bluuebunny/crossref_metadata_2025 huggingface dataset:
Wirkung des pflanzengesundheitsfördernden Rhizobakteriums Agrobacterium radiobacter Stamm G12 gegen den Kartoffelzystennematoden Globodera pallida bei unterschiedlicher Temperatur und Bodenfeuchte
Authors: Hackenberg C. , Sikora R. A.
Published: May 2008

Influence of temperature and soil moisture on the biological control of the potato‐cyst nematode Globodera pallida using the plant‐health‐promoting rhizobacterium Agrobacterium radiobacter

Treatment of potato tubers with the plant‐health‐promoting rhizobacterium A.radiobacter (G 12) resulted in significant (P 0.05) reductions in G. pallida penetration (25%) in green‐house studies conducted in a non‐sterilized sandy‐loam soil. Significant reductions (P 0.05) in nematode infection were obtained when soil moisture was maintained between 60 and 90% of field capacity. When moisture levels were held at 30% of field capacity, nematode infection was also reduced, but not significantly. A. radiobacter repeatedly reduced nematode root‐infection levels but did not affect the final population density. A. radiobacter reduced the hatch of G. pallida significantly (P 0.01) in vitro up to 70%. The bacterium effectively reduced nematode hatch at both 20 and 25°C.
Pathogenicity of Pseudomonas syringae subsp. savastanoi Mutants Defective in Phytohormone Production
Authors: Iacobellis N. S. , Sisto A. , Surico G. , Evidente A. , DiMaio E.
Published: May 2008

The present study compares the pathogenicity on olive and oleander plants of three wild‐type strains of Pseudomonas syringae subsp. savastanoi (ITM317 and PBa230 from olive and ITM519 from oleander) and three phytohormone‐deficient mutants of ITM519: ITM519‐41 (Iaa+/cytokinins‐), ITM519‐7 (Iaa−/cytokinins+), ITM519‐6 (Iaa−/cytokinins−), Mutants not producing IAA (ITM519‐7and ITM519‐6) only induced necrosis of the inoculated tissues (ITM519‐,6) or swellings on the stems attributed to cytokinin production accompanied by necrosis (ITM519‐7). By contrast, the Iaa+/cytokinins− mutant (ITM519‐41) induced attenuated symptoms on stems and knots similar to those obtained with the parent strain on oleander leaves. Olive strains induced necrosis of oleander leaves and were virulent and avirulent, respectively, on olive and oleander stems.

Strain ITM519 and its three mutants were all able to multiply in oleander leaves at similar rates, reaching the same final populations. By contrast, the two olive strains multiply poorly, reaching populations c.102‐fold lower.

These results confirm that expression of IAA genes alone is sufficient to initiate the development of knots on oleander while cytokinins are necessary for the full expression of the disease symptoms (determining knot size). The findings also indicate that the plant tissues (stems and leaves) react differently to the various strains of the bacterium and, furthermore, suggest that, besides phytohormones, other pathogenetic factors could be involved in this host‐pathogen interaction. The necrotic reaction of oleander leaves heavily inoculated with olive strains was interpreted as a possible form of hypersensitivity reaction.
Induction of a Thionin, the Jasmonate‐Induced 6 kDa Protein of Barley by 2,6‐Dechloroisonicotinic acid
Authors: Wasternack C. , Atzorn R. , Jarosch B. , Kogel K. H.
Published: May 2008

The systemic acquired resistance (SAR) was studied in barley to find out specific molecular markers for this type of resistance. Such markers may serve as diagnostic tools to indicate the defense‐status of a plant and, additionally, may be used to identify new resistance‐inducing compounds in broad screening experiments. Upon treatment of barley leaves with the resistance‐inducing compound 2,6‐dichloroisomicotinic acid (INA) we found, in addition to a yet unidentified basic protein of 45 kDa (designated BIR‐1) induction of a specific 6kDa polypeptide. Using Northern‐and Western blot analysis this small polypeptide was identified as JIP‐6, a known member of the jasmonate‐induced protein (JIP)‐family of barley that was previously demonstrated to be a leaf thionin (ANDRESEN et al. 1992).
Signal Molecules Inducing Systemic Resistance and Susceptibility in Barley Seedlings
Authors: Hiramoto T. , Tobimatsu R. , Abe N. , Shiraishi T. , Oku H. , Yamada T. , Ichinose Y.
Published: May 2008

