bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of Rhizoctonia species to different fungicides
Authors: KATARIA H. R. , HUGELSHOFER U. , GISI U.
Published: April 2007

Of 14 fungicides with different modes of action, cyproconazole and tolclofos‐methyl were generally inhibitory both in vitro and in vivo against all tested isolates of five Rhizoctonia species belonging to the teleomorphs Thanatephorus cucumeris, Waitea circinata or Ceratobasidium cereale. Triadimenol and carboxin provided considerable variation in activity against different species and isolates, whereas prochloraz was ineffective against all isolates. Imazalil and fenarimol showed moderate control, whereas flusilazole, propiconazole, fenpropimorph and benomyl showed strong activity against R. zeae and R. oryzae, but were much less effective against R. sasakii, R. cerealis and R. solani. Benodanil and iprodione controlled all isolates of R. cerealis and R. solani, but were not very effective against R. zeae and R. oryzae. Pencycuron showed strong activity against R. sasakii and most R. solani isolates, moderate activity against R. zeae, and was ineffective against R. oryzae and R. cerealis.
Reaction of leek cultivars to infection by Puccinia allii
Authors: UMA N. U. , TAYLOR G. S.
Published: April 2007

Six components of susceptibility (incubation period, latent period, pustule size, infection frequency, sporulation intensity and reaction type) were measured for seven cultivars of leek following inoculation with urediniospores of Puccinia allii. Variation among cultivars was observed for each component. Sporulation intensity, latent period, infection frequency and reaction type were correlated and appeared to be better criteria for describing variation in host response than incubation period and pustule size. Cultivars Olaf and Kajak were‘fast rusting’while cultivars Agria, Winterreuzen, Odin Longstanton, Gennevilliers Splendid and Platina exhibited varying levels of ‘slow rusting’. The ‘;slow‐rusting’ cultivars Agria and Winterreuzen are of sufficiently high agronomic quality to be worthy of consideration for commercial production.
Serological relationships between five fungally transmitted cereal viruses and other elongated viruses
Authors: JIANPING CHEN , ADAMS M. J.
Published: April 2007

F(ab')2 and protein A ELISA tests were used to investigate the serological affinities of five fungally transmitted cereal viruses: barley yellow mosaic (BaYMV), barley mild mosaic (BaMMV), oat mosaic (OMV), wheat yellow mosaic (WYMV) and oat golden stripe (OGSV). Within this group only BaYMV and WYMV were related. Chinese and UK isolates of BaYMV appeared to be similar. In tests using antisera to 29 other elongated viruses, BaYMV was related to one isolate of bean yellow mosaic poty virus (BYMV‐G) and OGSV had affinities with BYMV‐G, potato virus M, red clover vein mosaic (both carlaviruses) and perhaps Hordeum mosaic virus. The results were confirmed in immunoelectron microscopic tests. No affinities were found for BaMMV, OMV or WYMV.
A comparison of methods to evaluate the susceptibility of potato cultivars to blackleg (caused by Erwinia carotovora subsp. atroseptica) in the field at different sites
Authors: GANS P. T. , JELLIS. G. J. , LITTLE. G. , LOGAN C. , WASTIE R. L.
Published: April 2007

Potato seed tubers were inoculated either using a needle or using a high‐pressure jet injector at a number of sites in the United Kingdom. Over 2 years, different cultivars showed different trends in blackleg symptoms. Comparisons with inoculation by infiltration of tubers under vacuum were made at two sites, and by damaging followed by dipping tubers in inoculum at one site. The relationship between plant vigour in July and yield was closer than that between blackleg symptoms and yield.
An hypothesis to account for the behaviour of dicarboximide‐resistant strains of Botrytis cinerea in vineyards
Authors: BEEVER R. E. , PAK H. A. , LARACY E. P.
Published: April 2007

Ten trials were established in the 1986 vintage year on vineyards in three vine‐growing districts of New Zealand, to examine changes in the frequency of resistance to dicarboximide fungicides of the Botrytis cinerea population under different fungicide programmes. The vineyards chosen encompassed sites with pre‐season resistance frequencies ranging from 0 to 97%. Under a non‐dicarboximide programme, using dichlofluanid and chlorothalonil, resistance frequency had decreased at harvest irrespective of the initial frequency. In programmes incorporating dicarboximides (chlozolinate, iprodione, procymidone, vinclozolin), the resistance frequency tended to increase if pre‐season resistance frequency was low, and decrease if it was high. The hypothesis is presented that for a given dicarboximide programme, resistance frequency tended to one value, the balance value, where selection for resistant strains due to fungicide application balanced selection against the resistant strains due to their low fitness. This value was estimated for the 1986 vintage year to be 38% for a programme where application of dicarboximides was restricted to the period from the veraison (sugar rise), and 64% where dicarboximides were applied from the pre‐bunch closure phase. Actual values observed at harvest 1987, after these same programmes had been applied for two consecutive years, were 39% (S.E. 8‐5%) and 68% (S.E. 8‐8%), respectively.
Detection of tomato spotted wilt virus and transmission by Frankliniella occidentalis in France
Authors: MARCHOUX G. , GÉBRÉ‐SELASSIE K. , VILLEVIEILLE M.
Published: April 2007

Tomato spotted wilt virus (TSWV) was isolated from pepper, tomato, eggplant, broad bean, lettuce, basil, chrysanthemum, aster, New Guinea impatiens, anemone and gloxinia plants. Virus identification was based on host range, vector transmission, serology and electron microscopy. TSWV was readily detected by ELISA in naturally or artificially infected cultivated or weed plants. The virus was also detected in individual F. occidentalis thrips. The spread of TSWV in vegetable and ornamental plants in greenhouses and/or in the open is related to the close relationship of the virus with the vector.
The assessment of infectious disease for brown rust (Puccinia hordei) of barley
Authors: BERESFORD R. M. , ROYLE D. J.
Published: April 2007

The measurement of infectious disease (sporulating area), as opposed to the more conventional visually estimated total disease (sporulating area and chlorosis), was investigated for brown rust on spring barley. Visual estimates by four assessors of percentage leaf area occupied by uredinia overestimated the actual percentages by, on average, 8.7 times. It was concluded that better estimates of infectious disease came from uredinium densities (uredinium counts and measurements of leaf area).

