bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of Involvement of Nutrients in the Latency of Colletotrichum gloeosporioides in Unripe Avocado Fruits
Authors: Prusky D. , Ascarelli A. , Jacoby B.
Published: May 2008

Hypobaric pressures prevented the ripening of avocado fruit discs and the development of Colletotrichum gloeosporioides infection on them. The same condition did not prevent the growth of C. gloeosporioides on potato dextrose agar. Using this system it was shown that the resistance of unripe avocado fruit discs does not originate in the lack of subsrate for fungal growth.
Infection and Stroma Formation byVenturia inaequalison Apple Leaves with Different Degrees of Susceptibility to Scab
Authors: Gessler C. , Stumm D.
Published: May 2008

Conidia ofVenturia inaequalisgerminated and formed appressoria on all leaves independently of age and origin within the first 15 hours after inoculation. On the youngest expanded leaves of the apple variety Golden Delicious 80% of the conidia developed stromata within the first 24 hours, sporulation occurred after 8 days. On the second leaf (counted from the top of the twig) stroma formation was slowed down compared to the first and sporulation occurred after 10 days only. On the third leaf the fungus rarely formed stromata and never sporulated. The fourth leaf already showed complete ontogenetic resistance. In the diploid variety Priscilla the gene Vf, which confers resistance against scab to apple leaves, was expressed as reduced stroma formation without sporulation, as in the case of ontogenetic resistance. In the triploid variety Sir Prize with the gene Vf, stroma formation was retarded and colonization and sporulation occurred later on the first leaf, similarly to the reaction of the second leaf of variety Golden Delicious.
High Levels of Resistance in Agropyron Species to Barley Yellow Dwarf and Wheat Streak Mosaic Viruses
Authors: Sharma H. C. , Gill B. S. , Uyemoto J. K.
Published: May 2008

Several Agropyron species were tested for new sources of resistance to barley yellow dwarf virus (Bydv) and wheat streak mosaic virus (WSMV). With BYDV strain PAV, 11 of the 17 Agropyron species showed no virus transmission when plants were given access feed by viruliferous Rhopalosiphum padi. Similar trials with BYDV strain RMV (vectored by R. maidis) indicated that all plants, except susceptible control plants, remained virus free. Virus status was confirmed by enzyme‐linked immunosorbent assays. When plants were mechanically inoculated with WSMV, 11 Agropyron species failed to express symptoms, while five other species showed a segregating response or had some accessions segregating and some resistant. Test results suggest that resistance to BYDV and WSMV in Agropyron species does not appear to be correlated with any specific genome of Agropyron species although most of the Agropyron species containing S genome were resistant to BYDV and WSMV.
Corn Stunt Spiroplasma in Dicotyledonous Plants
Authors: Alivizatos A. S.
Published: May 2008

Corn stunt spiroplasma (CSS) was transmitted by the leafhopper vector Euscelidius variegatus (Kirschbaum) and produced symptoms on four dicotyledonous plant species, Sinapis alba L. (mustard), Pisum sativitm L. (pea), Raphanus sativus L. (radish) and Spinacia oleracea L. (spinach). The vectors became infective by microinjection with a broth culture of CSS. This insect also acquired CSS from infected mustard plants and transmitted it to healthy ones.
Detection of Prune Dwarf Virus by ELISA in Meristem‐Propagated Sour Cherry Plants During in vitro Culture
Authors: Baumann Gisela , Casper R. , Kornkamhaeng Pajchima
Published: May 2008

Tissue‐cultured plantlets which were derived from meristems of a sour cherry plant infected by prune dwarf virus were examined by enzym‐linked immunosorbent assay (ELISA). The virus could be detected with sufficient reliability in 17‐week‐old rooted plant‐lets still growing in vitro.
Electro‐Blot Immunoassay—A Means for Studying Serological Relationships among Plant Viruses?
Authors: Burgermeister W. , Koenig R.
Published: May 2008

The coat proteins of tymo‐, tombus‐, como‐, nepo‐, tobamo‐, potex‐, carla‐ and potyviruses were subjected to sodium dodecylsulphate (SDS)‐polyacrylamide gel electrophoresis, electro‐blotted onto nitrocellular membranes and reacted with homologous and heterologous antìsera to intact plant viruses. Immune complexes were detected after reaction with alkaline phosphatase‐labelled goat anti‐rabbit antibodies. SDS coat proteins of comoviruses reacted only with antisera which were homologous for their intact particles. In all other groups, however, a rather broad range of serological relationships was detected. With a number of viruses, serological relations to other members of the same group were demonstrated for the first time. SDS coat proteins of maclura mosaic virus, a possible potyvirus, and of beet necrotic yellow vein virus, a possible tobamovirus, did not react with antisera to definitive members of the respective groups. Several unexpected reactivities of SDS coat proteins of viruses from one group with antisera to viruses in other groups were, however, also observed. This indicated that electro‐blot immunoassay, like other serological methods, cannot be used reliably to assign a virus to a certain group. The SDS coat proteins of several tombusviruses were able to mimic serological reactions by a direct binding of enzymelabelled antibodies which occurred also without serum treatment.
Search for Viroids and Other Small RNAs Associated with Forest Damage
Authors: Schumacher J. , Loss P. , Riesner D.
Published: May 2008