Exudate collected from the cut end of barley seedlings exhibited both activities that induced systemic resistance and susceptibility against Erysiphe graminis f. sp. hordei race Hh4 depending on the time after pruning. Exudates collected between 3–6 h after pruning showed maximum activity that induced systemic resistance, whereas those during 9–12 h conversely induced susceptibility in barley seedlings. The accumulation of antifungal substances in barley leaves correlates to the timing, of induced resistance. The antifuntingal substances were watersoluble and severely affected the infection of E. graminis f. sp. hordei.
Effect of Ustilago maydis (DC) Corda and its Toxin on Some Maize Cultivars
Authors: Alaa M. Abou‐Zeld
Published: May 2008

The pathogenic effects of Ustilago maydis (DC) Corda to five maize cultivars and four other plants were studied. It was found that none of the maize cultivars tested was resistant to the common smut disease whereas cultivars Balady was slightly susceptible. Only Sorghum rulgare from the other tested plants showed moderate susceptibility to the disease. With respect to gall formation only cultivars Giza 2 and single cross hybrid 10 formed galls after 2 weeks. The pure toxic material (Ustizeain) from Ustilago maydis was obtained, it caused chlorosis and necrosis on detached maize leaves, but it had no effect on growth of some fungi tested. Sporidia treatment showed also chlorosis on detached maize leaves.
Untersuchungen zur Lagerung und Aggressivität von Peronospora parasitica und Ergebnisse im Hinblick auf die Sortenanfälligkeit des Erregers an Winterraps
Authors: Klodt‐Bussmann E. , Paul V. H.
Published: May 2008

Results on preservation and aggressiveness of Peronospora parasitica and results with regard to the disease reistance of the paAogen on winter oilseed rape

Laboratory‐tests showed, that a long‐time preservation of Peronospora parasitica‐coiaia in a freezer at ‐ 21° C for a period of 1 year was possible using glycerine, poiyethylenglycol (PEG) 400 or PEG 1000 as cryoprotective agents. Glycerine in a concentration of 20% was ascertained as most suitable additive with germination‐rates of 21% after a storage of 1 year.

Using a cotyledon‐test a simple and non‐time‐consuming method could be established to find out differences in winter oilseed rape varieties and differences in the aggressiveness of different P. parasitica isolates. Of 32 winter‐oilseed rape varieties Synra was the least susceptible variety to the pathogen; Diadem, Doublol and Accord were the most susceptible varieties. The research on aggressiveness of different isolates gave evidence, that only the British isolate P003. differed in aggressiveness from the other isolates.
Behaviour of the Phenolic Compounds on Capsicum annuum Leaves Infected with Phytophthora capsici
Authors: Lizzi Yves , Roggero Jean Pierre , Coulomb Philippe Jean
Published: May 2008

In Capsicum annuum leaves, some phenolic compounds, such as chlorogenic acid and various apigenin or luteolin glycosides, can be separated by HPLC technique. During infection with Phytophthora capsici (the agent of pepper mildew), the concentrations of these compounds decreased. A fungal glucosidasic activity may be implicated, producing apigenin aglycon in the necrotic areas. Some of the phenolic compounds were only present in intercellular spaces, where their concentration increasedduring fungal infection, mostly in the resistant pepper cultivar.

