bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytopathologie von viroid‐infiziertem Pflanzengewebe
Authors: Rosenberg Francis , Wahn K. , Sänger H. L. 
Published: May 2008

Abstract Cytopathology of viroid‐infected plant tissue II. Light‐ and electron microscopical investigations on the leaf tissue of the Chrysanthemum morifolium cultivar “Mistletoe” after infection with the chrysanthemum stunt viroid (CSV) The infection of the Chrysanthemum morifolium cultivar “Mistletoe” with the chrysanthemum stunt viroid (CSV) leads to the appearance of numerous yellowish leaf spots 2–5 mm in diameter. The cells of these chlorotic leaf areas were investigated by phase contrast‐ and electron microscopy and compared with the cells of the adjacent green tissue and the tissue of healthy plants. Phase contrast microscopy showed that the chlorotic tissue containes about 50 % more cells per area and that their size is reduced by 30–60 %. The parenchymatic cells of the xylem and phloem are irregular and their walls are malformed. In these cells the chloroplasts are reduced to about half in their size and number.In the electron microscope an accumulation of osmiophilic material between the thylakoid membranes of the chloroplasts of the chlorotic cells and a deterioration of the chloroplast stroma can be observed. Moreover, malformations of the cell wall and in the cell wall‐associated plasmalemma‐somes are found, which lead to an increase in contrast and to irregularities of their surface and internal structure. The most prominent CSV‐specific cytopathic effect in cells of the vascular tissue is the extreme accumulation of microfilament bundles which were analysed in detail with the aid of a goniometer. The observed viroid‐induced ultrastructural changes are compared with previously described changes caused by conventional plant viruses and the possible functional implications are discussed.
Virulence and Enzyme Production of Erwinia carotovora ssp. atroseptica on Potato Tuber Tissue
Authors: Weber Jürgen , Wegener Christina 
Published: May 2008

AbstractThe elicitation of pathogenesis on potato tuber slices by 6 strains of Erwinia carotovora ssp. atroseptica was investigated by neutral red vital staining and has been compared with bacterial growth rate, penetration ability, enzyme production and enzyme spectrum. The induction of enzyme synthesis (particularly, of the extracellular polygalacturonase) elicites the rot attack on tuber tissue and this requires a sufficient bacterial density.Due to wound healing, the inductors of enzyme production are removed, and after 48 h enzymes do not attack tuber tissue any more. Therefore, growth rate and penetration ability (to get the necessary bacterial density and inductor substances) may limit virulence. A similar influence of enzyme production and enzyme spectrum of the strains on the virulence was not detected.
Uptake, Translocation, Distribution and Persistence of 14C‐Metalaxyl in Pearl Millet (Pennisetum americanum) [L.] Leeke)1
Authors: Singh U. S. , Tripathi R. K. , Kumar J. , Dwivedi T. S. 
Published: May 2008

AbstractTime course absorption and desorption of metalaxyl by seeds of pearl millet was analysed by following chemical kinetics equations. Uptake of metalaxyl through roots, leaves and seed, its translocation and distribution in different plant parts and persistence following seed application were studied in pearl millet using 14C‐metalaxyl. Both uptake and efflux of metalaxyl by pearl millet seeds were complex and compartmentalized. Distribution inside the seed was not uniform. A major part of applied fungicide remained within the treated plant part, particularly after seed and foliar applications. Metalaxyl was ambimobile inside the plant and was found to get accumulated at apex and margins of leaf blade. No metalaxyl could be detected in grains, harvested from plants grown from metalaxyl treated seeds.
Fungitoxic and Phytotoxic Studies with Essential Oil of Ocimum adscendens
Authors: Asthana A. , Tripathi N. N. , Dixit S. N. 
Published: May 2008

AbstractOn screening the leaf extracts of some higher plants for their volatile antifungal activity against the test organism Aspergillus flavus, the extract of Ocimum adscendens exhibited the strongest fungitoxicity. The leaves showed maximum, fungitoxicity as compared with other plant parts. The volatile fungitoxic fraction obtained as an essential oil was standardized by various physico‐chemical properties. The oil showed its fungicidal nature and broad range of activity at its minimum inhibitory concentration. The oil was thermostable and the toxicity remained unchanged even on autoclaving and on storage for up to 360 days. Moreover, the oil proved more active than some prevalent synthetic fungicides and exhibited no phytotoxic effect onVigna radiata.
Seasonal Variation in Pathogenicity of Phytophthora infestans
Authors: Sujkowski Ludwik S. 
Published: May 2008

