bluuebunny/crossref_metadata_2025 huggingface dataset:
Association of Peronospora parasitica with Albugo candida on Brassica juncea Leaves
Authors: Bains S. S. , Jhooty J. S.
Published: May 2008

Associated infections between Peronospora parasitica and Albugo candida were observed on Brassica juncea leaves. A. Candida appeared first and was followed by P. parasitica. A. candida predisposes the host tissues towards susceptibility to P. parasitica.
Studies on two Serologically Distinct Raspberry Ringspot Virus Strains from Artichoke
Authors: Rana G. L. , Castrovilli S. , Gallitelli D. , Kyriakopoulou P. E.
Published: May 2008

Two raspberry ringspot virus variants, RRV‐T and RRV‐G, found in artichoke of Turkish and Greek origin, were compared biologically (indexing), biochemically and serologically to two strains of the same virus, RRV‐S and RRV‐E originating from Scotland and England, respectively. Molecular weight values of protein and nucleic acid of RRV‐T and RRV‐G were in good agreement with those already known for RRV. RRV‐T and RRV‐G appeared serologically very similar to each other (serological differentiation index = 1) and well distinguishable from RRV‐S and RRV‐E (serological differentiation indices varying between 3 and 6). Phaseolus vulgaris cv. La Victoire, Ocimum basilicum cv. Foglia di Lattuga, Cucumis sativus cv. Delicatezza, and Cucurbita pepo cv. Zucchetta striata d'ltalia seemed herbaceous hosts useful for differentiating each strain from the others on symptomatological basis.
The Effect of the Date of Rindite Treatment on the Concentration of Potato Virus Y in Tubers
Authors: EHLERS U.
Published: May 2008

The concentration of potato virus Y (PVY) in tubers after artificial break of dormancy by Rindite treatment at three different dates (September 8, November 10, and January 11) after harvest (August 25, 1983) was examined by enzyme‐linked immuno‐sorbent assay (ELISA). The increase of virus concentration was more rapid after the early Rindite treatment than after the later ones. The virus concentration observed after the second and the third treatment varied among the cultivars and reached maximum values considerably later than after the first treatment. There seems to be a direct effect of the Rindite treatment on PVY multiplication in tubers.
Phenolic Compounds in Stems of Sunflower Plants Inoculated with Sclerotinia sclerotiorum and their Inhibitory Effects on the Fungus
Authors: Bazzalo M. E. , Heber E. M. , Del Pero Martinez M. A. , Caso O. H.
Published: May 2008

Sunflower plants at I (vegetative), II (closed flower‐buds) and III (open flower‐buds) growth stages were experimentally inoculated with Sclerotinia sclerotiorum. At the 5th day after inoculation, all plants from I, III and 70 % of II (IIT) did not present wilt symptoms while 30 % of age II plants (IIs) presented severe wilt symptoms in all their leaves and had collapsed. Total soluble phenols were measured in the “lesion” (L) and its “healthy” (H) surrounding zones of all inoculated and control plants. A significant increase in phenols was found in the L and H zones of tolerant plants (I, IIt and III). The corresponding methanolic extracts showed a strong inhibitory effect on the mycelial growth (MG) of the fungus. On the other hand no statistically significant increase took place in the L zones from susceptible plants; their methanolic extracts did not inhibit MG. The chemical analysis of methanolic extracts showed that the isochlorogenic acid was the more inhibitory compound. It significantly accumulated in the L of tolerant plants but did not in those of susceptible ones.
Untersuchungen zum Vorkommen von Pythium spp. im Boden
Authors: Böttcher Ingeborg , Behr L.
Published: May 2008

Investigations on the occurrence of Pythium spp. in soil: I. The isolation of Pythium spp., their distinction to macroscopically characteristics and their determination

The aim of the present paper consisted in detection of Pythium spp. directly in the soil. This was possible by using a selective medium and by crumbling smallest particles of agar‐covered soil on its surface. On the basis of simple morphologically criteria (growth patterns) this method allows to decide concerning the presence of high and less pathogen or apathogen Pythium spp. in a soil sample within 48 hours. About 700 isolates have been cultivated from hyphal tips, determinated and about 230 tested for pathogenicity to sugar beet seedlings in vitro. Most of the Pythia pathogen to sugar beet belong to P. ultimum Trow followed by P. paroecandrum Drechsler and P. debaryanum sensu Drechsler non Hesse. The taxonomically characteristics are demonstrated by figures of the three species.
An Electron Microscope Study of Tubules in Homogenates of Chenopodium quinoa Infected with Strawberry Latent Ringspot Virus
Authors: Hicks R. G. T.
Published: May 2008

Tubular structures found in tissue homogenates of Chenopodium quinoa, infected with a parsnip isolate of SLRV, were described. Virus‐like particles within the tubules had been differentially penetrated by “negative” stain. The presence within some tubules of particles fully penetrated by stain was apparently a new observation for SLRV.
Whiteflies Population and its Impact on the Incidence of Tomato Yellow Mosaic Virus in Venezuela
Authors: Anzola D. , Lastra R.
Published: May 2008

The heavy incidence of Tomato Yellow Mosaic Virus in Venezuela is related to the high population densities of its vector, the whitefly Bemisia tabaci Genn. The main factor affecting the population of the vector is the rainfall pattern; during the rainy season the populations are low but they increase rapidly in the drier months. A good correlation was found between the number of whiteflies trapped and the incidence of infested plants. It seems that in the low laying areas of the tropics the temperature does not have a marked effect on the whitefly population since it remains quite stable throughout the year.
Root Rot of Trifolium subterraneum Induced by Fusarium solani
Authors: Mills L. J.
Published: May 2008

A fungus disease of Trifolium subterraneum, previously unknown in South Africa, was identified as Fusarium root rot caused by F. solani (Mart.) Sacc. Diseased plants were severely stunted. The characteristic internal root discolouration observed in the field, is described. The disease occurred mainly between Swellendam and Humansdorp in the southern and south‐eastern Cape Province. The subterranean clover fields inspected were between 95 and 100 % infected with the root rot disease. T. repens and T. pratense were also susceptible.
Comparison of Some Isolates of Potato Leaf Roll Virus in Poland
Authors: Syller J.
Published: May 2008

18 PLRV isolates differed in severity of symptoms induced on Physalis floridana and on three potato cultivars (Osa, Pola, and Giewont). Reactions of potato cultivars to individual isolates were not always related.

