bluuebunny/crossref_metadata_2025 huggingface dataset:
Befall‐Schaden‐Relationen für das Wirt‐Parasit‐Paar Weizen‐Septoria nodorum Berk.
Authors: Kelaniyangoda D. B.
Published: May 2008

Infestation‐damage relationship for the host‐parasite system wheat‐Septoria nodorum Berk.

It was the aim of these investigations to elucidate the relationship between infestation by Septoria nodorum Berk. and the damage caused thereby to the winter wheat varieties grown in the GDR. In 1983 and 1984 the varieties Alcedo and Taras were tested, and for the identification of typical varietal reactions, another 4 cultivars (Arkos, Compal, Mironovskaya 808 und Ilyitshovka) were included, in 1984.

Artificial inoculation was carried out when the ears were emerging, using spore suspensions of varying density to achieve various degrees of infestation. For each variety, ear and flag leaf infestations were recorded on 800 culms and these were thengrouped into the categories I, II and III according to the number of points they had received (9 = without any infestation, 7 and 5 = number of points decreasing as infestation increased). Altogether 5–6 assessments were made, with the points given at the growth stage “beginning of the milky ripeness” being used as the basis for the calculation of the infestation‐damage relationship. The most important criterion for each group was the mean single ear weight, the 1000‐grain weight and the number of grains per ear, were also taken into consideration.

Comparing ear infestation with yield it can be stated that the variety Compal and the early ripening Soviet varieties Mironovskaya 808 and Ilyitshovka showed relatively low losses. The variety Taras ranked in the middle. Alcedo and Arkos suffered the highest yield losses. Depending on the variety, an infestation level rated with 7 points at the beginning of milky ripeness implied yield losses of 5–13 %, whereas a 5 rating point would represent losses of 13–23 %.

The results obtained make it clear that the wheat cultivars tested were not damaged by S. nodorum to the same degree, indicating differing varietal susceptibility, which does not allow a generalization with respect to the infestation‐damage relationship for the host‐parasite pair wheat‐S. nodorum.
Studies on the Extracellular Polysaccharides (EPS) Produced in vitro by Pseudomonas phaseolicola III. Kinetics of Levan and Alginate Formation in Batch Culture and Demonstration of Levansucrase Activity in Crude EPS
Authors: Gross M. , Rudolph K.
Published: May 2008

In batch culture Pseudomonas phaseolicola converted ca. 8–11% of the substrate (sucrose) into extracellular polysaccharides (EPS). The percentage of conversion was independent of the concentration of sucrose in the medium. However, the increase of total EPS observed with enhanced substrate concentration was largely due to a drastic stimulation of the levan produced. Production of alginate, in contrast, was stimulated to a much lower extent. EPS production was highest during the middle phaseof exponential growth and gradually terminated as the cultures grew older. With sucrose as substrate, the formation of alginate followed the levan synthesis. With glucose or gluconate, however, there was no production of levan, and the alginate synthesis, started immediately after the lag‐phase of the culture.

Levansucrase activity was detected in the protein fraction of crude EPS produced by a culture grown in sucrose containing medium. Enzyme activity was demonstrated both by the release of glucose and the formation of levan from sucrose. Upon ion exchange chromatography on DEAE‐fractogel levansucrase behaved as a rather acidic protein. Native polyacrylamide gel electrophoresis of the enzyme fraction revealed a major band with an apparent molecular weight of ca. 68,000 d. Several grams of levan were synthesized with a partly purified enzyme preparation in the absence of bacteria.
Grapevine Fanleaf Virus Monoclonal Antibodies: their Use to Distinguish Different Isolates
Authors: Huss Brigitte , Muller Sylviane , Sommermeyer Ghislaine , Walter B. , Van Regenmortel M. H. V.
Published: May 2008

Monoclonal antibodies (MCAs) specific for Grapevine Fanleaf Virus (GFV) were obtained by fusion of a non‐secreting myeloma cell line with the spleen cells from Balb/c mice immunized with GFV isolate F 13. The MCAs were tested with apanel of GFV isolates, using both crude extracts and purified virus particles.

Some of the MCAs recognize all 41 isolates tested and are suitable as a diagnostic reagent for GFV detection. Certain MCAs do not bind to some of the isolates, while others show a lower reactivity for certain isolates than for the immunogen F 13. MCAs make it possible to distinguish GFV isolates which until now could not be distinguished by using polyclonal antiserum.
Effects of Disease Intensity and Application Type on Efficacy and Synergy of Fungicide Mixtures Against Phytophthora infestans
Authors: Samoucha Y. , Hugelshofer U. , Gisi U.
Published: May 2008

Of eleven tomato cultivars ‘Baby’ was the most susceptible to Phytophthora infestans. The sporangium concentration of the fungus and the methods of fungicide application had a significant effect on the efficacy of oxadixyl, mancozeb and cymoxanil when tested singly or in mixture against sensitive and phenylamide resistant strains of P. infestans on tomato. Mancozeb was the least effective fungicide, its activity decreased significantly with increasing numbers of sporangia used for inoculation (increasing disease pressure) and its efficacy was dependent on the method of application. Oxadixyl and cymoxanil showed much stronger antifungal activities (except oxadixyl against resistant strains) which did not depend on the number of sporangia or method of fungicide application. The mixture of oxadixyl, mancozeb and cymoxanil was equally active and was independent of application type, sporangium concentration and level of sensitivity of the fungus. Mixtures of the single components showed synergistic interactions up to levels of 20, depending on the activity of the individual fungicide and the different disease intensities. Three‐way mixtures containing oxadixyl, mancozeb, and cymoxanil represent therefore promising possibilities in practice for strong disease pressure, even when resistance problems are expected.
Transfer of Alternaria macrospora from Cotton Seed to Seedling: Light and Scanning Electron Microscopy of Colonization
Authors: Bashan Yoav , Levanony Hanna
Published: May 2008

