bluuebunny/crossref_metadata_2025 huggingface dataset:
Phytophthora cinnamomi: the Dynamics of Chlamydospore Formation and Survival
Authors: Weste Gretna
Published: May 2008

Chlamydospore activity was investigated by inoculating 10 day old seedlings of Lupinus angustifolius with Phytophthora cinnamomi. Infected roots were excised and buried in 4 non‐sterile media: – glass beads, gravel, sand or soil at different water potentials and incubated at 22°C. Roots were examined and chlamydospores counted initially and after 10, 20 and 30 days. Large numbers of spores formed in the roots buried in the various media. Spore formation was rapid in glass beads and gravel, and slower in soil, but more chlamydospores survived the 30 day period when roots were buried in soil.

Nylon mesh squares 1 cm2were inoculated with 38 chlamydospores and buried in the same 4 media. 70–100% of chlamydospores germinated and colonised 90–100% of the mesh, producing mycelia and an increased number of chlamydospores. In some instances there was a ten‐fold increase in spore numbers and numbers were still increasing at 28 days. Maximum numbers and maximum survival occurred on mesh buried in soil. The role of the chlamydospores is considered, as that of a dynamic unit with a saprobic phase in the life cycle of the fungus which is independent of host, and has the capacity to increase both population density and distribution of the pathogen.
Investigations on Transmission of Grapevine Leafroll, Yellow Speckle and Fleck Diseases by Dodder
Authors: Woodham R. C. , Krake I. R.
Published: May 2008

Attempts were made to transmit the infective agents of leafroll, yellow speckle, and fleck diseases from infected grapevmes to several herbaceous species and to healthy vines using dodder (Cuscuta campestris). Dodder transmitted leafroll to all and fleck to half of the respective receptor vines, but none of the three dieases were transmitted to herbaceous plants including Chenopodium, Gomphrena and Nicotiana species, Cowpea, Bean, Cucumber, Squash and Petunia. Suggested transmission of yellow speckle to vine was inconclusive because this disease may have been spread naturally.
Verstärkung der antiphytoviralen Wirkung von 2,4‐Dioxohexahydro‐l,3,5‐triazin durch Kombination mit Verbindungen mit Guanidinstruktur
Authors: Schuster G.
Published: May 2008

Intensified antiphytoviral activity of 2,4‐dioxohexahydro‐l,3,5‐triazine by combination with guanidines

Combined application of the antiphytoviral compound 2,4‐dioxohexahydro‐l,3,5 triazine (DHT) and different guanidines (GDs) that were either unsubstituted or substituted only by low‐molecular substituents reduced the concentration of potato virus χ (PVX) in leaves or Nicotiana tabacum L. cv. Samsun much more than application of either agent alone. In secondarily PVX‐infected leaves, the activity of 2,4‐dioxohexahydro‐ 1,3,5‐triazine was increased by a larger number of GDs and to a greater degree than in inoculated ones. The activities of GDs against tobacco mosaic virus (TMV) in Nicotiana tabacum L. cv. Samsun as well as against brome grass mosaic virus (BRV) in Hordeum vulgare L. cv Vogelsanger Gold were only insignificantly increased by combination with DHT. On the other hand, in experiments with so‐called identical potato eye cuttings, in which several eye cuttings were obtained from each potato tuber, one serving as a control and the others being treated with DHT, N‐cyano guanidine or a combination of these substances, the number of cuttings with symptoms of potato leaf‐roll virus (PLRV) could be much more greatly reduced by the combination than by the individual preparations. The number of cuttings with symptoms of potato virus Y and potato virus A was significantly reduced by treatment with the combined preparation, but not by treatment with DHT or N‐cyano guanidine alone. Additional investigation with N‐cyano‐GD, and, beside this, with acetyl‐GD and N N′ N triamino‐GD indicated a close correlation between the diminution of numbers of potato eye cuttings with virus symptoms and the increase in tuber weight. The greater the reduction in the number of cuttings showing virus symptoms, the greater was the increase in tuber weight. These relationships were observed even in those cases where controls had been treated with ammonium nitrate solutions whose N contents equivalent to the N contents of the preparations. The observed effects of the preparations therefore are not attributable to N‐fertilizing effects.
The Use of Enzyme‐Linked Immunosorbent Assay (ELISA) for Detection of Cacao Swollen Shoot Virus (CSSV) in Theobroma cacao
Authors: Sagemann W. , Paul H. L. , Adomako D. , Owusu G. K.
Published: May 2008

Cacao swollen shoot virus (CSSV) was readily detected in different parts of Theobroma cacao using the ELISA technique. Different plant tissues contained varying amounts of CSSV; highest concentrations were found in leaf lamina. Methods to preserve the serological activity of CSSV were evaluated, and best results obtained with samples stored in a buffer or freeze‐dried.
Acetone Inhibition of Rhizoctonia solani Growth
Authors: Madkour M. A. , Abou‐Taleb E. M. , Okasha A. M.
Published: May 2008

Acetone (5% v/v) inhibited growth of four isolates of Rhizoctonia solani which differ in their pathogenicity on squash seedlings. Acetone (5% v/v) showed best inhibition on the most aggressive isolate 4 followed by the less aggressive ones (1, 2 and 3, respectively); IAA had no effect on the growth of all R. solani isolates compared to the controls.
Number of Colonies Produced by 22 Isolates of Powdery Mildew on Primary Leaves of 10 Barley Cultivars
Authors: KimChoong Hoe , Hermansen J. E.
Published: May 2008

