bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of the Reaction Sites Associated with the Resistance of Coleoptiles of Barley, Oats and Wheat to Infection by Septoria nodorum
Authors: Hargreaves J. A. , Keon J. P. R.
Published: May 2008

A novel technique has been developed to inoculate the outer epidermal cells of coleoptiles of barley, oats and wheat with S. nodorum. Using this technique, which results in a large number of attempted penetrations, the composition of the material deposited at unsuccessful penetration sites in these cereals have been compared. Although the deposits reacted in a similar manner with some histochemical reagents (ammoniacal silver solution, Coppick‐Fowler reaction, p‐nitrobenzene tetrafluoroborate and Coomassie brilliant blue R250) marked differences occurred between the reactions sites formed by barley and wheat and by oats with other stains (bromophenol blue, nile blue sulphate and Toluidine blue). Chemical treatments used to delignify tissue also revealed differences in these reaction sites. It is concluded that although the reaction sites share some similar components there are significant differences in their chemical structure.
Studies on the Relationship of Urdbean Leaf Crinkle Virus and its Vectors, Aphis craccivora and Acyrthosiphon pisum
Authors: Bhardwaj S. V. , Dubey G. S.
Published: May 2008

Pre and Post‐virus‐acquisition starvation of Aphis craccivora Koch, and Acyrthosiphon pisum Harris resulted in appreciable increase in percentage of transmission of urdbean leaf crinkle virus. Highest transmission occured when aphids were starved for 90 min prior to virus‐acquisition. A. pisum and A. craccivora on 20 and 80 min of post‐acquisition starvation and 10 and 20 min of virus‐acquisition, respectively inoculated more number of plants. Both the aphids transmitted the virus in probes lasting for one min. However, beyond 5 min of successive transfer on test plants loss in transmissibility was apparent. Viruliferous aphid off the plant retained the virus for a much longer period than on maize plant. The virus appears to be non‐persistently borne in the aphids.
Protection of Wheat Seedlings from Helminthosporium Infection by Seed Treatment with Chemicals
Authors: Hait G. N. , Sinha A. K.
Published: May 2008

Twenty of twenty‐four chemicals known to induce phytoalexin production in other plants, when used to soak seed, provided effective protection to 3‐week‐old susceptible wheat seedlings against inoculation with Helminthosporium sativum. The number of lesions was very significantly reduced in most of these treatments and there was evidence for inhibition of lesion expansion in a few. Studies with twelve of the more effective chemicals showed that the protective effect persisted at significant levels even in 5‐week‐old plants and that at this stage the inhibitory effect on lesion expansion was more pronounced in most of the treatments. Different treatments led to the development of a moderate to high level of fungitoxicity in young wheat seedlings which gradually declined with age of the plant and disappeared in 5‐week‐old plants. When inoculated at the age of 3 or 5 weeks, plants receiving most of the treatments developed appreciably higher fungitoxicity than the untreated plants.
Detection of Zucchini Yellow Mosaic Virus in Intact Leaf Disks and Tissue Extracts by Enzyme‐Linked Immunosorbent Assay
Authors: Menassa R. , Makkouk K. M. , Abbasher A. A.
Published: May 2008

An indirect enzyme‐linked immunosorbent assay (ELISA) was used for the detection of zucchini yellow mosaic virus (ZYMV) in cucumber tissues and in its aphid vector Myzus persicae Sulz. Results showed that the indirect ELISA was more sensitive, than the direct ELISA for ZYMV detection. Indirect ELISA detected ZYMV in leaf disks as well as in leaf extracts, and four 6‐mm‐diameter leaf disks per well were found sufficient for reliable ZYMV detection. In addition, the readings with virus‐free leaf disks were much lower than those of leaf extracts. When using leaf disks, it is possible to shorten the indirect ELISA protocol to one working day but with reduced sensitivity. ZYMV was also detected in its aphid vector by the indirect but not with thedirect ELISA. The best extraction buffer for aphids was found to be 0.2 M phosphate at pH 6.0. However, the difference between the ELISA readings of viruliferous and virus‐free aphids was always very small, and results were not always reproducible.
Quantitative Analysis of the Early Powdery Mildew Infection Stages on Resistant Barley Genotypes
Authors: ANDERSEN J. B. , TORP J.
Published: May 2008

A classification system was developed, that allowed quantification of the leaf surface development of the barley powdery mildew fungus on barley. An experiment with Manchuria and Pallas as susceptible controls and 4 resistance gene each represented by three lines with different gene backgrounds showed two types of gene background effects. First a general effect comprised of different distributions of the elongating secondary hyphae (ESH) in the stomatal and interstomatal region between Manchuria and, Pallas, and a higher number of lobes per appressorium on Pallas than on Manchuria. These effects also applied to isolines of Manchuria and Pallas possessing each of the four genes investigated. Second a specific effect was noticed on the ESH frequency on Ml‐k lines. The ESH frequency varied significantly at the 5% level between the highest and lowest value.

An experiment with Pallas as susceptible control and Pallas isolines with 11 different resistance genes, showed that powdery mildew development was unaffected by host genotype until after the formation of an appressorium. The first host effect observed was on the number of lobes on the appressorium, which reflects the number of penetration attempts. This number increased as the degree of resistance increased, i.e. the ESH frequency decreased. The penetration stage also invariably proved to be the limiting stage, where the largest proportion of fungal propagules was stopped.
Quantitative Differences in Powdery Mildew Resistance Among Spring Barley Cultivars
Authors: Heun M.
Published: May 2008

Quantitative powdery mildew resistance in compatible host‐pathogen‐combinations was measured by the number of pastules/cm2 leaf area. Spring barley cultivar ‘Proctor’ was significantly less infected than ‘Golden Promise”. Using these two cultivars (having no effective major resistance gene) as controls, MO‐ and AR‐resistant cultivars were inoculated with virulent mildew isolates. ‘Mona”, ‘Grit’ and ‘Nudinka’ had a higher or, at least, the same level of quantitative resistance as ‘Proctor”. None of the remaining cultivars showed the high susceptibility expressed by ‘Golden Promise”. Ranking of host genotypes was nearly constant while that of mildew isolates varied considerably. Only a small portion of the observed variance was due to interaction between host cultivars and pathogen isolates.