We examined whether viroids may be involved as the causative agents of forest damages which have been observed in Germany during the last decade. A crude RNA extract was prepared from healthy and diseased copper beech, spruce, and pine trees and was analysed by two‐dimensional gel electrophoresis which resolves RNA bands in the molecular weight range from 25,000 to 106. Viroids are known to consist of single stranded circular RNA and are clearly differentiable in the electrophoresis used here from cellular RNA. Viroids could not be found in any of the samples investigated. In all samples from diseased trees, however, other additional RNA bands were discovered which were more similar to cellular RNA than to viroids in their electrophoretic properties. It is uncertain whether these diseased‐associated RNAs are due to an infection or originate from a modified nucleic acid metabolism.
Barley Yellow Mosaic Virus: Purification, Electron Microscopy, Serology, and other Properties of two Types of the Virus
Authors: Huth W. , Lesemann D.‐E. , Paul H.‐L.
Published: May 2008

From naturally infected barley plants two types of barley yellow mosaic viruses have been isolated in Federal Republic of Germany. Both are identical in morphology, showing a bimodal length distribution (270–289 nm and 568–600 nm), and in symptomatology. Both induce conspicuous cytoplasmic inclusions of the pinwheel type and laminated aggregates, as well as threedimensional crystal‐like arrays of membrane material. The types differ, however, in buoyant density, serology, and transmissibility. One is transmissible by soil as well as mechanically (BaYMV‐M), and does not react with a Japanese antiserum to the Japanese virus (BaYMV‐J). The other type (BaYMV‐NM) is only transmissible by soil and reacts with BaYMV‐J‐antiserum. From mechanically infected plants BaYMV‐M was purified, and an antiserum was produced, from soil‐infected plants only mixtured BaYMV‐NM and ‐M could be obtained. BaYMV‐NM prevailed during winter, but with rising temperatures in spring BaYMV‐M was predominant.

BaYMV‐M and the ‐M‐NM mixture had each two species of nucleic acids (2.7–2.8 × 106 and 1.4–1.5 × 106 d) and two major protein subunit bands were found in SDS‐PAGE (35–36 × 103 and c. 29 × 103 d).
Activité Fongicide du N‐cetyl N,N,N‐triméthylammonium Contre Botrytis cinerea Pers.
Authors: Pezet R. , Pont V.
Published: May 2008

Fungicidal activity of N‐cetyl N,N,N‐trimethyl ammonium chloride to Botrytis cinerea Pers.

Grey mould of grapes caused by Botrytis cinerea is the most important phytopatho‐logical problem in swiss vineyards, since the appearance of resistant strains to dicarboxi‐mides. Research for new chemicals is necessary. One compound, a cationic surfactant, the N‐cetyl N,N,N‐trimethyl ammonium chloride (CTAC), is very active in vitro against Botrytis cinerea. This product disturbs lethally the plasma membrane of conidia.
Further Electron Microscopical Studies of Induced Resistance of Barley against Erysiphe graminis f. sp. hordei
Authors: Ebrahim‐Nesbat F. , Schönbeck F.
Published: May 2008

Barley leaves were treated with a resistance inducer and inoculated with Erysiphe graminis two days later. 68 hours after inoculation many infection sites with cytoplasmic aggregations with increased number of golgi apparatus and increased endoplasmic reticulum could be observed. The extrahaustorial membrane invaginated and some free pieces of membrane appeared in the matrix. The haustoria vacuolized partially and curly filamentous electron dense material occurred. These changes took place after protective as well as after curative treatment. Due to cytochemical studies the vacuolar electron dense material in the vacuoles of the haustoria contained polymers of mannose or glucose.
Peroxidase and Polyphenol Oxidase Associated with, Induced Resistance of Mung Bean to Rhizoctonia solani Kuhn
Authors: Arora Y. K. , Bajaj K. L.
Published: May 2008

Peroxidase and polyphenol oxidase activities and peroxidase isozyme patterns were determined at different stages of hypocotyls of mung bean infected with Rhizoctonia solani. The effect of ethephon (2‐chloroethyl phosphonic acid) has been studied. Peroxidase activity increased at 24 h after inoculation as compared with controls followed by a decline later. It increased at 120 h. Polyphenol oxidase activities increased after inoculation. Ethephon treatment increased the resistance to Rhizoctonia solani and enhanced peroxidase and polyphenol oxidase activities. Peroxidase isozyme pattern was found to change as a result of inoculation and ethephon treatment. The results indicated that ethephon‐induced resistance was related to peroxidase and polyphenol oxidase activities.
Effets de Traitements Fongicides aux Imides Cycliques sur les Populations de Sclerotinia minor dans le Sol
Authors: Davlt P. , Martin C.
Published: May 2008

About the effects of cyclic imides fungicidal treatments on soil populations of Sclerotinia minor

When S minor selerotia were incubated in natural soils, they were gradually attacked by a varied antagonistic flora. This phenomenon was seriously slackened when cyclic imides (iprodione of vinclozolin) at 25 or 50 mg.l‐1 were incorporated into the soil, in laboratory trials or in normal conditions of cultivation. These fungicides (which are currently used to control S. minor) seemed to protect selerotia by preventing the development of antagonistic fungi. Selerotial germination was inhibited by vinclozolin but, if the duration of contact was less than 5 weeks, the phenomenon was fully reversible, even in the presence of very high concentrations (500 mg.l‐1).

When an inoculum of Trichoderma sp. was added to natural soils, selerotia were rapidly damaged. An even faster decrease of S. minor populations resulted from the incorporation of cyclic imides into these Trichoderma‐enriched soils. These organisms are not very susceptible to such fungicides. It is suggested that a joint utilization of these biological auxiliaries and of cyclic imides should be a way to avoid the appearance of a biological unbalance due to an exclusive use of fungicides.
Production of Pectic Enzymes by Fusarium oxysporum f. sp. cepae and its Involvement in Onion Bulb Rot
Authors: Holz G. , Knox‐Davies P. S.
Published: May 2008

Fusarium oxysporum f. sp. cepae produced an exo‐polygalacturonase (exo‐PG) and endopectin‐trans‐eliminase (endo‐PTE) in a mineral medium supplemented with a restricted supply of either D‐galacturonic acid or onion cell walls. These enzymes were also extracted from infected onion tissue, but only endo‐PTE caused tissue maceration and cell death.