Alternaria macrospora is transferred from an infected seed, through the plant stem to the cotyledon and sporulates on its surface. However, at the beginning of the process, there is no difference between resistant and susceptible plants. In later stages, lower levels of fungal mycelium and sporulation were detected on the seedlings of a resistant cultivar. The fungus grew inside the plant from the underground to the upper parts. The mycelia which originated from surface spores could penetrate, through stomata and result in leaf colonization. A. macrospora sporulated ultimately on plant surfaces whereas the internal leaf tissue was colonized by mycelium only. This study suggests that cotyledon infection is a result of seed infection.
Lack of Involvement of Nutrients in the Latency of Alternaria alternata in Unripe Mango Fruits
Authors: Droby S. , Jacoby B. , Prusky D.
Published: May 2008

The possible relation between changes in mango fruit composition during ripening and the latency of Alternaria alternata infections was investigated. The main increase in total soluble solids and the decrease in acid content in ripening mangofruits occurred during the initial 13 days after harvest, while symptoms of A. alternata appeared only 5 days later. Susceptibility of resistant peeled mango fruits flesh could not be increased by infiltration with sucrose, at a concentration that sustains maximal growth in vitro.
A Naturally Occurring Resistant Forma Specialis of Phytophthora drechsleri to Metalaxyl
Authors: Chauhan V. B. , Singh U. P.
Published: May 2008

Metalaxyl was assayed in vitro against six species or formae speciales of Phytophthora. The ED50 values of metalaxyl for P. drechsleri, P. drechsleri, P. megasperma f. sp. medicaginis, P. megasperma f. sp. glycinae, P. boehmeriae, P. citricola and P. drechsleri f. sp. cajani ranged from 0.09–19.00 μg ml−1. The values for P. citricola and P. drechsleri f. sp. cajani were 6.45 and approximately 19.0 μg ml−,1. The ED90 values of all the species or forma speciales ranged from 0.9 to 199.0 μg ml−1. The ED90 for P. citricola and P. drechsleri f. sp. cajani was 48 and 199 μg ml−1, respectively. <P. drechsleri f. sp. cajani appears to be a naturally resistant forma specialis against metalaxyl.
Some Physiological Aspects of Bacterial Wilt of Forage Grasses Caused by Xanthomonas campestris pv. graminis
Authors: Leyns F. , Cleene M. De , Bogaert G. Van , Van de Vijver L. , Ley J. De
Published: May 2008

The effect of host‐plant age, environmental humidity and temperature on the development of the wilting disease of Lolium perenne L., caused by Xanthomonas campestris pv. graminis, was examined. Very young plants were more resistant than older ones. Dry and warm conditions favoured the development and expression of the disease symptoms. Losses in yield were observed under several environmental conditions.
The Expression of Partial Resistance of Wheat to Puccinia recondita
Authors: Poyntz B. , Hyde P. M.
Published: May 2008

A range of winter wheat cultivars, which appeared to show no race‐specific resistance to Puccinia recondita f. sp. tritici, was studied at seedling and adult growth stages to determine the components of partial resistance which might contribute to slow‐rusting in the field. Under controlled environmental conditions, adult plants of cvs Atou, Bouquet, Cappelle‐Desprez and Maris Freeman produced less uredospores per unit area than the control cv. Armada, and uredosori were smaller on these cultivars. Fewer uredosori erupted on cv. Cappelle‐Desprez than on the control, and both cv. Bouquet and cv. Cappelle‐Desprez showed longer latent periods than other cultivars. Cultivar Holdfast had a shorter latent period, with larger and more numerous uredosori than even the highly susceptible cv. Armada. Cultivar Waggoner displayed a similar response to infection to that of the control. The components of partial resistance detected in adult plants were not displayed by seedling leaves.
Nutritional Requirement for Production of Antifungal Substance by Enterobacter aerogenes and Bacillus subtilis Antagonists of Phytophthora cactorum1
Authors: Gupta V. K. , Utkhede R. S.
Published: May 2008

Anker's medium with glucose and Thornton's medium were most suitable for growing Enterobacter aerogenes and Bacillus subtilis respectively, antagonists of P. cactorum, the causal agent of apple crown rot. Calcium nitrate was thebest source of nitrogen for growing cultures of E. aerogenes and B. subtilis. E. aerogenes produced the maximum amount of antifungal substance at 200 and 400 mg/l of nitrogen in the medium. Phosphate supplied either in the potassium or calcium form did not change the growth of either antagonist. An addition of 200 mg/l of N and 400 mg/l of P significantly enhanced the production of antifungal substance by E. aerogenes on Anker's medium with glucose. Thornton's medium supplemented with 200 mg/l of N and 100 mg/l of P produced the maximum amount of antifungal substance from B. subtilis. Generally, soil extracts without enrichment did not support the growth of either antagonist; E. aerogenes required at least 400 mg/lof, both N and P while B. subtilis required 200 mg/l of N and 800 mg/l of P for the maximum production of antifungal substance. When ammonium phosphate was added to soil extracts, only a small amount of antifungal substance was produced by E. aerogenes and none by B. subtilis. These results indicate that E. aerogenes and B. subtilis need N and P fertilization of the sterilized soil for the maximum production of the antifungal substance that inhibits the growth of P. cactorum.
Temperature‐Light Intensity Effect on the Antagonism of Species of Cladosporium to Melampsora larici‐populina on Cultivars of Populus X euramericana (Dode) Guinier
Authors: Sharma I. K. , Heather W. A.
Published: May 2008