‘Triesdorfer Diva’ gave a resistant infection type after inoculation with different AR‐virulent isolates, indicating that this cultivar has major resistance other than that conditioned by gene Ml‐a12.
The Detection of the Abutilon Mosaic Virus Depends on the Experimental Daytime
Authors: Jeske H.
Published: May 2008

Fluorescence and electron microscopical studies show that the detection of structures associated with the Abutilon Mosaic Virus disease is dependent on the sampling daytime. Moreover the infectivity of plant sap may vary during the day. The results emphasize the importance to consider the daytime as an essential parameter in experimental design in virological research.
Association of Mycoplasmalike Organisms (MLOs) with Mild Type of Hydrangea virescence: A Study with 60–1000 nm Thick Sections
Authors: Marie‐Thérèse Cousin , Sharma A. K.
Published: May 2008

The study of the agent associated with the mild type of Hydrangea virescence in France involved three steps, with the aid of transmission electron microscope (TEM). In the first step, we observed the presence of polymorphic procaryotes in thephloem sieve tubes of diseased plants and their absence from corresponding healthy plant parts. The procaryotes were detected in the areas suspected in 1000 nm thick sections stained with thionin‐acridine orange. In the next step, the ultrastructure of their unit membrane was studied at magnifications higher than 100 000. The two osmiophilic layers of the membrane were 6 nm distant and no preliminary parietal shape was detected. These observations on ultrathin (60 nm) sections allowed us to classify the, particles into the class “Mollicutes”. The third step involving the examination of 350–1000 nm thick sections revealed the absence of spiral forms.

The TEM observations are consistent with the hypothesis that the agents associated with the mild type of Hydrangea virescence observed in France should be included within the MLO group. A method specially adjusted to the fixation of MLO inside sieve tubes has been mentioned.
Phenols in Cotton Seedlings Resistant and Susceptible to Alternaria macrospora
Authors: Yoav Bashan
Published: May 2008

In healthy cotton seedlings, stems have a lower phenol content than leaves, but resistant plants have an altogether relatively higher phenol content than susceptible plants. Phenols extracted from infected plants can inhibit the growth of A. macrospora in vitro. In cotton plants infected with A. macrospora, phenols are oxidized by polyphenoloxidase rather than peroxidase and catalase. The main oxidative activity was around the developing necrotic area but activity was detected far from, necrosis as well. Though pre–inoculation mechanical injuries operated the phenol oxidation mechanism in the plant, they neither prevented nor encouraged the increase in disease severity. Isozyme pattern showed that contribution of all participants in the pathological interaction to the oxidative mechanism occurred in the diseased plant. A negative linear correlation was found between polyphenoloxidase activity, phenol accumulation and resistance. This study suggests that the phenol oxidative mechanism, participates in cotton plant resistance to A. macrospora.
Induction of Resistance in Cucumber to Colletotrichum lagenarium by 6–benzylaminopurine
Authors: Mills P. R. , Gussin E. J. , Wood R. K. S.
Published: May 2008

Application of 6–benzylaminopurine to cucumber leaves before inoculation with Colletotrichum lagenarium substantially decreased lesion development; decrease was accompanied by an increase in certain plant metabolites. Leaves systematically protected from infection by C. lagenarium by earlier inoculation with the same pathogen showed similar decrease in lesion size without increases in these metabolites.
Changes in Mineral Content ofEucalyptus marginataandE. calophyllaGrown under Controlled Conditions and Inoculated withPhytophthora cinnamomi
Authors: Cahill D. , Wookey C. , Weste G. , Rouse J.
Published: May 2008

Mineral concentrations in infected roots and shoots were compared with similar material, but pathogen free, for the susceptibleEucalyptus marginataand the field resistantE. calophylla.All plants were mycorrhiza‐free, grown under controlled conditions and inoculated with an axenic suspension of zoospores ofPhytophthora cinnamomi.Plant material was ashed 30 days after inoculation and analyzed in an external proton beam using PIXE and nuclear reaction analyis to detect differences in mineral concentrations.

The mineral content of infected roots ofE. marginatawas below that of the uninfected roots for all elements detected except chlorine, chromium and rubidium. The reductions were significant for calcium and copper. No such reduction was found, inE. calophyllaroots, but some changes were detected. Shoot: root ratios ofE. marginatashowed significant differences associated with infection in phosphorus, calcium, copper and zinc. Relatively large differences were also recorded for sulphur chlorine and potassium. Shoot: root ratios of infectedE. calophyllashowed fewer differences but contained only half the concentrations of sulphur and potassium present in the controls.