The patterns of host tissue colonization and pectic enzyme production were followed during bulb rot development. Stem plates were invaded within two weeks of inoculation. The pathogen then remained confined to the stem plates for several weeks or months, before spreading to the outer fleshy scales to initiate a basal rot. In most cases the inner leaf sheaths containing the lateral bud remained healthy. Exo‐PG activity m stem plate tissue was greatest at two weeks after inoculation, then it declined. Endo‐PTE was not detected in newly invaded stem plate tissue, but was recovered from infected stem plates before decay and from the bases of bulb scales and leaf sheaths at the onset of bulb rot. There was no pectic enzyme activity in uninvaded onion tissue.

Spread of the fungus and pectic enzyme production in two Caledon Globe genotypes susceptible or tolerant to F. oxysporum f. sp. cepae were similar, but the onset of bulb rot in tolerant genotypes was considerably delayed.
Pectic Enzyme Production by Fusarium oxysporum f. sp, ccpac: Induction by Cell Walls from Different Parts of Onion Bulbs at Different Growth Stages
Authors: Holz G. , Knox‐Davies P. S.
Published: May 2008

Fusarium oxysporum f. sp. cepae produced significantly different amounts of pectic enzymes when grown on cell walls from morphologically different parts of onion bulbs. Cell walls from stem plate tissue of both tolerant and susceptible onion genotypes allowed a rapid and high production of both exo‐polygalacturonase and endo‐pectin‐frans‐eliminase. Bulb scale cell walls from susceptible genotypes induced synthesis of these enzymes at much lower rates and levels, whereas bulb scale cell walls from tolerant genotypes gave poor induction of pectic enzyme synthesis. Leaf sheath cell walls from both susceptible and tolerant genotypes were poor inducers of enzyme synthesis. Enzyme induction by cell walls from leaf sheaths and bulb scales of tolerant genotypes increased dramatically during ageing. Differences in pectic enzyme accumulation on cell walls were not related to fungal growth. These patterns of enzyme induction could help to explain susceptibility or tolerance of bulb scale and leaf sheath tissue of the different genotypes.
The Relationship Between Peroxidase Activity and the Resistance of Tomatoes (Lycopersicum esculentum) to Verticillium dahliae
Authors: Reuveni R. , Ferreira J. F.
Published: May 2008

The levels of peroxidase activity in roots of non‐infected tomato plants resistant to Verticillium dahliae Kleb., were found to be considerably higher than those in the roots of susceptible plants. Similar differences were found in the leaves but were not significant as in the roots. Peroxidase activity increased in leaves, stems and roots of both susceptible and resistant plants after infection with V. dahliae. The ratio of the increase in leaves and roots of susceptible plants was greater than those of resistant plants. A positive correlation was found between the peroxidase activity in the roots of eleven cultivars/breeding lines and presence of Ve gene.
Ultrastructural Studies on the Microconidia of Botrytis cinerea Pers. and their Phialoconidial Development
Authors: Urbasch I.
Published: May 2008

The genesis and ultrastructure of microconidia of Botrytis cinerea Pers. were studied, using TEM and SEM.

Microconidia are produced in flask‐shaped, terminal or lateral phialides. The first microconidium develops holoblastically, subsequent microconidia are formed enteroblastically, in basipetal succession from a fixed conidiogenous locus.

Mature microconidia are characterized by a two‐layered spore wall covered by mucilage, a single, sickle‐shaped nucleus, one or two large lipid bodies, a few mitochondria of the cristae‐type, ribosomes, sparse endoplasmatic reticulum close to the plasmalemma and a small amount of cytoplasma. The basal septum which is surrounded by a collar‐like rim is perforated by a simple central pore with a pore plug.

Differences in genesis and ultrastructure of microconidia compared with macroconidia are discussed in relation to the function of these two spore types.
Untersuchungen zur Anfälligkeit und Resistenz von Kopfsalat (Lactuca sativa) gegen falschen Mehltau (Bremia lactucae): II. Licht‐ und elektronenmikroskopische Untersuchungen zur Morphologie des Wirt‐Parasit‐Verhältnisses
Authors: Zinkernagel V.
Published: May 2008

Investigations on the susceptibility and resistance of head lettuce (Lactuca sativa) to downy mildew (Bremia lactucae)

II. Light and electron microscopic examinations of the host‐parasite interface

Infected leaves of lettuce varieties susceptible and incompletely resistant to Bremia lactucae were observed by light and electron microscopy. Primary infection structures in the epidermal cells as well as intercellular hyphae with the adjacent haustoria could be seen by differential interference contrast microscopy. The haustoria in host cells of susceptible varieties collapsed before degeneration of the invaded host cell. On the contrary, host cells of incompletely resistant varieties died before the haustoria in these cells showed any sign of degeneration. Electron microscopic investigations confirmed the observations with light microscopy. In incompletely resistant varieties, an electron transparent sheath enveloped the haustorium. In the sheath fragments of membranes are localized. These membrane particles as seen by using the goniometer in electron microscopic work were flat faced. The sheath material consists of transformed host cell wall material and involves fragments of the host plasmalemma as well as fragments of the unit membrane separating the sheath from extrahaustorial matrix. The sheath has an important role as a special filter to prevent the passage of nutrients from the host cell into the haustorium. Thus the incomplete resistance is based not only on an impeded penetration of the parasite into the epidermal cells and their hypersensitive reactions in case of a successful penetration but also on hypersensitivity of mesophyll cells which does not necessarily lead to death of the parasite but does impede the absorption of nutrients.
Dispersal of Septoria nodorum Pycnidiospores by Simulated Rain and Wind
Authors: Brennan R. M. , Fitt B. D. L. , Taylor G. S. , Colhoun J.
Published: May 2008