The antagonistic and colonistic effect of post‐inoculation temperature and light intensity was investigated in a factorial experiment involving four Cladosporium spp., three poplar cultivars, two levels of temperature and light intensity, anda race of Melampsora larici‐populina. The species of Cladosporium were more antagonistic to uredinial production on the inoculated leaf discs of the cultivars when these were incubated in high temperature – high light intensity than in any other regime. Whilst colonisation of the uredinia was usually minimal in discs incubated on the high temperature – high light intensity regime, the condition of incubation favouring maximum colonisation varied with the cultivar and the species of Cladosporium employed. All the major factors and most of their two‐, three‐ and four‐way interactions were significant determinants of variation in both antagonism to uredinial production and in colonisation of the uredinia produced. The validity ofextrapolation from such experiments to the field environment is discussed.
The Influence of the Concomitant Microflora on Establishment and Dieback of Decay Fungi in Standing Timber
Authors: Gramss G.
Published: May 2008

The microbiological aspects that designate development of decay in standing timber were assessed by determining the resistance to succession as well as the competitive saprophytic ability (kratovirulence, KV) of 40 species of wood destroying basidiomycetous fungi (WBF), proved to be members of 7 ecological categories. The categories (i) to (iv) comprise predominantly pathogenic WBF (pathogens) with high pathovirulence (PV) and correspondingly low KV properties that are dominant in the decay of standing timber. The categories (v) to (vii) include saprophytic WBF (saprophytes) with occasional or no PV and increasingly dominant KV properties which are native to slash and plant residues. On sterilely overgrown blocks of fertilized wood meal which had been exposed to airborne contaminants, most pathogens displayed the same degree of resistance to the insinuation of successive microbes as did the saprophytes. In the inoculation attempts of randomly contaminated wood meal, however, the low‐kratovirulence, pathogens were unable to repress the multitude of the antagonistic resident microorganisms in order to establish themselves in this substrate. In contrast, most high‐kratovirulence saprophytes reduced the number of, or completely eliminated, these antagonistic resident microorganisms in wood meal to create the preconditions for colonizing this substrate themselves for up to 1,200 days. In application of these results to the conditions in standing timber it is concluded that the wounded living tree involuntarily promotes the entry of a pathogenic WBF by keeping its natural antagonists down. The once established WBF can then protect its vegetative thallus itself from being overgrown by successive microbes.
Purification and Identification of a South African Isolate of Watermelon Mosaic Virus – Morocco
Authors: van der Meer Francine W. , Garnett Helen M.
Published: May 2008

Cucurbit crops in South Africa are seriously affected by a flexuous rod‐shaped virus 706 to 770 nm long which causes the plant to be stunted, the leaves to display symptoms of chlorotic mosaic, dark green blisters and malformation, and fruit to be malformed. The virus was purified from infected Cucurbita pepo by extraction in 0.5 M borate buffer, pH 8, containing ethylenediaminotetra‐acetic acid and mercapto‐ethanol, clarification with chloroform, addition of Triton X‐100, sedimentation by ultracentrifugation for which a sucrose cushion was used and centrifugation in 10 to 40 % sucrose gradients. The virus was mechanically transmitted to a limited host range with Chenopodium album, C. amaranticolor, C. quinoa and Gomphrena globosa being the only hosts infected outside the Cucurbitaceae. Luffa cylindrica, Cucumis metuliferus, Coccinia sessilifolia and Citrullus ecirrhosus all members of the Cucurbitaceae, were not infected by the virus. The virus was non‐persistently transmitted by Myzus persicae, produced pinwheel and bundle inclusions in the plant cell cytoplasm and has a single coat protein with a molecular weight of 36,000 daltons and a degraded lighter component of 26,000 daltons. Serological comparisons with antiserum to watermelon mosaic virus 2, Papaya ringspot virus strain W and watermelon mosaic virus Morocco (WMV‐Mor.) identified the virus as an isolate of WMV‐Mor. It was found that WMV‐Mor. is the dominant virus in all the main cucurbit producing areas of South Africa which were surveyed.
Analysis of Resistance to Eyespot in Wheat Using Small Seed‐Samples
Authors: Heun M. , Mielke H. , Martin Regina
Published: May 2008

Six different inoculation methods have been tested to determine Pseudocercosporella herpo‐trichoides resistance of wheat using small seed‐samples. The observed differentiation among hosts corresponds to that known from the literature:‘Diplomat’ and ‘Caribo’ are susceptible whereas ‘VPM1’, ‘Rendezvous’ and ‘Roazon’ carry resistance transferred from Aegilops ventricosa. The modified method of Frauenstein and Roskothen (1979) seems to be most efficient: it is timesaving, easy to use and only small seed‐samples are necessary. Such resistance testing can be used in early generations of breeding programmes.
An Attempt to Predict Response of Sunflowers to Races of Plasmopara halstedii Using Cultured Sunflower Cells
Authors: Gray A. Bruce , Sackston W. E.
Published: May 2008

Cultured sunflower cells reacted alike to inoculation in compatible and incompatible combinations with three races of Plasmopara halstedii, cause of downy mildew. Infection structures formed on the surfaces of cells derived from both resistant and susceptible sunflowers, but no intracellular fungal structures or other signs of penetration were evident in either case. There was no indication of a hypersensitive reaction (rapid death) in cells within 20 h of inoculation in incompatible combinations. The reaction of cells in culture was not like that of intact plants in either compatible or incompatible combinations.
The Effect of Temperature on Symptom Expression and Colonization in Resistant and Susceptible Carnation Cultivars Infected with Fusarium oxysporum f. sp. dianthi
Authors: Harling R. , Taylor G. S. , Matthews P. , Arthur A. E.
Published: May 2008

