bluuebunny/crossref_metadata_2025 huggingface dataset:
Susceptibility of Cut Rose Flower Cultivars to Infections by Different Isolates of Botrytis cinerea
Authors: Pie K. , Brouwer Y. J. C. M.
Published: May 2008

A method was developed for the inoculation of flowers of cut roses with conidia of Botrytis cinerea. Flower buds were inoculated by spraying of conidial supensions that were ultrasonicated for 10 s. The differences in susceptibility between 8 rose cvs to infections of isolate Bc‐33 and the differences in pathogenicity between 14 5. cinerea isolates to cv. ‘Sonia’ were evaluated. Isolates obtained from rose flowers caused higher infection rates than those obtamed from various other hosts. The CVS ‘Madelon’, ‘Melody’ and ‘Sonia’ were found to be highly susceptible, whereas the cvs ‘Caramboie’, ‘Gabriella’, ‘Pasadena’ and ‘Rubinette’ were only slightly susceptible. The lower disease severity in the less susceptible cvs was based on a retardation of the growth of mfection hyphae in the petals, which may have been due to partial resistance. The formation of symptoms is effectuated already by the initial stages in the infection process. Thus, the apparent existing partial resistance to infections of B. cinerea cannot prevent the loss of ornamental value.
Systemic Infection of Tobacco by Pepper Veinal Mottle Potyvirus (PVMV) Depends on the Presence of Potato Virus Y (PVY)
Authors: Marchoux G. , Delecolle B. , Selassie K. Gebre
Published: May 2008

In single inoculations, both PVY and PVMV replicated in inoculated leaves of Nicotiana tabacum cv. ‘Xanthi nc’ plants, but only PVY infected the tobacco plants systemically, whereas PVMV caused localized infection.

A mixed infection by the PVY‐To72 and PVMV‐type strains was experimentally realized in ‘Xanthi nc’ plants. In the presence of PVY, PVMV migrated systemically into the upper leaves of the tobacco plant, as was proved by back inoculation.

It would appear that in tobacco, PVY acts as a “helper” virus, providing PVMV with the necessary component factor for migration.

In extracts from the co–infected leaves. Immune Electron Microscopy (IEM) revealed phenotypic mixed particles which contained a mixture of coat proteins of PVY and PVMV.

The role of the structural and functional interactions between the two viruses, which enable PVMV to migrate systemically in tobacco plants, is discussed.
Variation of Cell‐free Translation Profiles Among Pathogenic Strains of Soybean Mosaic Virus
Authors: Mansky L. M. , Durand D.P. , Bailey T. B. , Hill J. H.
Published: May 2008

Cell‐free translation products from isolates representing soybean mosaic virus (SMV) strains G1 to G7 and G7a, along with several other SMV isolates, were analyzed. SMV RNAs were translated in both rabbit reticulocyte lysates and wheat germ extracts, yielding approximately 20 translation products for each strain from each translation system. Comparison of translation profiles by the presence or absence of proteins allowed for the formation of distinctive groups from each cell‐free translation system. Groupings formed by analysis of products from rabbit reticulocyte lysates correlated with pathogenicity; groupings formed by analysis of products from wheat germ extracts had no apparent biological significance.
Effect of Microdochium nivale and Low Temperature on Winter Survival of Perennial Ryegrass
Authors: Prończuk Maria , Zagdańska Barbara
Published: May 2008

Winter survival of perennial ryegrass (Lolium perenne L.) depends mainly on the plant resistance to low freezing temperature and to snow mould fungi (Microdochium nivale). Field evaluation of these plant characters gave irreproducible results. A comparison of field trials with laboratory tests pointed to the close correlation between the yield level of examined varieties and strains and their resistance to Microdochium nivale and frost. A lack of correlation between snow mould resistance and frost tolerance was shown.
Production and Use of Monoclonal Antibodies to Pseudomonas andropogonis
Authors: Li Xiang , Wong W. C. , Hayward A. C.
Published: May 2008

Pseudomonas andropogonis is an important pathogen of worldwide distribution in ornamental and other plant species from 15 families. This paper reports the production and characterization of monoclonal antibodies (MAbs) to P. andropogonis and evaluation of their use in the detection of the pathogen in carnation cuttings. Ten stable hybridoma cell lines were produced. Results of indirect ELISA and indirect immuno‐fluorescence showed that MAb 6B3 was specific for P. andropogonis; MAb 3D5W1 reacted with both P. andropogonis and P. caryophylli; six other MAbs reacted with all strains of seven species of rRNA group II pseudomonads tested except P. solanacearum and P. pickettii. Eight of the ten MAbs failed to cross‐react with other non‐fluorescent or fluorescent pseudomonads, xanthomonads and other bacteria tested. P. andropogonis was similar in protein profile to other rRNA group II pseudomonads tested except P. solanacearum and P. pickettii. Epitopes were clearly located within the cell by immunogold labelling. Of four MAbs that were isotyped, two possessed IgGl and two the IgM heavy chain. P. andropogonis was readily detected by combining immunofluorescence and detached carnation leaf assay using an initial inoculum of 4 × 10° colony forming units (cfu) ml−1 after enrichment at room temperature for 4 days.
Physiological Responses of Tomato Plants Grown in Fusarium Suppressive Soil
Authors: Tamietti G. , Ferraris L. , Matta A. , Abbattista Gentile I.
Published: May 2008

Tomato plants grown in a Fusarium wilt suppressive soil and in the same soil steamed and amended with non‐pathogenic Fusarium strains were protected from subsequent infection with Fusarium oxysporum f. sp. lycopersici.

