bluuebunny/crossref_metadata_2025 huggingface dataset:
Stoffwechsel phenolischer Verbindungen in gesunden und Braunrost‐infizierten Gersten‐ und Weizenvarietäten
Authors: Harms H. , Terbea Maria
Published: May 2008

Metabolism of phenolic compounds in healthy and brown rust‐infected barley and wheat varieties

Infections with Puccinia isolates cause an accumulation of phenolic compounds both in resistant and susceptible isogenic lines of barley and wheat seedlings. The increased de novo biosynthesis of hydroxy‐cinnamic and ‐benzoic acids is catalysed by the enzyme phenylalanine‐ammonia‐lyase (PAL) whose activity seems to be controlled not only by the substrate (phenylalanine) but also by the formed products (phenols). Depending on its actual physiological state every plant species shows as a reaction upon infection a typical behaviour. It is remarkable that healthy and rust‐infected plants contain the same percentage of individual phenolic acids. An infection does not lead to an increase of individual hydroxycinnamic‐ or benzoic acids. There are only differences in quantity but no differences in quality. The pattern of phenolic acids seems to be largely genetically determined and formed according to the developmental stage of the plants. The hydroxycinnamic and ‐benzoic acids formed during the host‐parasit‐interactions seem to be, at least for the analysed combinations, more the consequence than the cause of resistance.
Phytotoxic Activity of Tenuazonic Acid Isolated from Alternaria alternata (Fr.) Keissler Causing Leaf Blight of Datura innoxia Mill. and its Effect on Host Metabolism
Authors: Janardhanan K. K. , Husain Akhtar
Published: May 2008

Tenuazonic acid isolated from Alternaria alternata (Fr.) Keissler causing leaf blight of Datura innoxia Mill. showed significant phytotoxic activity when tested on monocot and dicotyledonous plants. The toxin induced chlorosis and necrosis on leaves of D. in noxia, D. stramonium, D. metel, belladonna, cowpea, wheat, rye, cabbage, cauliflower and maize at 200μg/ml and wilting of seedlings of D. innoxia at 100μg/ml concentration. It also caused complete inhibition of root and shoot elongation of germinating seeds of D. innoxia, wheat, rye, green gram and lettuce at 100μg/ml concentration. It was a nonspecific phytoxin and appeared to have significant role during pathogenesis.

Tenuazonic acid did not cause any significant change in the rate of respiration and in sugar, carbohydrate, total phenol and nitrogen contents of D. innoxia leaves. But its treatment on host plant induced 64 % reduction of chlorophyll content in leaves after 72 hours and 40 % reduction in protein content after 24 hours.
Die Isolierung bodenbewohnender Feinde des Maisbranderregers Ustilago maydis
Authors: Geyer A. , Schnürlein‐Land G. , Beiderbeck R.
Published: May 2008

The Isolation of Soil‐Inhabiting Enemies of Ustilago maydis

Using sporidial lawns of Ustilago maydis in water agar layers as indicator plates 2 organisms could be isolated from soil samples which produce plaques. These organisms were identified as Acanthamoeba polyphaga and Myxococcus spp. Both organisms control populations of Ustilago maydis in sterile soil too.

The isolation method may be gainfully used in the search for further organisms with more specific potential for the biological control of Ustilago maydis.
Occurrence of Tobacco Necrosis Virus in Strawberry Cultivars and Frageria vesca Indicators
Authors: Tanne Edna
Published: May 2008

Tobacco necrosis virus (TNV) was found occasionally in roots of indicator plants such as UC‐4, UC‐5 and alpine, commonly used for screening of strawberry virus diseases. The virus was purified and identified as TNV by its host‐range, physical properties, electron microscopy and serological tests. The implication of the possible occurrence of TNV in indicator plants on reliable diagnosis of virus disease in strawberry is discussed.
Der Einfluß von Infektionen mit dem Kartoffel‐X‐Virus und Behandlung mit der antiphytoviralen Substanz 2,4‐Dioxohexahydro‐1,3,5‐triazin auf die Bildung und den Apikaltransport 14C‐markierter Assimilate und die Konzentration freier Aminosäuren
Authors: Schuster G. , Sölter Barbara , Byhan O.
Published: May 2008

The influence of infections with potato virus X and treatment with the antiphytoviral substance 2,4‐dioxohexahydro‐1,3,5‐triazine on the formation and the apical transport of 14C‐labeled assimilates and on the concentration of free amino acids