Six commercial carnation cultivars were inoculated with Fusarium oxysporum f. sp. dianthi race 2, and grown under three different temperature regimes. Colonization by the pathogen and development of wilt symptoms were assessed at intervals up to 40 days. No symptoms and very little colonization were seen in any of the cultivars at 14–15°C. At a temperature of 22°C, the cultivars were clearly differentiated into three groups: those with resistance, partial resistance or susceptibility to the pathogen depending on the severity of symptoms and the extent of fungal colonization. Symptom severity was associated with the extent of colonization. This differentiation was not seen at 26°C, when all cultivars except the most resistant, cv.‘Carrier 929′, rapidly became diseased and died by 23 days after inoculation. ‘Carrier 929’ also showed some wilt symptoms at this temperature and was colonized throughout the height of the stem after 40 days. The pathogen caused disease at 26°C by a combination of vascular wilting and stem base and root rotting.

Fungal colonization was assayed at 22°C by the dilution plate/homogenization method and by estimation of fungal chitin in a highly resistant (‘Carrier 929′) and in a highly susceptible (‘Red Baron’) cultivar. Both methods of assay gave similar results. In ‘Red Baron’, colonization increased slowly up to 20 days after inoculation then progressed rapidly, closely following the development of severe wilt symptoms. In ‘Carrier 929’, colonization remained very low. The low level of fungal biomass in ‘Carrier 929’ compared with ‘Red Baron’ indicated that the former cultivar showed true resistance as opposed to tolerance to the disease.
Reduction of Take‐all Inoculum by Rotation with Lupins, Oats or Field Peas
Authors: Cotterill P. J. , Sivasithamparam K.
Published: May 2008

The feasibility of use of lupins, oats and field peas as alternative rotation crops to reduce inoculum of the take‐all fungus (Gaeumannomyces graminis var. tritici) (under Western Australian field conditions) and disease in following wheat was investigated with a one year field trial, the soil from which was used in two succeeding pot experiments. The possible mechanisms of reduction of inoculum and disease by these crops were examined testing the soil for pathogen and disease suppression. Rotation with lupins or oats for two seasons reduced (P <0.05) inoculum of the take‐all fungus and lupins, oats or field peas reduced (P <0.05) disease in following wheat. Lupins alone reduced inoculum and disease, (P <0.1) after one season. No apparent suppression of the pathogen in the absence of host plants was recorded after one season of rotation, but after two seasons, lupins, oats or field peas all suppressed (P <0.02) growth of the pathogen within soil. However only field pea soil suppressed take‐all in comparison with the wheat control.

Although after two seasons all rotation crops were effective in reducing inoculum and disease the mechanisms of reduction appear to differ between the rotation crops used in this study.
Resident Populations of Pseudomonas syringae pv. syringae on Leaves, Blossoms, and Fruits of Apple and Pear Trees1
Authors: Mansvelt E. Lucienne , Hattingh M. J.
Published: May 2008

Populations of pathogenic Pseudomonas syringae pv. syringae were monitored on apparently healthy leaves, blossoms, and fruit from two apple orchards with known histories of blister bark and a pear orchard with a known history of blossom blast. Populations on blossoms and fruits were higher on pears than on apples. Yellow‐pigmented, non‐pathogenic bacteria might have suppressed or masked the presence of P. syringae pv. syringae on apple trees. Populations of P. syringae pv. syringae on apple and pear leaves fluctuated sharply but higher levels generally occurred during the 1984/85 growing season than during the drier 1983/84 season. This investigation indicates that the resident phase of P. syringae pv. syringae is probably a major source of inoculum for apple blister bark and pear blossom blast in South Africa.
Effect of Moisture and Temperature on the Survival of Sclerotia of Sclerotium rolfsii in Soil
Authors: Maiti Satyabrata , Sen Chitreshwar
Published: May 2008

The sclerotia of Sclerotium rolfsii Sacc. survived in natural soil for 225 days under controlled moisture at 50% water holding capacity (WHC) after which there was a progressive reduction in the population of viable sclerotia. At 390 days only 48% were recovered. Sclerotia survived well at moisture contents upto 75% WHC but at 100% the population declined rapidly and none were recovered after 60 days. The contents of the sclerotia were found to lyse without germination leaving hollow rinds. Such lysis was found to be favoured between 25 and 40°C. At and below 20°C no such lysis was recovered and more than 80% sclerotia were recovered even after 60 days.
Morphologie und Physiologie von Rebblättern mit lokalen Aufwölbungen
Authors: Blanke Michael
Published: May 2008

Anatomy and photosynthesis of grapevine leaf affected by protuberant growth

Grapevine cultivated under controlled environmental conditions developed leaves affected by abaxial protuberant growth in form of raised patches in the intercostal region which were examined by SEM and porometry. Cross‐sections of freeze‐fractured raised patches without prior fixation showed an increase in the number of mesophyll cells responsible for the emergence, without superficial epidermal cracks, necrosis or deformed stomata. Leaves with wide spread symptoms appeared more shiny and curled and, showed a larger reduction in photosynthesis, by up to 76 %, than in transpiration, by up to 20 %, relative to unaffected leaves. It is concluded that this reduction in photosynthesis may be caused by increased mesophyll resistance to CO2 andless light transmission. The protuberant growth was not correlated with ambient CO2 concentrations ranging from 340–700 μl CO2 l−1.
Characterization of Pseudomonas fuscovaginae and Differentiation from Other Fluorescent Pseudomonads Occurring on Rice in Burundi
Authors: Duveiller E. , Miyajima K. , Snacken F. , Autrique A. , Maraite H.
Published: May 2008