The involvement of phenolics in C. annuum resistance is discussed in relation to oxidative metabolism.
Effect of Leaf Rust on Yield Components of Winter Rye Hybrids and Assessment of Quantitative Resistance
Authors: Miedaner T. , Sperling Ursel
Published: May 2008

Leaf rust (Puccinia recondita f. sp. secalis) is common in all winter rye growing areas, but little is known about its effect on yield in hybrid rye. Ten single crosses without any hypersensitive response to leaf rust were grown at three environments (Hohenheim, 1991; Halle, 1991; Hohenheim, 1992) in an inoculated and a non‐inoculated, fungicide protected, treatment block. Resistance traits were mean leaf rust ratings of the upper three leaves (F‐2, F‐1, F) assessed with 10 arbitrarily, chosen tillers per plot at four assessment dates, selected leaf rust rating on two leaves at one assessment date, and area under disease progress curve (AUDPC). Additionally, kernel number per head, grain weight per head and thousand kernel weight were assessed on the individual tillers in three environments and plot yield and thousand kernel weight of the thresheld plot samples in two environments. Correlations among AUDPC values and mean leaf rust ratings on the respective leaves and selected leafrust rating were high (r∼0.9, P = 0.01). Resistance among the upper three leaves was closely correlated (r∼0.9, P = 0.01) for AUDPC value and mean leaf rust rating. Leaf rust epidemics significantly reduced grain weight per head, plot yield and thousand kernel weight in three environments; kernel number per head was not significantly affected. Thousand kernel weight was reduced on average by 14% ranging from 11 to 27% among single crosses. Significant genotypic variation was observed for the affected yield components at Hohenheim 1991 and 1992. Genotype‐year interaction variance was large in the combined analysis for yield components. Quantitative resistance can be assessed by visual rating of maximal two leaves at one optimal assessment date. Relative, thousand kernel weight from thresheld plot samples can be used additionally as resistance trait when disease severity is high enough during kernel filling.
Restriction Fragment Length Polymorphism Analysis of the Mitochondrial DNA of Fusarium oxysporum f. sp. ciceris
Authors: Pérez‐Artés E. , Roncero M. I. G. , Jiménez‐Díaz R. M.
Published: May 2008

Seven isolates of Fusarium oxysporum f. sp. ciceris, representing pathogenic races 1, 2, 3, and 4 from India and 0, 5, and 6 from Spain, were assayed for restriction fragment length polymorphisms (RFLPs) in the mitochondrial DNA,(mt DNA). The mt DNA fraction of total fungal DNA was purified and digested with the restriction endonucleases Bam HI, Bgl II, Eco RI. Kpn I, Sac I, Sal I, Sma I, and Xho I. The mt DNA is a circular molecule of 40.5 kb. No RFLP in the mt DNA was detected among the seven races of F. o. ciceris. The identical restriction patterns of mt DNA indicates an extensive conservation in the gene composition of mt DNA without sequence variation, and suggests that mt DNA of F. o. ciceris may not be responsible for pathogenic diversity. The restriction map of mt DNA from the race 6 isolate Fo 8272 was constructed by digestion of the mt DNA with five restriction enzymes: Eco RI, Kpn I, Sac I, Sal I, and Xho I, either singly or in selected pairs.
Fungi Associated with Foot Rots on Winter Wheat in Northwest Italy
Authors: Rossi V. , Cervi C. , Chiusa G. , Languasco L.
Published: May 2008

In a 3‐year survey on bread and durum wheat grown in Northwest Italy, brown root rot was the most important disease of the basal part of culm. Year, wheat‐growing area, cultivar and their interactions significantly influenced brown root rot incidence. The most important fungal species isolated from lower stems with browning were Microdochium nivale, Drechslera sorokiniana, Fusarium avenaceum, F. graminearum, and F. culmoniliforme, and Pythium spp. were frequently isolated. F., crookwellense was also isolated. Sharp eyespot was a frequent disease; take‐all and eyespot occurred only occasionally.
Characterization of Pyrenophora Isolates Associated with Spot and Net Type Lesions on Barley in South Africa
Authors: Louw J. P. J. , Victor D. , Crous P. W. , Holz G. , Janse B. J. H.
Published: May 2008