The progress of uredinium density in crops was exponential up to the time when leaves senesced at the end of their development. Three‐parameter exponential functions were fitted to epidemics on 26 different leaf layers in five crops grown in three years. It is suggested that the lack of sigmoid progress curves, as would be found with conventional total disease assessments, occurred because chlorosis was excluded from the assessment. Chlorosis, which can affect a large proportion of leaf area, has an upper limit which gives rise to the asymptotic form of conventional disease progress curves. Uredinium densities had skewed distributions and the variances were correlated with the mean values. These characteristics were rectified most effectively by cube‐root transformation. An incidence‐severity relationship between the percentage of diseased leaves in a sample and the mean cube‐root transformed uredinium density was linear up to incidences of about 83%.
A potato wilt disease in South Africa caused by Erwinia carotovora subspecies carotovora and E. chrysanthemi
Authors: SERFONTEIN S. , LOGAN C. , SWANEPOEL A. E. , BOELEMA B. H. , THERON D. J.
Published: April 2007

In South Africa during the 1988 season, a wilt disease appeared in seed‐potato crops. The disease was initially characterized by a one‐sided wilt of the upper leaves, and in its advanced stage was indistinguishable from verticillium, fusarium and pseudomonas wilts. A basal stem rot was occasionally associated with wilted plants when wet, humid conditions prevailed. Erwinia carotovora ssp. carotovora and E. chrysanthemi were isolated from wilted plants, but E. carotovora ssp. carotovora was the predominant pathogen. Stem inoculations in the glasshouse showed that both pathogens were capable of causing wilt symptoms. An indication was found that E. chrysanthemi was more virulent at a higher temperature range (28‐32°C) and E. carotovora ssp. carotovora at a lower temperature range (20‐25°C). It was found that the potting compost, irrigation water and some parent tubers used for the propagation of plantlets at the Foundation Seed Scheme, Eastern Transvaal, were contaminated with E. carotovora ssp. carotovora.
Effects of leaf susceptibility and fungicide seed treatment on leaf spot of Pima cotton caused by Altenaria macrospora
Authors: SHTIENBERG D.
Published: April 2007

Effects of leaf susceptibility and seed treatment with the systemic fungicides tebuconazole (Raxil) or difenoconazole (Dragon) on Altenaria macrospora in Pima cotton were examined under glasshouse conditions and in the field. In the absence of fungicide, the susceptibility of cotyledons to Alternaria‐induced shedding increased with seedling age. Effects of seed treatment with fungicide were evident even on the third true leaves, and persisted up to 39 days after planting. Disease suppression was determined both by the fungicide and also by the susceptibility of the host tissue: seed treatment suppressed Alternaria‐induced shedding of cotyledons for 18 days, but not 29 days after planting In a field trial, disease progress was delayed by 20‐24 days in plots planted with treated seeds. The effect persisted for up to 86 days after planting. Alternaria‐induced defoliation at later stages of the season was not affected by the seed treatment. No significant differences in disease control were detected between the two fungicides.
Use of ELISA for assessing major gene resistance of potato leaves to Phytophthora infestans
Authors: HARRISON J. G. , LOWE R. , DUNCAN J. M.
Published: April 2007

Hypersensitivity and susceptibility of potato leaflets of different genotypes to Phytophthora infestans were distinguished using ELISA. Estimates of pathogen growth indicated that an intermediate reaction sometimes occurred. Visual symptoms of disease were not always closely related to the pathogen content (mycelium, μg fresh weight) of leaflets estimated by ELISA. Leaflets inoculated with 1000 zoospores in a droplet had to be incubated for at least 6‐8 days at 15 C before reliable estimates of the reaction by ELISA could be determined. Increasing the inoculum load improved the differentiation between hypersensitivity and susceptibility.
Survival of Phytophthora meadii in Sri Lankan soils
Authors: LIYANAGE N. I. S. , WHEELER B. E. J.
Published: April 2007

In laboratory tests, mycelium and sporangia of Phytophthora meadii survived in soil for about 3 weeks, whereas chlamydospores survived for 12 weeks. When petioles of rubber (Hevea brasiliensis) colonized by P. meadii were buried in soil, chlamydospores formed in the tissues after about 2 weeks and P. meadii could be reisolated up to 22 weeks after burial. Colonized petioles buried in soil in a rubber plantation decayed more rapidly than those in laboratory tests, and attempts to reisolate P. meadii after 18 weeks were unsuccessful, although chlamydospores were still visible. P. meadii was isolated most readily from soil in a rubber plantation during epidemics of pod and leaf disease, suggesting that sporangia from these sources maintained soil inoculum at a high level. Inoculum detected in soil before pod and leaf infection may have arisen from subclinical infections or from chlamydospores surviving in petioles from the previous season.
Interactions between Fusarium oxysporum f. sp. racheiphilum and Meloidogyne spp. in Vigna unguculata. 2. Specificity of different taxa
Authors: HARRIS A. R. , FERRIS H
Published: April 2007