In various pathogenicity, serological, physiological and biochemical tests, performed in Belgium and Japan, the Pseudomonas fuscovaginae strains associated above 1,350 m elevation in Burundi with sheath brown rot of rice, rusty seed and black, stripes on seedlings, were found to be similar to reference strains of this pathogen from Japan. The same bacteria was detected on rice seeds imported from Asia to Burundi. Beside the serological characteristics, P. fuscovaginae can be differentiated from other oxidase and arginine dihydrolase positive non‐pathogenic fluorescent pseudomonads, also isolated from lesions on rice seedlings, by the simultaneous occurrence of no production of 2‐ketogluconate, acid production from trehalose, but not from inositol. Occasionally, other symptoms inducing, oxidase positive, fluorescent pseudomonads, different from any described species, were isolated from rice seedlings and sheath rot in Burundi.
Serological Studies on Mung Bean Yellow Mosaic Virus
Authors: Ikegami Masato , Shimizu Shin‐ichi
Published: May 2008

Particles of mung bean yellow mosaic virus (MYMV) were purified by a method that yields up to 3 mg per kg of systemically infected Phaseolus vulgaris“Top Crop” and used to prepare antiserum. MYMV antiserum prepared gave a single precipitin line and had a titre of 1/512 with homologous virus in gel double‐diffusion tests. MYMV was shown to be serologically related to other whitefly‐transmitted viruses, bean golden mosaic virus, tobacco leaf curl virus and cassava latent virus.
Effects of Fusarium graminearum Metabolites on Wheat Tissue in Relation to Fusarium Head Blight Resistance
Authors: Wang Y. Z. , Miller J. D.
Published: May 2008

Fusarium head blight (FHB) of wheat is caused by Fusarium graminearum which produces many secondary metabolites including the trichothecene mycotoxins deoxynivalenol (vomitoxin) and 3‐acetyldeoxynivalenol. Coleoptile tissue segements from 14 spring wheat cultivars were exposed to the F. graminearum metabolites deoxynivalenol, 3‐acetyldeoxynivalenol, butenolide (all known mycotoxins), sambucinol, culmorin and dihydroxycalonectrin in a bioassay. The tissue of most cultivars was inhibited, at a concentration of 10−6M by the trichothecenes tested and up to 10−3M for the other compounds. Deoxynivalenol and 3‐acetyldeoxynivalenol, which affect protein synthesis at the ribosome, are therefore potent phytotoxins in addition to being mycotoxins. The resistance or susceptibility of each cultivar to FHB was established in a field experiment. A comparison of the two sets of data indicated that resistant cultivars could tolerate much higher concentrations of the metabolites tested than susceptible cultivars. Some resistant material can tolerate 10 to 1000 times the concentration of the trichothecenes, compared with susceptible cultivars, with no effect on growth. The data suggest that it may be possible to screen germplasm rapidly for FHB resistance in vitro and a new type of resistance in wheat to this disease is proposed based on the apparent insensitivity to trichothecenes by resistant cultivars, additional to the three types of resistance described in the literature.
Methode zum Nachweis der Dauersporen des Kohlhernieerregers Plasmodiophora brassicae in gärtnerischen Kultursubstraten
Authors: Botz Thomas , Mattusch Peter , Hilgenberg Willy
Published: May 2008

Method for the demonstration of resting spores of the clubroot causing fungus Plasmodiophora brassicae in horticulture soil samples

The investigation based on the biochemical determination of the polymer chitin for a specific demonstration of the clubroot causing fungus Plasmodiophora brassicae. For separation of resting spores from soil material a special apparatus has been constructed which allows the continuous isolation and concentration of this fungal developmental stage.

The specificity of the test is improved by a differential density gradient centrifugation. N‐acetyl glucosamine as the measurable reaction product was formed by chitinase. Only two days are necessary for the whole test procedure. Its sensitivity is 2.5 × 107 resting spores/litre soil material. The method allows a first screening of soil samples and increases the efficiency of common biological tests.
Necrotrophic Mycoparasitism of Chalara elegans (Thielaviopsis basicola) by a Sterile Basidiomycete
Authors: Baard S. W.
Published: May 2008

Interactions between Chalara elegans and a sterile hyaline basidiomycete (SHB) were studied by light, scanning and transmission electron microscopy. Young colonies of C. elegans were quickly overgrown by the mycoparasite, with lysis of, hyphae and conidia. Direct penetration of host hyphae and conidia was observed, but simple coiling around these also occurred. Chlamydospore development was inhibited, but 12.5% of mature chlamydospores were able to survive attack for 120 days. Chlamydospore germination was apparently stimulated by the SHB, whereupon lysis followed. Evidence of invasion of intact chlamydospores is also presented.
Evaluation of Rate‐Limiting Resistance to Blast Disease in Rice Cultivars Using Sub‐Lethal Concentrations of a Systemic Fungicide
Authors: Brodny Uzi , Zapata J. Castano , Nelson R. R.
Published: May 2008

Six rice cultivars were shown to have measurable levels of rate‐limiting resistance (RLR) to blast disease in the seedling stage in the greenhouse, as compared to a susceptible cultivar. The criteria for RLR were: a consistent ability to reduce receptivity, sporulation capacity and an extension of the latent period. Another method for a quantitative evaluation of the RLR to blast disease was developed. This procedure used sub‐lethal concentrations of the systemic fungicide Tricyclazole. It was found, that a certain threshhold (225–525 μg a.i./ml) of fungicide concentration could be used to determine different levels of RLR and that the minimum concentration of the fungicide needed for complete inhibition of the disease in a given cultivar is related to the level of its RLR.
Changes in Chemical Constituents of Tobacco Leaves Infected with Corynespora cassiicola and Colletotrichum nicotianae
Authors: Oke O. A.
Published: May 2008