Primary leaves of 10 barley cultivars were uniformly inoculated with 22 virulent powdery mildew isolates using a jet spore trap. The number of colonies per unit area leaf was counted. Significant differences in number of colonies among cultivars were found, indicating different degrees of susceptibility among cultivars. While cultivars were rather consistent in their rankings for number of colonies produced by most isolates, interactions between some cultivars and isolates were found. In spite of great differences in geographical origin of cultivars and isolates, the interactions were not associated with origin.
Differential Responses of Erysiphe polygoni Conidia to Living and Non‐living Substrata
Authors: Singh U. P. , Singh H. B.
Published: May 2008

Conidial germination and appressorium formation of Erysiphe polygoni on living and non‐living substrata have been studied. Among living hosts, peelings from bulbs and leaves of Allium sativum and Allium cepa, or from stems of Azadirachta indica and rhizomes of Curcuma longa supported good germination. Zingiber officinale rhizome peelings inhibited germination. Germination and appressorium formation were maximum on the host (Pisum sativum) as compared to some other leguminous hosts. Little morphological variation was noticed among appressoria developed on various substrata, although they differed in size. Conidial germination was enhanced in leaf extract of pea.
m‐Hydroxyphenylacetic and m‐Methoxyphenylacetic Acids of Rhizoctonia solani: Their Effect on Specific Root‐Nodule Activity and Histopathology in Soybean
Authors: Orellana R. G. , Mandava N. B.
Published: May 2008

m‐Methoxyphenylacetic acid (m‐OMePAA), a derivative of m‐hydroxyphenylacetic acid (m‐OHPAA), having the same chemical composition as that phytotoxic compound produced in culture by Rhizoctonia solani, a fungal pathogen of soybean, reduced growth and symbiotic N2‐fixation activity of ‘Tracy’ soybeans in soil: perlite at 1.5 × 10‐4 M, the lowest concentration used. At twice this concentration m‐OMePAA was strongly teratogenic and caused root hypertrophy and root fasciation. At 1.2 × 10‐3 M, m‐OMePAA nearly suppressed seed germination. m‐OMePAA at the minimum concentration used and equivalent concentrations of the culture filtrate fraction (m‐OHPAA and m‐OMePAA) caused cytopathological and histopathological disturbances in the nodule central tissue, extrusion of the nucleoli, and abnormal nuclci. The data indicate that these phytotoxic compounds of R. solani are involved in nodule impairment and reduced N2‐fixation in soybean.
Ultrastructural Studies of the Interaction Between Trichoderma spp. and Plant Pathogenic Fungi
Authors: Elad Y. , Barak Rina , Chet I. , Henis Y.
Published: May 2008

The uhrastructural changes during parasitism of the biocontrol agents Trichoderma harzianum and T. hamatum, were observed under a transmission electron microscope. Electron micrographs show that during the interaction of Trichoderma spp. with either Sclerotium rolfsii or Rhizoctonia solani the hyphae of the parasites contact their host, and then enzymatically digest their cell walls. Extracellular fibrillar material is deposited between the interacting cells. Parasite organelles, e.g. mitochondria, vesicles and dark osmiophilic inclusions, accumulate in the parasitizing cells. In response to the invasion, the host produces a sheath matrix which encapasulates the penetrating hypha and the host cells become empty of cytoplasm.
Hyperparasitism of Aphanocladium album on Aecidiospores and Teliospores of Puccinia graminis f. sp. tritici
Authors: Koç N. K. , Forrer H. R. , Défago G.
Published: May 2008

Aphanocladium album invaded rapidly 100% of aecidiospores of Puccinia graminis f. sp. tritici resulting in total collapse of the cells. Only 2% of teliospores were invaded. A. album penetrated through the germ pores. The precocious formation of teliospores which occurs immediately following uredial infection may be regarded as defence mechanism of the rust against its hyperparasite.
Phytophthora‐Stammbasisfäule an Dieffenbachia maculate (Erreger: P. mexicana Hots. et Hart.)
Authors: Kröber H. , Kiewnick L. , Richter J.
Published: May 2008

Stem base rot of Dieffenbachia maculata caused by Phytophthora mexicana During the last years a stem rot of Dieffenbachia maculata (Lodd.) G. Don has been observed in greenhouses of several commercial nurseries, located in different parts of the Federal Republic of Germany. The disease partly caused heavy losses. From all diseased plant parts (stem base, petiole and root) the same fungus could be isolated. It was diagnosed as Phytophthora mexicana Hots, et Hart., which is closely related to P. palmivora (Butl.) Butl. Apparently the former species is recorded for the first time as the causal organism of a Dieffenbachia stem rot and also for the first time in Europe. It is supposed that the fungus was imported to Germany via the Netherlands because all plants had been bought there, which diseased later.
Poinsettia Mosaic Virus — a Tymovirus?
Authors: Lesemann D.‐E. , Koenig R. , Huth W. , Brunt A. A. , Phillips S. , Barton R. J.
Published: May 2008