Protected plants had higher laminarinase, chitinase, N‐acetyl‐glucosaminidase and β‐l, 4‐glucosidase activity than unprotected plants grown in steamed unamended soil. Higher peroxidase and polyphenoloxidase activity and higher content of phenols were also associated with suppressive soil conditions, although in a less consistent way.

Among 5 non‐pathogenic Fusarium strains, strain 5a1 was the most suppressive and enhanced enzyme activity more than did the other strains, whereas strain T was inactive and did not induce changes in activity.

These results are in accordance with previous work showing that induced resistance is associated with enhanced activity of glycosidases and phenol oxidizing enzymes, and increased phenols content. It is suggested that induced resistance is part of the mechanism of the natural suppressiveness of soil and that this resistance is induced by non‐pathogenic Fusarium strains.
Cross‐reactive Antigens between Xanthomonas campestris pv. citri Pathotypes and Citrus Species
Authors: Bach Erna E. , Alba Aluisio P. C.
Published: May 2008

Cross‐reactive antigens were detected in crude and semi‐purified preparations from acetone powder of Citrus aurantifolia and Citrus sinensis leaves with antisera to Xanthomonas campestris pv. citri pathotypes A and C by DAS‐ELISA. Antiserum to X. campestris pv. citri pathotype C revealed an antigenic disparity between C. aurantifolia (susceptible host to pathotype C) and C. sinensis (resistant host to pathotype C) whereas antiserum to X, campestris pv. citri pathotype A did not reveal any antigenic disparity between these hosts, both susceptible to pathotype A. The occurrence of “key” cross‐reactive antigens in Citrus species and X. campestris pv. citri and their possible involvement in such interaction are discussed.
Effect of Coronatine on Plant Cell Cultures
Authors: Perner B. , Schmauder H.‐P.
Published: May 2008

The effect of the phytotoxin coronatine, formed by pathovars of Pseudomonas syringae, on the plant cell cultures of Lycopersicon peruvianum, Lycopersicon esculentum, Chenopodium album and Solanum tuberosum was investigated. The parameters studied were growth, triphenyltetrazolium chloride activity (test for reductases), cell protein content and activities of polyphenol oxidase and peroxidase, both within the cells and in the culture liquid. The cultures of Lycopersicon peruvianum and Lycopersicon esculentum cultures were more sensitive than Chenopodium album and Solanum tuberosum. The more resistant cultures possess a high level of extracellular polyphenol oxidase.
Cellular Fatty Acid Composition of Nine Pathovars of Xanthomonas campestris
Authors: Wells J. , Civerolo E. , Hartung J. , Pohronezny K.
Published: May 2008

Cellular fatty acids of 80 strains of Xanthomonas campestris, representing 9 different pathovars, were analyzed by gas‐liquid chromatography and mass spectrometry. A total of 48 fatty acids were identified, the most important being the 16:0 (averaging at least 4.5 % of the total), the cis‐ and trans‐ 9 16 : 1 (over 14.4 %), and the iso and anteiso 15 : 0 (over 30 %). Other major fatty acids (averaging over 1 % of total) were the saturated 14 : 0 and 15 : 0, the hydroxy‐substituted iso 3‐OH 11 : 0, 3‐OH 12 : 0 and iso 3‐OH 13 : 0, and the branch‐chained iso 11 : 0, iso 16 : 0, iso 17 : 1, iso 17 : 0 and anteiso 17 : 0. Of 33 minor fatty acids detected and identified, only 7 have been previously reported in the xanthomonads. Significant differences in mean percentages of 5 major fatty acids and 4 (chemical) class totals were detected among pathovars, which statistically segregated into three groups by rank analysis. X. campestris pv. dieffenbachiae was in a group by itself; pvs. campestris, citri (pathotypes A and B), manihotis, phaseoli, pruni and vesicatoria were in a seond group, and pvs. glycines, begonia and citri (pathotype E) were in a third.
Aggregation of Colletotrichum acutatum in Response to Simulated Rain Episodes
Authors: Madden L. V.
Published: May 2008

The influence of rain splash dispersal on the aggregation and variability of spores of Colletotrichum acutatum, the causal agent of strawberry anthracnose, was studied with simulated rain over a soil surface. In the first experiment, rains with intensities of 15 and 30 mm/h were generated and sampling plates, with a selective medium for Colletotrichum, were positioned under rainshields at both 20 and 60 cm from an inoculum point source (five infected fruit) for 1‐min exposure periods. Number of colonies growing in plates were used to measure spore density. For each distance, time, rain intensity, and replication, the mean (m), variance (v), and Lloyd's index of patchiness (LIP) were calculated. Estimated (LIP) exceeded 1, indicating the high variability and clustering of colonies, and hence spores, resulting from splash dispersal. LIP increased with distance from the source and with rain intensity at the greater distance. Aggregation was further quantified by Taylor's power law describing the linear relation between ln (v) and ln (m). The slope (b) of the relation for all data points was 1·67, which was significantly (P < 0·01) greater than 1, a further indication of clustering. Distance form the source had a slight positive effect on b. Colony means (Y) were transformed to Y*=Y1/5 based on an approximate b of 1·6. Analysis of Y* indicated an expected significant main effect of rain duration and a significant interaction of distance and rain intensity. In another experiment, six infected fruit and the sampling plates were uniformly placed over the surface. LIP again exceeded 1, and Taylor's b equaled 1·63. In a final study, the inoculum source and sampling plates were raised 46 cm above the soil surface. There was a drastic reduction in Y* compared to surface values, supporting the prior hypothesis that surface topography strongly affects splash dispersal. Results indicate that the physical process of splash dispersal produces a degree of aggregation similar to that produced by population dynamic and other ecological processes.
Use of Rhizobia in the Control of Root Rot Diseases of Sunflower, Okra, Soybean and Mungbean
Authors: Ehteshamul‐Haque Syed , Ghaffar A.
Published: May 2008