Changes in nicotine alkaloids, total sugars, reducing sugars, nitrogen and phenol contents were determined in young and matured leaves of healthy and infected leaves of tobacco (cv. Spheight). These constituents accumulated as the healthy leaves aged. In infected leaves, all constituents investigated decreased except nitrogen which increased. Possible effects of the changes in chemical constituents on the quality of tobacco leaves are discussed.
Influence of Mycorrhizal Tobacco Roots, Incorporated Into the Soil, on the Development of Thielaviopsis basicola
Authors: Tosi L. , Giovannetti M. , Zazzerini A. , Torre G. della
Published: May 2008

The interaction between the soil‐borne pathogen Thielaviopsis basicola and mycorrhizal roots infected by Glomus microcarpum has been studied during 4 months. A significant reduction in the number of propagules was observed in soils treated with mycorrhizal roots and an inhibition of T. basicola growth by a substance produced by mycorrhizal roots is suggested.
Pseudomonas fluorescens and Erwinia herbicola Reduce Wilt of Grasses Caused by Xanthomonas campestris pv. graminis
Authors: Schmidt Dorothea
Published: May 2008

Pseudomonas fluorescens and Erwinia herbicola were isolated from Italian ryegrass surviving to infection by Xanthomonas campestris pv. graminis.

They reduced symptom expression and mortality of young ryegrass plants when inoculated simultaneously with or prior to the parasite. Protection from wilt was a quantitative effect, depending on the ratio pathogenic/non‐pathogenic bacteria: it was good with 1/99, less with 10/90 and moderate to low with 50/50.

The effect of preinoculation by leaf‐clipping with scissors contaminated by P. fluorescens or E. herbicola could be detected at least seven days after clipping and at a distance of 2 cm below the clipping level. Preinoculation of roots, or stem bases did not protect the plants from leaf infection by the parasite.
Phytoalexin Induction as a Factor in the Protection of Capsicum annuum L. Fruits Against Infection by Botrytis cinerea Pers.
Authors: Adikaram N. K. B. , Brown AverilE. , Swinburne T. R.
Published: May 2008

Immature Capsicum annuum fruits treated at wound‐sites with glucans from the hyphal walls of Glomerella cingulata and incubated for 24 h or longer accumulated levels of capsicannol phytoalexins sufficient to inhibit rot development by Botrytis cinerea. Elicitor application to intact fruits induced the accumulation of relatively low levels of capsicannol compounds but further phytoalexin accumulation in fruits after wound‐inoculation with B. cinerea was much more rapid than in untreated fruits and rot development was suppressed.

Capsicannol phytoalexins were produced in the live cells of the epidermis and little or no necrosis was associated with quantities produced in intact tissues. Elicitor treatment of intact fruits to protect against rot development by B. cinerea was achieved without the fruits sustaining unsightly damage.
Incidence of Three Major Cassava Diseases on Local Susceptible Cassava Cultivars at Three Planting Dates
Authors: Pacumbaba R. P.
Published: May 2008

Incidence of African cassava mosaic (ACMD), cassava bacterial blight (CBB), and cassava anthracnose (CA) on local susceptible cassava cultivars planted in December, February, and April was investigated. December cassava planting had a higher incidence of ACMD, CBB, and CA diseases compared with February and April plantings. CA seemed to be more prevalent at an older stage (8 months old) of plant growth. April planting had significantly lower incidence of major cassava diseases, and higher mean tuber, yield than the same cassava cultivars planted earlier. The length of exposure of cassava plants to the inocula and/or to the vector during the rainy season determines the occurrence of diseases. In the absence of resistant cassava cultivars and through, partial disease escape of susceptible cultivars from ACMD, CBB, and CA, planting the same cultivars in April can still produce a profitable cassava crop.
Detection of Sap‐Transmissible Viruses by ELISA in Tissue‐Propagated Plants of Red Raspberry during in vitro Culture
Authors: Baumann Gisela , Theiler‐Hedtrich R. , Casper R.
Published: May 2008

Apple mosaic virus and raspberry bushy dwarf virus were detected by ELISA in plantlets of red raspberry still growing in vitro. The plantlets were derived from explants which were excised from plants infected by either of the viruses mentioned. Detection by ELISA of prune dwarf virus in 4‐month‐old in vitro cultures of sour cherry was reported earlier. Thus, application of ELISA to tissue cultured plants in vitro seems to be an appropriate method for early detection of virus‐infected plant cultures.
Increase of Free Space Solutes in Tobacco Leaves in Relation to the Localized Cellular Response Following Injections of a Bacterial Protein‐Lipopolysaccharide Complex*
Authors: Mazzucchi U. , Gasperini C. , Noli E. , Bonatti P. Medeghini
Published: May 2008

Variations in pH, cell ultrastructure, conductivity, calcium ion molarity, reducing sugars, uronic acids and in protein of the intercellular washing fluid were studied at 0, 12, 24 and 48 h in tobacco leaf halves intercellularly injected with a bacterial pr‐LPS complex (250 μg‐ml−1). These injections induced a localized cellular reaction (LCR) in points opposite to intercellular structured deposits on the plant cell walls. The intercellular fluid pH was higher at 24 h than in the control, but not at 12 and 48 h. The conductivity, the calcium ion molarity, the free and hydrolyzed sugar content were higher at 12, 24 and 48 h than in the control tissue; the uronic acid content was higher at 24 and 48 h, but not at 12 h. There was a peak for, all 5 parameters at around 24 h, when LCR showed its highest activity. The protein content was significantly higher at 24 and 48 h than in the control intercellular fluid.