Some isolates induced more severe symptoms than others in all host plants. Isolates producing more severe symptoms reached a higher concentration in potato cultivars (evaluated with ELISA test) and were more virulent to Capsella bursa‐pastoris.

An interaction between PLRV isolates and host plants could be demonstrated. In general, the severity of the reaction of cv. Pola was related to that of P. floridana but not to the reaction of cvs. Osa and Giewont. The reactions of cvs. Osa and Giewont were closely related.

All six isolates selected for a more detailed study could infect C. bursa‐pastoris with obvious disease symptoms if potato cv. Osa served as source of the virus. Some isolates failed to infect this plant when other cultivars were used.
Pathogenicity of Fusarium Isolates from Wheat, Rye and Triticale Towards Seedlings and their Ability to Produce Trichothecenes and Zearalenone
Authors: Manka M. , Visconti A. , Chełkowski J. , Baottalico A.
Published: May 2008

37 Fusarium isolates (F. culmorum 20, F. graminearum 4, F. avenaceum 3, F. solani 4, and F. equiseti 6 from wheat, rye and triticale) were examined for pathogenicity and tested for zearalenone (F‐2) and trichothecenes production in vitro. Strong pathogens (F. culmorum and F. graminearum) produced deoxynivalenol and 3‐acetyl‐deoxynivalenol and zearalenone in considerable quantities.
Races of Phytophthora megasperma f.sp. glycinea (Phytophthora Rot) Affecting Soybeans in North Alabama
Authors: Collins D. J. , Pacumbaba R. P. , Tsapra V.
Published: May 2008

Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin (Pmg) was isolated for the first time from the northern counties of Alabama (MORGAN and MADISON). TWO predominant Pmg races, R2 and R11, were identified by the reactions of standard soybean differential cultivars. Other soil‐borne pathogens isolated from the soil and suspected Pmg‐affected root samples in Morgan, Adadison, and Limestone counties were Pytbium spp., Fusarium ssp., Sclerotium rolfsii, and Rbizoctonia solani. Further study is in progress to obtain a proper assessment of Pmg races in Alabama.
Changes in the Proteins of Bean Leaves Infected With Tobacco Necrosis or Alfalfa Mosaic Viruses
Authors: Szczepański M. , Redolfi P.
Published: May 2008

Acidic extracts from TNV and AMV infected “Saxa” bean leaves were electrophoretically examined for protein content. In native conditions of resolution (PAGE) at least three protein bands (PS1–3) not present in the control were found. In denaturing conditions (SDS–PAGE) at least one (PSa), but often two or three such proteins (PSb, c) were found in the same extracts.

Chromatographic resolution of proteins on Sephadex G‐100 column resulted in partial purification of the PS‐proteins. Additional, not known before, slow‐migrating protein (PS0) induced by hypersensitive viral infection was discovered in some of the eluted fractions. Both PS0–3 and PSa–c proteins were present in the same fractions. This fact suggests their similarity in molecular weights and/or shapes.
Tomato‐Fusarium oxysporum f. sp. lycopersici Interaction: “in vitro” Analysis of Several Possible Pathogenic Factors
Authors: Scala A. , Bettini P. , Buiatti M. , Bogani P. , Pellegrini G. , Tognoni F.
Published: May 2008

The behaviour of Tomato cultures from known resistant and susceptible cultivars and lines was examined for callus growth on culture media containing increasing concentrations of Fusarium oxysporum f. sp. lycopersici race 1 culture filtrate and phytoalexin synthesis elicited by Fusarium cell wall components. A strict correlation was found between in vivo resistance to the fungus and in vitro hypersensitive response and phytoalexin induction. On the other hand in vitro tolerance to toxic filtrate does not seem in this case a good indicator of in vivo resistance to the pathogen.
Scanning Electron Microscopy of the Influence of Fixation Vehicle Osmolality on Cell Morphology of Spiroplasma, Acholeplasma, and Mycoplasma spp. grown on Agar
Authors: De Leeuw G. T. N. , Van Vught P. A. M. , Samson R. A. , Polak‐Vogelzang A. A.
Published: May 2008

Young Spiroplasma citri, corn stunt spiroplasma, and honey bee spiroplasma colonies fixed in 5% glutaraldehyde in M 199 cell culture medium with 0.25 M sucrose showed elongated mycelium‐like cells which were sometimes branched or helical. In older colonies beaded chains and rounded bodies were formed. Fixation in 6 % glutaraldehyde in distilled water resulted in amorphous masses in which rounded bodies were present. The spiroplasma cells did not remain osmotically active after glutaraldehyde fixation. Acholeplasma laidlawii and Mycoplasma hyorhinis colonies fixed in glutaraldehyde with or without M 199 medium with 0.25 M sucrose showed little difference in cell morphology.
Effects of Salicylate on Virus‐Infected Tobacco Plants
Authors: Pennazio S. , Roggero P. , Gentile Irene Abbattista
Published: May 2008

Salicylate watered onto the soil of tobacco plants in pots reduced the antigen accumulation and local lesion growth of tobacco necrosis virus mechanically inoculated on the leaves. It also retarded the growth of the necrotic centres of lesions and, in parallel, inhibited ethylene production from infected leaves. However, the therapeutic index of salicylate was very small and the chemical had to be applied in advance of, or at the same time as virus inoculation to give good levels of resistance. The number of lesions and their rate of appearance were not affected by salicylate. In addition, it did not induce resistance against multiplication, systemic spread or symptom severity in tobacco plants inoculated with a necrotic strain of potato virus Y.