Nicotiana benthamiana was found to be a useful indicator and propagation host for poinsettia mosaic virus (PoiMV). It is not susceptible to poinsettia cryptic virus. The isometric particles of PoiMV sedimented as two components with sedimentation coefficients (s°20,w) of 55 S (“top” component) and 117 S (“bottom” component) and, after fixation, with buoyant densities (g cm‐1) in caesium chloride of 1.29 (“top”) and 1.41 (“bottom”). The A260/A280 ratios were 1.8 and 1.0 for “top” and “bottom” components, respectively. “Top” and “bottom” component particles measured 26 and 29 nm in diameter when mounted in 2 % uranyl acetate; “top” component particles were severely disrupted by 2 % neutral potassium or sodium phosphotungstate or 2 % ammonium molybdate, a phenomenon which is not observed with recognised tymoviruses. The virus particles contained c. 37 % ss‐RNA (mol. wt 2.3° 106) with a base composition of 21 % guanine, 24% adenine, 31 % cytosine and 24% uracil. PoiMV particles were detected in the cytoplasm, vacuoles and nuclei of infected poinsettia and N. benthamiana cells. As in tymovirus infections, the particles within the nuclei were apparently devoid of nucleic acid. The virus induced conspicuous peripheral vesiculation of chloroplasts; the vesicles, however, unlike those induced by recognised tymoviruses, were bound by the inner membrane only of the double chloroplast envelope. PoiMV thus lacks a group‐specific character of the tymovirus group. Serologically it is not related to any of the 17 recognised tymoviruses. It is therefore probably best recognised as a possible member of the tymovirus group.
Transmission, Particle Size and Additional Hosts of the Rhabdovirus Causing Maize Mosaic in Shiraz, Iran1
Authors: Izadpanah K. , Ahmadi A. A. , Parvin S. , Jafari S. A.
Published: May 2008

The rhabdovirus causing maize mosaic in Shiraz, Iran, is transmitted by Ribautodelphax notabilis Logvinenko (Homoptera, Delphacidae). Average size of bullet‐shaped virus particles in negatively stained leaf‐dip preparations of naturally or experimentally infected plants was 81 × 179 nm. The virus is transmitted to wheat and barley causing mosaic and severe stunting. Similar virus particles have been observed in leaf‐dip preparations of naturally infected wheat, barley and Sudangrass. This is believed to be the first record of the involvement of R. notabilis in virus transmission. The relationship of the described isolate with similar viruses infecting gramineous plants is discussed.
A Comparison of Some Serological and Biological Properties of Seven Isolates of Tobacco Ringspot Virus
Authors: Gergerich R. , Asher J. H. , Ramsdell D. C.
Published: May 2008

Seven isolates of tobacco ringspot virus (TRSV) from grape, cherry, two cultivars of blueberry, tobacco, soybean and watermelon were compared in this study. The most virulent isolate was from‘Jersey’blueberry and the least virulent isolate was from soybean. The‘Jersey’blueberry isolate and the watermelon isolate could be distinguished serologically from all other isolates. The‘Jersey’blueberry isolate was different in electrophoretic mobility from the soybean and tobacco isolates. A unique technique for comparing the in vitro translation products of three of the TRSV isolates is described.
Development of a Differential Set for the Race analysis of Puccinia hordei Otth.
Authors: Grunewaldt‐Stöcker Gisela
Published: May 2008

Investigations for the race analysis of P. hordei (location Cologne, W.‐Germany) showed, that most of the resistant genotypes in the International differential set with Pa1 to Pa8 were ineffective for that purpose.

Out of 80 selected barley genotypes with different degree of resistance against the field‐collection RG 1975 hosts with a strongly differentiating effect were chosen. This was done using three parameters: mean resistance x̄w, its standard deviation x̄w and the range z. They were calculated from evaluating the reaction types of 80 barley genotypes infected with 116 single‐pustule lines of barley brown rust. Eight hosts with strongly differentiating reactions towards the 116 rust lines were composed into a differential set, which could characterize the heterogeneity of the Cologne P. hordei‐population essentially better and more precisely than the International differential set.
The Effect of Temperature, Light and Leaf Age on the Frequency of Appressoria Formation and Infection with Uromyces phaseoli (Pers.) Wint.
Authors: von Alten H.
Published: May 2008

The frequency of appressoria formation is reduced by changed conditions of infection such as adult leaves, higher temperature, or continuous light during penetration. In correlation with the reduced number of appressoria, the infection frequency decreases too. The behaviour of growing germ tubes on the plant surfaces did not show any indication of the fungus being led to the stomates by leaf surface structures. Obviously a recognition signal proceeds from the stomates sometimes helping the fungus to get into the leaf. Probably the gas exchange through the stomates is involved. Carbon dioxide, produced by the leaves in the dark, can build up pH‐gradients towards the stomates as the inoculated leaves are covered with a water film.
Contents of Sugars, Fruit Acids, Amino Acids and Phenolic Compounds of Apple Fruits i n Relation to their Susceptibility to Botryosphaeria ribis
Authors: Hwang B. K.
Published: May 2008

Five apple cultivars showing different levels of susceptibility to Botryosphaeria ribis were used to study the relationship between susceptibility and contents of sugars, fruit acids, amino acids and phenolic compounds in the fruits at various stages of maturity. Immature fruits of all the cultivars tested were completely resistant until 10 July. The fungus grew better on the yellow‐coloured cultivars than the red‐coloured cultivars. The low amount of reducing sugars and also the high levels of fruit acids, amino acids and total phenols were found in immature apple fruits, irrespective of cultivar. No consistent differences between the cultivars were recognized with regard to the contents of soluble sugars, fruit acids and phenols in fruit flesh during the maturity of fruits. However, only the levels of total soluble amino acids in fruit flesh and of total phenols in fruit peel at late stage of maturity consistently varied between the cultivars. The dark red‐coloured, resistant cultivars Miller spur and Starkrimson showed higher contents of amino acids and phenols in fruit tissues than did the yellow‐coloured, susceptible cultivars.
Bekämpfung von Rapskrankheiten
Authors: Krüger W.
Published: May 2008

The reduction of root collar and stalk. rot of rape. caused by Phoma lingam (Desm.) Tode ex. Fr. has been achieved by growing more resistant cultivars developed during the past few years. The reaction of these cultivars towards the disease is tabulated.