Single‐spored isolates of Pyrenophora associated with spot and net type net blotch of barley were compared using total DNA banding patterns, morphological and cultural characteristics, symptomatology and mating studies. Isolates of spot and net type net blotch were found to vary regarding conidium length and cultural growth rate. Mating studies among and between ascospore, spot and net type isolates proved unsuccessful under the conditions studied. Total DNA polymorphisms of the net spot and ascospore isolates digested with the restriction enzymes HpaII and HaeIII showed that the isolates have similar banding patterns. Random amplified polymorphic DNA (RAPD) showed that the banding patterns of the spot and net type isolates were again similar but were distinct from outgroups such as P. semeniperda and P. triticirepentis. The homology in DNA banding patterns of local isolates indicated that the difference in conidium length is insufficient to separate them as two species. It is concluded that spot and net type isolates occurring in South Africa belong to P. teres. Therefore spot type lesions are caused by P. teres f. sp. maculata and not by P. japonica as reported previously.
Difference Between Xanthomonas campestris pv. phlei and X.c pv. graminis Revealed by Genomic Fingerprinting and Restriction Fragment Length Polymorphism Patterns
Authors: Wang H. M. , Sletten A. , Klemsdal S. S.
Published: May 2008

Genomic DNA was prepared from 16 strains of Xanthomonas campestris pv. graminis and Xanthomonas campestris pv. phlei isolated from six species of forage grasses in four countries. The two pathovars could be distinguished clearly by genomic fingerprints generated by EcoRI, BamHI or HindIII digestion. DNA profiles produced by HindIII digestion could differentiate not only between the two pathoars but also among strains within the same pahtovar from different countries. A 1.6 kb EcoRI fragment was cloned from genomic DNA of strain LMG726 and used to detect restriction fragment‐length polymorphism among the same strains. EcoRI and BamHI polymorphisms were seen between the two pathovars probed with this 1.6 kb EcoRI fragment (p726EI probe). These polymorphisms appeared to be highly conserved and unique for each pathovar, consistent with previous grouping of the strains based on other criteria.
Ranking Block Mixture Patterns of Differing Host Genotype Unit Area by the Use of Long‐Term Rates of Disease Increase
Authors: Goleniewski G.
Published: May 2008

A spatial component is added to a model for the spread of a disease composed of m pathotypes in an n cultivar mixture and is employed to simulate disease progress in a series of fixed block mixture geometries of varying host genotype unit area. The spatial model contains only one pathotype for simplicity. It is demonstrated numerically that it possesses a rate of disease increase p in common with spore pool mixture models which do not posses explicit spatial structure. This parameter is used to rank block mixture patterns of differing host genotype unit area. The variation in rate of disease increase with autodeposition is shown graphically for the chosen set of block geometries.
Infection of Grapevine Roots by Agrobacterium vitis and Meloidogyne hapla
Authors: Süle S. , Lehoczky J. , Jenser G. , Nagy P. , Burr T. J.
Published: May 2008

Combined inoculation of grapevine roots with Meloidogyne hapla and Agrobacterium vitis at the level of 102–3 bacteria/g of soil resulted in root infestation by A. vitis. When inoculation of M. hapla and A vitis was applied, most of the feeder roots were dead and at points of secondary root branching, dark lesions could be observed. Along the secondary living roots, typical nematode induced galls could be seen. In many cases the infection stopped growth ofthe main or secondary roots. Plants inoculated with A. vitis alone did not show any galls or swellings on roots and its infection did not stop root growth. However in the M. hapla only treatment, small swellings or elongated galls were readily apparent on secondary roots. These galls were always exempt of A. vitis. Xylem sap, collected in spring 2 years after inoculation of A. vitis+M. hapla yielded many A. vitis cells demonstrating that the bacteria became systemic in plant vessels.
Increase of Complex Pathotypes of Erysiphe graminis f. sp. hordei in Two‐Component Mixtures of Spring Barley Cultivars
Authors: Huang R. , Kranz J. , Welz H. G.
Published: May 2008