After two hours of exposure of lower leaves of Nicotiana tabacum L. 'Samsun’to an air containing 15.91 MBq 14CO2 per liter of air, the bulk of the activity of assimilated 14CO2 was found in glucose. Lower activities at different RF values were obviously assignable to intermediates of photosynthesis. Saccharose was not labeled. Infections with potato virus X (PVX) resulted in the incorporation of 14CO2 into the assimilates being reduced by about 28 %, but the relative proportion of apically transported labeled assimilates in virus‐infected plants was only insignificantly diminished compared with that in healthy plants. Treatment with the antiphytoviral compound 2,4‐dioxohexahydro‐1,3,5‐ triazine (DHT = 5‐azadihydrouracil) had no appreciable effect upon 14CO2 incorporation of healthy plants. By contrast, 14CO2 incorporation into assimilates was greatly increased by DHT in the case of virus‐infected plants, now reaching values that exceeded those of healthy plants receiving no treatment. The main reason for this is seen in the great reduction in the concentration of PVX and, consequently, in the virus‐induced reduction of photosynthesis. Apical transport of assimilates from exposed leaves was substantially reduced, after treatment with DHT, in healthy as well as in virus‐infected plants. Obviously, the afraction of by older leaves exposed to 14CO2 has been increased by cytoKinin activities of DHT to such an extent that the source‐to‐sink conditions influencing the intensity of phloem transport have been substantially changed. The pattern of detected free ammino acids had, in the leaves exposed to 14CO2 been expanded, after infection with PVX, by histidine and phenylalanine. In the apical leaves, in which a larger number of free amino acids had been detected than in the lower leaves exposed to 14CO2, there was also observed an additional occurrence of phenylalanine in plants infected with PVX, whereas two not specified amino acids disappeared. Treatment with DHT did not change the amino acid pattern of healthy control plants. In plants infected with PVX, DHT had the effect of canceling virus‐induced variations in the amino acid pattern (one exception being phenylalanine in apically inserted leaves). Evidently, this was brought about indirectly by strong inhibition of virus replication and, consequently, by elimination of virus‐induced variations.
When a Virus‐like Particle is a Virus
Authors: Kassanis Basil
Published: May 2008

Reasons are given why the term “virus‐like particle” should not be used when describing viruses of the cryptic group. Also, an attempt is made to define viruses taking into consideration recent knowledge.
Transmission of Alternaria macrospora in Cotton Seeds
Authors: Bashan Yoav
Published: May 2008

Alternaria macrospora was isolated from seeds only after the natural opening of the bolls and exposure of seeds to an environment in which the fungus was present. The fungus lacks the ability to penetrate the boll wall and reach the seed site. Attempts to isolate the pathogen from seeds of immature bolls at different developmental stages failed. Internal infection by slow injection resulted in seed infection and partial shedding of the injected plant parts which was high in buds and decreased with the ripening to mature bolls. Severity of seed infection was not dependent on either inoculum level, boll physiological age or even if the boll itself was not diseased. Infection of flowers under field conditions caused flower shedding. Naturally infected seeds or inoculated seeds with inoculum levels of 100 spores/ml and above resulted in diseased cotyledons, the incidence of which was, for inoculated seeds, positively correlated with inoculum level. A small difference was observed between cultivars in susceptibility to artificial inoculation at the cotyledon stage. A. macrospora survived on commercial cotton seeds and on post‐season plants left growing at the field edges. Survival in plant debris under field conditions was minimal and may only have a minor effect on field reinfestation.
Effect of Alfalfa Wilts on the Hydroxyproline Content in Cell Wall
Authors: Krátká J. , Kůdela V.
Published: May 2008

The Hyp content was studied in cell wall of alfalfa susceptible and resistant strains on the 3rd, the 7th and on the 14th day after inoculation with Verticillium albo‐atrum or Corynebacterium michiganense pv. insidiosum. The changes of Hyp content after inoculation with both pathogens were markedly expressed in alfalfa roots.

Resistant plants of R 337 strain responded to inoculation with V. albo‐atrum or C. michiganense pv. insidiosum by the decrease of Hyp content mainly on the 3rd and on the 7th day. On the 14th day after inoculation Hyp content practically did not differ from that of the control. Susceptible plants of S 354 and S 321 srains responded to inoculation with wilt pathogens by the slight decrease of Hyp content at the 3rd day after inoculation. A significant increase of Hyp content was found on the 7th and mainly on the 14th day after inoculation in comparison with control plants.

The cell wall Hyp content was also determined with 7 R‐strains and 7 S‐strains at 120 days after inoculation with both pathogens. In each R and S strain two categories of plants were used for chemical analyses: Wilt‐free plants (0 to 1 classes) and diseased, wilted plants (2 to 6 classes). In the resistant alfalfa strains no differences in Hyp content between the wilt‐free and diseased plants were found. In the susceptible alfalfa strains the Hyp content was significantly higher in roots of diseased plants comparing with the wilt‐free ones.

Only negligible changes in Hyp content were registered in the overground parts of all inoculated alfalfa strains.
Etiology and Epidemiological Observations of Elaeagnus Leaf Spot Caused by Septoria elaeagni
Authors: Lorenzini G. , Vannagci G. , Triolo E.
Published: May 2008

A foliar disease, causing necrotic spots and severe defoliation of Elaeagnus angustifolia, was detected in Tuscany, Italy, in 1979. The causal agent was identified as Septoria elaeagni. It was not pathogen to E. umbellata, E. pungens, E. multiflorum, and Hippophae rhamnoides.

Ultrafiltrates from liquid cultures showed toxicity against E. angustifolia and some herbaceous species, non hosts of the pathogen.

Disease was significantly more severe in an overhead irrigation system than when water was delivered to the soil alone.
Cross‐Protection and Multiplication of Mild and Severe Strains of TMV in Tomato Plants
Authors: Burgyán J. , Gáborjányi R.
Published: May 2008

The presence of virus having mixed coats has been demonstrated serologically in tomato plants cross‐protected with a mild strain (M 11–16) against the severe (UI) strain of tobacco mosaic virus (TMV). The proportion of virus having mixed coats remained constant throughout at ca. 40% even in top leaves where severe symptoms caused by the challenge virus (U1) first appeared.