The increase in conductivity, calcium ions, sugar, uronic acids and proteins in the intercellular fluids of the pr‐LPS injected tissue were interpreted as direct or indirect effects of the LCR, i.e. as an exocytosis induced by pr‐LPS injections. The associated high sugar and uronic acid content of the intercellular fluid at 12 and 24 h was not correlated to its capacity to prevent the hypersensitive confluent necrosis when injected intercellularly into tobacco tissue.
Cucumis sativus Cryptic Virus, a New Virus in Cucumber
Authors: Jelkmann W. , Maiss E. , Casper R. , Lesemann D. E.
Published: May 2008

Isometric virus‐like particles (VLPs) have been purified from cucumber leaf tissue. Three dsRNA segments with estimated molecular weights of 1.8, 1.1 and 1.0 × 106d have been isolated from VLPs occurring in CsCl density gradient fractions but were also readily detected in preparations from as little as 1 g of fresh leaf tissue. The VLPs resemble dsRNA containing cryptic viruses and have been named Cucumis sativus cryptic virus (CsCV).
Pectolytic and Cellulolytic Activity of Botrytis cinerea Pers. Related to Infection of Non‐ripening Tomato Mutants
Authors: Barkai‐Golan Rivka , Lavy‐Meir Gila , Kopeliovitch E.
Published: May 2008

Enzymes of Botrytis cinerea were detected in vitro using various carbon sources. Pectin‐pectate as a sole carbon source induced both polygalacturonase (PG) and pectin lyase (PL) activity, whereas carboxymethylcellulose served as an inducer for cellulase (Cx) activity. PG activity appeared earlier than Cx activity when induced by their respective sources. Both PG and PL activities were detected earlier and their level was higher on cell walls of the normal tomato fruit, than of the nor mutant, and in each case activity was higher on cell walls of the mature fruits than of the mature‐green ones. Whereas relatively high rates of PG and PL activity were recorded on autoclaved tomato homogenate (TH) of both the normal and the nor fruits, only trace levels of PG activity were recorded on unautoclaved media, except for those prepared from ripe normal fruits, and no PL activity was detected on either of the unsterilized media.

Botrytis‐infection resulted in PG activity in the enzyme‐less rin and nor mutant fruits at both stages of maturity and in the normal and hybrid fruits at their mature‐green stage. In the ripe normal and hybrid fruits, infection increased the level of PG activity recorded prior to inoculation. An association was drawn between the low PG activity recorded in the nor mutant and its hybrid at initial stages of invasion and their resistance to infection.

Following infection an increase in the level of Cx activity over that recorded in healthy fruits was found in all the tomato genotypes, whereas no PL was recorded in either healthy or infected fruits.
Cellulolytic Ability of the Scab Fungus, Venturia inaequalis
Authors: Wagner K. , Hitz‐Germann Luzia , Seng J. M. , Gessler C.
Published: May 2008

Cellulase and β‐D‐glucosidase activity have been identified in Venturia inaequalis, the causal agent of apple scab. Most of the activity of the enzymes was associated with the mycelium after homogenization. The activities were relatively weak in vitro compared to those of other plant pathogens. With a new screening technique, β‐D‐glucosidase hyperproducing mutants were obtained.
Rhabdoviruses in Mentha piperita
Authors: Intert F. , Amelunxen F.
Published: May 2008

Bacilliform and bullet‐shaped particles measuring 360 × 80 nm and 180x 80 nm respectively, were found in the perinuclear space of parenchymatous cells in the vascular bundles of leaves, or roots of Mentha piperita. All particles contained bullet‐shaped, electron dense cores and were enveloped by a unit membrane with spikes on its surface. The typical morphology and the intracellular occurrence of these particles leads us to the conclusion that they are rhabdoviruses.
Presence of Malformin‐Like Substances in Malformed Floral Tissues of Mango
Authors: Singh Zora , Dhillon B. S.
Published: May 2008

Malformin‐A like substances were detected in malformed floral tissues of mango at four stages of development, viz., fully swollen buds, bud inception, fully grown panicles prior to full bloom and in panicles at full bloom. Spraying with 2000 ppm ascorbic acid, prior to flower bud differentiation significantly reduced the incidence of malformation and resulted in increased fruit yield.
Carbohydrate Composition and Acid Invertase Activity in Rice Leaves Infected with Pyricularia oryzae
Authors: Hwang Byung Kook , Kim Ki Deok , Kim Young Bae
Published: May 2008

Ethanol‐soluble carbohydrates in healthy and blast‐infected leaves and also cultures of Pyricularia oryzae were analyzed using gas chromatography. Arabitol, mannitol, and trehalose occurred in infected leaf tissue, but not in healthy controls. Cultures of P. oryzae contained mannitol and trehalose, but not arabitol and sucrose. The presence of arabitol only in blast‐infected rice leaves suggests that arabitol synthesis may be induced in infected leaf tissue as a result of the rice‐blast fungus interaction, but may not be within blast fungus itself. The amounts of glucose, fructose, and sucrose in infected leaves were slightly increased until 5 days, and greatly enhanced at 7 days after inoculation, There were no differences in amounts of these sugars between the cultivars Nakdong and Dobong. At 7 days after inoculation, increases in amounts of arabitol, mannitol, and trehalose were pronounced in the susceptible cultivar Nakdong than in the moderately susceptible cultivar Dobong. The increased amounts of glucose and fructose in infected plants of the two cultivars were closely correlated with the presence of a very active invertase.
Influence of Phospholipids on Growth, Sporulation and Virulence of the Endoparasitic Fungi Drechmeria coniospora, Verticillium balanoides and Harposporium anguillulae in Liquid Culture
Authors: Lohmann Ulrich , Sikora Richard A. , Höfer Milan
Published: May 2008