AbstractDuring a four year study it was shown that the mean lesion area (M.L.A.) developed on leaflets of different potato cultivars by isolates of P. infestans after artificial inoculation varied periodically during the year.Disease symptoms observed changed from pinpoint necroses to regular sporulating lesions depending on the season and the cultivar.Analysis of variance revealed that differences in lesion size between experiments performed in different seasons were significant. The largest M.L.A. was found in late spring or in autumn but autumnal increase of M.L.A. was usually significantly lower than that in spring.Periodicity of M.L.A. was accompanied by a similar phenomenon in sporulation density of P. infestans isolates cultured in vitro. However, the peaks of sporulation, in comparison with peaks of M.L.A. appeared in different seasons. The highest disease level coincided with a decline in sporulation density of P. infestans cultured in vitro and the decrease of M.L.A. corresponded with an increase in sporulation density per cm2 of medium.Variation in M.L.A. found in this study seemed not to be related to variability in plant reaction. In this connection a hypothesis has been proposed that the changes of M.L.A. were due to variation in pathogenicity of the fungus.
Parassitismo di Trichoderma harzianum su cistosori di Polymyxa betae
Authors: D'Ambra V. , Mutto S. 
Published: May 2008

AbstractParasitism of Trichoderma harzianum on Cystosori of Polymyxa betaeTransmission electron microscope investigations revealed that cystosori of Polymyxa betae Keskin are, in vitro conditions, parasitized and completely degraded by Trichoderma harzianum Rifai. The hyperparasite showed a high ability in colonizing excised, surface‐sterilized lateral roots of sugar beet and in invading the cystosori present in them. Both the walls of the root cells and of the cysts are enzymatically perforated. However, in cysts penetration, mechanical forces are also involved. After penetration, cysts undergo a rapid degradation and finally they appear to be completely empty or to contain only small amounts of degradated cytoplasm.Cyst walls are also strongly altered and deformed and only two thin osmiophylic residual layers are detectable.
A Comparison of the Reaction Sites Associated with the Resistance of Coleoptiles of Barley, Oats and Wheat to Infection by Septoria nodorum
Authors: Hargreaves J. A. , Keon J. P. R. 
Published: May 2008

AbstractA novel technique has been developed to inoculate the outer epidermal cells of coleoptiles of barley, oats and wheat with S. nodorum. Using this technique, which results in a large number of attempted penetrations, the composition of the material deposited at unsuccessful penetration sites in these cereals have been compared. Although the deposits reacted in a similar manner with some histochemical reagents (ammoniacal silver solution, Coppick‐Fowler reaction, p‐nitrobenzene tetrafluoroborate and Coomassie brilliant blue R250) marked differences occurred between the reactions sites formed by barley and wheat and by oats with other stains (bromophenol blue, nile blue sulphate and Toluidine blue). Chemical treatments used to delignify tissue also revealed differences in these reaction sites. It is concluded that although the reaction sites share some similar components there are significant differences in their chemical structure.
Studies on the Relationship of Urdbean Leaf Crinkle Virus and its Vectors, Aphis craccivora and Acyrthosiphon pisum
Authors: Bhardwaj S. V. , Dubey G. S. 
Published: May 2008

AbstractPre and Post‐virus‐acquisition starvation of Aphis craccivora Koch, and Acyrthosiphon pisum Harris resulted in appreciable increase in percentage of transmission of urdbean leaf crinkle virus. Highest transmission occured when aphids were starved for 90 min prior to virus‐acquisition. A. pisum and A. craccivora on 20 and 80 min of post‐acquisition starvation and 10 and 20 min of virus‐acquisition, respectively inoculated more number of plants. Both the aphids transmitted the virus in probes lasting for one min. However, beyond 5 min of successive transfer on test plants loss in transmissibility was apparent. Viruliferous aphid off the plant retained the virus for a much longer period than on maize plant. The virus appears to be non‐persistently borne in the aphids.
Protection of Wheat Seedlings from Helminthosporium Infection by Seed Treatment with Chemicals
Authors: Hait G. N. , Sinha A. K. 
Published: May 2008