Biocontrol potential of Rhizobium and Bradyrbizobium against soilborne root infecting fungi was tested. In vitro tests Rhizobium meliloti inhibited growth of Macrophomina phaseolina, Rhizoctonia solani and Fusarium solani while Bradyrhizobium japonicum inhibited M. phaseolina and R. solani producing zones of inhibition. In field R. meliloti, R. leguminosarum and B. japonicum used either as seed dressing or as soil drench reduced infection of M. phaseolina, R. solani and Fusarium spp., in both leguminous (soybean, mungbean) and non‐leguminous (sunflower and okra) plants.
Ultrastructure of Tobacco Ringspot Virus‐Induced Local Lesions in Lima Bean Leaves
Authors: White J. A. , Sehgal O. P.
Published: May 2008

Tobacco ringspot virus (TRSV), a nepovirus, induced unusually large, expanding lesions in the primary leaves of lima bean (Phaseolus lunatus cv. Nemagreen). During the course of lesion development, two phases were identified on the basis of ultrastructural observations. In the primary phase, cytological changes followed a pattern that was characteristic of compatible or systemic nepovirus infections. Such changes included the formation of large, membranous inclusion bodies in the cytoplasm of mesophyll parenchyma and the accumulation of phytoferritin in the stroma of chloroplasts. The cells maintained their structural integrity and appeared metabolically active. The secondary phase was degradative in nature. Ultrastructural changes observed during this phase were representative of those that occur in a virus‐induced incompatible or hypersensitive (necrotic) reaction. Such changes included rounding of chloroplasts, vesiculation and disintegration of the plasma membrane and tonoplast, degeneration of cell organelles, and generalized plasmolysis. Subsequently, the cell walls collapsed, developing folds and loops around the shrunken cytosol. The collective result of these two ultrastructurally distinctive phases was the production of large necrotic lesions in the inoculated leaf, but no systemic viral spread.
The Effect of Environmental Conditions on the Expression of Disease in Cultured Tissues of Brassica napus ssp. oldfera Infected with Leptosphaeria maculans
Authors: Gretenkort Marie A. , Ingram D. S.
Published: May 2008

As a basis for devising an in vitro screening programme, culture conditions were optimized so that tissue cultures from two resistant cultivars of Brassica napus ssp. oleifera (Mikado, Bienvenu) and two susceptible cultivars (Lesira, Ceres) could be differentiated using a disease scoring scheme, when inoculated with Leptosphaeria maculans. Tissues inoculated included thin cell layer explants from soil‐grown plants and in vitro‐grown shoot cultures and callus tissue formed on such explants. The period of incubation and the incubation temperature were of importance in the development of differential disease reactions. Increasing temperature generally resulted in an increase in infection and too great an incubation period resulted in total overgrowth of the tissue. Increasing concentrations (1 × 10−6 M‐1 ×10−4 M) of the auxins 1‐naphthylacetic acid (NAA), 2,4‐dichlorophenoxyacetic acid (2,4‐D) and mdole‐3‐acetic acid (IAA) in the culture medium, resulted in a decrease in disease score of the thin cell layer (TCL) explants from soil‐grown plants. The cytokinins examined 6‐benzyl‐aminopurine (BAP) and 6‐4‐hydroxy‐3‐methyl‐2‐enylaminopurine (zeatin), reduced the extent of infection of the TCL explants when used in combination with the auxin NAA. Medium containing NAA at a concentration of 1 × 10−6 M in combination with BAP at a concentration of 1× 10−6 or 1 × 10−4 M allowed differentiation of the disease reactions of the resistant and susceptible cultivars, when the explants were incubated for 10 days at 20 °C after inoculation. Similar conditions of incubation and the addition of NAA (1 × 10−6 M) combined with BAP (1 × 10−6 M) to the medium also allowed the differentiation of the disease reactions on TCL explants from stems of in vitro shoot cultures of the cultivars Mikado and Lesira. Increasing concentrations of the auxin NAA and the cytokinin BAP resulted in a reduction in the mean disease score of the callus tissue produced on TCL explants from soil‐grown plants, and NAA (1 × 10−5 M) combined with BAP (1 × 10−6 or 1 × 10−5 M) allowed differentiation of resistance and susceptibility in callus tissues when incubated for 5 days at 20 °C. 2,4‐D did not allow differentiation of the cultivars. This was in contrast to the inoculation of callus tissue attached to TCL explants of in vitro shoot cultures, where combinations of 2,4‐D and BAP at concentrations of 1 × 10−6 M allowed differentiation of the resistant and susceptible cultivars.

These findings provide a basis for designing selection protocols of value in both traditional as well as in vitro breeding programmes to select lines of oilseed rape with resistance/novel resistance to L. maculans.
Severe Erwinia‐Caused Damage on Opuntia ficus‐indica in Italy
Authors: Varvaro L. , Granata G. , Balestra G. M.
Published: May 2008

Erwinia carotovora subsp. carotovora. was consistently isolated from diseased tissues of prickly pear cactus (Opuntia ficus‐indica) in Sicily. The bacterium was identified on the basis of morphological, cultural, biochemical and physiological characters as well as on the basis of pathogenicity. Symptoms were observed on cladophylls and fruit: watersoaked spots became brown and coalesced; the external tissue became dry and frequently cracked; the internal tissue turned brown to almost black. The disease was first localized in a few plantations, then seriously spread to all the modern intensive cultivations of prickly pear cacti.
Resistance of Sclerotinia minor Isolates to Cyclic Imides in Lettuce Field Soils of Roussillon, France
Authors: Davet P. , Martin C.
Published: May 2008