A California isolate of Meloidogyne javanica increased Fusarium wilt symptoms in cowpea cultivars California Blackeye No. 3 (CB3) (resistant to wilt) and Grant (tolerant) inoculated with each of the three races of Fusarium oxysporum f. sp. tracheiphilum. The same isolate of M. javancia did not similarly increase wilt in wilt‐resistant cultivar CB7977 inoculated with two isolates of race 3 of F. o. tracheiphilum. Six of seven isolates of M. javanica caused similar increases in vascular discoloration in cultivar CB3. but one isolate of M. javanica and seven of M. incognita did not. Vascular discoloration rating was positively correlated with galling severity. However, increasing the initial inoculum density, and thus galling index, of one isolate of M. incognita did not increase vascular discoloration. The vascular discoloration ratings for the wilt‐susceptible CB5 controls in each experiment were higher than those for the wilt‐resistant cultivars infected with M. javanica. It is hypothesized that M. javanica but not M. incognita reduces, but does not eliminate, resistance to all races of F. o. tracheiphilum in cultivars CB3 and Grant.
Interactions between Fusarium oxysporum f. sp. tracheiphilum and Meloidogyne spp. in Vigna unguiculata. 3. Pathogenesis by F. o. tracheiphilum as affected by M. javanica and host cultivar
Authors: HARRIS A. R. , FERRIS H.
Published: April 2007

Experiments were conducted to determine the temporal and spatial effects of Meloidogyne jav anica and host cultivar on pathogenesis by Fusarium oxysporum f. sp tracheiphilum in cowpea. In the wilt‐susceptible cowpea cultivar California Blackeye No. 5 (CB5). F. o. tracheiphilum proliferated rapidly in both the hypocotyl and first internode 6 weeks after inoculation. The fungus spread quickly upward as plants grew, colonized most tissues within 6 weeks, and caused severe wilt. In wilt‐resistant cultivar CB3. there was little proliferation of F. oxysporum in any tissue, whether or not plants were infected by St. javanica. The fungus was found above the primary internode in 15”., of all CB3 plants, but did not continue to spread upward after 4 weeks Vascular discoloration was greatest when St. javanica was added 4 weeks before F. o. tracheiphilum, but simultaneous inoculation also increased wilt symptoms Root wounding did not increase wilt. Split‐root experiments provided no evidence that infection by, M. javanica results in a translocatable factor that reduces wilt resistance. When hypocoivls were inoculated with F. o. tracheiphilum at different intervals after roots infected by St. jav anica were removed, there was no evidence that the effect of the nematode on wilt susceptibility was translocated or persistent.
Powdery mildews on borage (Borago officinalis) and evening primrose (Oenothera biennis)
Authors: O'NEILL T. M. , GLADDERS P. , COOK R. T. A.
Published: April 2007

The powdery mildews Erysiphe cynoglossi and E. howeana, causing disease on borage (Borago officinalis) and evening primrose (Oenothera biennis), respectively, are reported for the first time in Britain.
Melanotus proteus: a newly recorded colonist of Sitka spruce stumps in Britain and a potential competitor for Heterobasidion annosum
Authors: REDFERN D. B.
Published: April 2007

The widespread occurrence in Scotland of M. proteus. which was previously regarded as rare, is reported. It is a common colonist of Sitka spruce stumps which merits consideration as a potential biological control agent against the tree‐root pathogen H. annosum. There is some evidence that it may act as a decay organism in wounded Sitka spruce.
Characterization of an isolate of beet mosaic virus from South Kazakhstan
Authors: ROGOV V. V. , KARASEV A. V. , AGRANOVSKY A. A. , GORBUNOVA N. I.
Published: April 2007

A filamentous virus isolated from a sugar‐beet plant showing systemic mosaic collected in South Kazakhstan was identified as an isolate of beet mosaic virus (BMV‐K). BMV‐K was transmitted by the green peach aphid Myzus persicae in a non‐persistent manner, and by sap inoculation to 11 out of 19 species from seven families tested. The virus could not be transmitted to Nicotiana tabacum, N. debneyi, N. glutinosa and N. clevelandii, cither mechanically or with M. persicae. The thermal inactivation point of BMV‐K in sugar‐beet sap was 55‐60 C, dilution end point 1:1000 and longevity in vitro 2 days at 20 C. A purification procedure produced 1‐5‐3 mg of purified virus from 100 g of infected Stellaria media plants. Purified virus contained a single protein species of molecular weight 34 700 Da. In ELISA tests, BMV‐K reacted positively with BMV‐specifc antisera obtained from Japan. Germany and Portugal. By competitive DAS‐ ELISA, the virus isolate was shown to be closely serologically related to all the three isolates of BMV, and very distantly related to bean yellow mosaic and soy bean mosaic viruses.
Assessment of in vivo screening systems for potential biocontrol agents of Gaeumannomyces graminis
Authors: RENWICK. A. , CAMPBELL R. , COE S.
Published: April 2007