The symptoms caused by the U1 in doubly‐inoculated plants occurred in the leaves where:

the amout of total virus (irrespective of the type of coat) protein was 52% that of U1 strain in singly inoculated plants,

the multiplication of the severe U1 strain was reduced to only 9% as compared with the leaves singly inoculated with U1,

the ratio of severe to mild strain was increased to near equality although there was a significant reduction in the multiplication of U1in these leaves,

the amount of infective U1RNA started to increase.
Ultrastructure of Soybean Leaf Cells Infected with Cowpea Mild Mottle Virus
Authors: Thongmeearkom P. , Honda Y. , Iwaki M. , Deema N.
Published: May 2008

Cowpea mild mottle virus (CMMV), a whitefly‐transmitted, rod‐shaped virus isolated in Thailand, induced feather‐like structures in the cytoplasm of infected soybean cells. These structures were the results of a complex arrangement of virus particles and occurred in all types of cells observed. An organized arrangement of virus particles in the form of layers was also observed in the cytoplasm of the infected cells. In ultrathin sections, the particles measured about 10 nm wide and more than 600 nm long, which corresponded to the size reported for the purified preparations of CMMV. No feather‐like structures or virus particles were observed in the comparable healthy tissues.
The Antimicrobial Efficiency of Root Oil Against Human Pathogenic Bacteria and Phytopathogenic Fungi
Authors: Jaiswal Ku , Batra Ku. Anita , Mehta B. K.
Published: May 2008

The in vitro antimierobial activity of root oil of C. orchioides were studied against human pathogenic bacteria and phytopathogenic fungi by comparing the results with standard microbial susceptibility testing biodises. The oil of C. orchioides in case of bacteria shows significant activity against Bacillus anthracis, B. subtilis, Salmonella pullorum, S. newport, and Staph. aureus. While in case of fungi root oil had excellent activity against Fusarium monili forme, F. solani, Asprgullus flavus and Cladosporium and shows significant activity against all other tested fungi.
Vorkommen von Tobacco Rattle‐Virus in Roggen (Secale cereale) in der Bundesrepublik Deutschland
Authors: Huth W. , Lesemann D.‐E.
Published: May 2008

Natural occurrence of tobacco rattle virus in rye (Secale cereale) in the Federal Republic of Germany

Near Bergen/Dumme in northern Germany, in an area known for the occurrence of tobacco rattle virus (TRV) on potatoes, 5–10 % of rye plants of one experimental plot were severely stunted and showed distinct chlorotic mottling of leaves. In these plants TRV was identified on the basis of particle morphology and serology (Immunoelectron microscopy and ELISA). TRV was also detected in Capsella bursa‐pastoris and Stellaria media from an area adjacent to the rye plot but not in nearby commercial rye fields.
Effect of Micronutrients on the Development of Bacterial Blight of Rice
Authors: Philip R. , Devadath S.
Published: May 2008

Diferent concentrations of miceonutrients (with one exception; Table 1) increased the degree of attack on rice plants by Xanthomonas oryzae. When a double dose of Mn or Cu was applied or when Mn was omitted, length of lesions was considerably smaller than with all micronutrients on normal concentration. No correlation was found between total phenols, total sugars, reducing sugars, non‐reducing sugars, amino acids, and total nitrogen and lesion development in different micronutrients combinations.
Infections of Jute, Maize and Rice ot Revealed by the Standard Blotter Method of Seed Health Testing
Authors: Michail S. H. , Mathur S.B. , Neergaard P.
Published: May 2008

In the standard blotter seed health testing of jute, maize and rice some ungerminated seeds, and seedlings with or without symptoms were eventually found to be infected by pathogenic fungi on prolonged incubation any by trans‐planting seedlings from blotters to autoclaved soil in pots.
Multiplication of Pseudomonas syringae pv. phaseolicola“in planta”
Authors: Rudolph K. , Mendgen K.
Published: May 2008

In the compatible combination of the halo blight disease of bean Pseudomonas phaseolicola was able to colonize large areas of the intercellular space of leaves, such that these confluent water congested areas became visible as water‐soaked spots. Most of the plant cell walls in the infected region maintained their normal shape, even when the cytoplasm had collapsed. Some inward bending of plant cell walls preceded their rather slow degradation and final replacement by bacterial masses. Neighbouring plant cells appeared to be metabolically active.

In resistant leaves no indications of active bacterial attachment or encapsulation could be observed. However, bacteria appeared to be more densely packed in resistant leaves, and relatively more plant cells completely collapsed as compared with susceptible leaves.

From 8—14 days after inoculation, the bacterial concentration did not change much in susceptible or resistant leaves, indicating the absence of bactericidal components. Even Pseudomonas pisi snowed some multiplication in bean leaves (immune reaction), but its growth stopped earlier than that of P. phaseolicola. in the resistant cultivars, probably due to a different mechanism of resistance. Although less bacteria were determined in the intercellular washing fluid (IF) compared with leaf homogenates, the high bacterial concentrations in the IF supported our observation that an effective encapsulation of bacteria in resistant leaves did not occur.
Slow Rusting of Wheat to Puccinia recondita
Authors: Poyntz B. , Hyde P. M.
Published: May 2008