Lettuce drop caused by Sclerotinia minor Jagger is the most common disease affecting lettuce crops during the fall and winter in Roussillon. Spraying of cyclic imide fungicides (iprodione, vinclozolin, and less commonly procymidone) generally provides satisfactory protection. However, since about 1985, the mean field efficacy of iprodione and vinclozolin has significantly decreased, whereas that of procymidone is currently not in question. The appearance of fungicide‐resistant isolates of S.minor could explain the reduced efficacy of these fungicides. We thus looked for iprodione and procymidone‐resistant isolates of S.minor in these problem fields. The investigations were earned on for over 3 years. Most of the isolates showed fungicide sensitivity (iprodione IC 50 = 0.17 mg 1−1), about one quarter showed average resistance (iprodione IC 50 = 0.59 mg 1−1) and a few were found to be highly resistant. Resistant isolates were also obtained in vitro when using high fungicide concentrations. Moreover, isolates resistant to iprodione were found to be resistant to procymidone. The most highly resistant isolates produced fewer and larger‐sized sclerotia than the sensitive isolates, they were also more quickly inhibited by high osmotic pressures. Field variability was quite low: 73 of 74 isolates obtained from one field were found to be sensitive, with only one showing mild resistance. There did not seem to be any correlation between the observed decrease in the field efficacy of iprodione and the presence of resistant isolates.
Compatible and Incompatible Interactions Between Callus Tissue and Mycorrhizal or Pathogenic Fungi
Authors: Sbrana Cristiana , Giovannetti Manuela , Buiatti Marcello , Storti Emanuela
Published: May 2008

Tissue cultures of Nicotiana tabacum were utilized to investigate the mechanisms associated with host specificity and non‐host incompatibility in mycorrhizal and pathogenic fungi. They were tested for expression of resistance to different species of mycorrhizal fungi and to a fungal pathogen of tobacco, Thielaviopsis basicola, by monitoring the production of callose, phenolic compounds and peroxidases in dual cultures. Tobacco cells reacted to the presence of all the mycorrhizal fungi with callose deposits, whereas callose was nearly always absent in tobacco cells inoculated with their pathogen T. basicola. The broad‐host range ectomycorrhizal fungi Hebeloma crustuliniforme, Lac‐caria laccata and Suilhis granulatus elicited less intense responses than did Hymenoscyphus ericae. The results obtained for phenolic production and peroxidase activity were consistently similar to those obtained for callose deposition. They showed that H. ericae, an endomycorrhizal symbiont of Ericaceae, was highly incompatible with tobacco cells and that the tobacco pathogen T. basicola did not elicit strong reactions in the cells of its host. In this paper, the possibility of utilizing callus cultures as a simple model system to study both the different degrees of compatibility and the early events of recognition between mycorrhizal fungi and their host or non‐host plants is discussed.
Effect of UV‐C on Phytoalexin Accumulation and Resistance to Botrytis cinerea in Stored Carrots
Authors: Mercier Julien , Arul Joseph , Julien Chantal
Published: May 2008

The effect of UV‐C (220–280 nm) on the accumulation of phytoalexin and resistance to Botrytis cinerea was studied in cold‐stored carrots. Carrots were surface‐wounded, treated with a range of UV doses and stored at 1 °C for 25 days in lots of 22 roots. The level of the phytoalexin, 6‐methoxymellein, in each lot was then assayed in the peel of eight roots. Twelve of the remaining roots were subsequently inoculated with mycelial plugs to evaluate their level of disease resistance. The elicitation of 6‐methoxymellcin by UV increased significantly the resistance of the roots to B. cinerea. The effect of UV in freshly harvested carrots was curvilinear, showing an optimum between 0.44 and 0.88 Merg/cm2. However, only a linear relationship was observed with aged (stored for 4 months at 1 °C) carrots for the same doses, suggesting a modification in the response to UV with age. Wounding was necessary for carrots kept at 1 °C to respond to UV treatment. Neither UV nor wounding alone caused any elicitation at this temperature. Since unwounded roots could respond to UV at 20 °C, it is hypothesized that the level of physiological activity of the roots determines their response to UV. An increase in the physiological activity by higher temperatures or wounding would allow the elicitation process to take place. Since UV irradiation can increase the level of disease resistance in treated tissues, this treatment has potential as an alternative method for the control of post‐harvest diseases m carrots.
A Comparison of Screening Techniques for Resistance to Verticillium Wilt in Alfalfa (Medicago sativa L.)
Authors: Yu Kang‐Fu , Christie B. R. , Pauls K. P.
Published: May 2008

Three screening tests for resistance to Verticillium wilt in alfalfa using stem cuttings were compared including: stem infusion with a fungal culture filtrate (SIF), leaf injection with a spore inoculum (LII) and stem infusion with a spore inoculum (SII). The disease severity indice (DSI) determined by the three tests were very similar on average and were significantly correlated for a population of 142 plants regenerated from tissue culture. The DSIs determined by the LII test were also significantly correlated with the DSIs determined by the North American Standard test in a population of 20 Vertus (c.v.) plants. The results suggest that the assays using stem cuttings are effective for determining resistance to Verticillium wilt in alfalfa. Because they are nondestructive and quicker than the North American Standard test, these methods should find application in alfalfa breeding.
Phytophthora infestans in Poland from 1987–1989; Nuclear DNA Content, Mating Type Distribution and Response to Metalaxyl
Authors: Therrien C. D. , Ritch D. L. , Sujkowski L. S. , Spielman L. J. , Fry W. E. , Daggett S. S. , Sim J. H. , Tooley P. W.
Published: May 2008