The influence of wind on the splash dispersal of Septoria nodorum pycnidiospores was studied in a raintower/wind tunnel complex with single drops or simulated rain falling on spore suspensions or infected stubble with windspeeds of 1.5 to 4 m/sec. When single drops fell on spore suspensions (depth 0.5 mm, concentration 7.8 × 105 spores/ml) most of the spore‐carrying droplets collected on fixed photographic film between 0–4 m downwind (windspeed 3 m/sec) were >200 μm in diameter. However, most spores were carried in droplets with diameter > 1000 μm, 70 % of which carried more than 100 spores. When simulated rain fell on infected stubble most of the spore‐carrying droplets collected beyond 1 m downwind (windspeeds 1.4 and 4 m/sec) were <200 μm in diameter and none were >600 μm; most of these droplets carried only one spore.

The distribution of splash droplets (with diameter >100 μm) deposited on chromatography paper showed a maximum at 40–50 cm upwind of the target but many more droplets were deposited 20–30 cm downwind, when single drops fell on a spore suspension (concentration 1.2 × 105 spores/ ml) containing fluorescein dye with a windspeed of 2 m/sec; droplets were collected up to 3 m downwind but not more than 70 cm upwind. With a windspeed of 3 m/sec, numbers of sporecarrying droplets and spores collected on film decreased with increasing distance downwind; most were collected within 2 m of the target but some were found up to 4 m. When simulated rain fell on infected stubble, increasing the windspeed from 1.5 to 4 m/sec greatly increased the number of spores deposited more than 1 m downwind. At 1.5 m/sec none were collected beyond 2 m downwind, whereas at 4 m/sec some were collected at 4 m. A few air‐borne S. nodorum spores were collected by suction samplers at a height of 40 cm at distances up to 10 m downwind of a target spore suspension on which simulated rain fell.
Pathogenicity of Fusarium avenaceum Isolates from Cereals and their Ability to Produce Substance with Yellow Fluorescence
Authors: Chelkowski J. , Mańka M. , Goliński P. , Visconti A.
Published: May 2008

Fusarium avenaceum isolates from wheat, rye, barley, triticale, corn and potato formed substance with yellow fluorescence with properties similar to citrinin. Pathogenicity of 17 isolates tested against cereals seedlings was weaker than F. culmorum isolates; one isolate only was strong, two medium and the remaining 82 % were very weak or non pathogenic.
Manifestation et Mode de Conservation de Leveillula taurica, Agent de l'Oïdium de la Tomate au Maroc
Authors: Besri M. , Hormattallah A.
Published: May 2008

Manifestation and conservation of Leveillula taurica on tomatoes in Morocco

Powdery mildew of tomato, caused by Leveillula taurica, was considered a minor disease until 1978 when serious outbreaks occurred. These outbreaks coincided with periods of a draught and the introduction of new hybrids from Europe.

The pathogen infects a variety of plants, including eleven cultivated and five wild species. Infections of tomato plants were obtained by isolates collected from cultivated plants (Cynara cardunculus, Cicerarietinum, Medicago sativa, Capsicum annuum, Tropaeolum majus) and wild species (Chenopodium ambrosioides, Sonchus asper, Oxalis cemua, Urtica urens).
The Influence of Ustilago maydis on Free Radicals Concentration in Zea mays Tissues
Authors: Michalov J.
Published: May 2008

In the plant Ustilago maydis causes: 1. A lowering of free radical concentrations in tissues of nodal roots and in internodial tissues close to the fungus. 2. Conversely, in tissues of the primary root, of aerial roots, of leaves and nodes 1–5, 13, 15 and 16 it causes a rise of free radicals concentration. Ustilago maydis has a similar effect upon free radicals concentration in maize leaves as Erysiphe graminis in barley leaves.
Role of Sugars and Phenols in Charcoalrot Resistance of Sorghum
Authors: Patil S. H. , Hedge R. K. , Anahosur K. H.
Published: May 2008

Total sugars, reducing sugars, and phenols were estimated in internodes of tolerant and highly susceptible sovhum genotypes to charcoal, ln tolerant genotypes the sugar level was 2 to 3 times higher than in susceptible ones; phenol concentration also was higher in tolerant genotypes. In tolerant genotypes, sugar and phenol concentration was high in the lower most and in the upper most mternode. This may be used to identify sources of resistance.
Effect of Fusarium moniliforme var. subglutinans Infection on Mangiferin Production in the Twigs of Mangifera indica
Authors: Chakrabarti D. K. , Ghosal S.
Published: May 2008

The effect of Fusarium moniliforme var. subglutinans on the concentration of mangiferin (1,3,6,7‐tetrahydroxyxanthone‐C2‐beta‐D‐Glucoside) was studied. The role of the temperature gradient on the severity of infection and mangiferin production was examined in the light of the proliferation of the fungus. The infection prevented the transportation of mangiferin from the site of its synthesis to the storage site (bark). The variation in the concentration of mangiferin was attributed to its conversion to a polymeric quinone.
Physico‐Chemical Properties of Linseed Oil as Affected by Various Seed‐Borne Fungi
Authors: Dubey G. L. , Vayas K. M. , Dubey Onkar
Published: May 2008