Seven cultivars of winter wheat were studied in field trials to determine their level of slow rusting ability towards brown rust. Cv. Bouquet was the most resistant, with greatly reduced infection levels, areas under die disease progress curve and infection rate compared with those measured on the control cv. Armadda. Cultivars Atou and Maris Freeman also showed evidence of slow rusting, but the responses of cultivars Waggoner and Flinor were not consistent in successive trials. Cv. Flanders appeared to be almost as susceptible as cv. Armada. The use of the Gompertz transformation of desease progress data for the calculation of apparent infection rates allowed better comparison of rates between cultivars than when the logistic transformation was used.
Studies on Induced Resistance to Tobacco Mosaic Virus, in Samsun NN Tobacco and Changes in Ribosomal Fractions
Authors: Stein A. , Spiegel S. , Loebenstein G.
Published: May 2008

Resistance to tobacco mosaic virus (TMV) was activated by various forms of induction in Samsun NN tobacco leaves, and the intensity of the different forms was compared. Induced resistance was highest in leaf tissue between TMV inoculated stripes parallel to the mid‐vein and after injection of ethylene maleic anhydride copolymer (EMA), followed by that induced in distal half leaves after inoculating the basal halves with TMV. Resistance in upper leaves following inoculation of the lower leaves with TMV was relatively low, while induction due to lesions caused by ethrel gave an intermediate degree of resistance. Estimation of resistance by size and number of local lesions was correlated with the amount of extractable virus as measured by enzyme‐linked immunosorbent assay (ELISA), thus indicating that in the resistant tissue virus replication, and not only the development of necrotic local lesions, is suppressed.

An increase in a specific ribosomal fraction (R2), recovered by a two‐step procedure, was observed in tissues where resistance was most intense, i.e., between TMV stripes and after EMA injection. It may be that this specific ribosomal fraction participates in maintaining the resistant state.
Occurrence of Melon Necrotic Spot Virus in Crete (Greece)
Authors: Avgelis A.
Published: May 2008

Since 1982 melon plants cv. Galia grown in plastic houses showed severe leaf and stem necrosis. A virus isolated from affected plants infected only Cucurbitaceae. Systemic infections were only developed in melon and Luffa acutangula, while a severe hypocotyl necrosis was observed in watermelon. Purified virus sedimented in sucrose gradients as a single component and reacted only with antisera to melon necrotic spot virus (MNSV). Seed transmission (22.5%) of the virus was observed m melon plants grown from seed of naturally infected melons, but the virus could not be detected in triturated seeds. The virus could be isolated from leachate of contaminated soil and melon plants became infected when grown in contaminated soil or when watered with suspensions of virus. These properties suggest that the virus is an isolate of MNSV.
Relative Heterothallism and Production of Hybrid Perithecia by Auxotrophic Mutants of Glomerella cingulata from Apple
Authors: Beraha L. , Garber E. D.
Published: May 2008

Glomerella cmgulata is a homothallic species but produces a ridge of fertile perithecia at a frontier between certain wild‐type strains on agar. To account for the presence or absence of perithecia earlier workers suggested that alleles at A and B loci control the formation of perithecia at mycelial frontiers in + and – strains. We propose that G. cingulata actually demonstrates “relative heterothallism”. Of 7 induced nutritionally deficient mutants (auxotrophs) in 2 wild‐type strains from apple, only one methionine (met‐1) and one arginine (arg) mutant in only one wild‐type strain gave a heavy ridge of perithecia at their junctures. Neither the met‐l nor arg mutations have been identified as those in the A or B locus. The perithecia were either homozygous (selfs) for met‐1 or arg, or heterozygous (hybrids). Paired met‐1 and arg segregants from hybrid perirhecia as well as diauxotrophic strains from met‐l or arg mutants also gave hybrids of selfs. Specific nutritional deficiencies in certain wild‐type strains which can direct sexuality are not yet known. Genetic studies are now feasible in G. cingulata to define enzymatic factors responsible for pathogenicity.
The Role of Ethylene in Growth and Endopolygalacturonase Production by Sclerotium rolfsii
Authors: Madkour M. A.
Published: May 2008

Growth of and endopolygalacturonase production by Sclerotium rolfsii was better on a defined mineral medium than on a medium containing segments of tomato leaf petioles. The effect of treatment with ethylene (10μl/l) upon endopolygalacturonase activity with investigated at various stages of growth, in a mineral defined medium. Addition of ethylene to a 10 days‐old culture of S. rolfsii resulted in a decrease in activity by day 14, whereas the addition of ethylene to a 4, 6 and 8 days old cultures resulted in an increase in endopolygalacturonase activity. Ethylene seems to have little or no stimulating effect upon growth of S. rolfsii when applied after 8 days. However, inhibited fungal growth, after the addition of ethylene at earlier stages of growth, was obtained due to the depletion of oxygen from sealed culture flasks. Endopolygalacturonase was extracted and purified from control cultures after 14 days of growth. Fractionation of this enzyme protein on Sephadex G‐100 gel filtration columns resulted in two peaks of activity measured by the release of reducing sugars from polygalacturonic acid (PGA).
Effect of Potassium Chloride vs. Potassium Sulphate Fertilization at Different Soil Moisture on Take‐All of Wheat
Authors: Trolldenier G.
Published: May 2008