Isolates of Phytophthora infestans were collected from all potato growing regions of Poland during the blight seasons of 1987—1989. All 1987 isolates were of Al mating type and were sensitive to metalaxyl. In 1988 and 1989, 46.5 % and 55.3 % of the isolates were sensitive to metalaxyl, respectively. The percentage of highly resistant (R) isolates increased from 25.6 % in 1988 to 39.5 % in 1989; however the percentage of intermediately resistant (I) isolates decreased during that period from 27.9 % to 5.3 %. A significant association was observed between the A1 compatibility type and metalaxyl resistance. The A2 mating type first appeared in 1988, and its frequency increased from 4.7 % of the population in 1988 to 47.6 % in 1989. Coincident with this change in mating type frequency, changes in ploidy levels of isolates were observed. Whereas 3 % of the 1988 isolates were diploid, 90 % of the 1989 A2 isolates and 28.6 % of the 1989 Al isolates were diploid. The approximate 1:1 ratio of the two mating types encountered in 1989, and the predominance of diploidy, indicates that the Polish population of P. infestans has the potential to become sexual.
Differential Accumulation of Translatable mRNA Species During a Specific Host‐pathogen Interaction Between Puccinia recondita tritici and Triticum aestivum
Authors: Heinz Ruth A. , Del Vas Mariana , Moratinos Laura C. , Favret Ewald A. , Hopp H. Esteban
Published: May 2008

The time‐course of mRNA induction in specific cultivar‐race combinations was examined using a criss‐cross interaction system consisting of nearly isogenic lines of wheat (Sinvalocho M.A. and Gamma 1R) and genetically related pathogenic races of leaf rust Puccinia recondita f. sp. tritici. Infection stimulated the differential accumulation of mRNA species, identified by in vitro translation, after only three days of inoculation with rust spores. Comparisons of different host‐pathogen combinations showed polypeptide pattern changes likely to be associated with gene‐for‐gene relationships. At least two specific mRNAs which code for polypeptide bands of 34 and 24 kDa are associated with the compatible interaction mediated by genes A1,/A2 from Gamma 1R wheat line and virulence gene pt/p2 of rust race FO1. Comparisons made using a mutant clone of rust, which elicits an inverse criss‐cross relationship with the same wheat lines, are consistent with the proposed specificity of the detected changes.

In addition, two wheat mRNAs (coding for polypeptide bands of 20.5 and 32.5 kDa) were elicited by infection with rust race FO1 regardless the plant genotype or reaction type. A cDNA clone involved in this kind of race specific induction has been isolated.
Xanthine Oxidase Activity in the Susceptible and Hypersensitive Responses of Tobacco Leaves to Tobacco Mosaic Virus Infection
Authors: Montalbini P.
Published: May 2008

A superoxide‐producing xanthine oxidoreductase was isolated and quantified after polyacrylamide disc gel electrophoresis of tobacco leaf extracts. The results obtained indicate that, like uricase activity, a slight increase in tobacco xanthine oxidase activity takes place in the susceptible interaction with tobacco mosaic virus (TMV). In contrast, out of three hypersensitive tobacco cultivars tested, only two showed the same slight increase m activity during the late stage of hypersensitive response.

Allopurinol [4‐hydroxypyrazolo(3,4‐d)pyrimidine] a specific and potent in vitro and in vivo inhibitor of xanthine oxidoreductase, applied to tobacco plants by root absorption, starting about 8 days before the inoculation, did not affect the hypersensitive response but weakened the hypersensitivity‐linked virus localization and promoted the movement of a certain amount of TMV particles and/or virus related material from necrotic lesions which induced systemic necrotic symptoms in uninoculated leaves. However, due to the inefficacy of allopurinol in preventing necrotic lesion development, all results are consistent with the hypothesis that xanthine oxidoreductase, the first enzyme in purine oxidative degradation, plays only a secondary role during induction of primary hypersensitive cell death in TMV infected tobacco leaves.
Preliminary Investigations on the Rusts of Perennial Ryegrass in Central Italy
Authors: Cappelli C. , Marte M. , Paul V.
Published: May 2008

The results of a four‐year investigation carried out in Central Italy on the occurrence of perennial ryegrass rusts from 1989—92 are reported. The crown rust (Puccinia coronata) was the most frequently recorded in the surveyed are while P. graminis was only occasionally detected. The causal agents were identified by the morphological criteria proposed by CUMMINS (1971).

A single‐pustule isolate of P. coronata was used to test the resistance of seven ryegrass cultivars under greenhouse conditions. Two cultivars, ‘Artal’ and ‘Score’, proved resistant to the fungus isolate while the remaining (‘Elka’, ‘Patora’, ‘Pleno’, ‘Sisu’ and ‘Vejo’) were high susceptible.
Inhibition of Some Rot Fungi Polygalacturonases by Allium cepa L. and Allium porrum L. Extracts
Authors: Favaron F. , Castiglioni C. , Lenna P. Di
Published: May 2008

Extracts of Allium cepa and A. porrum‐ contain factors that inhibit to various extents polygalacturonases (PGs) produced in vitro by Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium moniliforme, Phoma terrestris, Sclerotium cepivorum, Macrophomina phaseolina, Didymella bryoniae andPhoma lycopersici. The PG inhibition rank changed using leek or onion extract. The inhibition factors are possibly proteins, do not present particular specificity and act against PGs of fungi pathogens and non pathogens for these plant species.
Agrobacterium tumehciens After in vivo Inoculation of Potato (Sohnum tuberosum L.) (Scanning Electron Microscopy)
Authors: Starkbauerova Zuzana , ŠRobárová Antonia
Published: May 2008

Five weeks after the in vivo inoculation of potatoes (Solanum tuberosum L.) with Agrobacterium. tumefaciens strain B6S3, bacteria were found in the non‐differentiated cells of tumors (formed from xylem parenchyma or other living cells), in xylem cells at the site of inoculation, as well as in xylem cells of the adjacent stem.