AbstractTwenty of twenty‐four chemicals known to induce phytoalexin production in other plants, when used to soak seed, provided effective protection to 3‐week‐old susceptible wheat seedlings against inoculation with Helminthosporium sativum. The number of lesions was very significantly reduced in most of these treatments and there was evidence for inhibition of lesion expansion in a few. Studies with twelve of the more effective chemicals showed that the protective effect persisted at significant levels even in 5‐week‐old plants and that at this stage the inhibitory effect on lesion expansion was more pronounced in most of the treatments. Different treatments led to the development of a moderate to high level of fungitoxicity in young wheat seedlings which gradually declined with age of the plant and disappeared in 5‐week‐old plants. When inoculated at the age of 3 or 5 weeks, plants receiving most of the treatments developed appreciably higher fungitoxicity than the untreated plants.
Detection of Zucchini Yellow Mosaic Virus in Intact Leaf Disks and Tissue Extracts by Enzyme‐Linked Immunosorbent Assay
Authors: Menassa R. , Makkouk K. M. , Abbasher A. A. 
Published: May 2008

AbstractAn indirect enzyme‐linked immunosorbent assay (ELISA) was used for the detection of zucchini yellow mosaic virus (ZYMV) in cucumber tissues and in its aphid vector Myzus persicae Sulz. Results showed that the indirect ELISA was more sensitive, than the direct ELISA for ZYMV detection. Indirect ELISA detected ZYMV in leaf disks as well as in leaf extracts, and four 6‐mm‐diameter leaf disks per well were found sufficient for reliable ZYMV detection. In addition, the readings with virus‐free leaf disks were much lower than those of leaf extracts. When using leaf disks, it is possible to shorten the indirect ELISA protocol to one working day but with reduced sensitivity. ZYMV was also detected in its aphid vector by the indirect but not with thedirect ELISA. The best extraction buffer for aphids was found to be 0.2 M phosphate at pH 6.0. However, the difference between the ELISA readings of viruliferous and virus‐free aphids was always very small, and results were not always reproducible.
Quantitative Analysis of the Early Powdery Mildew Infection Stages on Resistant Barley Genotypes
Authors: ANDERSEN J. B. , TORP J. 
Published: May 2008

AbstractA classification system was developed, that allowed quantification of the leaf surface development of the barley powdery mildew fungus on barley. An experiment with Manchuria and Pallas as susceptible controls and 4 resistance gene each represented by three lines with different gene backgrounds showed two types of gene background effects. First a general effect comprised of different distributions of the elongating secondary hyphae (ESH) in the stomatal and interstomatal region between Manchuria and, Pallas, and a higher number of lobes per appressorium on Pallas than on Manchuria. These effects also applied to isolines of Manchuria and Pallas possessing each of the four genes investigated. Second a specific effect was noticed on the ESH frequency on Ml‐k lines. The ESH frequency varied significantly at the 5% level between the highest and lowest value.An experiment with Pallas as susceptible control and Pallas isolines with 11 different resistance genes, showed that powdery mildew development was unaffected by host genotype until after the formation of an appressorium. The first host effect observed was on the number of lobes on the appressorium, which reflects the number of penetration attempts. This number increased as the degree of resistance increased, i.e. the ESH frequency decreased. The penetration stage also invariably proved to be the limiting stage, where the largest proportion of fungal propagules was stopped.
Quantitative Differences in Powdery Mildew Resistance Among Spring Barley Cultivars
Authors: Heun M. 
Published: May 2008

AbstractQuantitative powdery mildew resistance in compatible host‐pathogen‐combinations was measured by the number of pastules/cm2 leaf area. Spring barley cultivar ‘Proctor’ was significantly less infected than ‘Golden Promise”. Using these two cultivars (having no effective major resistance gene) as controls, MO‐ and AR‐resistant cultivars were inoculated with virulent mildew isolates. ‘Mona”, ‘Grit’ and ‘Nudinka’ had a higher or, at least, the same level of quantitative resistance as ‘Proctor”. None of the remaining cultivars showed the high susceptibility expressed by ‘Golden Promise”. Ranking of host genotypes was nearly constant while that of mildew isolates varied considerably. Only a small portion of the observed variance was due to interaction between host cultivars and pathogen isolates.‘Triesdorfer Diva’ gave a resistant infection type after inoculation with different AR‐virulent isolates, indicating that this cultivar has major resistance other than that conditioned by gene Ml‐a12.
The Detection of the Abutilon Mosaic Virus Depends on the Experimental Daytime
Authors: Jeske H. 
Published: May 2008