The reduced mineral concentrations reflect the failure in conduction of water and minerals through the infected and susceptible root system.
Elution Profiles of Pisatin Elicitor Activity from Extracts of Monilinia fructicola, Pisum sativum and Diffusates from their Interaction*
Authors: Cruickshank I. A. M. , Smith M. M.
Published: May 2008

Pisatin elicitor activity was examined in diffusate of the M. fructicola–pea endocarp interaction, leachate of pea endocarp, extracts of ungerminated conidia and filtrates of conidia germinated in vitro in a simple nutrient broth, or in filter–sterilized diffusate or pea leachate. Extracts were made after 18 h incubations which represents the half–time of the primary phase of pisatin accumulation in the M. fructicola–pea model system. These were chromatographed on a Bio–Gel, P–2 column and elicitor activity in eluate fractions was located by bioassay for the ability to induce pisatin accumulation.

A characteristic elution profile of pisatin elicitor activity was obtained from diffusate of the pea–M. fructicola interaction. Other preparations obtained from pea leachate, ungerminated conidial extracts or culture filtrates of the fungus germinated in a simple nutrient broth or pea leachate (6 h) did not contain the same profile of elicitor components. No further production of elicitor was detected in early diffusate (6 h) filtrates when they were incubated in vitro alone or withM. fructicola. Elicitor activity was significant in some conidial germination filtrates in vitro. The elution profiles of elicitor activity obtained from these filtrates were shown to be dependent on the physical conditions of culture used (still or shaken).

Incubation of the pea leachates with M. fructicola in vitro resulted in the formation of a high molecular weight elicitor which did not correspond with that of the diffusate preparations. Its reapplication to pod tissue did not suggest that it was significantly metabolized by pea tissue to produce the same elicitors found in diffusate preparations.

The results emphasize the importance of in vivo studies in the search for elicitors of phytoalexins where two living systems, the plant and the fungus are intimately involved.
Acquired resistance of Alternaria solani and Sclerotium rolfsii to Polyoxin‐D
Authors: Maria Rose , Sullia S. B.
Published: May 2008

Acquired resistance to the antibiotic polyoxin‐D was studied in two phytopathogenic fungi, Alternaria solani Sorauer, and Sclerotium rolfsii Sacc. The ED50 value of the antibiotic for A. solani was 100 μg/ml and S., rolfsii 200 μg/ml. A. solani and S. rolfsii could be trained to tolerate concentrations upto 1.000 μg/ml and 2.200 μg/ml respectively. The acquired resistance in both cases was not lost on continued subculturing in fungicide‐free, media. On transfer to fungicide‐free media, Polyoxinresistant strains of both the fungi showed faster growth rate and appreciable reduction in sporulation compared to the original strains. The adapted strain of A. solani showed cross‐resistance to Cycloheximide and Difolatan but not to Hinosan and Bayleton.
Soil‐Behaviour of Phytophthora clandestina
Authors: Wong D. H. , Sivasithamparam K. , Barbetti M. J.
Published: May 2008

Investigations were undertaken to study the nature and behaviour of P. clandestina in soil. The pathogen was recovered only from soil sievings 250–499 μm and 500 μm–0.99 mm, containing small root fragments. In soil the introduced inoculum of the fungus was incapable of saprophytically and competitively colonizing the dead cotyledons of subterranean clover used as bait material. Exposure of the inoculum to increasing numbers of microbes by adding greater proportions of nonsterile fields, oil to the growth medium of the plant had no significant effect on survival rate and fresh shoot weight of subterranean clover. However, microbes present in the field soil reduced the severity of root rot of subterranean clover. P. clandestina was, able to spread between 15–30 mm through pasteurized soil within a period of 20 days.
Elimination in vitro of two Grapevine Nepoviruses by an Alternating Temperature Regime*
Authors: Monette P. L.
Published: May 2008

A 40 day in vitro treatment with 6 h at 39°C followed by 18 h at 22°C was effective in eliminating both grapevine fanleaf virus (GFLV) and arabis mosaic virus (AMV) from the developing shoot tips (2 mm) of grapevine shoot tip cultures. Longer treatment durations with consecutive 12 h periods at 35°C and 22°C eliminated GFLV in some cases, but did not eliminate AMV.
Studies on Antifungal Properties of Essential Oil of Trachyspermum ammi (L.) Sprague
Authors: Tripathi S. C. , Singh S. P. , Dube S.
Published: May 2008

The essential oil from the fruits of Trachyspermum ammi exhibited toxicity at 800 ppm against Aspergillus flavus and A. niger, the nature of toxicity being cidal. The toxicity of the oil was not affected by autoclaving, temperature treatment and storage upto 365 days. The oil killed the test fungi within 50 seconds; withstood heavy inoculum density and was inhibitory to as many as 21 fungi at its minimum inhibitory concentration. However the seeds of Arachis hypogea whentreated with oil at 5000 ppm and stored for 12 months did not show the appearance of any fungi indicating thereby the grain protectant activity of the oil. The oil was characterized by various physico chemical properties and on chemical investigation Thymol and p‐cymene were isolated as antifungal principles of the oil exhibiting toxicity against the test fungi at 1000 ppm.
Postinfectional Changes of Lipid Metabolism in Potato Tuber Resistant and Susceptible to Phytophthora infestans
Authors: Floryszak‐Wieczorek J. , Stroiński A.
Published: May 2008

The effect of Phytophthora infestans on the lipid content and composition as well as lipid acyl hydrolase activity in the potato tuber of two cultivars, Nysa – horizontal resistant and Bintje –susceptible were investigated.

In the susceptible cultivar the infection resulted in: a qualitative changes in aminolipids, an increase in steroid content, an inconsiderable decrease in amount of glycolipids and a slight drop in FFA, no significant changes in composition of total, FA and slight loss in acyl hydrolase activity.

The following changes were observed in the resistant cultivar: a considerable enhancement of steroid content (reached in about 400 %), a slight increase in amount of glycolipid, a rapid drop of acyl hydrolase activity and FFA content and a considerable increase in oleic acid level in total FA.