A screening programme was used to search for biocontrol agents against Gaeumannomyces graminis causing take‐all disease of wheat. Of the 1800 rhizosphere microorganisms tested, 10% controlled the disease in a secondary screen. The 30 most effective isolates were further investigated for mode of action. Although 72% of the sites sampled for antagonistic microbes were planted to continuous cereals, they yielded only 23% of the most effective isolates. Of all the isolates selected, 63% belonged to the genera Bacillus, Pseudomonas and Penicillium; Beauveria and Rhodococcus were also antagonistic. Fluorescent pseudomonads, all producing siderophores in low‐iron medium, accounted for 23% of the isolates. Over 50% of strains produced β‐glucanases and chitinases. Less than 50% of the strains selected by the in vivo screen inhibited G. graminis in agar plate tests. In the gnotobiotic system used, the Pseudomonas strains were faster in colonizing the wheat roots than the majority of the Bacillus and fungal strains.
Genetics of resistance to beet western yellows virus in lettuce
Authors: PINK D. A. C. , WALKEY D. G. A. , McCLEMENT S. J.
Published: April 2007

Resistance to beet western yellows virus (BWYV) in the lettuce cultivars Burse 17 and Crystal Heart was controlled by a single recessive gene designated bwy. ELISA tests showed that resistant plants were not immune to infection by BWYV, and may develop some mild symptoms. However, the concentration of virus found in resistant plants was less than in susceptible ones. The cultivar Crystal Heart is being used as a source of resistance for breeding BWYV‐resistant crisp lettuce (iceberg) cultivars.
Characteristics of strains of Septoria nodorum adapted to wheat or to barley
Authors: NEWTON A. C. , CATEN C. E.
Published: April 2007

Sixty‐four strains of Septoria which had been isolated from a range of hosts at different locations and in different years were characterized for their adaptation to wheat or barley, growth at near‐maximum temperature, fluorescence, colony morphology, conidial (pycnidiospore) length and hexokinase and alkaline phosphatase isozymes. For each character except conidial length, the strains could be divided into two or three discrete groups. The variation in these six characters was strongly associated, such that 60 strains could be classified into two groups, designated W‐type and B‐type. W‐type strains are adapted to wheat, produce large colonies at 31 C, fluoresce, produce brown‐pigmented colonies, and have fast isozymes. B‐type strains are adapted to barley, produce small colonies at 31 C, do not fluoresce, produce pink‐pigmented colonies, and have slow isozymes. A few strains differed from these norms in one of the six characters, but only one showed an atypical host adaptation. The four unclassified strains differed from W‐ or B‐type in two or more characters. The many differences between the W‐ and B‐types suggest they are genetically distinct populations within Septoria nodorum.
A comparison of cultural, morphological and DNA markers for the classification of Pseudocercosporella herpotrichoides
Authors: NICHOLSON P. , HOLLINS T. W. , REZANOOR H. N. , ANAMTHAWAT‐JONSSON K.
Published: April 2007

Isolates of Pseudocercosporella herpotrichoides were classified by a variety of established techniques including colony morphology, colour, pathogenicity on seedlings and spore morphology. In all cases, certain isolates could not be clearly classified and correlation between the systems was incomplete. In particular, the typing system of Nirenberg in which two varieties of P. herpotrichoides (var. herpotrichoides and var. acuformis) are recognized did not correlate with the widely used UK system based on colony morphology on PDA: fast, even (F E) and slow, feathery (S/F). Restriction fragment length polymorphisms in total DNA and rDNA indicated groupings related to morphology (and pathogenicity) with considerable polymorphisms in rDNA of F/E isolates. Generally, good correlation was found between RFLP markers and other tests.
Phenotypic instability of flusilazole sensitivity in Venturia inaequalis
Authors: KÖLLER W. , SMITH F. D. , REYNOLDS K. L.
Published: April 2007

Sensitivities of 16 monoconidial isolates of Venturia inaequalis to the sterol demethylation inhibitor flusilazole were found to be stable, when cultures which had been successively transferred to inhibitor‐free nutrient agar and maintained at 20 C were retested 6 months after isolation. In contrast, with storage of these isolates at 2 C for 7 additional months, phenotypic sensitivities were subject to change. A high degree of phenotypic instability was also observed for 77 representative strains which had been subcultured for 10 months. In both cases, the majority of strains became more sensitive to flusilazole. The frequency and magnitude of these changes were most pronounced for strains with moderate levels of resistance. More than 70% of the strains investigated were collected from wild‐type populations, suggesting that the reversion of resistant strains was not related to a process of unstable adaptation but to a high degree of plasticity in the genetic control of sensitivities to sterol demethylation inhibitors.
Occurrence of Tapesia yallundae apothecia on field and laboratory‐inoculated material and evidence for recombination between isolates
Authors: NICHOLSON P. , REZANOOR H N. , HOLLINS T. W.
Published: April 2007

Tapesia yallundae was observed in early July on wheat straws, which had been inoculated with isolates of Pseudocercosporella herpotrichoides (W‐type) 9 months previously and placed in plots of winter wheat, to act as inoculum in a resistance screen. A perfect state was not observed on straws inoculated with R‐type isolates in the same experiment. One hundred and thirty‐four single‐ascospore isolates were obtained and observations on morphology in culture, pathogenicity to wheat and rye seedlings, resistance to benomyl and the pattern of restriction fragment length polymorphisms demonstrated that all isolates were W‐type, although some grew at half the expected rate on agar, and at least two isolates were involved in the production of apothecia. Apothecia were produced in vitro on straws inoculated with single isolates of P. herpotrichoides only when they were incubated in contact with other straws similarly inoculated with certain other isolates. No apothecia were produced on straws with only isolate present, suggesting the need for at least two strains, possibly representing different mating types, for apothecium formation. Apothecia of T. yallundae were produced in vitro on straw pieces which had been inoculated individually with W‐type isolates, 14‐16 weeks after straws of different isolates were mixed. Evidence for genetic recombination between isolates was obtained when single‐ascopore colonies were analysed for resistance to benomyl in culture and for restriction‐length polymorphisms (RFLPs).
Pestalotiopsis leaf spot of Brazil wood, Caesalpinia echinata
Authors: de LOURDES MENDES MARIA , MUCHOVEJ J. J.
Published: April 2007