AbstractFluorescence and electron microscopical studies show that the detection of structures associated with the Abutilon Mosaic Virus disease is dependent on the sampling daytime. Moreover the infectivity of plant sap may vary during the day. The results emphasize the importance to consider the daytime as an essential parameter in experimental design in virological research.
Association of Mycoplasmalike Organisms (MLOs) with Mild Type of Hydrangea virescence: A Study with 60–1000 nm Thick Sections
Authors: Marie‐Thérèse Cousin , Sharma A. K. 
Published: May 2008

AbstractThe study of the agent associated with the mild type of Hydrangea virescence in France involved three steps, with the aid of transmission electron microscope (TEM). In the first step, we observed the presence of polymorphic procaryotes in thephloem sieve tubes of diseased plants and their absence from corresponding healthy plant parts. The procaryotes were detected in the areas suspected in 1000 nm thick sections stained with thionin‐acridine orange. In the next step, the ultrastructure of their unit membrane was studied at magnifications higher than 100 000. The two osmiophilic layers of the membrane were 6 nm distant and no preliminary parietal shape was detected. These observations on ultrathin (60 nm) sections allowed us to classify the, particles into the class “Mollicutes”. The third step involving the examination of 350–1000 nm thick sections revealed the absence of spiral forms.The TEM observations are consistent with the hypothesis that the agents associated with the mild type of Hydrangea virescence observed in France should be included within the MLO group. A method specially adjusted to the fixation of MLO inside sieve tubes has been mentioned.
Phenols in Cotton Seedlings Resistant and Susceptible to Alternaria macrospora
Authors: Yoav Bashan  
Published: May 2008

AbstractIn healthy cotton seedlings, stems have a lower phenol content than leaves, but resistant plants have an altogether relatively higher phenol content than susceptible plants. Phenols extracted from infected plants can inhibit the growth of A. macrospora in vitro. In cotton plants infected with A. macrospora, phenols are oxidized by polyphenoloxidase rather than peroxidase and catalase. The main oxidative activity was around the developing necrotic area but activity was detected far from, necrosis as well. Though pre–inoculation mechanical injuries operated the phenol oxidation mechanism in the plant, they neither prevented nor encouraged the increase in disease severity. Isozyme pattern showed that contribution of all participants in the pathological interaction to the oxidative mechanism occurred in the diseased plant. A negative linear correlation was found between polyphenoloxidase activity, phenol accumulation and resistance. This study suggests that the phenol oxidative mechanism, participates in cotton plant resistance to A. macrospora.
Induction of Resistance in Cucumber to Colletotrichum lagenarium by 6–benzylaminopurine
Authors: Mills P. R. , Gussin E. J. , Wood R. K. S. 
Published: May 2008

AbstractApplication of 6–benzylaminopurine to cucumber leaves before inoculation with Colletotrichum lagenarium substantially decreased lesion development; decrease was accompanied by an increase in certain plant metabolites. Leaves systematically protected from infection by C. lagenarium by earlier inoculation with the same pathogen showed similar decrease in lesion size without increases in these metabolites.
Changes in Mineral Content ofEucalyptus marginataandE. calophyllaGrown under Controlled Conditions and Inoculated withPhytophthora cinnamomi
Authors: Cahill D. , Wookey C. , Weste G. , Rouse J. 
Published: May 2008

AbstractMineral concentrations in infected roots and shoots were compared with similar material, but pathogen free, for the susceptibleEucalyptus marginataand the field resistantE. calophylla.All plants were mycorrhiza‐free, grown under controlled conditions and inoculated with an axenic suspension of zoospores ofPhytophthora cinnamomi.Plant material was ashed 30 days after inoculation and analyzed in an external proton beam using PIXE and nuclear reaction analyis to detect differences in mineral concentrations.The mineral content of infected roots ofE. marginatawas below that of the uninfected roots for all elements detected except chlorine, chromium and rubidium. The reductions were significant for calcium and copper. No such reduction was found, inE. calophyllaroots, but some changes were detected. Shoot: root ratios ofE. marginatashowed significant differences associated with infection in phosphorus, calcium, copper and zinc. Relatively large differences were also recorded for sulphur chlorine and potassium. Shoot: root ratios of infectedE. calophyllashowed fewer differences but contained only half the concentrations of sulphur and potassium present in the controls.The reduced mineral concentrations reflect the failure in conduction of water and minerals through the infected and susceptible root system.
Elution Profiles of Pisatin Elicitor Activity from Extracts of Monilinia fructicola, Pisum sativum and Diffusates from their Interaction*
Authors: Cruickshank I. A. M. , Smith M. M. 
Published: May 2008