A pot experiment was conducted with two moisture levels to study the influence of KC1vs. K2SO4 fertilization on the growth of healthy and take‐all infected spring wheat.Transpiration and diffusive resistance were measured in the flag leaves. The flag leaves of healthy plants had the highest rate of transpiration.Transpiration declined with higher incidence of Gaeumannomyces grminis var. trutici (Ggt).With low soil moisture and also with sulphate fertilization transpiration tended to be lower.The difference between sulphate and chloride fertilization was relatively greater in more severely affected than in healthy plants, in particular with lower soil moisture. The flag leaves of plants were maintained in a green state for a longer period of time by chloride fertilization. This indicates a higher and prolonged metabolic activity which is reflected in the grains yields. Yield depressions as a consequence of Ggt infection were smaller with KC1 than with K2SO4 fertilization and more marked under water stress than with optimal water supply.
Studies on the Diagnosis of Bacterial Ring Rot of Potatoes
Authors: Zeller W. , Xie Y.
Published: May 2008

The eggplant test, described by Olsson (1976) and Lelliott and Sellar (1976) as a means of detecting Corynebacterium sepedonicum, the causal agent of bacterial ring rot, has been tested for its reliability. Eggplants inoculated with a pure suspension of bacterial cells developed typical chlorotic symptoms at a minimum concentration of 2 × 103 cells/ml inoculum. Whereas with an inoculum which consisted of potato tissue equally mixed with the bacterial suspension, the first symptoms developed at a concentration of 104 cells/ml. Reisolation of the pathogen by the IFAS‐test or on YDC‐medium was possible following innculation at a concentration of 2 × 103 cells/ml. It was mostly possible to isolate the bacteria in pure culture. Further solanaceous host species tested in comparison with the eggplant did not develop typical symptoms following inoculation with C. sepedonicum. On this account, the eggplant test should currently be considered as the most suitable biological assay to detect C.sepedonicum.
On the Enhanced Callose Deposition in Barley with ml‐o Powdery Mildew Resistance Genes
Authors: Skou J. P.
Published: May 2008

Carborundum treatment of barley leaves induced a callose deposition which was detected as diffuse blotches in the epidermal cells of susceptible barleys and as deeply stained tracks along the scratches in barleys with the ml‐o powdery mildew resistance gene. Subsequent inoculation with powdery mildew resulted in appositions that enlarged inversely to their size in the respective varieties when inoculated without carborundum treatment.

Aphids sucking the leaves resulted in rows of callose containing spots along the anticlinal cell walls. The spots were larger in the ml‐o mutant than in the mother variety.

Callose was deposited in connection with the pleiotropic necrotic spotting in barleys with the ml‐o gene. Modification of the necrotic spotting by crossing the ml‐o gene into other gene backgrounds did not result in any change in the size of appositions upon inoculation with powdery mildew.

Callose deposition was never observed in cells subsidiary to the guard cells, and the absence of callose in such cells is suggested to be the reason for the sporadic occurrence of powdery mildew colonies on barleys with the ml‐o gene.
Water Stress‐Induced Changes in the Morphology of the Powdery Mildew, Leveillula taurica (Lèv.) Arn.
Authors: Caesar J. Cartey , Clerk G. C.
Published: May 2008

Water stress in Capsiucm annuum L., induced by means of polyethylene glycol influenced the length and branching frequency of conidiophores and conidial dimensions of the powdery mildew, Leveillula taurica (Lèv.) Arn. Conidiophore branching frequency and length as well as conidial length and width decreased with decreasing relative water content. The availability of water to host plants seems to have a direct effect on the growth vigour and development of the powdery mildew possibly is suggested that water stress may be imposed on host plants by the dry harmattan season resulting in reduced growth vigour of the powdery mildew. Morphology of powdery mildew developing under low water potential may be altered.
Einfluß von Tricyclazol auf die Entwicklung und Melaningehalte der Sklerotien von Botrytis cinerea
Authors: Zeun R. , Buchenauer H.
Published: May 2008

Effect of tricyclazole on production and melanin contents of sclerotia of Botrytis cinerea

Tricyclazole retarded production of sclerotia of Botrytis cinerea on agar medium more severely than mycelium growth. At a concentration range (50–200 mg/l) that did not control Botrytis on grape leaves, sclerotia production was significantly reduced. There was a negative relation between the bleaching duration of sclerotia and the tricyclazole concentrations in the medium on which they were formed. Light microscopical studies showed that sclerotia from tricyclazole‐containing medium contained a significantly poorer developed outer melanin layer than that from the control medium. Ultrastructural studies with 5 days old untreated sclerotia revealed intense electron impermeable deposits in the intercellular spaces and a small electron dense layer in the outer cell walls, on the other hand treated sclerotia of the same age showed only sporadic small pigmented deposits between the cells and the pigmentation of the outer cell wall was absent.
Rôle de L'éthylène dans L'Accumulation de Capsidiol et la Sensibilité a Phytophthora capsici chez le Piment Traite par un Eliciteur
Authors: Molot P. M. , Toppan A. , Mas P.
Published: May 2008

Role of ethylene in both the synthesis of capsidiol and the susceptibility to Phytophthora capsici of pepper treated with an elicitor

With inoculated plants, there is a strong increase of ethylene, specially with Phyo 636. But, with plants inoculated and treated with G5 15 the quantities of ethylene are less important than with those ones inoculated and untreated with G5 15.

After contamination (and only in this case), there is capsidiol synthesis as well wit h treated plants as with untreated ones, and the quantities are not significantly different.

Generally, the level of induced resistance is higher wit h Phyo 636 (genetically resistant) than with Yolo Wonder (genetically susceptible).