The effect of six seed‐borne fungi on linseed oil was studied. Alternaria alternate, Aspergillus flavus, Aspergillus repens, Fusarium culmorum and Torula allii reduced oil content while Cladosporum herbarum slightly increased it. All fungi increased the free fatty acid content and saponification number linseed oil. Iodine number was decreased except in Cladosporium herbarum and Fusarium culmorum. Aspergillus flavus was the most destructive parasite in altering quantity and quality of linseed oil.
Uredospore Germination and Development of Some Cereal Rusts from South‐central Chile at Constant Temperatures
Authors: Tollenaar H.
Published: May 2008

The minimum and maximum temperatures for germination of uredospores of Puccinia striiformis, P. recondite, P. coronata and P.gramnis isolates from south‐central Chile were 0°C and 26°C, 0°C and 32°C, 8°C and 30°C, and 4°C and 34°C, respectively, whereas the shortest latent period was 8.5 days for P. struformis at 20°C, 5 days for P. recondite at 26°C, 5.5 days for P. coronata at temperatures, reaching the minimum and maximum threshold temperatures at 0.006°C and 23°C for P. strüformis, 0.31°C for P. recondita, 2.87°C and 30°C for P. coronata, and 1.72°C and 32°C for P. graminis. rspectively.

The cardinal temperatures give no explanation as to the observed sequential appearance of these rusts during the growing season. Other phenomena like the systemic mycelial growth of P.striiformis might be involved here.

At temperatures between 19°C and 22°C, the average daily increase of the area of sporulation of P.striiformis in wheat leaves varied between 9.05 and 22.48 mm2/infection site. This variation was due to substrate (plant) history and environmental factors.
Relationship between Field Levels and Light and Darkness on the Development of Phytophthora Blight of Pigeon Pea (Cajanus cajan (L.) Millsp.)
Authors: Singh U. P. , Chauhan V. B.
Published: May 2008

The incidence of Phytophthora blight of pigeon pea (Cajanus cajan (L.) Millsp.) caused by Phytophthora drechsleri f. sp. cajani was observed in the whole area of an experimental field plot where the topography varied. There was a positive correlation between low level of the field and maximum disease incidence. The incidence of disease was lowest at high field levels. This may be due to high or low moisture contents in both the levels. Leaf blight developed more rapidly under conditions of night darkness in the field and this was confirmed under conditions of artificial darkness in the glasshouse.
Obtaining a High Percentage of Explants with Negative Serological Reactions against viruses by Combining Potato Meristem Culture with Antiphytoviral Chemotherapy
Authors: Borissenko S. , Schuster G. , Schmygla W.
Published: May 2008

A high percentage of plantlets, in which PVX, PVM, and PVS were no longer detectable by precipitin tests was obtained from 100% virus‐infected stocks of the potato varieties Rosa and Priobskij rannija by combining meristem (tip) culture with antiphytoviral chemotherapy. When 2,4 ‐ dioxohexahydro 1,3,5‐triazinc (DHT) was added to the nutrient media, no virus was detectable serologically in 72% of the corresponding explants of the variety Rosa and in 66% of that of the variety Priobskij rannija, respectively. Contrary to this, all untreated control explants proved virusinfected. Treatment with 2‐thiouracil resulted in 46.6%, with cyanoguanidine in 28.6% of plantlets, in which no virus was detectable serologically.
Freeing Sweet and Sour Chery Trees from Prunus Necrotic Ringspot Virus by Injections of 2,4‐Dioxohexahydro‐1,3,5,‐triazine (DHT)
Authors: Bogusch L. J. , Verderevskaja T. D. , Schuster G.
Published: May 2008

After three injections of 1 ml of 0.01% DHT solutions under the cortex of the stems of 100% artificially or naturally with prunus necrotic ringspot virus infected sweet and sour cherry plants of 4 varieties axillary buds were grafted onto the indicator plant Shirofugen. 99% of these buds proved virus free. Contrary to this, only 28 to 32% of the buds from solvent injected control plants proved free of viruses. About 65% of the fruit‐trees grown up from buds of DHT treated plants were still virus free, when the test procedures were performed again two years later. Treatments of the sour cherry variety Podbelskaja with DHT were by far less effective.
Pathogenicity of Fusarium oxysporum Isolates from Malaysia and F. oxysporuin f. sp. elaeidis from Africa to Seedlings of Oil Palms (Elaeis guineensis)
Authors: Ho Y. W. , Varghese G. , Aylor G. S. T.
Published: May 2008

Pathogenicity tests with Fusarium oxysporum isolated form Malaysian oil palm were made with oil palms seedlings raised form Malaysian seed as well s with wilt‐susceptible seedlings gown from African seed. Oil palm seedlings grown form Malaysian seed were also inoculated with African isolates of F. oxysporum f. sp. elaeidis and F. oxysporum var. redolens. The experiments were made under normal soil moisture conditions and under water stress.

F. oxysporum f. sp. elaeidis isolates form Africa were pathogenic to oil palm seedlings from Malaysian seeds but the Malaysian F oxysporum isolates were non‐pathogenic to plams grown from Malaysian seed or the wilt‐susceptible palms from African seed. Seedlings from Malaysian seed proved to be highly susceptible to the vascular wilt disease caused by F. oxysporum f. sp. elaeidis as 75–90% of the palms were infected. The susceptibility of the palms from Malaysian seed varied with different African isolates tested. The Yaligimba isolate from Zaire which was found to be F. oxysporum var. redolens was the most virulent.

