5% of the variance across all experiments, and was:

y= 100(1‐e10‐4×(393+165 L‐141T))

where y= yield loss (%); X= stripe rust (leaf area affected, range 0‐99%) at early milk; L= time from 1% disease to early milk (range 0‐70 days); and T= mean daily maximum temperature from 7 days before to 14 days after early milk (range 198‐27.5°C).