These findings suggest that salicylate is not likely to prove useful as polyvalent chemotherapeutic agent.
In vitro Production of Halo Blight Inducing Toxin by Pseudomonas phaseolicola (Burkh.) Dowson
Authors: Bisen P. S. , Sharma Anjana , Agarwal G. P.
Published: May 2008

Three pathogenic strains of Pseudomonas phaseolicola (strain 1 and 3 virulent and strain 5 weakly virulent) were tested for their toxic activity. All three strains produced detectable amounts of toxin in vitro. Cultural conditions and length of incubation greatly influenced toxin production. Maximum amount of toxin was produced at 20°C and pH 6.5. Glycerol served as the best carbon source and 1‐cysteine as the best amino acid for toxin production.
The Relationship Between Peroxidase Activity and Resistance to Sphaerotheca fuliginea in Melons
Authors: Reuveni R. , Bothma G. C.
Published: May 2008

The levels of peroxidase activity in leaves of non‐infected melon plants resistant to Sphaerotheca fuliginea (Schl. ex. Fr.) Poll. were considerably higher than those in the leaves of susceptible plants. After infection the ratio of peroxidase activity to that in non‐infected plants reached a value of up to 47.5 in susceptible plants whereas in resistant plants it remained between 1 and 2. Changes in isozyme pattern were investigated by polyacrylamide gel electrophoresis. In non‐infected resistant leaves slowly migrating isozymes were found. Their intensities increased with time following infection. These isozymes were absent in the susceptible leaves but appeared after the leaves had been infected with S. fuliginea. The role of these isozymes in the resistance mechanism is discussed.
Extracellular Enzymes and Nutritional Physiology of Ampelomyces quisqualis Ces., Hyperparasite of Powdery Mildew, in vitro
Authors: Philipp W.‐D.
Published: May 2008

In vitro, the powdery’ mildew hyperparasite Ampelomyces quisqualis produced constitutively two groups of extracellular enzymes; β‐glucosidase, β‐N‐acetylglucosaminidase and acid phosphatase possessing unusual high molecular weights (M, about 340 000), and ribonuclease, β‐l→3‐glucanase and α‐l→4‐glucanase representing smaller molecules (M, about 15 000–55 000). As can be concluded from adsorption to Concanavalin A‐Sepharose 4 B, these enzymes are of glycoprotein nature Furthermore, traces of phospholipase could be detected in all of the isolates tested, whereas only phosphorylated carbohydrate components and nucleotides including cAMP as nutrients.

The results of these studies suggest that in the biotrophic phase of parasitization A. qwsqualis interferes with energy metabolism, protein synthesis, cell wall synthesis and, possibly, regulation of the host, whereas proteins and membranes remain nearly unaffected. Thus, depletion of the energy reserves of the powdery mildew may be mainly responsible for the degeneration of host ultrastructure which represents the beginning of the necrotrophic phase of parasitization.
The Expression of Race‐Specific Resistance of Wheat Seedlings to Puccinia recondita
Authors: Poyntz B. , Hyde P. M.
Published: May 2008

A range of wheat cultivars with resistance factors effective against Puccinia recondita f. sp. tritici was studied to investigate the mode of action and expression of resistance at first and third seedling leaf stages. In most cultivars, resistance to isolate 74/2 resulted in extremely low levels of infection, apparently linked with a predominantly hypersensitive response by the host. In seedlings of cultivars Mans Fundin and Sterna, however, race‐specific resistance was expressed as increased pathogen latent period and intermediate infection levels.
Acquired Resistance in Hypersensitive Tobacco against Tobacco Mosaic Virus, Induced by Plant Cell Wall Components
Authors: Modderman P. W. , Schot C. P. , Klis F. M. , Wieringa‐Brants D. H.
Published: May 2008

Isolated cell walls from Nicotiana tabacum L. cv. Xanthi‐nc were partially digested with enzymes present in the fungal preparation cellulase Onozuka R‐10. Released carbohydrate material was separated from the enzymes by gel filtration and fractions were injected into the intercellular spaces of one half of each of several Xanthi‐nc leaves. Two to three days after injection the whole leaves were inoculated with TMV. A large reduction in mean lesion diameter was observed in the injected areas compared with those in untreated tissue.
The Effect of Post Inoculation Treatment with Mineral Oil on TMV Multiplication in Tobacco Leaves and Protoplasts
Authors: White R. F. , Forde S. M. D.
Published: May 2008

Half leaves of N. tabacum dipped into a 0.2 % emulsion of meneral oil 15min after inoculation with tabacco masaic virus (TMV) developed significantly fewer lesion than when not dipped Dipping reduced lesion numbers when applied up to 2½ h after inoculation and multiple dippings were more effective than one. The effect of oil was the same whether the inoculum was whole virus or RNA. Tobacco protoplasts treated with mineral oil contained less virus than untreated protoplasts. The oil probably acted by killing the protoplasts and was effective only when protoplasts were centrifuged through the oil emulsion, When water‐treated leaves were dipped into a TMV solution there was an effect on TMV infection similar to that caused by dipping in oil after TMV inoculation.
Purification, Properties and Serology of Strawberry Mild Yellow‐Edge Virus
Authors: Martin R. R. , Converse R. H.
Published: May 2008