In the response to both infection and aging in both cultivars no significant quantitative changes in lipid‐phosphorus and sulfolipids were noted.
Identification of Acetobacter liquefaciens as Causal Agent of Pink‐Disease of Pineapple Fruit
Authors: Gosselé F. , Swings J.
Published: May 2008

Two bacterial strains causing pink‐disease of pineapple were identified as Acetobacter liquefaciens and compared with 8 other Acetobacter liquefaciens, 10 Gluconobacter oxydans and 7 Frateuria aurantia strains. The similarieties and differences between these bacteria are discussed.
Systemic Migration and Establishment of Xanthomonas campestris pv. pruni in Plum Leaves and Twigs
Authors: du Plessis H. J.
Published: May 2008

The systemic migration of Xanthomonas campestris pv. pruni (Xcp) through vascular bundles of leaves and twigs of plum was investigated. A rifampicin‐resistant strain of Xcp was inoculated into leaves located midway from the tip of new green twigs of Golden King plum trees in a glasshouse. High numbers of the pathogen were recovered 4 and 8 weeks after inoculation from sections of uninoculated and symptomless veins, petioles, and twig tissue. Symptoms of bacterial spot developedwithin 8 weeks on main and secondary veins of uninoculated leaves located as far as 13 cm from the inoculated leaf on the same twig. Weekly isolation indicated the constant presence of Xcp in apparently unaffected shields of twig tissue obtained from a naturally infected Golden King orchard. Xcp apparently enters plum twigs through veins of infected leaves and migrates systemically through twigs to leaves.
Inhibition of Seed Germination and Root Development Caused by Xanthomonas campestris pv. vesicatoria in Pepper and Tomato
Authors: Yoav Bashan
Published: May 2008

Inoculation of pepper seeds with the leaf pathogen Xanthomonas campestris pv. vesicatoria inhibited pepper germination. The inhibitory effect, which was stronger in non‐sterilized light textured soils, decreased with time, and after 20, days or more, there was no difference between inoculated and non‐inoculated seeds. Inhibitory substance(s) within the cytoplasmatic fraction of pathogen cells inhibited the germination of non‐host tomato seeds. No relationship between pathogenicity to pepper leaves and inhibition of pepper seed germination was detected. The inhibitory substance(s) was found in two out of four X. campestris pv. vesicatoria strains. Heat‐killed bacteria suppressed growth of pepper but not tomato seedlings. It is, therefore, suggested that the inhibition of seed germination and the decrease in root development are different modes of X. campestris pv. vesicatoria pathogenesis toward pepper plants.
Presence of Plant Viruses in some Rivers of Southern Italy
Authors: Piazzolla P. , Castellano M. A. , De Stradis A.
Published: May 2008

Water samples were collected from some rivers of Southern Italy whose water is normally used for irrigation and checked for the presence of plant viruses. The assayes were carried out by centrifuging at 5000x g one liter of water, resuspending the sediments in phosphate buffer and testing their infectivities on Chenopodium quinoa Willd. It was possible to isolate tobacco mosaic virus, cucumber mosaic virus and two more viruses not identified yet.
Possible Involvement of Lipoxygenase in the Mechanism of Resistance of Oats to Puccinia coronat avenae
Authors: Yamamoto H. , Tani T.
Published: May 2008

Possible participation of the peroxidation system in the cultivar‐race specificity was studied for the oat‐crown rust system. The levels of lipid peroxidation and total lipoxygenase (LOX) activity were extensively increased in leaves of cv. Shokan l responding with resistance to race 226. One anionic and one cationic LOX isozyme was detected in the extract of Shokan 1 leaves inoculated with race 226. In addition, three anionic and one cationic isozymes were consistently found in the extract of uninoculated and compatible race 203‐inoculated leaves. The blockage experiments with race 226‐inoculated leaves using RNA and protein synthesis inhibitors indicated that the two LOX isozymes characteristic of the incompatible combination are de novo synthesized and their activity is causally linked to the resistance expression. Production of the two isozymes was also demonstrated in the five resistant Pc oat lines, but not in the two susceptible Pc lines.
Isolation and Identification of Eutypa lata from Pistacia vera in Greece
Authors: Rumbos Ioannis C.
Published: May 2008

The fungus Eutypa lata (syn. E. armeniacae), known as the causal agent of the death of many different woody plants, was found on dead branches of pistachio (Pistacia vera L.) in Greece. Isolations from diseased branches yielded consistently typical colonies of the asexual stage of the fungus (Libertella blepharis, syn. Cytosporina sp.), which proved to be undistinguishable from other cultures of the pathogen obtained from 15 different hosts. Furthermore, all isolates from pistachio tested for pathogenicity on apricot were pathogenic and yielded characteristic cankers.
Protein‐Lipopolysaccharide Complexes Produced by Virulent and Non‐Virulent Isolates of Verticillium albo‐atrum and V. dahliae are Non‐Specific Toxins to Tomato and Potato
Authors: Harling R. , Scheffer R. J. , Elgersma D. M.
Published: May 2008

Toxic protein‐lipopolysaccharide complexes (PLPC) were isolated from culture filtrates of Verticillium albo‐atrum (isolate WCS 800) and V. dahliae (WCS 070) isolates, both virulent to tomato and potato cultivars, and from an isolate of,V. albo‐atrum (V22W) which was non‐virulent to these hosts. The virulent isolates each produced one major PLPC in culture and the non‐virulent isolate produced two (fractions 1 and 2, characterized by their elution pattern after gel filtration). Virulence in these three isolates was not related to quantity of PLPC produced in culture. However, PLPC from the virulent isolates were toxic to tomato in a leaf bioassay at 4μg ml‐1 (WCS 800) and 20μg ml‐1 (WCS 070) but the two PL, PC from the non‐virulent isolate required concentrations of 100 and 1000 μg ml‐1 for toxicity. Production of a modified, less toxic PLPC in V22W may partly account for its non‐virulence.