Bacteria were attached by fibrillar aggregates to the tumor cell walls. They were also attached to a fibrillar mass which arose from agrobacteria connected to this mass in the tumor. Agrobacteria, singly or in pairs, were attached to an electron dense formation (possibly bacterial extracellular polysaccharides) found both inside the xylem cells of the stem adjacent to the tumor and at the site of inoculation. Some A. tumefaciens cells were attached by means of a pedestal‐like structure at the inoculation site.

A possible function of the different means of attachment of A. tumefaciens in both nontransformed plant cells and tumors is discussed.
The Inhibition of Fungal Growth in Resistant Cotton Plants Infected by Fusarium oxysporum f. sp. vasinfectum
Authors: Shi J. , Mueller W. C. , Beckman C. H.
Published: May 2008

The vascular colonization of cotton plants by Fusarium oxysporum f. sp. vasinfectum was determined by examining growth of the fungus from free‐hand cross sections taken from 0 to six days after inoculation at various distances above the points of root inoculation. Fungal spread in both longitudinal and lateral directions in the susceptible cultivar Rowden was evident four days after inoculation, whereas fungal spread in the resistant cultivar Seabrook Sea Island was restricted. The quantity of viable fungus in infected tissues was determined from macerated tissues plated on Czapek‐ Dox agar. The colony counts declined within six days after inoculation in resistant Seabrook Sea Island, but not in susceptible Rowden, implying that an inhibition of fungal growth in vascular tissues occurred in resistant Seabrook Sea Island. This inhibition could contribute to the restriction of fungal spread and thus be a factor in the resistance of cotton plants to F. oxysporum f. sp. vasinfectum.
Use of Random Amplified Polymorphic DNA (RAPD) Analysis and Genetic Fingerprinting to Differentiate Isolates of Race O, C and T of Bipolaris maydis
Authors: Nicholson P. , Rezanoor H. N. , Su H.
Published: May 2008

Isolates of three races of Bipolaris maydis from China (races O, C and T) were compared using two techniques. Random Amplified Polymorphic DNA (RAPD) analysis using 24 primers indicated that race O and C isolates were more similar to one another than to the race T isolate. Twenty of the primers produced RAPD profiles that were similar for the race O and C isolates but differed for the race T isolate (four primers did not amplify products in any of the isolates). Four primers produced profiles which differed for all three races and two of these (A‐09 and B‐18) clearly differentiated the race O and race C isolates. Genetic fingerprinting of B. maydis using M13 DNA as a probe differentiated race O and C isolates from the race T with all four restriction enzymes used. Furthermore, when DNA was digested with Hind III, the hybridization profiles of the race O and C isolates differed from one another.
A Simple Method for the Production of Large Volumes of Rhynchosporium secalis Conidial Suspension
Authors: Speakman J. B.
Published: May 2008

A method is described by which large volumes of conidial suspension of Rhynchosporium secalis can be obtained easily.
Interaction hôte‐parasiteSolanum gilo(Raddli)Stemphylium floridanum(Hannon et Weber). Relation entre teneur en acide chlorogénique foliaire et résistance au pathogène
Authors: Clerivet A. , Macheix J. J.
Published: May 2008

Phenolic profile ofSolanum giloleaves was investigated after incubation withStemphylium floridanumculture filtrates. The amount of chlorogenic acid, largely dominant, was in correlation with foliar resistance either by a high constitutive level in some leaves (apical leaves of productive plants) or by a fast increase induced in other leaves by fungus elicitors (youngest leaves of plants nursery). An additional role of other identified phenolic compounds was also proposed so that a sufficient resistance level was conferred toS.giloleaves.
Studies on the Biology of Polymyxa betae, the Vector of Beet Necrotic Yellow Vein Virus
Authors: Ahm H. D , Buchenauer H.
Published: May 2008

The development of Polymyxa betae within the roots of a sugar beet variety susceptible to Rhizomania was observed in hydroponic culture over a period of 10 days. Light microscope studies showed that at an average temperature of 20 °C the life cycle of the fungus, containing beet necrotic yellow vein virus (BNYW), was completed within 10 days. A change from the multiplication phase to the survival phase of P. betae became evident. At the beginning of the life cycle the fungus produced mainly zoospores whereas at a later stage plasmodia developed into resting spores. Zoospore density in the nutrient solution reached a maximum between the 5th and 7th day after inoculation and then declined to the initial concentration. The number of zoospores attached to the root surface increased progressively at 48 h intervals, correlated with a parallel increase in BNYW‐content of the roots. Light‐ and fluorescence microscopy revealed that zoospores of P. betae often attach near the point of release and do not move very long distances. In addition it became evident that zoospores may attach to the thallus wall inside the zoosporangium that they have developed in.
Morphology of a New Pathotype ofBipolaris zeicola(Stout) Shoemaker
Authors: Levic Jelena , Pencic Viktorija
Published: May 2008

Conidia of a new pathotype ofBipolaris zeicola(Stout) Shoemaker, which causesHelminthosporiumcorn leaf spot (HCLS) on inbreds derived from B73, are morphologically atypical on potato dextrose agar (PDA). The average conidial length on PDA (31.9 μm) is half that on naturally infected leaf (65.2 μm). Conidiogenuous cells terminally and subterminally located on short conidiophores produce new conidia which behave as initial conidia, i.e. they immediately elongate or germinate. Sometimes, they appear in chains. Based on conidial morphology on leaf materials and on wheat straw agar (WSA), the investigated fungus was identified asB. zeicola.
Barley Yellow Dwarf Virus Multiplication and Host Plant Tolerance in Durum Wheat
Authors: Cheour F. , Comeau A. , Asselin A.
Published: May 2008