Oregon isolate My‐18 of strawberry mild yellow‐edge virus (SMYEV) was purified by comminution in liquid nitrogen, extraction in 0.1 M phosphate, 0.01 M DIECA, 1 % thioglycollic acid (pH 7.0) and differential and rate‐zonal density gradient (dg) centrifugation. The resulting ultraviolet‐absorbing dg band (A254 nm), not seen in healthy control preparations, contained isometric, 23 mm‐diameter, virus‐like particles. The partially purified MY‐18 virus was not transmitted to Fragaria vesca by means of membrane‐fed or injected Chaetosiphon fragaefolii. MY‐18 has an in vivo thermal inactivation point between 45 and 50 °C as determined by feeding C. fragaefolii on detached leaves that had been immersed in water for 10 min at various temperatures. In ELISA, rabbit antisera against MY‐18 differentiated between partially purified preparations from root and leaf tissue and between crude root but not crude leaf extracts from healthy and MY‐18‐infected Fragaria. Our data support the generally held hypothesis that SMYEV is a luteovirus. However, comparative ISEM and ELISA tests failed to reveal any serological releationship between MY‐18 and potato leafroll, beet western yellows, legume yellows, pea leafroll, or tobacco necrotic dwarf viruses.
Detection and Comparison of some Ghanaian Isolates of Cacao Swollen Shoot Virus (CSSV) by Enzyme‐Linked Immunosorbent Assay (ELISA) and Immunoelectron Microscopy (IEM) Using an Antiserum to CSSV Strain 1A
Authors: Sagemann W. , Lesemann D.‐E. , Paul H. L. , Adomako D. , Owusu G. K.
Published: May 2008

Various isolates of Cacao Swollen Shoot Virus (CSSV) were detected without difficulty in leaves of Theobroma cacao L. by ELISA and immunosorbent electron microscopy (ISEM) using an antiserum to severe strain 1A. Many isolates were detected with relatively high values at dilutions of 1:30, whereas some other isolates were hardly or not at all detected at this dilution. Strain 1A was detected at dilutions of up to 1: 2560 of crude leaf extracts. All isolates yielding high reactions seem to be serologically closely related to strain 1A. Strains of the mottle‐leaf type (AD 191, AD 196, AD 7, AD 36, AD 135, Kpeve) and others were poorly detected; their relationship to strain 1A is discussed. A close correlation was found between results obtained by ELISA and ISEM.
Non‐Specific Induction of Pisatin and Local Resistance in Pea Leaves by Elicitors from Mycosphaerella pinodes, M. melonis and M. ligulicola and the Effect of Suppressor from M. pinodes
Authors: Yamamoto Y. , Oku H. , Shiraishi T. , Ouchi S. , Koshizawa K.
Published: May 2008

The accumulation of pisatin was induced non‐specifically by elicitors prepared from the high molecular weight fraction (molecular weight: more than 10,000 daltons) of the spore germination fluid of three species of Mycosphaerella‐plant pathogens in pea leaves with epidermis removed, regardless of the pathogenicity of the fungi to pea. Before the elicitation of pisatin synthesis, local resistance to infection by Mycosphaerella pinodes was induced by elicitors again non‐specifically inpea leaves in which wax had been removed from the leaf surface. The substance responsible for local resistance could be extracted with ethylacetate from the elicitor‐containing drop diffusate which was placed on pea leaves. The substance prevented the penetration of M. pinodes through heat‐killed pea epidermis, but did not affect spore germination. The suppressor prepared from the low molecular weight fraction (molecular weight: less than 10,000 daltons) of the spore germination fluid of M.pinodes counteracted the ability of elicitors to induce both phases of resistance mechanisms.
The Control of Fusarium solani f. sp. phaseoli by Fungicide Mixtures
Authors: Ahmed Mussa Ahmed El‐Tayeb
Published: May 2008

Six fungicides were used either alone or in binary combination to control Fusarium solani f. sp. phaseoli. Of the three methods of application used, seed treatments and soil drenches were the best, although phytotoxicity was evident in some instances. Application as a seed soak for 1 h proved to be the worst method with most treatments showing signs of phytotoxicity.

The results are discussed with reference to the use of fungicide mixtures to control foot rot of beans.
Immunoenzymic Localization of Plant Virus on Aphid Stylets
Authors: Jellison J.
Published: May 2008

An enzyme‐linked antigen distribution assay (Makleret al. 1981) was used to detect and to visualize the location of the lentil strain of pea seed‐borne mosaic virus, a non‐persistently transmitted potyvirus, on dissected vector stylets.
A Leaf Spot of Water Hyacinth Caused by Drechslera spicifera
Authors: Abdel‐Rahim A. M. , Tawfig S.
Published: May 2008

In the present study, corn meal agar was found as the best medium for growth of Drechslera spicifera, a pathogen of water hyacinth.

Small water hyacinth plants exhibited a smaller number of lesions/leaf when inoculated with D. spicifera compared with inoculated medium and large plants. However, percentage total diseased area/leaf was almost the same among the different plant sizes.

The pathogen did not interfere with the vegetative plant growth, since, both infected and healthy water hyacinth plants of the same age showed similar percentages of new leaf growth.