The adjunction of ethylene precursor (ACC) to G5 15 elicitor increases induced resistance with Yolo Wonder but decreases with Phyo 636: the inverse effect is observed when using ethylene inhibitor (AVG).

It is suggested that, in the interaction Pepper—Phytophthora capsia, neither ethylene production nor capsidiol synthesis can be considered as biochemical tracers of induced resistance.
Dispersal of Septoria nodorum Pycnidiospores by Simulated Raindrops in Still Air
Authors: Brennan R. M. , Fitt B. D. L. , Taylor G. S. , Colhoun J.
Published: May 2008

Simulated raindrops, diameter c. 3 or 4 mm, fell 13 m down a raintower onto suspensions of Septoria nodorum pycnidiospores, depth 0.5 mm, or infected straw pieces. Splash droplets were collected on pieces of fixed photographic film. It was estimated that one drop generated c. 300 spore carrying splash droplets, containing c. 6000 spores, from a concentrated spore suspension (6.5 × 105 spores/ml) and c. 25 spore‐carrying droplets, containing c. 30 spores, from infected straw pieces (11 × 106 spores/g dry wt).

When the target was a spore suspension in water without surfactant, most spore‐carrying droplets were in the 200—400 μm size category and most spores were carried in droplets with diameter >1000 μm. When surfactant was added to spore suspensions, most spore‐carrying droplets were in the 0–200 μm category and most spores were carried in droplets with diameter 200–400 μm and none in droplets >1000 μm. Regression analyses showed a significant (p < 0.001) relationship between square root (number of spores per droplet) and droplet diameter; the slope of the regression line was greatest when surfactant was added to the spore suspensions.

The distribution of splash droplets with distance travelled from the target was better fitted by an exponential model than by power law or Gaussian models. The distributions of spore‐carrying droplets and spores with distance were fitted better by an exponential model than by a power law model. Thus regressions of log, (number collected) against distance were all significant (p < 0.01); the slopes of the regression lines were steepest when surfactant was added to the spore suspension. At a distance of 10 cm from target spore suspensions most splash droplets and spore‐carrying droplets were collected at height 10–20 cm, with none above 40 cm; at a distance of 20 cm there were most at heights 0–10 cm and 40–50 cm.
Modulation des Réactions de Défense du Palmier a Huile Contre le Fusarium oxysporum f. sp. elaeidis (Schlecht) Toovey: Applications: Prémunition et Stimulation Chimique
Authors: Taquet B. , Ravisé A. , Renard J. L. , Kunesch G.
Published: May 2008

Defence reactions of palm trees to Fusarium oxysporum f. sp. elaeidis (Schlecht) Toovey Cross protection and stimulation of inhibitory substances

In palm tree genetic characters of tolerance to Fusarium oxysporum f. sp. elaeidis are correlated with synthesis of fungal inhibitors in infected tissues. Individual variation of synthesis level is also observed among plants of a same line. Defence reactions are triggered by pre‐inoculation of an avirulent strain of Fusarium oxysporum. Similar results are obtained by application of analogs of fungal elicitors like arachidonic acid. Quite the contrary, treatment of plants with a competitive inhibitor of PAL downs natural barriers and in a same way the effects of cross protection and arachidonic treatment. Seven phenolic compounds, mainly benzoic acid derivatives, inhibit in vitro the growth of pathogen like spores germination. The variability of the host reaction and its stimulation by elicitors could be used to improve the resistance.
Mise en Évidence d'une Induction de Résistance chez le Piment et la tomate Après Absorption par les Racines d'une Fraction Élicitrice Hydrosoluble
Authors: Molt P.M. , Mas P.
Published: May 2008

Resistance induction on pepper and tomato after dipping roots into watersoluble elicitor

Fractions issued from Phytophthora casici culture filtrate are generally tested for the elicitor activity on detached cotyledons, Another technic is proposed: young plants (pepper or tomato) are uprooted and their roots dipped into elicitor; after detaching the foliar organs, resistance induction is controlled against Phytophthora capsici or Phytophthora infestans.

With pepper, dipping time optimum is about 48 hours; the leaves are better protected than the cotyledons.

After elicitation and transplanting, resistance induction remains at the level of the leaves during about one month (50% protection) and decreases progressively beyond.

Systemicity of induction is discussed and several hypothesis proposed.
Host‐Parasite Relationship in a Susceptible and a Resistant Rose Cultivar Inoculated with Sphaerotheca pannosa: I. Fungal Growth, Mechanical Barriers and Hypersensitive Reaction
Authors: Conti G. G. , Bassi M. , Maffi D. , Bonecchi R.
Published: May 2008

Conidial germination and development of Sphaerotheca pannosa were studied on a susceptible and a resistant cultivar (rose Cardinal and rose Queen Elisabeth, respectively) in relation to the morphology of the leaf surface which was examined by scanning and transmission electron microscopy.

Conidial germination was completed within 24 h in both cultivars and seemed to be higher in the resistant cultivar; fungal development, however, was stopped when the haustoria containing cells became necrotic.