A Canadian PAV‐like isolate of barley yellow dwarf virus (BYDV) was used to infect durum wheat (Triticum durum) cultivars previously identified in field trials involving artificial inoculation as highly sensitive (12 IDSN74), slightly tolerant (La Dulce), and relatively tolerant (Boohai and 12 IDSN227) to BYDV. The cultivars were inoculated in the greenhouse as seedlings, and indexed for virus accumulation by enzyme‐linked immunosorbent assay (ELISA) at various intervals between 3 and 60 days thereafter. Mean ELISA values were somewhat consistent with tolerance levels for 4 durum wheat cultivars, but the use of ELISA to screen for BYDV resistance in durum wheat is not practical. The magnitude of the difference between sensitive and tolerant cultivars for the mean ELISA value is not high enough, and it may be necessary to average readings between 3 and 60 days after inoculation to obtain somewhat meaningful ELISA data. The effect of vector aphid numbers on virus titre and aerial biomass in the sensitive durum wheat cv. Karim was also evaluated. There was no significant effect on virus content in a preliminary trial, but a second trial revealed that more viruliferous aphids per plant resulted in higher ELISA values. Infestation with 32 or 50 viruliferous Rhopalosiphum padi per plant depressed biomass yield below the level observed with 1–10 aphids per plant.
Cytopathology of Mature Ovaries from Lettuce Plants Infected by Lettuce Mosaic Potyvirus
Authors: Hunter D. G. , Bowyer J. W.
Published: May 2008

The location of lettuce mosaic potyvirus (LMV) in mature ovaries of lettuce plants (Lactuca sativa) was studied by conventional thin‐section electron microscopy and immunogold cytochemistry. Flexuous filamentous particles and inclusion bodies characteristic of LMV infection were observed in the integumentary tapetum, integument and ovary wall of the mature ovary but not in the embryo sac.
Biological, Serological and Coat Protein Properties of a Strain of Turnip Mosaic Virus Causing a Mosaic Disease of Brassica campestris and B. juncea in India
Authors: Haq Q. M. R. , Srivastava K. M. , Raizada R. K. , Singh B. P. , Jain R. K. , Mishra A. , Shukla D. D.
Published: May 2008

Biological, serological and coat protein properties of a potyvirus (Poty‐Rape) causing a mosaic disease of Brassica campestris and B. juncea in India were investigated. The virus readily infected 4 of the 5 plant species in the family Brassicaceae in which it induced severe systemic mosaic symptoms; it also induced chlorotic and necrotic local lesions in Chenopodium amaranticolor, but failed to infect 4 other species of Chenopodiaceae or 20 species of Amaranthaceae, Apiaceae, Canabinaceae, Compositae, Cucurbitaceae, Euphorbiaceae, Leguminosae and Solanaceae. The virus was transmitted in a non‐persistant manner by Myzus persicae, Brevicoryne brassicae and Aphis gossypii. The Average size, of the virus particles in a purified preparation was 740 nm × 12 nm. SDS‐PAGE analysis of the viral coat protein showed two major bands of approximately 37 kDa and 31 kDa, a pattern very similar to that of a reference isolate of turnip mosaic virus (TuMV) from the U.S. In Western‐blot immunoassay, an antiserum to TuMV reacted with both the coat protein bands of the Poty‐Rape islate and the reference TuMV, but not with the coat proteins of four other potyviruses. The high performance liquid chromatographic profile of tryptic peptides from the coat protein of Poty‐Rape was found to be very similar to that of the reference TuMV, but differed substantially from those of four other potyviruses. The Poty‐Rape isolate is considered to be a distinct strain of, TuMV.
Population Dynamics of Virulence Genes of Xanthomonas campestris pv. malvacearum on Cotton
Authors: Duttamajumder S. K. , Verma J. P.
Published: May 2008

Population genetic principles in relation to the pathogenicity genes have been applied on the genotypes (races) of Xanthomonas campestris pv. malvacearum(Xcm) which are characterized on the basis of bacterial blight resistant host genes (B‐genes) attacked. Observed (OF) and expected (EF) frequencies were determined to predict the intensity of selection pressure operating in the pathogen population due to the introduction of particular host resistant gene(s). Race 32 (Vp, V7 V2 V10 VN) was the most prevalent genotype representing 41.55% of the Xcm population. Other prevalent genotypes were race 30 (11.08%, Vp V2 Vin VN), race 20 (8.56%, Vp V2 VN), race 9 (6.80%, Vp Vin) and race 8 (11.59%, Vp V2). The OF (observed frequency) of race 32 was 41.55%, whereas EF (expected frequency) was 15.74% indicating a strong selection pressure favouring this highly virulent genotype. Whereas, race 31 (V7 V2 Vin VN) also overcomes four major genes like race 32 but not the polygene complex, it was less fit and possessed low EF and OF, i.e. 0.25% and 1.18% respectively. Xcm genotypes capable of attacking 3–4 major B‐genes were prevalent on G. hirsutum, while genotypes with virulence against 1–2 B‐genes favoured G. barbadense cottons. High virulence level in pathogen genotypes, was maintained on resistant/tolerant host genotypes of G. arboreum and G. hirsutum whereas, it was diluted on the highly susceptible G. barbadense.
Development of Ramularia Leaf Spot on Sugar Beet as Influenced by Temperature and the Age of the Host Plant
Authors: Hestbjerg H. , Wolffhechel H. , Dissjng H.
Published: May 2008