Leaf diffusates of water hyacinth plants significantly reduced conidiospore germination in D. spicifera.
Soybean Mosaic Virus: Vector Specificity and Coat Protein Properties
Authors: O'Connell‐Ziegler P. , Benner H. I. , Hill J. H.
Published: May 2008

Aphid transmission studies of two soybean mosaic virus isolates have shown that both isolates are transmitted by Myzus persicae. Only one of the isolates is transmitted by Rhopalosiphum maidis. The R. madis non‐transmissible isolate could be transmitted from plants co‐infected with the R. maidis transmissible isolate; aphid acquisition factor did not seem to mediate this transmission. The two isolates could be differentiated by enzyme‐linked immunosorbent assay experiments, but peptide mapping experiments revealed few differences between the isolates.
Response to Gamma Irradiation and Induced Virulent Mutation in Melampsora medusae of Poplars
Authors: Prakash C. S. , Heather W. A.
Published: May 2008

When the urediniospores of three races of Melampsora medusae, the causal agent of leaf rust of poplars, were exposed to Co60 gamma irradiation (range 100–1000 Gy), there were significant differences in the radiosensitivity of the races as assessed, in vitro, by incubation period to flecking and the uredinial survivability percentage. In race 5A the frequency of mutation to virulence on Populus deltoides cv. T‐173, normally a resistant cultivar, was maximum (1.688 %) at an irradiation dose of 400 Gy. Importance of mutations as source of variability in pathosystems and usefullness of artificially induced mutations in the context of host‐pathogen interactions are discussed.
Die Parasitierung des Bohnenrostes Uromyces appendiculatus var. appendiculatus durch den Hyperparasiten Verticillium lecanii: Untersuchungen zur Wirt‐Erkennung, Penetration und Abbau der Rostpilzsporen
Authors: Grabski G. C. , Mendgen K.
Published: May 2008

Hyperparasitism of Uromyces appendiculatus var. appendiculatus by Verticillium lecanii Host Recognition, Penetration and Degradation of Spores

Culture filtrates of the hyperparasite Verticillium lecanii contain numerous lytic enzymes. When specific substrates were added to the filtrate, degradation of chitin is increased by a factor of 2,25 and degradation of starch is increased by a factor of 1,5. The degradation of uredo‐ and teliospores of Uromyces appendiculatus var. appendiculatus is documented cytologically. Appressoria‐like structures initiated direct penetration of the spore walls. Additional routes of penetration through the germpores of both sporetypes and the pedicles of the teliospores were observed. Degradation of the spore cytoplasm is described. Sugars on the surface of uredo‐ and teliospores and on hyphae of the hyperparasite were characterized using the gold‐marked lectins Con A and WGA. Their role in the host‐parasite recognition process is discussed.
Cyanogenesis of Hevea brasiliensis during Infection with Microcyclus ulei1)
Authors: Lieberei R.
Published: May 2008

Eight Hevea species have been shown to be cyanogenic.

They all liberated HCN following mechanical tissue injury. Infection of Hevea leaves with conidia of the plant pathogen Microcyclus ulei leads to a large reduction of hydrocyanic acid potential, while only small amounts of HCN are set free from the leaves into the atmosphere. HCN production by infected leaves follows a reproducible pattern with a maximum between 40 and 60 hours after infection.

During the entire time of infection free HCN can be detected in the leaves. From leaves of susceptible clones high amounts of HCN are liberated whereas from resistant clones only very little HCN is released. In Hevea infections with M. ulei, cyanogenesis does not lead to defense of the fungal pathogen but impairment of the resistance reaction.
Comparative Studies on Aphid Transmission of the Sudanese Strain of Peanut Stunt Virus
Authors: El Sadiq E. O. , Ahmed A. H.
Published: May 2008

The Sudanese strain of peanut stunt virus was transmitted by Aphis craccivora, Aphis solanella, Myzus persicae and Liaphis erysimi. Of these, A. solanella and L. erysimi were reported for the first time as vectors of peanut stunt virus. A. gossypii, A. solani and Rhopalosiphum maidis failed to transmit the virus. Viruliferous aphids retained the virus for 30 minutes but post‐acquisition starvation beyond 30 minutes resulted in almost complete loss of the virus. A. craccivora transmitted the virus to four consecutive test plants and A. solanella, L. erysimi and M. persicae transmitted the virus to three consecutive test plants. It has been suggested that future research programmes should, include resistance to the virus in the major legume crops and that a crop like lucerne (Medicago sativa) which harbours both the virus and its vectors, should not be introduced in the major peanut‐growing areas of the Sudan.
Accumulation of phytoalexins and isoflavone glucosides in a resistant and a susceptible cultivar of Cicer arietinum during infection with Ascochyta rabiei
Authors: WEIGAND F. , KÖSTER J. , WELTZIEN H. C. , BARZ W.
Published: May 2008

After infection with spores of a virulent strain of Ascochyta rabiei the chickpea (Cicer arietinum) cultivars ILC 1929 (susceptible) and ILC 3279 (resistant) were compared with regard to pterocarpan phytoalexin and isoflavone accumulation. Quantitative HPLC analyses of total extracts of aerial parts were used to measure the induced formation of the phytoalexins medicarpin and maackiain and the accumulation of the constitutive isoflavones biochanin A and formononetin together with their, 7‐0‐glucosides and their 7‐0‐glucoside‐6″‐0‐malonates. The two cultivars showed no significant difference in the level of isoflavones and isoflavone conjugates. On the other hand, the resistant cultivar ILC 3279 rapidly accumulated large amounts of both, phytoalexins (20–26 nmole g−1 fr.w.) whereas cultivar ILC 1929 only produced very small amounts (5 nmole g−1 fr.w.) of medicarpin. The data are discussed with regard to isoflavonoid metabolism and the significance of induced and constitutive levels of phytoalexins and isoflavones in resistance of chickpea towards A. rabiei.
Untersuchungen zur Anfälligkeit und Resistenz von Kopfsalat (Lactuca sativa) gegen falschen Mehltau (Bremia lactucae) III. Peroxydase‐, peroxydatische Katalase‐und Polyphenoloxydase‐Aktivitäten
Authors: Zinkernagel V.
Published: May 2008

Investigations on the susceptibility of head lettuce (Lactuca sativa) to downy mildew (Bremia lactucae) III. Activities of peroxidase, catalase and polyphenoloxidase

Host cell walls in contact with intercellular hyphae of Bremia lactucae stain electron positively in susceptible and incompletely resistant varieties of lettuce after appropriate electron microscopy preparation for peroxidase activity. The outer membranes of the mitochondria of the parasite also stained darkly in susceptible varieties whereas in incompletely resistant plants Bremia innermost mitochondrial membranes and host cell mitochondria were darkly stained. This latter observation suggests increased respiration and could be explained as a resistance reaction. Catalase activity was observed in the microbodies of susceptible, in incompletely resistant and healthy varieties. There were no differences in stain intensity in the three kinds of varieties suggesting that catalase activity is not involved in resistance reactions.