Disease was more severe when oil palm seedlings were subjected to a period of water stress. The incidence of death in the seedlings under stress conditions was 45% as compared with only 15% for palms grown under normal conditions.
Survival of Phytophthora cinnamomi in Buried Eucalyptus Roots
Authors: Mackay A. , Weste G. , Sharpe K.
Published: May 2008

Colonization and survival of Phytophthora cinnamomi in roots was tested in 3 months old, axenically grown seedlings of Eucalyptus maculata (field resistant) and E. sieberi (susceptible). The roots were inoculated, then one week later were excised and buried in three non‐sterile, conducive soils; a lateritic gravel, an infertile duplex soil, a loamy sand as well as in a fertile, suppressive krasnozem. Pathogen viability, percentage root colonization and chlamydospore numbers were examined at matric potentials of −1/3, −5 and −10 bar after periods of 10, 100 and 200 days at 21°C.

At 10 days, survival was 100% in the form of mycelium and the only significant difference was between the two Eucalyptus species. At 100 days survival was solely due to chlamydospores, but the pathogen was viable in all inoculated roots and at each matric potential. At 200 days soils had dried to less than −10 bars and the pathogen failed to survive. No significant differences were found between the two pathogen isolates but significant differences were obtained between the susceptible and field resistant Eucalyptus species.

Pathogen viability, percentage root colonization and chlamydospore number were highly correlated with soil types and matric potential. These components declined with decreasing soil matric potential. The Krasnozem was only suppressive at relatively high soil matric potentials (−1/3 bar). At lower values (−5, −10 bar) survival of the pathogen, chlamydospore numbers and percentage colonization of the roots in the Krasnozem were comparable with that of the 3 conducive soils tested.

Chlamydospores were present, but in low numbers in roots buried in the suppressive soil at −1/3 bar.
The Action of Polygalacturonase and Cellulase Enzymes of Botryodiplodia theobromae Pat. on Yam (Dioscorea spp.) and Sweet Potato (Ipomoea batatas) Tissues
Authors: Arinse A. E.
Published: May 2008

The action of an endo‐polygalacturonase PG3 and cellulase of Botryodiplodia theobromae, in the crude and pure forms, on sweet potato and yam slices was investigated. The purified isoenzyme PG3 and the crude pectic enzyme preparations macerated and killed the cells of both tissues although the former did so at a faster rate. Purified cellulase neither macerated nor killed cells from either plant. Although the action was delayed, the crude preparation of cellulase slightly macerated and killed the cells of sweet potato. Yam tissue was, however, not macerated by crude cellulase.

Plasmolysis of the cells of both tissues delayed the toxicity and macerating action of the pure PG3 on the tissues. This delay in cell death was, however, not observed when the plasmolysed cells were treated with the crude cellulase preparation.
Fusarium oxysporum f. sp. psidii as a Pathogen Causing Wilt of Guava in Varanasi District, India
Authors: Pandey R. R. , Dwivedi R. S.
Published: May 2008

A serious wilt disease of guava has been observed in the Varanasi district of eastern Uttar Pradesh of India. The causal organism has been identified as Fusarium oxysporum f. sp. psidii. Pathogenicity tests were performed in pot experiments to confirm the causal agent of the disease. Infected plants developed chlorosis followed by wilting of entire seedlings and leaf abscission. Histopathological studies showed the presence of hyphae in xylem vessels of roots of the wilted seedlings and when sections of such roots were transferred to potato dextrose agar medium, this pathogen grew in culture.
World Wide Distribution of a Bacterial Stripe Pathogen of Rice Identified as Pseudomonas avenae
Authors: Shakya D.D. , Vinther F. , Mathur S.B.
Published: May 2008

Sixty‐two sample of rice from 29 countries were tested for presence of Pseudomonas avenae and 55 from 28 countries proved to be infected. The presence of the bacterial stripe pathogen constitutes the first report from these countries. Infection ranged from 1 to 75%. P avenae was identified by symptoms in the seedings and its identity confirmed serologically. The bacterium was found even in 8‐year‐old seed samples which had been stored at 5°C.
Induction of Susceptibility and Resistance of Wheat Leaves by Preinoculation with High and Low Virulence Races of Puccinia recondita f. sp. Tritici
Authors: Bahamish H. S. , Wood R. K. S.
Published: May 2008

Isolates R1 and R2 of Puccinia recondita f. sp. tritici of low or high virulence on leaves of a series of cultivars of wheat behaved very similarly up to the formation of appressoria above stomata and sub‐stomatal vesicles. Differences in growth of hyphae and in responses of host cells became clearly apparent only 24 h after infection; they then increased so that 10 days after inoculation high virulence isolates had produced freely sporulating sori (infection type 4) whereas low virulence isolates produced small colonies which did not erupt and sporulate and were associated with large numbers of dead host cells.

The cultivar Timmo was selected for experiments on induced susceptibility and induced resistance. It was highly susceptible (infection type 4) to isolate Rl and to a mutant RlM, similar in pathogenicity on many cultivars but with uredospores different in colour from those of R1 and those of isolate R2 to which Timmo was highly resistant (infection type 0). This difference facilitated interpretation of results of experiments in which leaves were inoculated with more than one isolate.

Inoculation with R1 (or with RUM which always behaved similarly) made leaves susceptible to R2 inoculated 4 days later. R2 sori were about 70 % the area of and about 70 % as frequent as Rl sori when inoculated on the same area on the same surface or on an area on the lower surface below a similar area on the upper surface inoculated with Rl. There also developed in the same area small, non‐erumpent colonies associated with large numbers of dead host cells; these necrotic lesions were very similar to those produced in leaves inoculated only with R2. There were significantly fewer sori and more necrotic lesions when Rl was inoculated 1 or 2 days before R2. Totals of sori and necrotic lesions were about the same when the interval between inoculations was 1, 2 or 4 days; they were also similar with an interval of 3 days when numbers of sori were substantially less than after 4 days.