Gel filtration of PLPC from the three isolates on a calibrated Sephacryl S‐400 column, eluted in phosphate buffer plus NaCl, indicated a compound of heterogeneous molecular mass with an average of 126,000 daltons for the PLPC of WCS 800, WCS 070 and, fraction 1 of V22W, and 25,000 daltons for fraction 2 of V22W. Attempts to extract a low molecular weight toxin from the PLPC by extended dialysis were unsuccessful.

The susceptibility of 12 tomato and 19 potato cultivars to the Verticillium isolates was compared with their sensitivity to PLPC. Susceptibility was not correlated with toxin sensitivity and the PLPC were concluded to be non‐specific toxins in these hosts.
In vivo‐Untersuchungen zur Entstehung und Funktion der Chlamydosporen von Botrytis cinerea Pers. am Wirt‐Parasit‐System Fuchsia hybrida – B. cinerea
Authors: Urbasch I.
Published: May 2008

In vivo‐investigations on the formation and function of chlamydospores of Botrytis cinerea Pers. in the host‐parasite‐system Fuchsia hybrida–B. cinerea

On naturally with Botrytis cinerea Pers. infected and artificially inoculated outdoor‐ and greenhouse‐plants of Fuchsia hybrida the extra‐ and intramatrical formation of the B. cinerea‐ chlamydospores was investigated.

The chlamydospores served 1. as structures of survival, which were tested with regard to their tolerance of drought, nutrient‐ and oxygen‐deficiency, attack by bacteria and pH‐requirements. 2. The chlamydospores represented dispersal units, which were capable of germination. 3. The chlamydospores could function as structures of infection, because after chlamydospore germination the outgrowing mycelium – either directly or after production of macroconidia – could serve as secondary inoculum and start new infections.
The Purification and Characterization of Gemini Particles from Abutilon Mosaic Virus Infected Malvaceae
Authors: Abouzid A. , Jeske H.
Published: May 2008

Gemini particles were purified from Abutilon Mosaic Virus infected Abutilon sellovianum, Sida micrantha and Malva parviflora. They sediment with 82 S, possess a density of 1.30 g/cm3 in Cs2SO4 and a nucleic acid percentage of 18 % calculated from ultra‐violett spectrometry. Their proteins are separated in SDS‐PAGE into two components of 28 000 and 27 000 mol. wt. Their nucleic acid consists of single‐stranded circular DNA with length distribution maxima of 2 800, 2 500 and 1 300 bases for the circular molecules and 2 050, 1 850, and 1 300 bases for the correspondmg linear molecules.
Pyrenophora graminea on Winter Barley Seed: Effect on Disease Incidence and Yield Losses
Authors: Porta‐Puglia A. , Delogu G. , Vannacci G.
Published: May 2008

Field experiments were carried out in 1982–83 and 1983–84 in Northern and Central Italy (3 locations) in order to investigate the effect of different levels of seed infection of Pyrenophora graminea on disease incidence and yield losses in ‘Perga’ winter barley.

Six levels of natural seed infection, assessed by the deep‐freezing blotter method have been compared in 8 row‐plots, 7.5 m long, arranged in randomized blocks with 4 replications.

The percentage of infected plants and tillers has been recorded in all locations and the yield in two of them.

A highly significant correlation was found between seed infection, plant infection, tiller infection and yield reduction. Major ratios found were: infected seeds/infected seedlings 1: 0.4, infected tillers/yield loss 1: 0.9, infected seeds/yield loss 1: 0.3.

The threshold of seed infection at which production was not significantly different from the healthy control was 14%. Therefore seed treatment is advisable, under the conditions of Northern and Central Italy, when the percentage of seed infection in commercial seed lots is above this level. A tolerance near zero is recommended in prebasic and basic seeds.
Characterization of Further Erwinia amylovora Strains and the Application of the API 20E System in Diagnosis
Authors: Vantomme R. , Rijckaert C. , Swings J. , Ley J. de
Published: May 2008

The former phenotypic study of Erwinia amylovora (VANTOMME et al. 1982) was extended with a collection of 54 Erwinia amylovora strains from a broad plant and geographic origin. From the 85 phenotypic features studied, 72 (85%) were present in at least 90% of the strains. Only 49 (58%) of the features were shared by all strains. Thirty‐eight strains were also examined by the API 20E system. The API 20E code numbers for E. amylovora are unique and, combined with an immature, (green) pear test, may be used for an accurate identification of Erwinia amylovora.
Factors Affecting the Germination of Septoria nodorum Pycnidiospores
Authors: Brennan R. M. , Fitt B. D. L. , Colhoun J. , Taylor G. S.
Published: May 2008

Most pycnidiospores of Septoria nodorum were released from pycnidia into water in 30 min, more than 50% being released in 10 min. The viability of pycnidiospores in aqueous suspension, assessed by germination on a selective agar medium, decreased more rapidly in daylight than in darkness but no spores germinated after 50 h. The presence of cirrhus extract stimulated germination of pycnidiospores in suspension.
Dynamics of Free Pisatin Elicitor Accumulation in Infection‐droplets of Monilinia fructicola on Pea Endocarp*
Authors: Smith M. M. , Cruickshank I. A. M.
Published: May 2008

Rapid elicitor accumulation in the infection‐droplet of the pea‐M. fructicola interaction began between 2 and 3 h after inoculation. Rapid accumulation of pisatin began between 2 and 3 h, however, low levels (0.06–0.1 μg/ml) were detected in the infection‐droplet as early as 1–2 h following inoculation with the fungus. The pisatin concentration reached levels inhibitory to the fungus between 6 and 12 h (ca. 1–5 μg/ml) and the ED50 value of 10 μg pisatin/ml for mycelial growth of M. fructicola was attained after 14 h.