A necrotic leaf spot of Brazil wood trees is reported as caused byPestalotiopsis maculans.This appears to be the first report of such a disease.
Quick decline of macadamia trees: association with Xylaria arbuscula
Authors: KO W. H. , KUNIMOTO R. K.
Published: April 2007

Some macadamia trees in a commercial orchard on the island of Hawaii showing symptoms of quick decline had club‐shaped fruiting bodies of Xylaria arbuscula on the trunk. X arbuscula was consistently isolated from diseased wood and was shown to kill branches of healthy macadamia trees on inoculation. Trunk infection by this pathogen leading to girdling resulted in a more rapid decline than would be expected with root infection by soil‐borne pathogens.
Incidence in Cyprus of citrus exocortis viroid and its mechanical transmission
Authors: KYRIAKOU ANASTASIA P.
Published: April 2007

A survey for citrus exocortis viroid (CEV) was conducted in commercial groves of the main citrus‐producing areas of Cyprus during 1987–1990. Of 573 trees sampled, representing 25 species and varieties, 506 (88.3%) were found to be infected when indexed by grafting to seedlings of‘Etrog’ citron (Citrus medica), selection Arizona 861. Levels of infection by CEV were lower in newer introductions than in introductions made before the 1940s. In greenhouse tests, CEV was readily transmitted from citron to healthy citron and gynura (Gynura aurantiaca) by knife‐blade inoculation. Retransmission of CEV from infected gynura back to citron was successful.
A rhabdovirus inducing vein yellowing in croton
Authors: BERTACCINI A. , BELLARDI M. G.
Published: April 2007

A rhabdovirus was found in some dwarfed plants of croton (Codiaeum variegatum) cv. Fred Sander. The plants showed malformations and yellow or pink veins. Bullet‐shaped particles (70–80 × 180–240 nm) were observed in leaf‐dip preparations and in ultrathin sections of diseased leaf tissue examined by electron microscopy. This rhabdovirus was mechanically transmitted by sap inoculation to Nicotiana glutinosa and Chenopodiun amaranticolor, and by leaf grafting to healthy croton plants in which it induced vein yellowing and dwarfing.
Occurrence of Verticillium dahliae on linseed (Linum usitatissimum) in the UK and Germany
Authors: FITT B. D. L. , BAUERS F. , BURHENNE S. , PAUL V. H.
Published: April 2007

In July and August 1990, symptoms of verticilliosis were common in maturing crops of linseed sampled in Hertfordshire, UK and throughout Germany. Grey chlorotic or brown stripes were observed on green stems; on maturing, light brown stems the stripes were dark brown. Symptoms frequently extended along the whole length of the stems and branches up to the capsules, and often spread completely round the stems. Black microsclerotia developed abundantly in stems with these symptoms and Vertkillium dahliae was consistently isolated from them. The incidence of verticilliosis increased from 50 to 100% in untreated plots (cv. Antares) between 8 and 22 August at Rothamsted, UK and was not decreased greatly by fungicide treatments. The incidence ranged from 49 to 98% on cultivars and breeding lines in trials at Thüle, Germany on 9 September. V. dahliae was isolated from seed from Rothamsted plots at an incidence of < 10%.
First record of Phytophthora inflata in the United Kingdom
Authors: HALL G. , DOBSON S. , NICHOLLS C.
Published: April 2007

The occurrence of Phytophthora inflata on Sambucus tenuifolium and Syringa vulgaris at a plant nursery in Suffolk, UK is reported. This is the first record of P. inflata since its description in the USA in 1949.
Genetic control of the response of Erysiphe graminis f.sp. hordei to ethirimol and triadimenol
Authors: BROWN J. K. M. , JESSOP A. C. , THOMAS S. , REZANOOR H. N.
Published: April 2007

A study was conducted on the genetic control of the response of Erysiphe graminis f.sp. hordei, the causal agent of barley powdery mildew, to two fungicides: the hydroxypyrimidine ethirimol, and the triazole, sterol demethylation inhibitor triadimenol. In tests of responses to both fungicides, sets of progeny of various crosses were classified by principal components analysis into discrete resistant and sensitive classes. A single allele controlled the response to ethirimol of the resistant isolate DH14 in crosses with the sensitive isolates CC52 and CC138. The ethirimol‐resistance alleles of DH14 and another resistant isolate. CC107, are at the same locus or are closely linked. Alleles at single loci controlled resistance and sensitivity to triadimenol in crosses of DH14 (sensitive) with CC107 (moderately resistant) and CC138 (highly resistant). There was no evidence for polygenic control of response to either fungicide. The ethirimol response locus and the two putative triadimenol response loci are designated Eth1 and Tdl1 and Tdl2, respectively. There was no evidence for linkage of Eth1 and Tdl2 in the cross CC138 × DH14, in which responses to both fungicides segregated.
The effect of sowing date on infection of sugar beet by Polymyxa betae
Authors: BLUNT S. J. , ASHER M. J. C. , GILLIGAN C. A.
Published: April 2007