Scoring of the cultivars was carried out according to a disease index scale 1–9. An analysis of variance. combined with a “reactivation” of each experiment within the range 1 – 9 was performed such that results from several years could be included even when the disease index was low; an unrealistic evening out of the results was thus avoided. This method of analysis has made it possible to more clearly visualize the differences between cultivars than was previously.
Bekämpfung von Rapskrankheiten
Authors: Krüger W. , Stoltenberg J.
Published: May 2008

Control of rape diseases

II. Measures for disease reduction caused by Sclerotinia sclerotiorum with consideration to economical aspects

The most widely distributed diseases of rape in the Federal Republic of Germany are Sclerotinia sclerotiorum (white stalk disease, formerly called rape canker) and Phoma lingam (root collar and stalk rot), and these can cause considerable yield losses.

S. sclerotiorum occurs sporadically and is more prevalent in the marsh land of northwest Germany than in the hilly landscape of Schleswig‐Holstein, where pockets of infection are found. Application of calcium cyanamid, formerly successfully used to control apothecia formation by S. sclerotiorum, has been replaced by fungicides (Vinclozolin) directed at preventing ascospore infection. Many experiments proved to be economically unsuccessful due to the low rate of infection and the high costs involved with such treatments. With an expected yield of 30 dt/ha, an 8 % increase in yield following spraying must be achieved in order to make the fungicide treatment profitable. In fields where only up to 12% of the plants were infected, 75 % of the experiments proved to be uneconomical. By a disease index of 13–25 %, 55 % of the trials were similarly uneconomical. Only where more than 25 % of the plants were infected did the fungicide application prove to have a considerable effect on the yield. A prophylactic treatment is not to be recommended. Only in those areas where severe disease occurs nearly every year should such treatment be practiced that is unless the Advisory Service advises otherwise due to extreme weather conditions (too wet or too dry) which may lead to only very slight infection.
Ultrastructure of the Interaction of Cells of Pseudomonas phaseolicola with Cell Walls of a Resistant and Susceptible Bean Cultivar
Authors: Ebrahim‐Nesbat F. , Slusarenko A. J.
Published: May 2008

Cells of Pseudomonas phaseolicola were observed entrapped against plant cell walls in both susceptible (Red Kidney) and resistant (Red Mexican) cultivars of French bean (Phaseolus vulgaris). After staining of samples with ruthenium red for electron microscopy pectic polysaccharide within plant cell walls became particularly well contrasted as did fibrillar material connecting bacteria to the plant cell walls. In places this fibrillar material appeared to emanate from the pectic polysaccharide in the plant cell wall, and the plant cell wall surface was eroded at such points. Ruthenium red also stains acidic, bacterial extracellular polysaccharide (EPS) and some of the fibrillar material in intercellular spaces is probably from this source. It is possible that bacteria become attached through an interaction between EPS and Pectic polysaccharide in plant cell walls.
Reduction of Yield Depressions in High Frequency Potato Cropping Soil after Seed Tuber Treatments with Antagonistic Fluorescent Pseudomonas spp.
Authors: Geels F. P. , Schippers B.
Published: May 2008

Severe yield depressions observed in high frequency potato cropping caused by microbial factors other than eelworms or known pathogens (narrow rotation effect) were reproduced in pot experiments. Total plant weight in a soil continuously cropped with potatoes was only 69% of that in a similar soil continuously cropped with wheat. Tuber weight in potato‐soil was only 13 % and number of tubers only 10% of that in wheat‐soil. Seed tuber treatment with cell suspensions of fluorescent antagonistic pseudomonads in carboxymethylcellulose (CMC) raised tuber yield in potato‐soil up to 70% (550 % increase), number of tubers up to 93% (934 % increase) and total plant weight up to 90% (31 % increase) as compared with CMC‐treatment in wheat‐soil. Antagonistic fluorescent Pseudomonas isolates WCS 365, WCS 358 and WCS 374 producing mainly siderophores, with little or no production of other inhibitory substances, were more effective in diminishing the narrow rotation effect than the isolates that produced mainly inhibitory substances of different nature.
Some Factors Influencing Immunofluorescence Microscopy as Applied in Diagnostic Phytobacteriology with Regards to Erwinia amylovora
Authors: Miller H. J.
Published: May 2008

The preparation of Erwinia amylovora isolations by different treatments or from different sources is shown to influence the results obtained by immunofluorescent microscopical examination. Where absorption of antisera is impracticable, serial dilutions of the antiserum involved when using constant numbers of the bacterium to be tested, can result in a reduction of cross‐reactions. Emphasis is made on standardization of such procedures in order to increase the chances of more accurate diagnosis.
Natural Infection of Cucumbers by Zucchini Yellow Mosaic Virus in Lebanon
Authors: Lesemann D.‐E. , Makkouk K. M. , Koenig R. , Samman E. Natafji
Published: May 2008

An elongated virus was isolated in the Sin‐El‐Fil Area east of Beirut from cucumber plants showing severe mottling. The particles were 799 nm long after fixation in glutaraldehyde, but were degraded to shorter pieces in unfixed preparations. Infected cells contained cylindrical inclusions with pinwheel and scroll elements accompanied by proliferated endoplasmic reticulum. The virus was purified and an antiserum was prepared. Different serological tests (slide precipitin test, immunoelectronmicroscopical decoration test, immunosorbent electron microscopy) indicated that it was closely related or identical with zucchini yellow mosaic virus (ZYMV) and more distantly related to watermelon mosaic virus 2 and bean yellow mosaic virus. ZYMV isolates from Italy, France and the Lebanon differ in some host reactions.
Linkage Between Virulence Genes, Compatibility Types and Sexual Recombination in the Swedish Population of Bremia lactucae
Authors: Gustafsson M. , Arhammer M. , Gustavsson I.
Published: May 2008