Polyphenoloxidase activity was infrequently observed on the host cell wall in susceptible and healthy plants, whereas strong activity in incompletely resistant varieties was observed in vesicles in the haustorial sheath. These vesicles were not surrounded by unit membranes and therefore could not have originated from the unit membranes of the extrahaustorial matrix or from the host plasmalemma. They may have been derived from the host protoplast and involved in inactivation of parasite produced toxins thereby contributing to resistance.
Structure‐Activity Relationships as Inferred from Comparative Phytotoxicity of Stemphyloxins and Betaenones
Authors: Manulis Shulamit , Netzer D. , Barash I.
Published: May 2008

Structure‐activity relationships of the phytotoxins stemphyloxin I and II from Stemphylium botryosum f. sp. lycopersici were investigated by quantitative comparison of their biological activity with chemically related phytotoxins from Phoma betae, betaenones A, B and C. Phytotoxicity was estimated by inhibition of incorporation of14C‐leucine into proteins of exponentially growing tomato cells. The values of 50 % inhibition for stemphyloxin I and II and for betaenones A, B and C were 0.075, 16, 55, 350 and 1 μM respectively. The β‐ketoaldehyde moiety appeared to be essential in, conferring biological activity and its toxicity was influenced by its spatial orientation. The presence of an hydroxyl group in stemphyloxin I and II enhanced activity in comparison with the respective compounds betaenones C and A which lack this group.
Biological Control of Fusarium spp. in Cotton, Wheat and Muskmelon by Trichoderma harzianum
Authors: Sivan A. , Chet I.
Published: May 2008

A new isolate of Trichoderma harzianum (T‐35) was isolated from the rhizosphere of cotton plants from a field infested with Fusarium. Under glasshouse conditions, the antagonist was applied to soil growing in a bran/peat mixture (1:1, v/v) or as a conidial suspension or used as a seed coating. When T. harzianum was tested against Fusarium oxysporum f. sp. vasinfectum, F. oxysporum f. sp. melonis or F. roseum‘Culmorum”, a significant disease reduction, was obtained in cotton, melon and wheat, respectively. Biological control of Fusarium wilt of cotton was achieved when tested at two inoculum levels of the pathogen (2 × 107 and 2 × 108 microconidia/kg soil), decreasing the Fusarium spp. soil population. The long term effect of T. harzianum on Fusarium wilt of cotton was studied using successive plantings. The antagonist persisted in soil throughout three consecutive plantings, reducing the Fusarium, wilt incidence in each growth cycle. At the first planting the largest amount of preparation was found superior, whereas at the third planting, no significant difference could be observed between the four rates of Trichoderma preparation.

T. harzianum (T‐35) controlled Fusarium wilt in cotton and muskmelon when applied in both naturally or artificially infested alluvial vertisol and sandy‐loam soils, respectively.

Soil or seed treatments with the antagonist provided a similar disease control of F. roseum‘Culmorum’ and of F. oxysporum f. sp. melonis.
Chemical Control of Basal Stem Rot Disease of Tomato (Lycopersicon esculentum Mill.) in Northern Nigeria
Authors: Wokocha R. C. , Ebenebe A. C.
Published: May 2008

Six fungicides (Aatopam‐N, Aldrex T, Calixin M, PCNB, captan and captafol) were evaluated at 200 mg a.i.l−1 for their effectiveness in reducing basal stem rot disease incited by Sclerotium rolfsii on tomato in pre‐ and post‐inoculation soil drenches in the glasshouse. The results showed that only PCNB effectively reduced disease severity when applied to soil 10 days before inoculation. Of the two application methods only pre‐inoculation soil drenching with the fungicides was efficacious in reducing disease severity. In field trials conducted in Samaru with Aldrex T, captan and PCNB, only PCNB was effective in combating the severity of the disease. It reduced the disease by about 88% in one trial.
Impact of Host Resistance on the Variability in Virulence of Xanthomonas campestris pv. oryzae
Authors: Nayak P.
Published: May 2008

Twenty isolates of Xanthomonas campestris pv. oryzae (Ishiyama) Dye each from susceptible and resistant rice cultivars, were inoculated on the susceptible genotype IR‐8 and resistant M Sungsong to measure the impact of host selection pressure on virulence change. Isolates virulent on resistant genotype tended to be less adaptive on susceptible cultivars. While isolates from susceptible genotype showed 2.2 times more general virulence (GV) than specific virulence (SV), isolates of resistant host origin had only 1.3 times GV, indicating that the resistant host plant displays considerable increase in virulence. The SV value increased 1.64 times after one cropping with resistants indicated the potential of the pathogen to change to be slow.
Factors Affecting the Parasitic Activity of Gliocladium virens on Sclerotia of Sclerotinia sclerotiorum and a Note on its Host Range
Authors: Phillips A. J. L.
Published: May 2008