The effect of sowing date on the infection of sugar‐beet seedlings by Polymyxa betae was examined in a small‐plot experiment on a naturally infested site. Seed was sown on seven occasions at weekly intervals from late March to early May. From each sowing, plant samples were taken at approximately weekly intervals over a period of 7 weeks. The extent of root infection by P. betae and the dry weight of plants was determined at each sampling date, and the progress of infection and rate of plant growth were examined against time and thermal time. Infection occurred sooner after sowing and the subsequent rate of fungal development was more rapid in late‐sown than in early‐sown plants. Early sowing allowed germination and growth of sugar beet at temperatures too low for fungal infection. The growth of late‐sown plants appeared to be reduced by P. betae infection. The implications of these findings for the development of rhizomania disease are discussed.
Variation in the resistance of barley cultivars and in the pathogenicity of Drechslera teres f. sp. maculata and D. teres f. sp. teres isolates from France
Authors: ARABI M. I. , BARRAULT G. , SARRAFI A. , ALBERTINI L.
Published: April 2007

Isolates of Drechslera teres that cause net or spot‐type symptoms on barley (Hordeum vulgare) were collected in 1986 and 1987 from fields in different regions of France. Variations in pathogenicity were evaluated using 12 barley cultivars. The Middle‐Eastern cultivars Arrivate and 79‐S10‐10 were resistant to all isolates except R5 and S5. The Ethiopian cultivar C1 5791, previously reported to be resistant, was susceptible to the R5 and S5 biotypes. There was a high correlation coefficient between the classification of cultivars for resistance to D. teres f. sp. teres and D. teres f. sp. maculata. A method for conserving the virulence of the isolates on straw is evaluated. The virulence level of the isolates was the same after 4 years of storage using this method.
Strategies for control of seed‐borne Alternaria dauci (leaf blight) of carrots in priming and process engineering systems
Authors: MAUDE R. B. , DREW R. L. K. , GRAY D. , PETCH G. M. , BUJALSKI W. , NIENOW A. W.
Published: April 2007

Laboratory and glasshouse experiments demonstrated that priming of carrot seeds infected with Alternaria dauci did not affect the rate of transmission of the pathogen. Iprodione applied as a dust to unprimed, infected seeds at 5 ga.i. per kg seed effectively reduced disease transmission. Iprodione (0.1% a.i.) or thiram (0.1% a.i.) added in polyethylene glycol (PEG; filter paper or bubble‐column priming systems) only partially reduced infection. Further dusting of the primed and dried seeds with iprodione, or alternatively application of that fungicide in a polymer film coat as the final stage in the process engineering of carrot seeds, was necessary to achieve complete control. The addition of thiram in the priming fluid, followed by an application of iprodione to the primed and dried seeds, improved the emergence and yield of carrots in the field.
Effect of inoculum source on root and tuber infection by potato blemish disease fungi
Authors: DASHWOOD E. P. , FOX R. A. , PERRY D. A.
Published: April 2007

The incidence of potato pathogens on healthy roots of micropropagated (MP) and seed tuber (ST) plants was examined on successive dates during the growing season in two field experiments. Microplants were grown in a glasshouse for 4–5 weeks in perlite or peal‐based substrates, and exposed or not to natural inoculum before planting in the field. The seed tubers originated from stocks of visually clean or moderately blemished tubers and were surface‐sterilized or not before planting. Polyscytalum pustulans and Helminthosporium solani only infected roots of ST plants and inoculated MP plants. The incidence of P. pustulans was affected by seed tuber‐borne inoculum and, in I year, by the substrate. H. solani was detected infrequently on roots. Rhizoctonia solani was present at low frequencies in most root samples, and more ST than MP plant roots were colonized; there were no substrate effects. In 1 year, increased inoculum levels increased root infection, but only in MP roots. Colletotrichum coccodes occurred at high frequencies and was most common in roots of ST plants. Progeny tubers showed some treatment effects when tested in September and after storage for 6 months, but there were no consistent relationships between root and progeny tuber infection.
Bacterial rot of witloof chicory roots caused by Erwinia chrysanthemi
Authors: LE GUERN J. , TIRILLY Y. , LE PICARD D. , LE STER D.
Published: April 2007

Erwinia chrysanthemi (biovars 5 and 6) was isolated from unusual symptoms on witloof chicory, both in the field and in hydroponic culture, in Brittany in 1989 and 1990. Symptoms included a greyish‐brown soft rot on the lower part of the root and the destruction of the cortical tissues. The cribrovascular and the medullary part of the bottom of the root sometimes became slimy. A few cases of vascular transmission were observed, which resulted in a red coloration of the infected vessels and a soft rot of the leaves.
The distribution of Calyptella root rot in commercial glasshouse tomato crops in England
Authors: SANDYS‐WINSCH D. C. , JEVES T. M.
Published: April 2007

The widespread distribution of Calyptella root rot in commercial tomato crops in England is confirmed. The disease is thought to be more prevalent than previously believed, having been isolated from over 50% of ostensibly Calyptella‐free crops in Lancashire.
Changes in abundance and infectivity of powdery mildew conidia from cucumber plants treated systemically with lithium chloride
Authors: ABOOD J. K. , LÖSEL D. M. , AYRES P. G.
Published: April 2007

Systemic treatment of cucumber plants with lithium chloride reduced the numbers of conidia produced by colonies of powdery mildew, Sphaerotheca fuliginea, growing on leaves, and lowered the infectivity of conidia produced from those leaves when they were applied to leaves of untreated plants. Production of conidiophores was lower in both lithium‐treated and calcium‐deprived plants, and lithium slightly decreased the calcium content of leaves. When the lithium‐containing growth medium was supplemented with phosphate, conidiophore production was still markedly reduced, although leaves had normal levels of calcium. Fungal development was not correlated with either the calcium or phosphorus content of leaves. It is concluded that, although severe calcium deficiency can inhibit fungal development, the inhibitory effects of lithium are not mediated through alterations in calcium or phosphorus uptake by host tissues.
Effect of powdery mildew (Erysiphe pisi) on nodulation and nitrogenase activity in pea (Pisum sativum)
Authors: SINGH U. P. , MISHRA G. D.
Published: April 2007