AbstractPisatin elicitor activity was examined in diffusate of the M. fructicola–pea endocarp interaction, leachate of pea endocarp, extracts of ungerminated conidia and filtrates of conidia germinated in vitro in a simple nutrient broth, or in filter–sterilized diffusate or pea leachate. Extracts were made after 18 h incubations which represents the half–time of the primary phase of pisatin accumulation in the M. fructicola–pea model system. These were chromatographed on a Bio–Gel, P–2 column and elicitor activity in eluate fractions was located by bioassay for the ability to induce pisatin accumulation.A characteristic elution profile of pisatin elicitor activity was obtained from diffusate of the pea–M. fructicola interaction. Other preparations obtained from pea leachate, ungerminated conidial extracts or culture filtrates of the fungus germinated in a simple nutrient broth or pea leachate (6 h) did not contain the same profile of elicitor components. No further production of elicitor was detected in early diffusate (6 h) filtrates when they were incubated in vitro alone or withM. fructicola. Elicitor activity was significant in some conidial germination filtrates in vitro. The elution profiles of elicitor activity obtained from these filtrates were shown to be dependent on the physical conditions of culture used (still or shaken).Incubation of the pea leachates with M. fructicola in vitro resulted in the formation of a high molecular weight elicitor which did not correspond with that of the diffusate preparations. Its reapplication to pod tissue did not suggest that it was significantly metabolized by pea tissue to produce the same elicitors found in diffusate preparations.The results emphasize the importance of in vivo studies in the search for elicitors of phytoalexins where two living systems, the plant and the fungus are intimately involved.
Acquired resistance of Alternaria solani and Sclerotium rolfsii to Polyoxin‐D
Authors: Maria Rose , Sullia S. B. 
Published: May 2008

AbstractAcquired resistance to the antibiotic polyoxin‐D was studied in two phytopathogenic fungi, Alternaria solani Sorauer, and Sclerotium rolfsii Sacc. The ED50 value of the antibiotic for A. solani was 100 μg/ml and S., rolfsii 200 μg/ml. A. solani and S. rolfsii could be trained to tolerate concentrations upto 1.000 μg/ml and 2.200 μg/ml respectively. The acquired resistance in both cases was not lost on continued subculturing in fungicide‐free, media. On transfer to fungicide‐free media, Polyoxinresistant strains of both the fungi showed faster growth rate and appreciable reduction in sporulation compared to the original strains. The adapted strain of A. solani showed cross‐resistance to Cycloheximide and Difolatan but not to Hinosan and Bayleton.
Soil‐Behaviour of Phytophthora clandestina
Authors: Wong D. H. , Sivasithamparam K. , Barbetti M. J. 
Published: May 2008

AbstractInvestigations were undertaken to study the nature and behaviour of P. clandestina in soil. The pathogen was recovered only from soil sievings 250–499 μm and 500 μm–0.99 mm, containing small root fragments. In soil the introduced inoculum of the fungus was incapable of saprophytically and competitively colonizing the dead cotyledons of subterranean clover used as bait material. Exposure of the inoculum to increasing numbers of microbes by adding greater proportions of nonsterile fields, oil to the growth medium of the plant had no significant effect on survival rate and fresh shoot weight of subterranean clover. However, microbes present in the field soil reduced the severity of root rot of subterranean clover. P. clandestina was, able to spread between 15–30 mm through pasteurized soil within a period of 20 days.
Elimination in vitro of two Grapevine Nepoviruses by an Alternating Temperature Regime*
Authors: Monette P. L. 
Published: May 2008

AbstractA 40 day in vitro treatment with 6 h at 39°C followed by 18 h at 22°C was effective in eliminating both grapevine fanleaf virus (GFLV) and arabis mosaic virus (AMV) from the developing shoot tips (2 mm) of grapevine shoot tip cultures. Longer treatment durations with consecutive 12 h periods at 35°C and 22°C eliminated GFLV in some cases, but did not eliminate AMV.