Verticillium balanoides mycelial growth was stimulated on solid corn meal agar (1.7 %) and in liquid corn meal broth (0.2 %) upon the addition of phospholipids at various concentrations. Sporulation differed with phospholipid products and was highest in pure corn meal. Drechmeria coniospora mycelial growth increased upon addition of phospholipids at all concentrations in solid or liquid culture. Sporulation increased at high concentration (1000 ppm) and decreased at low concentration (100 ppm) of phospholipids in the medium. For both fungi, infectivity of conidia produced in liquid culture decreased when compared to conidia from parasitized nematodes. Addition of phospholipids partly restored this effect. Harposporium anguillulae mycelial growth and sporulation was not affected by addition of phospholipids to solid or liquid corn meal medium.
Bodenbewohnende Schädlinge und Seitenwurzelfäule der Zuckerrübe in Abhängigkeit von der Rotation – Ergebnisse eines Fruchtfolgeversuches
Authors: Schäufele W. R. , Winner C.
Published: May 2008

Soil inhabiting pests and rot of feeding roots of sugar beet depending on rotation ‐ Results of a long‐term trial

Over a period of 17 years a trial was carried out with sugar beet, cereals and oilseed rape in different crop rotations on a field near Göttingen (Lower Saxony). The frequency of sugar beet in the rotation was 17, 25, 33 and 67 %.

In absence of beet nematodes, root and sugar yield of the beet decreased after repeated growing of sugar beet in short rotations compared to variants with long rotations. Sugar content and beet quality were only slightly influenced.

By applying a bioassay (BW‐Test) with young beet plants in the greenhouse it was shown that increasing infections on the tips of rootlets of the beet plants were the cause for decreasing beet yield in close rotations. Mortality of young beet plants and progress of infection in the test indicated roughly the quantity of pathogenic fungi in the soil. In the roots of the bait platits the parasitic fungus Aphanomyces cochlioides predominated.

Rate of infection and yield reduction in the field were decisively influenced by weather conditions. Differences in yield between sugar beet grown in a three‐year and a four‐year rotation, however, were not significant.

An occurrence of beet pests depending on crop rotation was stated only for Atomaria linearis and this only in a few years.
Occurrence of Aggregate Sheath Spot of Rice in Iran
Authors: Rahimian H.
Published: May 2008

Aggregate sheath spot of rice caused by Rhizoctonia oryzae‐sativae (Swa.) Mordue was found in several locations in Mazandaran Province. The polyacrylamide gel electrophoretic pattern of cell proteins of isolates from different regions were identical. The protein profiles of Iranian isolates were also identical with that of an anastomosis group (AG)‐Bb tester isolate of binucleate Rhizoctonia from Japan, but distinctly different from an AG‐Ba tester strain.
Hormonal Changes Associated with Vegetative Malformation of Mango (Mangifera indica L.)
Authors: Singh Zora , Dhillon B. S.
Published: May 2008

Malformed seedlings of mango showed lower mean content of indole‐3‐acetic acid, gibberellic acid and a higher mean content of zeatin, abscisic acid and ethylene than healthy seedlings.
ACC Synthesis as the Activated Step Responsible for the Rise of Ethylene Production Accompanying Citrus Exocortis Viroid Infection in Tomato Plants
Authors: Bellés J. M. , Granell A. , Durán‐vila N. , Conejero V.
Published: May 2008

Ethylene production was stimulated during the period when systemic symptoms appeared in tomato plants infected with citrus exocortis viroid (CEV).

Neither methionine nor S‐adenosylmethionine increased ethylene production in leaf discs. In contrast, 1‐aminocyclopropane‐l‐carboxylic acid (ACC) stimulated ethylene production notably. Whether viroid infection acted upon ACC production, its conversion to ethylene, or both, was studied by determining the time course of the concentration of ACC and its in vivo production and conversion rates. During early symptoms, ACC synthesis increased and then remained steady during the development of symptoms, but no difference in the capacity of conversion of ACC to ethylene between healthy and CEV‐infected tissues was observed. This indicates that ethylene production in tomato leaves showing systemic symptoms to CEV is activated at the level of ACC production.
Structure‐Biological Activity Relationships in Alfalfa Antimycotic Saponins: The Relative Activity of Medicagenic Acid and Synthetic Derivatives Thereof Against Plant Pathogenic Fungi1
Authors: Levy M. , Zehavi U. , Naim M. , Polacheck I. , Evron R.
Published: May 2008

The antimycotic activity of medicagenic acid and of some synthetic derivatives thereof was tested against plant pathogenic fungi. In general they all possess antimycotic activity. Furthermore, in the case of Sclerotium rolfsii, compounds where the hydroxyl functions of the aglycon remained unchanged (medicagenic acid and its dimethyl ester) or could be enzymically released (3‐0‐β‐D‐glucoside of medicagenic acid dimethyl ester) were significantly more active than compounds where these functions were modified by acetylation or methylation.

Selective 2‐0‐methylation of medicagenic acid and comparison of the antimycotic activity of the resulting derivative against S. rolfsii to that of other derivatives suggests that a potential free hydroxyl at position 3 is essential to antimycotic activity.