The host pathogen interaction between Lactuca sativa and Bremia lactucae fits a gene‐for‐gene model well. Twelve resistance genes of the host are matched by twelve genes for virulence in the pathogen. The evolution of the parasite involves drastic changes in virulence frequencies, and a great diversity in virulence even on a sub‐poipulation level. Bremia is a heterothallic, obligate parasite, in which presence of two mating types is needed for sexual reproduction. Sexual recombination probably occurs frequently, indicated by simultaneous occurrence of mating types in commercial lettuce crops, zygote formation, and sufficiently high oospore germination. The pattern of variation agrees well with that of a diploid, out‐ crossing organism with frequent sexual recombination. Unexpected high frequencies of some of the unnecessary v‐genes are probably due to genetic linkage with another “necessary” v‐gene.
Toxicity of Some Terpenoids Against Fungi Infesting Fruits and Seeds of Capsicum annuum L. During Storage
Authors: Tripathi N. N. , Asthana A. , Dixit S. N.
Published: May 2008

On mycoflora analysis of dried fruits and seeds of chilli stored for six months, Aspergillus flavus and A. niger were the more frequent out of eighteen fungi isolated. Some terpenoids viz, Citral, Citronellal, Citronellol, Eugenol, Farnesol and Nerol showed absolute toxicity against A. flavus and A. niger at 0.5 per cent concentration. The minimum inhibitory concentration (MIC) and nature (fungistatic/fungicidal) of all the terpenoids against both these fungi were determined, Citral, Eugenol and Nerol exhibited a broad range of toxicity and were found to be more efficacious than some synthetic fungicides.
Relationship of Endopolygalacturonase Inhibitor Activity to the Rate of Fungal Rot Development in Apple Fruits
Authors: Brown Averil E.
Published: May 2008

An inhibitor extracted form the cell walls of apple fruits suppressed the activity of endopopygalacruronases (endo‐PGs) produced in vivo and in vitro by Nectria galligena, Phomopsis mali, Fusarium Lateritium and Glomerella cingulata but not the endo‐PGs produced by Penicillium expansum or Phytophtobora syringae. Of four apple cultivars tested Granny Smith tissue contained the highest levels of inhibitor and Cox's Orange Pippin contained the least.

Linear rot expansion in the four apple cultivars inoculated with N. galligena was inversely related to inhibitor activity in the fruit tissue, rot development being slowest in Granny Smith fruits and most rapid in Cox's Orange Pippin fruits. Rot expansion in fruits inoculated with P. expansum bore no such relationship to inhibitor activity in the tissue Apple tissue maceration by the endo‐PGs from N. galligena, P. mali. F. lateritium and G. cingulata was similarly related to inhibitory activity in the fruit. The properties of the partially purified inhibitor were consistent with it being proteinaceous but the relative slowness with which it was hear inactivated and the presence of a small percentage of carbohydrate might indicate that it was a glycoprotein.
The Influence of Cultural Factors on the Direct Antifungal Activities of Fosetyl‐Al, Propamocarb, Metalaxyl, SN 75196 and Dowco 444
Authors: Guest D. I.
Published: May 2008

The effects of the systemically active disease control compounds Fosetyl‐Al, Metalaxyl, Propamocarb, SN 75196 and Dowco 444 on the growth, in vitro of two Oomycetes have been studied. Fosetyl‐Al, Propamocarb and SN 75196 are only weakly antifungal, and their activities, in vitro are sensitive to nutrition, pH and temperature. Factors which increase the growth of the fungus decrease its sensitivity to these compounds. These compounds display no selectivity for Oomycetes in vitro which belies their reported selectivity in vivo.

Metalaxyl and Dowco 444 are selective for, and very active against Oomycetes in vitro and this activity could account for their modes of action in vivo.
Strains of Zucchini Yellow Mosaic Virus in Muskmelon (Cucumis melo L.)
Authors: Leoq H. , Pitrat M.
Published: May 2008

According to the reaction of muskmelon line PI 414723, 22 natural isolates of Zucchini Yellow Mosaic Virus (ZYMV) were grouped into two pathotypes. When inoculated by isolates belonging to pathotype 0, most of the PI 414723 plants (over 70%) remained symptomless while few plants developed systemic chloronecrotic spotting and more rarely yellowing, stunting, mosaic and leaf deformations. When contaminated by pathotype 1 all PI 414723 plants developed systemic chloronecrotic spotting.

Two variants were obtained from representative strains of these two pathotypes, able to induce yellowing, stunting, mosaic and leaf deformation on all inoculated PI 414723 plants. These variants could not be differentiated from their originating strains either by host range, serology or aphid transmission properties. Therefore they are regarded as belonging to a third group called pathotype 2. No relation was observed between the type of symptom developed on PI 414723 and the ability to induce a rapid wilting reaction of melon cv. Doublon (pathotype F).
Effect of Fungal Infection and Temperature on Physiological Changes in Banana Fruit
Authors: Schiffmann‐Nadel Mina , Michaeli H.
Published: May 2008

An attempt was made to investigate which factor temperature or fungal infection, has a greater effect in accelerating physiological processes such as respiration and ethylene evolution in fruit.

For this study the effect of infection with Trichothecium roseum, Alternaria alternata and Diplodia natalensis on banana fruit, at 14°C and 20°C was examined.