A method of inoculating sugar beet plants (Beta vulgaris L.) with Ramularia beticola Faut. & Lamb, is described. Following inoculation, disease development in relation to temperature and plant age was studied for more than a month. The incubation period was 18 days at 10°C compared to 14 days at 17°C. At 25°C no symptoms appeared. Both temperature and plant age significantly influenced disease level and rate of disease development. Plants incubated at 17°C were more severely diseased 33 days after inoculation than plants incubated at 10°C. Young plants (3 weeks at inoculation) Were more susceptible than older plants (5 and 8 weeks at inoculatson) under growth chamber conditions. In the field, symptoms of Ramularia leaf spot appear relatively late in the season and young leaves are rarely attacked. The inconsistency of these observations is discussed.
ACTG‐Toxins Produced by a Strain of Alternaria altemata That Does Not Originate From Citrus Species
Authors: Liebermann B. , Ellinger R. , Ihn W.
Published: May 2008

AGTG‐toxins designated as host‐specific toxins were isolated at first from a pathotype of Alternaria alternata attacking Citrus species. A strain of Alternaria alternata isolated from Brassica sinensis in Central Germany and improved to a high tentoxin content, also produces two ACTG‐toxins. It is doubtful, therefore, if both substances can be denoted as host‐specific toxins.
Diversity in Pathogenicity to Tobacco and in Elicitin Production among Isolates of Phytophthora parasitica
Authors: Bonnet Ph. , Lacourt I. , Venard P. , Ricci P.
Published: May 2008

The pathogenicity to tobacco of a large set of Phytophthora parasitica isolates has been assessed using several procedures: root inoculation of young plants, leaf inoculation on detached disks and stem inoculation of decapitated plants, with or without healing. Analysing various aspects of the plantpathogen interaction with this array of tests led to the discrimination between three groups of isolates. In the isolates from hosts other than tobacco, none was truly pathogenic to tobacco, and all but one produced parasiticein, a proteinaceous elicitor of the elicitin family which induces a hypersensitive‐like response in tobacco. Isolates producing parasiticein in vitro induced necrotic fleks on the leaves upon inoculation of roots orof, freshly wounded stems. Most tobacco isolates, including all the highly virulent ones, were characterized by a lack of elicitin production. However, those collected in Australia and Zimbabwe differed in that they exhibited reduced virulence, induced leaf, necrotic flecks and produced parasiticein. The incidence of elicitin production on virulence and the significance of two types of tobacco‐pathogenic strains for tobacco pathology are discussed.
Characterization and Plasmid Profile of Xanthomonas campestris pv. Glycines from Maharashtra, India
Authors: Sharma A. , Syed A. N. , Nair P. M.
Published: May 2008

Xanthomonas campestris pv. glycines, (Xcg), the causative agent of the bacterial pustule disease of soybean was isolated and characterized. On susceptible soybean the pathogenic isolates displayed characteristic chlorotic lesions around the site of infection within 48 h of inoculation. The pathogenic isolates were found to contain two cryptic plasmids. A smaller plasmid of 1.5 kb and a larger one of size about 25 kb. SDS‐PAGE profile of the soluble proteins of the pathogenic isolatess, howed a different pattern compared to that of the non‐pathogenic isolates.
Le Paraquat, un Outil pour la Révélation Rapide d'Infections Fongiques Latentes et de Champignons Endophytes
Authors: Gindrat D. , Pezet R.
Published: May 2008

Paraquat: a tool for the quick development of latent fungal infections and endophytic fungi.

Detached winter wheat leaves without any symptom of fungal infection were thoroughly washed, surface desinfected, treated with paraquat (0.03–0.32% a.i.) and incubated on nutrient agar or in moist chambers under sterile conditions. Microscopic examinations showed that hypae and yeast cells emerged from several stomata within 48–72 h after treatment. Fungal colonies developed on agar within the same period of time. More than 27 filamentous fungal genera and yeasts were identified during a wheat cropin healthy, green leaves. Non‐treated leaves showed very few early emergences of fungi from stomata, but senescent leaves eventually yielded several fungal taxa observed after paraquat treatment. Similar observations were made on non‐detached wheat leaves, and on detached sugarbeet leaves. Paraquat also induced development ofFusariumspp. from detached healthy winter wheat ears before or after heading. In grape berries, paraquat induced the development of latent infections ofBotrytis cinerea, a few days after treatment.

The usefulness of paraquat for the detection of endophytes and for the diagnosis of early and latent fungal infections in plants, and the possible involvement of endophytes in tissue senescence are discussed.
Bacterial Antagonists to Verticillium dahliae Kleb.
Authors: Berg G. , Ballin G.
Published: May 2008

Bacteria were isolated from the rhizosphere of Verticillium dahliae hosts and from environments. A total of 1394 bacterial isolates were screened for their ability to inhibit in vitro the growth of the phytopathogenic fungi V. dahliae; 15% (203 of the isolates) showed antifungal effects. Seventeen isolates were selected and determined for further investigations, seven different species were identified. Several of the bacterial species listed, e.g. Erwinia herbicola, Pseudomonas chlororaphis, Pseudomonas paucimobilis and Xanthomonas maltophilia have not been reported previously as bacterial antagonists of V. dahliae. Bacillus subtilis, Pseudomonas fluorescens and Xanthomonas maltophilia are strong antagonists. We proved that lytic enzymes and siderophores are involved in the inhibition of growth. Ultrastructural and morphological changes were induced in Verticillium dahliae by the antagonistic bacteria.