Elicitor activity in infection‐droplets after 4 and 18 h was a function of inoculum concentration and pisatin accumulation in diffusate after 40 h was a function of elicitor concentration (linear doseresponse curve). However, when elicitor was applied at zero time, the rate of pisatin accumulation over the first 12 h was indistinguishable from that which occurred when M. fructicola conidia were applied to the endocarp and elicitor accumulated with time. The initial rate of pisatin accumulation therefore appears to be dependent on the pea pod and independent of any time delays associated with conidial germination and elicitor accumulation. However, the final pisatin concentration which accumulated in the infection‐droplet was dependent on the, dose' of elicitor irrespective of the nature and timing of the elicitor treatment.

The presence of elicitor activity was demonstrated in the interaction in space and time where and when these molecules could function as elicitors of pisatin in vivo.
Une phytotoxine de Xanthomonas campestris pv. vasculorum
Authors: Ducourneau C. , Auriol P.
Published: May 2008

A phytotoxin from Xanthomonas campestris pv. vasculorum II. Production in vivo

A phytotoxin produced in vitro by Xanthomonas campestris pv. vasculorum has also been detected in infected susceptible host tissues. The toxin shows a strong affinity to a plant cellular fraction leading, in vivo, to a complex the involvement of which in the disease development is discussed.
Mycoplasmalike Organisms (MLOs) Associated With the Witches' Broom Disease of Poplar
Authors: Sharma Ajay Kumar , Cousin Marie‐Thérèse
Published: May 2008

The witches' broom disease has been recently observed on poplars in Paris and its suburbs. The incidence of the disease appeared to be considerably high along main roads. The electron microscopic examination of 350 nm thick sieve tube sections revealed the presence of wall‐less mycoplasmalike organisms (MLOs) in diseased samples of Populus alba var. nivea Wesm. They could not be found in their healthy counterparts.
Cellulolytic and Pectolytic Activity of Cylindrocarpon destructans (Zins.) Scholt. Isolates Pathogenic and Non‐Pathogenic to Fir (Abies alba Mill.) and Pine (Pinus sylvestris L.)*
Authors: Dahm H. , Strzelczyk E.
Published: May 2008

In studies on cellulolytic and pectolytic activity of C. destructans, it was found that only one of the twenty isolates studied exhibited cellulolytic activity. The total activity of this isolate was similar in media with CMC and powdered cellulose. The specific activity was, however, two times higher with powdered cellulose.

All isolates identified as pathogenic to fir and to pine produced pectolytic enzymes. Not all of them, however, exhibited exo‐ and endo‐PMG activity. In general, an increase of total activity of exo‐PMG was accompanied by an increase in the specific, activity. Of the non‐pathogenic isolates, only one did not show pectolytic activity.

The results of our studies have revealed that there exist no significant differences in pectolytic activity between the isolates pathogenic and non‐pathogenic to fir and pine. Also, the isolates belonging to both groups were not cellulolytic except one non‐pathogenic.
Hemmung von Pflanzenviren durch Membranlipidanaloga unter besonderer Berücksichtigung von Alkanmonosulfonaten
Authors: Schuster G.
Published: May 2008

Inhibition of plant viruses by membrane lipid analogs under special regard of alkane monosulfonates

Under investigation was the inhibition of plant viruses by compounds, which could be comprehended as membrane lipid analogs because of some structural similarities to these lipids. Among these analogs, alkane monosulfonates (AMS, preparation “Emulgator E 30”) exhibit distinctly marked antiphytoviral activities, which are reported in detail. The mentioned AMS reduced the concentrations of PVX (potato virus X) as well as of TMV (tobacco mosaic virus) markedly in inoculated leaves of Nicotiana tabacum L. ‘Samsun’ and remarkably in secondarily infected ones. The formation of local lesions on leaves of hypersensitive hosts is influenced strongly by AMS. Likewise, the activity of the free virion is reduced in vitro. The mentioned effectsproved dependent on the length of the alkane chains and the concentration of AMS. Innertherapeutical effects of AMS have been pointed out. Several substances proved excellent coergists of AMS and vice versa, above all DHT (2,4‐dioxohexahydro‐1,3,5‐triazine), several guanidines, a thiourea compound, a thiadiazole compound and ribavirin. In part full synergistic effects were obtained. AMS as well as combinations of AMS with some of the mentioned coergists also influence potato viroses. Using so‐called identical potato eye cuttings, it was demonstrated that the mentioned treatments resulted in a significant and in part considerable reduction of the number of potato eye cutting plants with virus symptoms and in a partially high increase in the weight of tubers formed by the eye cutting plants. Likewise, the number of plants with virus symptoms was reduced and the tuber mass was increased by newly developed granulated AMS. A combined treatment with granulated AMS and granulated DHT resulted in a strong reduction of the number of potato eye cutting plants with virus symptoms, but the tuber mass was not augmented.
Differentiation between Xanthomonas campestris pv. graminis (ISPP List 1980), pv. phleipratensis (ISPP List 1980) emend., pv. poae Egli and Schmidt 1982 and pv. arrhenatheri Egli and Schmidt 1982, by Numerical Analysis of Phenotypic Features and Protein Gel Electrophoregrams
Authors: Van den Mooter M. , Steenackers M. , Maertens C. , Gosselé F. , De Vos P. , Swings J. , Kersters K. , De Ley J.
Published: May 2008