The results show that the development of rot caused by different fungi and the physiological changes in the infected fruit may depend not only on the effect of temperature on fungi (as in vitro) but also on fruit ripening, or on processes connected with fruit ripening, which may accelerate fungal development.
Comparative Study on Coat Proteins of an Attenuated, a Temperature Sensitive and Their Parent Strains of Tobacco Mosaic Virus
Authors: Nishiguchi M. , Nozu Y. , Oshima N.
Published: May 2008

An attenuated strain (L11A) of tobacco mosaic virus (TMV) induces no remarkable symptoms on tomato plants (Goto and Nemoto 1971) and has been used to protect tomato against virulent strains of TMV (Oshima 1981), A temperature sensitive strain (Ls1) of TMV was isolated and found to have a malfunction of virus movement from cell to cell (NISHI‐GUCHI et al. 1978, 1980). Those two strains are derived from a wild virulent strain (L). Coat proteins of them were compared with one another and with that of Dahlemense (D) strain of TMV, in order to see whether coat protein was associated with their respective characters.

The coat proteins of the four strains behaved similar in both SDS‐polyacrylamide gel and 8 M urea polyacrylamide gel electrophoresis, suggesting that they are similar in molecular weight and charging effect in the gels. There was no significant difference in chromatographic pattern of tryptic peptides among the four strains. Amino acid compositions of tryptic peptides revealed that three strains, L11A, Ls1 and L, were identical to one another and that they differed from D slightly. These results suggest that coat protein is related neither to virus attenuation of L11A nor to the malfunction of Ls1.
Comparative Studies on Callose Formation in Powdery Mildew Compatible and Incompatible Barley
Authors: Skou J. P. , Jørgensen J. Helms , Lilholt Ulla
Published: May 2008

Callose formation in barley mutants, lines and varieties with different genes for resistance to powdery mildew in seven different loci was compared. Only barley with resistance genes in the ml‐o locus showed so carly a callose formation passing off at such a high rate that it prevented fungal penetration. Ml‐(La) resistant varieties and near‐isogenic lines in‘Manchuria’with resistance genes in five other loci showed only a tendency to a larger callose formation than their susceptible counterparts after inoculation with avirulent as well as virulent powdery mildew.

The callose formation in ml‐o resistant barley was independent of the powdery mildew culture applied. This supports the hypothesis set forth as to why the ml‐o mutants are resistant against all known cultures or races of barley powdery mildew, and why this resistance may be more durable than other powdery mildew resistances. Further, this is the first case where the effect of callose refers to the action of a specific gene.

Six susceptible Japanese varieties formed very large appositions but they were initiated as late as in other susceptible varieties, and their colour was plaer than in other barleys.

Nine Hordeum species fell in one group with small appositions and another with appositions of the most common size in barley. Wheat reacts strongly with deep coloured appositions, rye with haloes with a somewhat diffuse margin, and oats large, central spots (papillae) nearly without any halo.
Control of Gaeumannomyces graminis Var. tritici in Wheat by Isolates of the G. graminis var. graminis/Phialophora sp. (Lobed Hyphopodia) Complex under Field Conditions
Authors: Speakman J.B.
Published: May 2008

In an experiment carried out under field conditions, wheat inoculated with Gaeumanmyces graminis var. tritics had less take‐all and yielded significantly more grain when simultaneously inoculated with G. graminis var. graminis and a lobed hyphopodiate phialophora sp. then when unprotected with these fungi.
Deposition Gradients Near to a Point Source in a Barley Crop
Authors: McCartney H. A. , Bainbridge A.
Published: May 2008

By measuring deposits of droplets downwind from a source in a barley crop during crop growth, gradients of deposition were established. Droplets were generated using a May spinning disc, which approximated to a point source. Droplets were labelled with thiabendazole so that deposit could be measured photometrically. Droplet diameter was approximately 20 micrometres, a size similar to spores of barley powdery mildew, an important foliar pathogen.

Gradients of deposition were influenced by the density of the crop, by wind speed and by air turbulence. At any one time these three factors could interact to change the gradient substantially.

Exponential and power law equations fitted the data equally well although due to experimental variation neither gave a very good fit. It is suggested that over the first few metres of dispersal from the source an exponential equation can be used to model the gradient. This has the advantage that it can be extrapolated to give an estimate of “self‐infection” i.e. the spores deposited on the plant on which they were produced.
Detection and Location of Seed‐Borne Inoculum of Didymella bryoniae and its Transmission in Seedlings of Cucumber and Pumpkin
Authors: Lee Du‐Hyung , Mathur S. B. , Neergaard Paul
Published: May 2008

Of the 91 tested cucurbit seed samples from thirteen countries nine from four countries were found to be infected with Didymella bryoniae. The pathogen is located on and in the seed coat including the perisperm and in the tissue of the cotyledons. Primary seedling infection occurred on the radicle, hypoctyl and cotyledons. Infection of the radicle generally caused pre‐emergence tot while infection on the hypocotyl and cotyledons developed furthere inoculum for infection of the first true leaves and the stem. Experimentally, all the isolates of D. bryoniae could infect cucumber (Cucumis sativus), oriental melon (Cucumis melo var. makuwa), pumpkin (Cucurbita pepo) and watermelon (Citrullus vulgaris) at different growth stages; the susceptibility of cucumber and pumpkin was markedly influenced by previailing humid conditions.The blotter method was found more suitable for detection of seed‐borne infection than the agar plate method.
Localization of α‐Mannan in the Hyphal Wall of Phytophthora megasperma f. sp. glycinea and it's Possible Relevance to the Host‐Pathogen Interaction of the Fungus With Soybeans (Glycine max)
Authors: Hermanns R. , Ziegler E.
Published: May 2008

At the apices of growing hyphae of Phytophthora megasperma f. sp. glycinea (Pmg) distinctly more fluorescein‐isothiocyanate labelled Concanavalin A was bound than else‐where in the mycelium. In combination with some other analytical evidence this observation conclusively indicates that the α‐mannan in the cell wall of the fungus is predominantly concentrated or exposed at the hyphal tips. The possible relevance of this fact to the host‐pathogene interaction between Pmg and soybean is discussed.
Fungistatic Activity of Essential Oils from Ocimum basilicum Chemotypes
Authors: Reuveni, A. Fleischer R. , Putievsky E.
Published: May 2008