The only morphological difference between the leaves of the two cultivars is a thinner cuticle in rose Cardinal. Wax deposits on the leaf surface are similar; a layer of substances reacting to rhutenium red, most likely glycoproteins or protein‐polysaccharide complexes, also are similar.
The Susceptibility of Monocotyledons to Agrobacterium tumefaciens
Authors: De Cleene M.
Published: May 2008

The susceptibility of 257 monocotyledon species belonging to 139 genera and 27 families, has been tested and the literature on this subject reviewed. In contrast with dicotyledons and gymnosperms, monocotyledons are much less susceptible to Agrobacterium tumefaciens: only 3 % of the species of monocotyledons tested were host plants, whereas 60 % of the dicotyledons and gymnosperms were susceptible. Only the closely related monocotyledon orders Liliales (6 families) and Arales (1 family) contained species that were susceptible. These results are consistent with a proposed taxonomic relationship between the Liliales and the dicotyledons. A correlation between host biochemical capabilities and susceptibility to crown gall is suggested.
Spore Deposition Velocities Measured Over a Barley Crop
Authors: McCartney H. A. , Bainbridge A. , Stedman O. J.
Published: May 2008

Deposition velocities, vg, to horizontal slides were measured over a barley crop for a range of air spora. Slides were either freely exposed, placed on a 60 cm2 table or placed in a large beaker. Deposition velocities calculated from the spore catch on freely exposed slides were 2–3 times the sedimentation velocity for all spore classes. While exposure of slides in protected enclosure reduced turbulent deposition, the values of vg were still almost twice the sedimentation velocity. Thus caution must be advised when interpreting such deposition measurements in terms of spore concentration.
Monitoring of Virulence in Populations of Pbytophthora infestans Using a Schwarzbach Spore Trap
Authors: Skidmore D. I. , Shattock R. C.
Published: May 2008

A modified Sehwarzbach jet spore trap was used to sample Phytophthora infestans populations in small crops of potato within polyethylene tunnels and in the field. Airborne sporangia were eaptured in the trap and deposited upon potato leaf discs, of a cultivar lacking race‐specific resistance genes, contained within the trap. Virulence characters of isolates captured in the spore trap were determined by subculturing the isolates on leaf discs of a range of potato genotypes with race‐specific resistance (R‐genes), incubating them and then recording compatible and mcompatible reactions, reactions. For four isolates of P. infestans the levels of sporulation on the differential leaf discs were noted and although cultivar × isolate interactions were inconsistent, variable light and temperature conditions had no significant effect on the reactions of the cultivars.
A Possible Role for Ferrous Complexes in Fungal Disease Suppression: Glume Blotch and Net Blotch of Cereals
Authors: Brown A. E. , Sharma H. S. S.
Published: May 2008

Germination of spores of Septoria nodorum and Pyrenophora teres was inhibited and germ‐tube growth in germinated spores was reduced b y ferrous ions complexed with a number of cheiating agents. No such inhibition was observed with ferric complexes and none of the chelating agents in the desferri form was toxic to the fungi. The germination mechanism in spores suspended in ferrous‐2,3‐dihydroxybenzoic acid (Fe11‐DHBA) for 24 h could not subsequently be released to any great extent by incubation with ethylenediamjne‐di (o‐hydroxyphenyl‐acetic acid) (EDDHA).

Lesion development by the fungi in the presence of ferrous complexes on detached leaves of host plants was almost totally suppressed, but compounds which preferentially chelate ferric ions, used in the desferri form significantly stimulated lesion development by S. nodorum on wheat leaves. Cermination, appressorium formation and lesion development on leaves of host plants were also significantly reduced by Fe11‐DHBA when plants were sprayed to run‐off up to 5 days prior to inoculation.

Disease development and subsequent 1000 grain weight loss were reduced by approximately 50 percent in wheat and barley plants when the flag leaves were treated with Fe11‐DHBA (5 × 10−4 M) prior to inoculation with S. nodorum and P. teres respectively, compared with inoculated, untreated plants.
Effect of Cuticle Treatments on Infection of Phaseolus vulgaris by Rhizoctonia solani
Authors: Stockwell Virginia , Hanchey Penelope
Published: May 2008

Rhizoctonia solani, the causal agent of stem canker of beans, does not commonly infect beans more than two weeks old. Treatment of the cuticular layer by abrasion or chloroform rinsing results in decreased cuticular autofluorescence and the ability of stains to penetrate the hypocotyl surface. Infection cushions preferentially formed near these treated areas on both young and old plants. The morphology of infection cushions on older plants is simpler than those found on young, susceptible plants, but they are fully competent to form lesions.
The Adsorption of a Polygalacturonase Isoenzyme of Botryodiplodia theobromae on Plant Tissues and the Implication on the Pathogenicity of the Fungus
Authors: Arinze A. E.
Published: May 2008

The polygalacturonase isoeazyme (PG 3) of Botryodiplodia theobromae extracted from rotted sweet potato was adsorbed by sweet potato, potato, carrot, bean stem and tomato fruit to various degrees. Adsorption was greater with sweet potato and tomato fruit tissues. Carrots, bean stem and potato absorbed the enzyme to more or less the same degree. The enzyme was not adsorbed on tomato stem. A spore/mycelial suspension of B. theobromae infected the test tissues to various degrees. The enzyme completely macerated sweet potato roots, potato tubers and tomato fruits within 5 h while the bean stem and onion tissues were little affected by the enzyme. The tomato stem was neither infected by the fungus nor macerated by the enzyme.
Interactions between the vesicular‐arbuscular mycorrhizal fungus Glomus fascicuhtum and Aphanomyces euteiches root rot of peas
Authors: Rosendahl S.
Published: May 2008

Interactions between Glomus fasciculatum and Aphanomyces euteiches root rot of peas (Pisum sativum), were studied in pot experiments using irradiated soil.