Inoculation with Rl had some but much less effect in making tissues susceptible to R2 when again it was inoculated later but about 2 mm away.

Although inoculation with R1 sufficiently in advance had the striking effect of making tissue almost as susceptible to normally low virulence R2 as it was to R1, colonies and sori of R1 which developed in association with those of R2 were substantially smaller than those which developed when R1 was inoculated alone. But there were similar differences in sizes of colonies and sori when R1 and RIM were inoculated together or separately. They probably depended on competition for nutrients. Possible mechanisms of induced susceptibility and induced resistance and implications for disease in the field are discussed briefly.
Sporenkeimung von Phoma lingam (Tode ex. Fr.) Desm. und Resistenzprüfung bei Raps im Gewächshaus
Authors: Wittern I. , Krüger W.
Published: May 2008

Spore germination of Phoma lingam (Tode ex. Fr.) Desm. and methods to determine resistance of oil seed rape in the greenhouse

It was the aim of this investigation to obtain more insight into the epidemiology of Phoma lingam (Tode ex. Fr.) Desm. (stat. gen. Leptosphaeria maculans (Desm.) Ces. et de Not.) and to improve the existing methods for resistance testing.

In laboratory experiments the differing demands on temperature of both, the sexual as well as the non sexual phase were observed. Many ascospores developed germ tubes after eight hours at 4‐8°C whilst pycnidiospores needed 24 hours at 16°C to have similar development.

In greenhouse experiments young plants were infected by spraying or by placing a droplet of spore suspension onto cotyledons or leaves. Generally, ascospores were more virulent than pycnidiospores. The ascospores were obtained from old rape stalks which could be stored at ‐18°C without losing virulence. The most severe attack was observed after incorporating infested oat kernels (3 % w/ w) into soil, but the difference between cultivars vanished which was already low with the other methods, and which did not always correspond with results obtained in the field at stage 85, so that all these methods are not as suitable as those in the field.

The distribution of pycnidiospores is also possible by adhering to the seed after threshing. The infection of the seedlings from this source was more pronounced in steamed than in unsteamed soil. The re‐isolation of P. lingam increased as well from plants grown in steamed soil. Furthermore, pycnidiospores are distributed by wind during combining to neighbouring fields, already prepared at that time for rape sowing.
Epidemiologische Untersuchungen bei der Wurzelhals‐ und Stengelfäule des Rapses, verursacht durch Phoma lingam
Authors: Krüger W. , Wittern F.
Published: May 2008

Epidemiological investigations in the root and collar rot of oil seed rape, caused by Phoma lingam

In this part of investigations on Phoma lingam (Tode ex. Fr.) Desm., epidemiological experiments were carried out on infection rates of oil seed rape and the fungus spectrum present during the vegetation period as well as on spore dispersal of Leptosphaeria maculans (Desm.) Ces. Et de Not.), the sexual stager of p. lingam.

The infection at the stalk base can take place in autumn and about 10 to 40% were found to have P. lingam inside the tissue with higher inoculum potential P. lingam was more frequently isolated at the connection points of the lower leave than at the height of the soil level.

The fungus spectrum and the frequency of the fungi isolated changed in course of the vegetation period. Whilst P. lingam and F. tabacinum increased and were isolated at high numbers, Alternaria spp. And P. eupyrena were found less at the beginning and at the end of the season. Two to three other species and further three to four were isolated at low level respectively occurred less common. The pathogenic importance of some of these species is not yet determined.

The low level of leaf infection occurring in the federal Republic of Germany may have several reasons as e.g. the short phase of ascospore ejection and the low temperature in November and December. Furthermore, deep ploughing early in autumn for wheat sowing decreased inoculum potential as could be observed in sore catches obtained in several years.

The development of the perithecia and the beginning of sport discharge was dependent on the rain fall. Generally, spore flight started a few hours after the rain fall began, but sometimes a high relative humidity seemed to be sufficient to initiate spore discharge. There was the tendency of spores been more discharged at slight winds (2–3) and consequently, because of winds being slightly stronger in the afternoon and evening, spores were more found in these daytimes.
Zur Verwendung von 2‐Hydroxyethyl‐Methacrylat (GMA) als Einbettungsmedium bei histologischen Untersuchungen in der Phytopathologie
Authors: Grunewaldt‐Stöcker Gisela
Published: May 2008

The use of 2‐hydroxyethyl‐methacrylate (GMA) as embedding medium for histological investigations in phytopathology

A new plastic embedding technique is described for subsequent thin sectioning of plant tissues. In comparison to the paraffinmethod the GMA polymerization system is less time consuming. The excellent preservation of well‐fixed tissue is fully asserted, as the embedding medium is not removed from the sections. In lightmicroscopic studies convincing results were obtained with different staining procedures; specific evidence for polysaccharides, pectine and nucleic acids was carried out with thin sections of 2‐8 μm thickness, also by fluorescence microscopy. The GMA‐embedding technique seems to be of value for various histological investigations in phytopathology.
Hyperparasitism of Puccinia horiana and other Microcyclic Rusts
Authors: Srivastava A. K. , Défago G. , Kern H.
Published: May 2008