Essential Oils from Ocimum basilicum and their components showed different inhibition effects against Fusarium oxysporum f. sp. vasinfectum and Rhizopus nigricans, The different antifungal activity of the essential oils is determined mainly by the percentage of the main components: cineol, linalool, methylchavicol and eugenol.
Occurrence of Tobacco Mosaic virus in Water Of the Danube and Sava Rivers
Authors: Tošić Mališa , Tošić Daniela
Published: May 2008

The result obtained showed that TMV isolates all of the type strain of the virus occurred in and could be isolated from water samples of the rivers Danube Sava collected in 1982 in Yugoslavia
Some Properties of an Extracellular Proteolytic Enzyme of Verticillium fungicola, a Pathogen of the Cultivated Mushroom Agaricus bisporus
Authors: Kalberer Peter P.
Published: May 2008

In a casein nutrient solution, Verticillium fungiocla, the causal agent of the dry bubble disease of the cultivated mushroom Agaricus bisporus, produces a proteolytic enzyme. The effects of the pH and of inhibitors on the protease activity and the heat stability of the enzyme are described. The protease is of interest in connection with the attacking mechanism of Verticillium fungicola.
Serological Comparison of Two Races of Fusarium oxysporum f. sp. lupini
Authors: Rataj‐Guranowska Maria , Wiatroszak I. , Hornok L.
Published: May 2008

Water‐soluble mycelial antigens from two physiological races (2 and 3) of Fusarium oxysporum L. sp. lupini were compared by tandem‐crossed immunoelectrophoresis. When antiserum against race 3 was tested some 50 antigens were detected. The two races had apparently almost identical antigenic patterns differing only in one antigen specific to race 3. This specific antigen might be related to the virulence of this fungus.
A Contribution to the General Theory of Host‐Parasite Specificity
Authors: Lebeda A.
Published: May 2008

A proposal is made of improved terminology concerning interactions between plants and non‐cellular or cellular organisms. Classification of the relationships is based on the existence of basic incompatibility (incongruity) and basic compatibility (congruity) characterized by non‐host‐non‐pathogen or host‐pathogen relationships. Basic compatibility is divided into 3 subsystems according to the expression of interaction specificity: 1. non‐specific, 2. specific differentiated and 3. specific non‐differentiated incompatibility or compatibility. Description is made of the expected mechanisms determining specificity and main criteria which can be used for their distinction. Some evolutionary aspects are also discussed.
Multiplicity of Cell Wall Degrading Glycosidic Hydrolases Produced by Apple Infecting Botrytis cinerea
Authors: Urbanek H. , Zalewska‐Sobczak Jadwiga
Published: May 2008

It was shown that Botrytis cinerea, an isolate infecting apples, secreted in vivo and in culture a variety of glycosidic hydrolases with substrate specificity towards the polysaccharides of cell walls. The following enzymes were partially separated by column chromatography on DEAE‐Sepharose CL‐6B: two cellulases, three xylanases, one arabinanase, polygalacturonase, β‐glucosidase, β‐xylosidase, β‐galactosidase, β‐mannosidase and α‐galactosidase. The activity of glycosidic hydrolases tested was strongly inactivated by NBS and weaker by PCMB, tetranitromethan, dibromoacetophenon and Fe3+, The results indicate synergistic action of the obtained cellulase, xylanase, polygalacturonase and arabinanase in apple cell wall degradation.
Differential Responses of Host and Non‐host Substrata on Germination of Ascospores of Sclerotinia sclerotiorum
Authors: Singh U. P. , Singh R. B.
Published: May 2008

Effect of host.(Cicer arietinum L.) and some non‐host (Allium cepa L., A. Sativum L., Ocimum sanictum L., Azadirachta indica Juss., Zingiber officinale Roscoe. And Curcuma longa L.) substrata on the germination of ascospores io Sclerotinia sclerotiorum (Lib.) de Bary has been observed. Maximum germination was noticed on flower petals of gram (C.arietinum) with minimum time (2.5 h) for germ tube initiation. Among the non‐host substrate germination was completely inhibited on ginger rhizome peeling whereas delayed germination (after 12h) and lowest germination percentage (48%) as compared with other non‐hosts, were observed on turmeric rhizome peeling. It is suggested that ginger extract may be effective in controlling stem rot and wilt of gram incited by S. sclerotiorum in the field.
Inhibition of the Hypersensitive Reaction in Tobacco Leaves by Extracellular Polysaccharides from Phytopathogenic Pseudomonads*)
Authors: Mazzucchi U. , El‐Banoby F. E. , Rudolph K.
Published: May 2008

Lipopolysaccharides (pr‐LPS) and extracellular polysaccharides (EPS) were prepated from in vitro‐cultures of phytopathogenic pseudomonads (Pseudomonas phaseolicola race 1 and race 2, P. aptata, P. tabaci) and purified. The preparations were dissolved in water (0.25–2.5 mg/ml) in infiltrated with P. aptata or P. pisi (9 × 107 cells/ml). Whereas the hypersensitive rzaction against P. aptata and P. pisi was inhibited by C.25 mg/ml of pr‐LPS in most of tae cases, the same concentration of EPS caused only partial or no inhibition. However, at 2.5 mg/ml most of the EPS‐preparations caused a complete inhibition. The LPS and EPS‐preparations of P. phaseolicola race 1 caused less inhibition than those of race 2.
Production and Pathogenicity to Wheat of Pseudocercosporella herpotrichoides Conidia
Authors: Higgins S. , Fitt B. D. L.
Published: May 2008

Weekly estimates of numbers of Pseudocercosporella herpotrichoides conidia on naturally infected wheat straw, made from February to July 1982, showed there were most conidia (8.1 × 106 per straw) in February and least (1.9 × 104 per straw) at the end of June. The viability of these spores remained high throughout this period, with an average of 85 % germination after 24 h.