Aspects of the biology of Gliocladium virens and parasitism of sclerotia of Sclerotinia sclerotiorum in soil were studied. G. virens parasitized and decayed sclerotia of S. sclerotiorum, S. minor, Botrytis cinerea, Sclerotium, rolfsii and Macrophomina phaseolina on laboratory media and caused a reduction in survival of sclerotia of S. sclerotiorum in soil. It was active over a broad range of soil moisture levels and over the entire agricultural soil pH range. The main factor limiting its use as a biological control agent was its temperature requirements.
In vitro‐Untersuchungen und mikroskopische Studien zur Entwicklung von Phoma chrysanthemicola Hollos f. sp. chrysanthemicola, dem Erreger einer Wurzel‐ und Stengelgrundfäule der Chrysantheme
Authors: Hauptmann G. , Schickedanz F.
Published: May 2008

In vitro investigations and microscopic studies about the development of Phoma chrysanthemicola Hollos f. sp. chrysanthemicola, the causal pathogen of a collar and root rot of chrysanthemums

Different media were tested for cultivation of Phoma chrysanthemicola. The pathogen grew best on PDA and carrot‐Agar at a temperature of 25°C. The three strains used showed many variations, concerning the structure and colour of the mycelium. Fructification has been promoted by irradiation (ultra‐violer ray). The morphogenesis, especially the formation of pycnidia, conidia and sclerotial structures has been examined with help of the scanning electrone microscope (SEM), results are presented., So far unknown organs probably belonging to the fungus were observed, their identity is still not clear.
Fungistatic Activity of Saponin A from Styrax officinalis L. on Plant Pathogens
Authors: Zehavi U. , Levy M. , Segal R.
Published: May 2008

The antimycotic activity of saponin A from Styrax and of its debenzoylated derivative, Saponin B, was studied on a number of plant pathogens and on Trichoderma viride. Saponin A demonstrated activity against Trichoderma viride, Fusarium oxysporum, Aspargillus niger and Rhizopus mucco. At the concentration tested, Saponin B had low activity only on Trichoderma viride‐ a result discussed in terms of mechanism of action.
Biotic and Abiotic Induction of a Fungitoxic Compound in Rice Bean (Vigna umbellata [Thunb.] Ohwi and Ohashi)
Authors: Datta D. K. , Mukherjee A. K. , Samaddar K. R.
Published: May 2008

Young leaves of rice bean produced relatively more fungitoxic compound(s) than the older leaves. Epicotyls, roots, mature leaves and pods, but not cotyledon and cotyledonary leaves, synthesized the antifungal compound(s) following inoculation with anon‐pathogen of this plant. Epicotyl segments when chopped or pinpricked produced the phytoalexin. Treatment of epicotyls with a dilute concentration of various chemicals caused induction of the fungitoxic compound(s). Induction by inoculation, injury and chemicals suggest a phytoalexin nature of the compound. Presence of phaseollin in the extracts of inoculated, injured or chemical‐treated epicotyls has been demonstrated.
Guignardia citricarpa a Cause of Black Spot on Mango Foliage in Florida1
Authors: McMillan R. T.
Published: May 2008

A strain of Guignardia citricarpa Kiely was isolated from infected mango (Mangifera indica L.) leaves. The morphological and physiological characteristics of perithecia and ascospores were identical with those described for G. citricarpa. Inoculated leaves developed lesions 7 to 10 days after ascospore germination. Young lesions appeared as minute, sunken, blackish depressions on upper and lower leaf surfaces. Mature lesions were roughly circular ranging from 1 to 2 mm in diameter. The fungus was consistently reisolated from the lesions which appeared on the leaves, arising from inoculation. Benomyl at 1.7 g/l provided control of black spot.
Rhizothyrium paraskicum sp. nov. (Coelomycetes), ein Blattparasit auf Araucaria araucana (Mol.) C. Koch*
Authors: Butin H.
Published: May 2008

Rhizothyrium parasiticum sp. nov. (Coelomycetes), a leaf parasite on Araucaria araucana (Mol.) C. Koch

An imperfect fungus, which causes leaf spots on Araucaria araucana in Chile is described. The usually fairly small necrosis are soon blocked off by a woundperiderm. The placement of this pathogene in the genus Rhizothyrium Naoumoff is discussed.
Diagnostic Procedure for Detection of Viroids and Viruses with Circular RNAs by “Return”–Gel Electrophoresis
Authors: Schumacher J. , Meyer N. , Riesner D. , Weidemann H. L.
Published: May 2008

A gel electrophoretic technique for the rapid and sensitive detection of viroids and virusoids is described. Starting from plant material, a typical analysis requires less than 5 hours. Viroid concentrations as low as 800 pg/g tissue can be detected unambiguously without the use of radioactivity, organic solvents, or highly specialized laboratory equipment. The sensitivity may be further increased by introducing additional purification steps. The technique is an essential improvement of the previously published bidirectional gel electrophoretic analysis (Schumacheret al.1983, Anal. Biochem. 135, 288–295). In the new procedure gel electrophoresis is first carried out under native conditions. Before the viroid (or virusoid) bands will leave the gel, conditions are changed to provide denaturing conditions which are achieved by increasing the temperature and changing the buffer. After changing the polarity of the electric field all nucleic acids in the gel “return” in that they now migrate towards their original starting point. Under the denaturing conditions in the second electrophoresis viroids (or virusoids) unfold into the conformation of a circle without in tramolecular base pairs, which structure is unique among the nucleic acids in the gel. The denatured circular viroids migrate in the gel much slower than all other nucleic acids of comparable molecular weight and, therefore stay well separated behind the edge of the other nucleic acids. Thus, viroids can easily be detected on the stained gel as a discrete band.
Slow Leaf Rusting Resistance in Wheat Cultivars VL 422 and Sonalika
Authors: Sharma D. L. , Gupta A. K.
Published: May 2008