The effects of powdery mildew (Erysiphe pisi) disease of pea (Pisum sativum) on the number and size of root nodules and on nitrogenase activity were investigated in pea plants grown in pots and in the field. There were significant reductions in nodulation and in the size of root nodules as well as in nitrogenase activity in infected plants.
Effect of crop age on primary gradients of late leaf spot (Cercosporidium personatum) on groundnut
Authors: SAVARY S. , VAN SANTEN G.
Published: April 2007

Artificial sources of late leaf spot were established by inoculation of one plant at the centre of several groundnut plots differing in age. First‐generation dispersal and resulting primary gradients of disease were then compared. The gradients were corrected for source strength, spontaneous infection (primary gradient), and interplot interference (first‐generation dispersal). The shapes of the gradients for spore dispersal and of the gradients of disease corresponded for each age of groundnut plot, but differed between the ages. The slopes of gradients were steeper in the older plots. Spore dispersal and the resulting disease gradients were not isodiametric, gradients being most protracted in a north‐to‐north westerly direction. The results suggest that the strength of the sources was reduced by abscission of infected leaves in the sources of the younger plots, whereas accessibility of the canopy to the transported spores was reduced by increasing canopy density in the older ones.
Differential production of parasiticein, an elicitor of necrosis and resistance in tobacco, by isolates of Phytophthora parasitica
Authors: RICCI P. , TRENTIN F. , BONNET P. , VENARD P. , MOUTON‐PERRONNET F. , BRUNETEAU M.
Published: April 2007

Fifteen isolates of Phytophthora parasitica, nine from tobacco (causing black shank disease) and six from other host plants, were compared by root inoculation with regard to their pathogenicity to young tobacco plants. A progressive invasion of the aerial parts over 1 week was observed only with the black shank isolates, while the non‐tobacco isolates induced leaf necrosis within 2 days. Similar necrosis occurred when the roots of tobacco plants were dipped in diluted culture filtrates from non‐tobacco isolates, but not in those from tobacco isolates. The necrosis‐inducing filtrates were shown to contain a c. 10‐kDa protein band which was not present in the other filtrates. This protein (named parasiticein) was purified by ion‐exchange chromatography to homogeneity in SDS‐PAGE and reverse‐phase HPLC. Parasiticein was serologically related to cryptogein, a member of the elicitin family of proteinaceous elicitors previously described from other Phytophthora species. Like the other elicitins, parasiticein induced necrosis in tobacco plants and protected them against black shank. It most closely resembled capsicein in being acidic and in inducing resistance at concentrations (10–100 μg per plant) that caused little leaf necrosis. It is suggested that the absence of parasiticein production by the black shank isolates might be a factor involved in their specific pathogenicity to tobacco.
Screening for resistance of Allium species to Sclerotium cepivorum with special reference to non‐stimulatory resistance
Authors: BRIX H. D. , ZINKERNAGEL V.
Published: April 2007

Approximately 150 seed lots of Allium cepa and more than 30 different Allium species were tested in the greenhouse under strictly controlled conditions against Sclerotium cepivorum, the causal fungus of Allium white rot disease. The quantity and quality of the inoculum was determined using a simple and rapid test to achieve a high degree of standardization. Only the A. cepa cultivar “Sweet Sandwich’ and A. porrum, A. rotundum, A. sphaerocephalon and two further unidentified Allium species showed significantly lower disease incidence than the cultivar ‘Golden Bear’. The stimulatory effect of the root exudates on sclerotial germination was compared with that of diallyl sulphide. With the exception of A. species‘PI 249549′, extracts of all species that showed low levels of disease incidence in the greenhouse test stimulated sclerotial germination only weakly.
Inhibition of Septoria tritici and other phytopathogenic fungi and bacteria by Pseudomonas fluorescens and its antibiotics
Authors: LEVY E. , GOUGH F. J. , BERLIN K. D. , GUIANA P. W. , SMITH J. T.
Published: April 2007

Pseudomonas fluorescens strain PFM2, antagonistic to Septoria tritici, also inhibited growth of several other phytopathogenic bacteria and fungi in vitro. Three inhibitory compounds were extracted from liquid glycerol‐peptone‐phosphate medium in which strain PFM2 was grown for 4 weeks. The compound recovered in greatest quantity (70 mg/1) was identified as 2,4‐diacetylphloroglucinol. The other two antibiotics, which were produced in small amounts (< 5 mg/l), were not identified. A similar pattern of inhibition against the different bacteria and fungi was exhibited by both 2,4‐diacetylphloroglucinol and strain PFM2 when grown in a medium of the same composition as that in which the antibiotic was produced.
Evaluation of a DNA probe for the detection of Erwinia herbicola strains pathogenic on Gypsophila paniculata
Authors: MANULIS S.
Published: April 2007

A 7.5‐kb DNA fragment carrying genes for indole acetic acid biosynthesis in Erwinia herbicola pv. gypsophilae was used as a DNA probe to detect gall‐forming E. herbicola strains. A quick colony hybridization procedure was developed to detect E. herbicola pv. gypsophilae in cuttings of gypsophila, and was compared with ELISA and pathogenicity tests. The sensitivity of the colony hybridization procedure was sufficient to detect less than 100 colony‐forming units after enrichment culture. In mixed cultures, with saprophytes associated with the gypsophila plant, about 104 CFU/ml of the pathogen were detectable. The colony hybridization is specific to gall‐forming E. herbicola strains, and is relatively easy to perform. The advantages of using the colony hybridization procedure for practical purposes, compared with ELISA and pathogenicity tests, are discussed.
Surveys of cassava plantations in Colombia for virus and virus‐like diseases
Authors: NOLT B. L. , PINEDA L. B. , VELASCO A. C.
Published: April 2007