A numerical analysis of 257 phenotypic features of 45 bacterial isolates from grasses, revealed three phenons corresponding to (i) X. campestris pv. graminis (ISPP List 1980), (ii) X. campestris pv. phleipratensis (ISPP List 1980) and (iii) X. campestris pv. poae Egli and Schmidt 1982 and X. campestris pv. arrhenatheri Egli and Schmidt 1982. In each phenon, the strains clustered together regardless of the geographical origin of the isolates orthe year of isolation. Polyacrylamide gel electrophoresis of soluble proteins and host range studies, revealed four groups corresponding to the pathovars mentioned above. The four pathovars constitute definite biological entities that can be differentiated by phenotypic, gel electrophoretic and host range features.
Effect of Macrophomina phaseolina Infection on the Physico‐Chemical Components of Groundnut Seed
Authors: Sharma R. C. , Bhowmik T. P.
Published: May 2008

Various aspects of groundnut seed deterioration due to M. phaseolina infection were studied. Fungal infection caused both quantitative and qualitative damage to the seed. It resulted in characteristic discoloration of pod and kernel. There was marked reduction in the pod and kernel yield, shelling percentage and oil content. The oil extracted from healthy kernels was barium yellow, whereas, oil from diseased kernels was amber yellow in color. The diseased kernels contained lesser amounts ofstearic and behenic acids but higher quantities of palmitic, oleic, linoleic and arachidic acids. Four fatty acids, namely, lauric, myristic, palmitoleic and eicosenoic acids were absent in diseased kernels.
Growth and Nitrogen Fixation Activity of Soybeans in the Presence of Bean Pod Mottle Virus
Authors: Orellana (ret.) R. G. , Reynolds S. L. , van Berkum P.
Published: May 2008

Pathological and physiological responses associated with the host‐microsymbiont interaction of soybeans (Glycine max‘Franklin’, ‘Dyer’, ‘Centennial’, ‘Marshall’, ‘Williams’, ‘Bedford’, and ‘Peking’), which were nodulated with Rhizobium japonicum (USDA strain 3I1b‐110) and inoculated with bean pod mottle virus (BPMV) in the greenhouse, varied with the cultivar and the substrate in which the plants were grown. In plants grown in a soil mixture, the virus significantly reduced canopy growth, nodulation, total N, and ureide‐N content of most cultivars but symbiotic N2 fixation was significantly reduced only for ‘Centennial’ and ‘Peking’. In vermiculite, in which the plants depended almost exclusively on symbiotically fixed N,2, the virus reduced canopy and nodule mass of some cultivars but these reductions were significant only for ‘Franklin’. In plants grown in this substrate, however, the virus had little effect as increases or decreases in measured components of symbiotic N metabolism were nonsignificant except for the increase in leaf ureides in ‘Marshall’. Results suggest that in either soil or vermiculite the symbiotic process in certain soybean cultivars can function at nearly a normal level despite root noduleinfection with this virus.
Further Studies on a Tomato Black Ring Virus Isolate from Artichoke
Authors: Rana G. L. , Franco A. Di , Piazzolla P. , Migliori A.
Published: May 2008

An isolate of tomato black ring virus from artichoke (TBRV‐A) was compared biologically, physico‐chemically and serologically with three strains of the virus, i.e. TBRV‐potato bouquet (TBRV‐BU), TBRV‐beet ringspot (TBRV‐W), and TBRV‐celery yellow vein (TBRV‐Ce).

Cytopathic effects of TBRV‐A infection in C. quinoa and its relationships with two strains of artichoke Italian latent virus (AILV‐S and AILV‐G) were also investigated. Physical properties in vitro, sedimentation coefficients and molecular weight of protein subunits and nucleic acid species of TBRV‐A were very similar to those known for TBRV. In serological tests, TBRV‐A appeared more closely related to TBRV‐W (SDI = 1) than to TBRV‐Ce and TBRV‐BU (SDI = 2–3). Finally, TBRV‐A was very, distantly related to AILV‐S and AILV‐G (SDI = 11–12).
Spore Dispersal and Plant Disease Gradients; a Comparison between two Empirical Models
Authors: Fitt B. D. L. , Gregory† P. H. , Todd A. D. , McCartney H. A. , Macdonald O. C.
Published: May 2008

Power law and exponential models were fitted to 325 sets of observations which described decreases with distance in deposition of air‐borne or splash‐borne spores, or pollen, or in amounts of plant disease caused by fungi, bacteria or viruses. There, was generally little difference between the models in the goodness of fit to these data, although deposition gradients for spores borne in splash droplets were fitted better by exponential models and gradients for fungi with air‐borne spores less than 10 μm in diameter were fitted better by power law models. The exponential model has the property that the observed variable decreases by half as the distance from the source increases by a constant increment (the half‐distance); this provides a measureof the gradient that is more easy to visualize than the exponent in power law model. The half‐distances of gradients for air‐borne pathogens were greater than those for splash‐borne or soil‐borne pathogens. The exponential model is easier to incorporate into models of disease development than the power law model because the boundary condition at the source (the estimated number of spores or amount of disease at the source) is finite rather than infinite. However, both these empirical models have limitations and should not be extrapolated to distances outside the observed range.
Deposition of Erysiphe graminis Conidia on a Barley Crop II. Consequences for Spore Dispersal
Authors: McCartney H. A.
Published: May 2008