After removal of spores produced in the field, straws were incubated at 5, 10, 15, 20 or 25°C and subsequent sporulation assessed after 3 or 5 weeks. The optimum temperature for spore production was 5°C and very few spores were produced at 25°C. There was no difference in viability between spores produced at different temperatures.

Wheat seedlings placed amongst infected straw collected and retained spores on the upper and lower surfaces of all leaf blades and on outer leaf sheaths. Both naturally dispersed spores and spores sprayed on to plants were not removed by subsequent rainfall.

When wheat seedlings were inoculated between the coleoptile and outer leaf sheath with different numbers of P. herpotrichoides spores, lesion development was most rapid in seedlings inoculated with the greatest numbers of spores. However, after incubation for 12 weeks visible lesions were present on all plants inoculated with > c. 10 spores.
Beet Necrotic Yellow Vein Virus: Purification, preparation of Antisera and Detection by Means of ELISA, and Electro‐Blot Immunoassay
Authors: Koenig R. , Lesemann D.‐E. , Burgermetster W.
Published: May 2008

The best results in attempts to purify beet necrotic yellow vein virus were obtained with a slightly modified Triton × 100 method originally described by Hullet al. (1976) for cauliflower mosaic virus. Immunosorbent electronmicroscopy (ISEM), the double antibody sandwich form of enzyme‐linked immunosorbent assay (ELISA) and electro‐blot immunoassay (EBIA) yielded similar result when sugar beets were tested for the presence of virus. ISEM and EBIA ofer the advantage that in addition to serology a second parameter, i.e. either particle morphology or coat protein molecular weight, is used to identify the virus. Specific and possibly nonspecific reactions are thus more readily distinguished and antisera can be used which may still contain some antibodies to normal plant constituents. However, with these methods only a limited number of samples can be studied at a time, therefore ELISA is presently the method of choice for large scale routine testing.

Beet necrotic yellow vein virus: Reindarstellung, Herstellung von Antiseren Und Nachweis Mit Hilfe von ELISA, Immunosorbent electronmicroscoy und Electro‐Blot Immunoassay

Bei Versuchen Zur Reindarstellung des beet necrotic yellow vein virus wurden die besten Ergebnisse mit einer leicht modifiziertem Triton × 100 Methode erzielt, die ursprüng für das cauliflower mosaic virus von Hullet al. (1976) entwickelt worden war. Immunosorbent electronmicroscopy (ISEM), double antibody‐sandwid, ELISA und electro‐blot immunoassay (EBIA) ergaben ähnliche Resultate bei der Unteuchung von Zuckerrübenwurzelproben. ISEM und EBIA haben den Vorteil, daß neber der scrolognchen Reaktivität noch ein zweites Merkmal zum Nachweis des Virus eingeserz wird, bei ISEM die Partikelmorphologie und bei EBIA das Molekulargewicht des Hüllprodtim badurda kännen spezifische und eventuell unspezifische Reaktionen besser unterschreden werden und es können Antiseten verwendet werden, die noch Antikörper gegen normale Pflauzenbestandteile enthalten. Da mit diesen Methoden jedoch nur eine begrenzte Anzabl von Probcagleichzeitig untersucht werden kann, ist für Massenuntersuchungen ELISA die Methode der Wahl.
Studies on Mechanisms of Splash Dispersal of Spores, using Pseudocercosporella herpotrichoides Spores
Authors: Fitt B. D. L. , Lysandrou M.
Published: May 2008

Simulated raindrops, 4 or 5 mm in diameter, fell 13 m onto target water films, with Pseudocercosporella herpotrichoides spores incorporated into either drops or targets. Resulting splash droplets were collected on fixed photographic film and numbers of droplets, spore‐carrying droplets and spores determined.

The patterns of dispersal of splash droplets, spore‐carrying droplets and spores with distance and droplet size were similar for 4 mm and 5 mm incident drops with spores incorporated into either targets or drops. Numbers of droplets, spore‐carrying droplets and spores decreased with increasing distance from targets and none were collected at 1 m. However, more spores were dispersed by 5 mm than by 4 mm drops and with spores in targets than with spores in incident drops. Whereas most splash droplets were in the smallest size category (0–100 μm), most spore‐carrying droplets were 200–400 μm and most spores were in droplets with diameter greater than 1000 μm. Regressions of square root (number of spores) on droplet diameter were significant (p < 0.001) in all cases. The slopes of regression lines were greater when spores were in targets than when they were in incident drops. Splash droplets were collected up to a height of 70 cm, with most between 15 and 20 cm. The dye experiment showed that most splash droplets contained liquid from both incident drop and target film.
Corynebacterium fascians: Phytopathogenicity and Numerical Analysis of Phenotypic Features
Authors: Elia S. , Gosselé F. , Vantomme R. , Swings J. , Ley J. De
Published: May 2008

Forty‐four Corynebacterium fascians strains from different geographical origins and host plants were characterized by their phytopathological capacity towards different host plants together with 206 morphological, biochemical and physiological features.

The numerical analysis of the phenotypic features utilizing the SSM similarity coefficient and the average unweighted pair‐group clustering method revealed that all Corynebacterium fascians strains form a rather homogeneous cluster: over 80%, SSM exists between the 44Corynebacterium fascians strains from phenon II. From the present results the reclassification of C. fascians as Rhodococcus rhodochrous is not obvious.