Wheat cultivars VL 422 and Sonalika were found to be slow rusters against two Indian cultures of Puccinia recondita, IL 005 and IL 007, at the adult plant stage, showing lower average disease score and maximum rust severity compared to cultivar CPAN 1425. This slow rusting could not be detected in seedlings of these cultivars.
Correlation between Light and Electron Microscopic Observations and Identification of Mycoplasmalike Organisms using Consecutive 350 nm Thick Sections
Authors: Cousin M. T. , Sharma A. K. , Misra S.
Published: May 2008

Serial sections of 350 nm thickness were used to make a correlation between electron and light microscopic observations. While thionin‐acridine orange staining gave a positive result to detect abnormal sieve tubes of phyllody affected Phlox drummondii Hook, when observed under light microscope, the same cells revealed the presence of typical mycoplasmalike organisms (MLOs) in electron microscopic examination. Advantage of 350 nm thick sections in electron microscopy, and the utility of the technique in MLO detection have been discussed.
Specificity of Interactions Between Wild Lactuca spp. and Bremia lactucae Isolates from Lactuca serriola
Authors: Lebeda A.
Published: May 2008

Specificity of interactions between eight Lactuca species and 8 Bremia lactucae isolates was studied in seedlings and adult plants of 36 Lactuca accessions plus one L. serriola × L. sativa hybrid. Pathogenicity of the isolates and/or plant susceptibility was expressed by sporulation intensity.

A highly compatible relationship was observed in all of L. serriola accession/isolate interactions tested. A differential reaction was found in numerous cases testifying to physiological specialization of the pathogen in a wild pathosystem. Nonspecific nondifferential compatibility (quantitative resistance) can be expected in L. serriola PI 281876. Age dependent resistance (seedlings versus adult plants, and vice versa) and heterogeneity of reactions were also recorded. The comparisonof B. lactucae isolates from L. sativa and L. serriola has shown a significant shift of pathogenicity in favour of L. serriola accessions. A high level of resistance was found in the L. serriola × L. sativa hybrid.

The existence of basic incompatibility can be expected in L. saligna and L. virosa as well as in such taxonomically remote species as L. viminea, L. squarrosa and L. biennis. Other taxonomically remote species, i.e. L. dentata and L. alpina, exhibited a compatible reaction, although the reaction of the former was differential. A high level of sporulation was recorded in all accession/isolate interactions of L. alpina.
The Hydroxyproline Content in Cell Wall of Resistant and Susceptible Alfalfa Plants Inoculated with Wilt Pathogens
Authors: Krátká J. , Kürdela V.
Published: May 2008

The changes of hydroxyproline (Hyp) content in cell wall after inoculation with Corynebacterium michiganense pv. insidiosum or Verticillium albo‐atrum in 8 cultivars of alfalfa (Medicago sativa) were studied.

In our experiments cultivars ‘Trek’ and ‘Vernal’– resistant, ‘Du Puits’ and ‘Vertus’– susceptible to C. michiganense;‘Vela’ and ‘Maris Kabul’– resistant to V. albo‐atrum, ‘Sabilt’ and ‘Lahontan’– susceptible to V. albo‐atrum were used.

In resistant plants inoculated with C. michiganense none or a small increase of Hyp content in comparison with control plants was registered. On the other hand, inoculated susceptible plants showed markedly increase of Hyp content in comparison with the control plants.

The differences in Hyp content between control and inoculated resistant and susceptible plants with V. albo‐atrum were not markedly expressed in comparison with the alfalfa –C. michiganense pair.

The changes had similar tendency both in C. michiganense and V. albo‐atrum.–alfalfa pairs.
Colonization of Claviceps purpurea sclerotia on Triticale by Fusaria in 1985
Authors: Chelkowski Jerzy , Kwasna Hanna
Published: May 2008

During 1985 60% of Claviceps purpurea sclerotia collected from Triticale heads were colonized by Fusarium acuminatum Ell. et Ev. and F. heterosporum Nees.
Effect of Source Strength, Distance and Direction on the Spread of Maize Dwarf Mosaic Virus
Authors: Madden L. V. , Knoke J. K. , Louie R.
Published: May 2008

Spread of maize dwarf mosaic virus (MDMV) from infected maize to trap plants was assessed at 8 successive weeks. During each week, 0, 9 or 81 infected plants were placed in the centre of a fallow area. Ten trap plants each were placed at each of eight compass directions at three distances (8, 16 and 24 m) from the source. Disease incidence varied with week, distance and source strength (number of infected plants at the source). Disease increased to a maximum by 27 August, and then decreased. There was a decline in disease with distance from the source but no change in disease with direction. There was little disease in the controls or at 24 m in the other plots. Number and species composition of aphids also varied with time, and a few species were highly related to disease incidence.
Zur Auswirkung von Resistenzreaktionen auf Pflanzenwachstum und Ertrag in inkompatiblen Wirt‐Parasit‐Systemen
Authors: Schönbeck F. , Grunewaldt‐Stöcker G. , Wilde T.
Published: May 2008

Effects of defense reactions on plant growth and yield in incompatible host‐parasite‐systems

Investigations in incompatible host‐parasite‐systems (barley –Erysiphe graminis and lettuce –Bremia lactucae) were carried out to prove, whether the induction of defense reactions leads to measurable effects on the yield performance of plants. Permanent or frequent inoculations with avirulent races decreased yield of barley and lettuce remarkably, expressed in reduced fresh weight and drym, atter. Less grains were produced and their contents of carbohydrates and amino acids were diminished significantly. In young plants a reduction in sugar content was evident already after a single inoculation. In barley as in lettuce this effect was shown, not only for inoculated, but also for plant parts not present at the time of inoculation. There, in addition especially aromatic amino acids increased, while glutamate, aspartate and their amides diminished. The consequences of a permanent maintenance of postinfectional resistance mechanisms either of a hypersensitive or non‐hypersensitive reaction type for growth and yield performance are discussed with regard to an increased consumption of energy and carbohydrates.