Infections with the pathogen were suppressed by VAM when plants were challenge inoculated after two weeks. No reduction of the pathogen was detected when the plants were inoculated with both fungi at the same time.

The suppression of the pathogen, obtained by preinoculation with G. fasciculatum, was not reduced when the inoculum level of the pathogen was increased thirty times.

The induced resistance to A. euteiches in VAM plants was partially a systemic effect. When root systems were split into two halves, one with mycorrhiza and one with A. euteiches, the oospore production was reduced in both root systems. The infection with the pathogen was only suppressed when both fungi were present in the same pot. The background for the induced resistance is discussed.
Cytopathologie von viroid‐infiziertem Pflanzengewebe
Authors: Rosenberg Francis , Wahn K. , Sänger H. L.
Published: May 2008

Cytopathology of viroid‐infected plant tissue

II. Light‐ and electron microscopical investigations on the leaf tissue of the Chrysanthemum morifolium cultivar “Mistletoe” after infection with the chrysanthemum stunt viroid (CSV)

The infection of the Chrysanthemum morifolium cultivar “Mistletoe” with the chrysanthemum stunt viroid (CSV) leads to the appearance of numerous yellowish leaf spots 2–5 mm in diameter. The cells of these chlorotic leaf areas were investigated by phase contrast‐ and electron microscopy and compared with the cells of the adjacent green tissue and the tissue of healthy plants. Phase contrast microscopy showed that the chlorotic tissue containes about 50 % more cells per area and that their size is reduced by 30–60 %. The parenchymatic cells of the xylem and phloem are irregular and their walls are malformed. In these cells the chloroplasts are reduced to about half in their size and number.

In the electron microscope an accumulation of osmiophilic material between the thylakoid membranes of the chloroplasts of the chlorotic cells and a deterioration of the chloroplast stroma can be observed. Moreover, malformations of the cell wall and in the cell wall‐associated plasmalemma‐somes are found, which lead to an increase in contrast and to irregularities of their surface and internal structure. The most prominent CSV‐specific cytopathic effect in cells of the vascular tissue is the extreme accumulation of microfilament bundles which were analysed in detail with the aid of a goniometer. The observed viroid‐induced ultrastructural changes are compared with previously described changes caused by conventional plant viruses and the possible functional implications are discussed.
Virulence and Enzyme Production of Erwinia carotovora ssp. atroseptica on Potato Tuber Tissue
Authors: Weber Jürgen , Wegener Christina
Published: May 2008

The elicitation of pathogenesis on potato tuber slices by 6 strains of Erwinia carotovora ssp. atroseptica was investigated by neutral red vital staining and has been compared with bacterial growth rate, penetration ability, enzyme production and enzyme spectrum. The induction of enzyme synthesis (particularly, of the extracellular polygalacturonase) elicites the rot attack on tuber tissue and this requires a sufficient bacterial density.

Due to wound healing, the inductors of enzyme production are removed, and after 48 h enzymes do not attack tuber tissue any more. Therefore, growth rate and penetration ability (to get the necessary bacterial density and inductor substances) may limit virulence. A similar influence of enzyme production and enzyme spectrum of the strains on the virulence was not detected.
Uptake, Translocation, Distribution and Persistence of 14C‐Metalaxyl in Pearl Millet (Pennisetum americanum) [L.] Leeke)1
Authors: Singh U. S. , Tripathi R. K. , Kumar J. , Dwivedi T. S.
Published: May 2008

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

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

During a four year study it was shown that the mean lesion area (M.L.A.) developed on leaflets of different potato cultivars by isolates of P. infestans after artificial inoculation varied periodically during the year.

Disease symptoms observed changed from pinpoint necroses to regular sporulating lesions depending on the season and the cultivar.

Analysis of variance revealed that differences in lesion size between experiments performed in different seasons were significant. The largest M.L.A. was found in late spring or in autumn but autumnal increase of M.L.A. was usually significantly lower than that in spring.

Periodicity of M.L.A. was accompanied by a similar phenomenon in sporulation density of P. infestans isolates cultured in vitro. However, the peaks of sporulation, in comparison with peaks of M.L.A. appeared in different seasons. The highest disease level coincided with a decline in sporulation density of P. infestans cultured in vitro and the decrease of M.L.A. corresponded with an increase in sporulation density per cm2 of medium.

Variation in M.L.A. found in this study seemed not to be related to variability in plant reaction. In this connection a hypothesis has been proposed that the changes of M.L.A. were due to variation in pathogenicity of the fungus.
Parassitismo di Trichoderma harzianum su cistosori di Polymyxa betae
Authors: D'Ambra V. , Mutto S.
Published: May 2008

Parasitism of Trichoderma harzianum on Cystosori of Polymyxa betae

Transmission electron microscope investigations revealed that cystosori of Polymyxa betae Keskin are, in vitro conditions, parasitized and completely degraded by Trichoderma harzianum Rifai. The hyperparasite showed a high ability in colonizing excised, surface‐sterilized lateral roots of sugar beet and in invading the cystosori present in them. Both the walls of the root cells and of the cysts are enzymatically perforated. However, in cysts penetration, mechanical forces are also involved. After penetration, cysts undergo a rapid degradation and finally they appear to be completely empty or to contain only small amounts of degradated cytoplasm.

Cyst walls are also strongly altered and deformed and only two thin osmiophylic residual layers are detectable.