Measured deposition rates of Erysiphe graminis conidia are often greater than those calculated from spore fall speed, vs, and mean wind speed. The predictions of two gradient transfer models of spore dispersal in crops, in which sedimentation and inertial impaction were calculated from vs and local wind speed or estimated from measured values (McCartney and Bainbridge 1987), were compared. Comparisons of the models suggest that deposition rates close to the source may be underestimated by a factor of two and deposition half distances may be doubled when deposition is calculated conventionally. The results illustrate the importance of accurately describing deposition processes when constructing spore dispersal models.
Susceptibility of Rubus Species and Cultivars to Blackberry Leaf Rust (Phragmidium violaceum) and its Control by Fungicides
Authors: Washington W. S.
Published: May 2008

Rubus cultivars were compared with R. procerus for their susceptibility to Phragmidium violaceum, a pathogen first recorded in Victoria in February 1984, by inoculation of detached leaflets in the laboratory. The cultivar ‘Thornless Evergreen’ was highly susceptible. Cultivars ‘Thornfree’, ‘Dirksen Thornless’ and ‘Smoothstem’ were moderately susceptible whilst cvs ‘Silvan’ and ‘Lawtonberry’ were resistant. Cultivars ‘Cherokee’, ‘Cheyenne’, ‘Comanche’, ‘Marionberry’, ‘Boysenberry’, ‘Youngberry’, and ‘Olallie’ were highly resistant. ‘Loganberry’ and the raspberry cv. ‘Malling Landmark’ were immune.

Seven fungicides were evaluated for their effect on P. violaceum. Mancozeb and triforine were the most effective against spore germination in vitro. RH 3866, triforine, propiconazole and mancozeb were the most effective in protective tests on detached leaflets of R. procerus, while RH 3866, propiconazole and flutriafol were the most effective in similar, curative tests. Phytotoxicity on detached leaflets was severe at high concentrations of triadimefon and propiconazole, and moderate to slight at similar concentrations of RH 3866 and copper hydroxide.
Der Haustorienkomplex von Erysiphe betae (Vanha) Weltzien
Authors: Hamacher J.
Published: May 2008

The haustorial complex of Erysiphe betae (Vanha) Weltzien

The haustorial complex of Erysiphe betae resembles the type of haustorium of other powdery mildew species on dicotyledonous plants. A collar of polysaccharide material with an invaginated electrondense channel surrounds the septed infection peg. The nearly elliptic haustorial body with appendices at both poles is surrounded by the plasmalemma, which had been transferred to the extrahaustorial membrane. Dictyosomes and endoplasmatic reticulum are presumably be involved in this process. Haustorial body and appendices contain many mitochondria, and with progressing senescence, the number of vacuoles with partly membrane‐like inclusions increases.
Activation of Glycosidases as a Consequence of Infection Stress in Fusarium Wilt of Tomato
Authors: Ferraris L. , Gentile I. Abbattista , Matta A.
Published: May 2008

Changes of β‐1,3‐glucanase, chitinase, β‐1,4‐glucosidase and N‐acetylglucosaminidase activity have been investigated in relation to the development of symptoms and colonization by the pathogen in roots, stems and leaves of susceptible (‘Improved, Pearson’) and resistant (‘Improved Pearson VF11’) tomato plants infected by Fusarium oxysporum f. sp. lycopersici.

Glycosidase activities increased after inoculation to different extents depending on the plant part and cultivar. Increases were always higher in susceptible than in resistant plants. Changes in the β‐1,3‐glucanase activity after inoculation were particularly large in stems of infected plants. In contrast, chitinase activity increased more in roots than in stems.

The β‐1,3‐glucosidase and chitinase activity decreased slightly from the basal to the apical third of stems.

The trend of changes of the glycosidase activity generally were well related with the severity of disease symptoms and the fungal colonization of basal stem segments.

There was no evidence that the increase of glycosidase activity after the infection was directly related with the resistance to Fusarium wilt in tomato.
The Influence of Glycoalkaloids and Impact Damage on Resistance to Fusarium solani var. coeruleum and Phoma exigua var. foveata in Potato Tubers
Authors: Olsson Kerstin
Published: May 2008

Potato glycoalkaloids were determined in tubers of a wide range of genotypes in order to study their influence on resistance to storage rots caused by Fusarium solani var. coeruleum and Phoma exigua var. foveata. No relationships were found. This indicates that breeders selection for low glycoalkaloid potato clones is not in conflict with the demands for high levels of resistance to these pathogens. It was also observed that genotypes susceptible to skin‐breaking types of, damage were more easily infected than genotypes susceptible to other types of damage.
Evaluation of Rice Cultivars under Greenhouse Conditions for Adult‐Plant Resistance to Pyricularia oryzae
Authors: Kim K. D. , Hwang B. K. , Koh Y. J.
Published: May 2008

Six rice cultivars showing various types of resistance or susceptibility to Pyricularia oryzae in the field were compared under controlled environmental conditions. The resistance of the cultivars with adult‐plant resistance was race‐specificat early growth stage. On all cultivars tested, blast infection became increasingly reduced on either leaves of adult plants or older leaves, as observed in rice plants of different leaf stages infected with different individual races. Their increase inhost resistance was marked by an apparent transition in infection type and reduced blast severity depending on leaf age and developmental stage of plants. The ranking of disease severity of the adult‐plantresistant cultivars to different races was constant during plant development, whereas that of the susceptible cultivars was differential. It is suggested that different degrees of resistance in rice cultivars may exist in seedlings and be consistently maintained during plant development, probably becoming more distinct as rice plants mature.