The cassava common mosaic virus (CsCMV) and the frogskin (FSD) disease agent have been reported to reduce cassava yields significantly in South America. However, little information is available on the distribution and incidence of these and other cassava virus diseases in Colombia. Cassava plants collected in three principal cassava production zones of Colombia were tested for the presence of CsCMV, cassava × virus (CsXV), and the Caribbean mosaic disease (CMD) and FSD agents. Some plants were also tested for the presence of double‐stranded RNA (dsRNA). CsCMV was not detected in any of the 870 plants from 86 plantations. CsXV was detected in 51% of the 150 plants collected in the Cauca Department in south‐central Colombia. The virus was present on all 15 cassava plantations surveyed. The CMD agent was detected in 17% of the 138 plants sampled in the Department of Magdalena in northern Colombia. FSD root symptoms were observed on 25 and 3% of plants examined in the Departments of Cauca and Magdalena, respectively. None of the 570 plants collected in areas west of the Rio Magdalena in the Departments of Atläntico, Bolivar, Córdoba and Sucre were found to be infected with any of these disease agents. However, some plants sampled in this region were found to contain multiple dsRNA species of unknown origin.
Expression of resistance to Mycosphaerella pinodes in Pisum sativum
Authors: CLULOW S. A. , LEWIS B. G. , MATTHEWS P
Published: April 2007

The infection of three resistant and two susceptible inbred lines of Pisum sativum by Mycosphaerella pinodes is described for the first time. Two types of resistance, one expressed in epicotyls and one in leaves, were found in all three resistant lines. On epicotyls of susceptible lines, abundant appressoria and penetrations occurred after a short period of hyphal growth. On epicotyls of resistant lines, hyphae grew extensively but rarely formed appressoria, and these failed to penetrate the cuticle. Attempted penetration was associated with the rapid death of 2–6 epicotyl cells, resembling a hypersensitive reaction. In contrast, resistance of leaves, which was only expressed after penetration, involved localization of the fungus by a mechanism involving delayed leaf cell death. It is suggested that a combination of these two types of resistance might provide effective protection against M. pinodes.
Occurrence of a new powdery mildew of greenhouse tomato in Greece, caused by Erysiphe sp.
Authors: VAKALOUNAKIS D. J. , PAPADAKIS A.
Published: April 2007

An epiphytic pathogen causing powdery mildew on greenhouse‐grown tomato (Lycopersicon esculentum) appears for the first time in Greece and is identified as belonging to the genus Erysiphe.
Specificity of polyclonal antibodies to different antigenic preparations of Pseudomonas syringae pv. pisi strain UQM551 and Pseudomonas syringae pv. syringae strain L
Authors: MAZAREI M. , HAJIMORAD M. REZA , KERR A.
Published: April 2007

Polyclonal antibodies were produced against sonicated and heat‐killed cells of Pseudomonas syringae pv. pisi strain UQM551 and Pseudomonas syringae pv. syringae strain L, and their specificities were compared. Evidence is presented that the serological specificity between these two pathovars lies in surface antigens. Of the surface antigens purified and tested, only flagella and lipopolysaccharide from the cell wall showed no cross‐reactivity with heterologous antisera. Antisera to glutaraldehyde‐fixed flagella of the two strains showed a high level of specificity. At a species or genus level, antisera prepared from heat‐killed cells ofP. syringae distinguished this species from all other bacterial species and genera tested, including strains of Pseudomonas fluorescens, Escherichia coli, Agrobacterium and Rhizobium.
Induction of systemic resistance to rust in Vicia faba by phosphate and EDTA: effects of calcium
Authors: WALTERS D. R. , MURRAY D. C.
Published: April 2007

Resistance in the upper leaves of broad bean (Vicia faba) plants to infection by the rust fungus, Uromyces viciae‐fabae, was increased following treatment of the lower leaves with 10 mm potassium phosphate or 5 mm EDTA. Increasing the interval between treatment of the lower leaves and inoculation of the upper leaves had little effect on rust infection. Thus rust infection was reduced by 50 and 34% if the upper leaves were inoculated 1 day after treatment of the lower leaves with potassium phosphate or EDTA, respectively, while there was a 75% reduction in infection if the interval between treatment and inoculation was increased to 12 days. Application of calcium nitrate (10 mm) after the phosphate or EDTA treatments prevented the induction of systemic resistance. Calcium nitrate applied alone to the lower leaves had no significant effect on rust infection of the upper leaves.
An evaluation of a virobacterial agglutination test for the detection of plant viruses
Authors: WALKEY D. G. A. , LYONS N. F. , TAYLOR J. D.
Published: April 2007

Agglutination of Staphylococcus aureus bacteria particles, conjugated with specific virus antibodies, has been used to identify a wide range of plant viruses in crude sap extracts. The test distinguishes between seven different potyviruses in homologous and heterologous reactions, but does not distinguish different strains of bean yellow mosaic virus. The sensitivity of the virobacterial agglutination (VBA) test compares favourably with virus detection in ISEM particle trapping and local lesion assay and is only slightly less sensitive than direct ELISA tests. The test is more sensitive and simpler to user than latex particle agglutination tests.