Verticillium lecanii and Aphanocladium album infected in 5 days 90–95 % of the teliospores of Puccinia horiana, the major pathogen of Chrysanthemum. This suggests the possibility to expand the use of V. lecanii, a commercial biocontrol agent against aphids, in order to control P. horiana, V. lecanii and A. album parasitized other microcyclic rusts but with a lesser frequency: P. dianthi (82 and 88 %), P. malvacearum (72 and 60 %) and P. glomerata (57 and 61 %). Cladosporium sphaerospermum and C. uredinicola were less effective than V. lecanii and A. album against all rust species tested.
Differentiation of Physiologic Races of the Rice Blast Fungus, Pyricularia oryzae Cav. by PAGE‐electrophoresis
Authors: Park W. M. , Lee Y. S. , Wolf G. , Heitefuss R.
Published: May 2008

Eighty‐three isolates of the rice blast fungus (Pyricularia oryzae) were tested with respect to genetic diversity and the possibility of race differentiation by electrophoresis. The fungus was genetically very heterogeneous. The isolates were differentiated into 6 races by pathogenicity on race differential varieties. There was little correlation between pathogenicity and zymogram types of one particular enzyme such as esterase, phosphatase or catalase. The isolates were divided into 14 groups by the combination of the zymogram types of the three enzymes. The isolates in the same group showed similar pathogenicity. A new method is proposed which differentiates the blast fungus races by the combination of zymogram type of enzymes. The details, are discussed.
Untersuchungen zum Einflufß von Aluminiumfosetyl auf den pflanzlichen Phenolstoffwechsel in den Pathogen‐Wirt‐Beziehungen Phytophtbora fragariae – Erdbeere und Bretmia lactucae ‐ Salat
Authors: Dercks W. , Buchenauer H.
Published: May 2008

Investigations on the influence of aluminium ethyl phosphite on the plant phenolic metabolism in the pathogen‐host‐interactions Phytophthora fragariae ‐ strawberry and Bremia lactucae ‐ lettuce

Aluminium ethyl phosphite exhibited pronounced preventive and very good curative activities. In strawberries, 4000 ppm of the compound affected an eminent protection against Phytophthora fragariae after root and leaf applications; the earlier the fungicide treatment was carried out, the more distinct was the control effect. Similar relations were established in the pathogen‐host‐interaction Bremia lactucae, in which 5000 ppm of the fungicide proved to be highly active following pre‐ and postinfectional applications.

In both parasite‐host‐interactions, an enrichment of phenolics in consequence of a de‐novo‐synthesis in diseased plant tissue was observed only very late and exclusively, when fungicide and parasite had come together; inoculation on one hand or fungicide treatment on the other resulted in no remarkable effect.

With great certainty, however, the augmentation of phenolics was not the cause, but rather the consequence of fungicidal efficiency which resulted in killing of the fungus and partial destruction of host tissue after direct influence of aluminium ethyl phosphite on the parasite itself. A clear proof for a main and causal evidence of aluminium ethyl phosphite‐induced phenolics for protection of strawberries against Phytophthora fragariae and of lettuce against Bremia lactucae could not be furnished.
Effects of Leaf Age, Inoculum Dose and Freezing on Development of Chocolate Spot (Botrytis fabae) Lesions on Field Bean (Vicia faba) Leaves
Authors: Creighton N. F. , Bainbridge A. , Fitt B. D. L.
Published: May 2008

Botrytis fabae spore suspensions containing c. 1, 10, 102, 103, 104, 105, or 106 spores/ml were used to inoculate 5, 17 or 30‐day‐old field bean leaves. The percentages of the leaf areas covered by, chocolate spot lesions and the percentages of the leaf areas bearing conidiophores were assessed 1, 6, 12, 14, and 19 days after inoculation. The percentage of the area covered by lesions and the percentage of the area bearing conidiophores (logit‐transformed) increased linearly with increasing spore concentration (log10‐transformed). The proportions of leaf areas covered by lesions and bearing conidiophores were both greater on 17 and 30‐day‐old leaves than on 5‐day‐old leaves. The rate of lesion growth increased with both increasing inoculum dose and increasing leaf age. Generally there was no interaction between the effects of leaf age and the effects of inoculum dose on either lesion growth or sporulation. Two days after inoculation with suspensions of either 104 or 106 spores/ml, 7‐day‐old leaves grown at 15°C were transferred to –16°C or 2.5°C or kept at 15°C for 4 days. Two days later more spores had been produced on leaves which had been frozen (–16°C) than on, leaves kept at 2.5°C.
Influence of Endotrophic Mycorrhizae on the Fusarial Wilt of Cassia tora L.
Authors: Chakravarty P. , Mishra R. R.
Published: May 2008

The wilting of Cassia tora caused by Fusarium oxysporum was reduced significantly when inoculated with VAM. Mycorrhizal fungi highly influenced growth stimulation of the seedlings. The population of F. oxysporum was reduced in the presence of VAM.
Purification and Properties of the Geminivirus Euphorbia Mosaic Virus
Authors: Jaramillo Sandra , Lastra Ramón
Published: May 2008

Euphorbia mosaic virus was purified from infected plants of Nicotiana benthamiana. Highest concentrations of virus particles were found in infected plant tissue between 10–12 days after inoculation. The enzyme driselase assisted in purification of the virus particles from the infected tissue yielding about 600 μg/kg of plant material. Purified preparations showed a maximum absorption at 260–263 nm and the ratio of absorption at 260 and 280 nm was 1.4. The viral nucleic acid was digestedby DNase I and S1 Nuclease but not RNase A. A single coat protein with a MW of 32,000 d and two DNA bands with a MW 0.96 × 106 d (2870 nucleotides) and 0.90 × 106 d (2700 nucleotides) were associated with the purified virus particles. Virus specific DNA was isolated from infected tissue between 7 and 15 days after inoculations.