Pathotypes of Erysiphe graminis f. sp. hordei were monitored at fortnightly intervals in pure stands of cultivars Golf with Laevigatum resistance [gene Ml(La)], Steina with Arabische resistance (Mla 12) and Harry with Monte Cristo resistance (Mla9), as well as in two two‐component mixtures [Golf + Steina (G + S) and Golf + Harry (G + H)] during the course of mildew epidemics in replicated field trials. The number of colonies per main tiller was also recorded. Virulence complexity (i.e. the average number of virulence genes per isolate with respect to the two matching resistance genes of the mixed cultivars) was always higher in mixtures than in pure stands. Linear regression of complexity on the number of elapsed mildew generations (based on actual temperature data) gave significant b‐values (slopes) of 0.039, 0.034, 0.022 and 0.018 on Golf in G + S, Steina in G + S, Golf in G + H and Harry in G + H, respectively. In pure stands, there, was no significant complexity increase on any cultivar. The fact that b‐values were higher on either component in the G + S than in the G + H mixture indicates stronger selection for the complex, i.e. two‐virulence, pathotypes in G + S. Complex pathotypes had a higher relative fitness than simple (one‐virulence) pathotypes in both mixtures but not in the pure stands. The absolute frequencies of complex pathotypes as measured by the area under the colony frequency curve (AUCFC) were higher on all cultivars in mixtures than in pure stands, except on Steina.
Comparison of Techniques for the Production of Sclerotinia trifoliorum Ascospores in the Laboratory for Forage Legumes Resistance Tests
Authors: Delclos B. , Raynal G.
Published: May 2008

This study aimed to improve the production, under controlled conditions, of Sclerotinia trifoliorum ascospores to be used for selection tests on forage legumes. Sclerotia of this fungus, produced in the laboratory, were buried 1–2 cm deep in permanently soaked vermiculite, at T = 15°C, 12/24 h of fluorescent light, air moisture >80% in order to differentiate apothecia. The ascospores were harvested by aspiration and collected on a membrane filter. Various types of apparatus containing sclerotia have been tested for their ability to maintain live apothecia and for the facility of spore catching. The aspiration method has been found to be much more efficient than the previous method of cutting off apothecia. Moreover, it was observed that using this harvesting technique the best apparatus presented small and independent compartments (truncated plastic bottles). The ascospores can be stored, on the membrane filter at 5°C and in dry conditions in order to preserve their germinating abilityfor, a period of 3 months at least. This spore harvesting method permits avaibility of large quantities of a cheap inoculum for S. trifoliorum resistance test on forage legumes all year round.
Surface Ultrastructural Studies on Ingress and Establishment of Pseudomonas syringae pv. mori on Mulberry Leaves
Authors: Gupta V. P. , Tewari S. K. , Datta R. K.
Published: May 2008

P. syringae pv. mori multiplied on leaf surface and colonized particularly on the cystoliths and in the grooves of veins. The masses of bacteria were associated with necrotic spots, which appeared 9 days after inoculation. The studies also revealed that the bacterium invaded leaf tissues through cystoliths. However, it did not enter through stomata and trichomes which had commonly been observed in most of the plant pathogenic bacteria.
Influence of pH on Suppression of Fusarium Wilt of Carnation by Pseudomonas fluorescens WCS417r
Authors: Duuff B. J. , Erkelens A. , Bakker P. A. H. M. , Schippers B.
Published: May 2008

The influence of the nutrient solution pH on suppression of fusarium wilt by Pseudomonas flurescens WCS417r in carnation grown in rockwool was investigated.

Experiments were conducted with carnation cultivars Lena and Pallas, susceptible and moderately resistant to fusarium wilt, respectively. WCS417r significantly reduced fusarium wilt in the susceptible cv. Lena, that was root‐inoculated with Fusarium oxysporum f.sp. dianthi (Fod), at pH 7.5, but not at pH 6.5 and 5.5 This corresponded with a higher in vitro siderophore production and antagonism of Fod by WCS417r at pH 7.5 than at pH 6.5 and 5.5. Fusarium wilt in the moderately resistant cv. Pallas, however, was also significantly reduced by treatment with WCS417r at pH 5.5 This corresponded with the low influence of pH on induced resistance by WCS417r in plants of cv. Pallas that were stem‐inoculated with Fod.

The results indicate that the influence of pH on control of fusarium wilt of carnation by Pseudomonas fluorescens WCS417r differs between carnation cultivars that differ in their level of resistance against fusarium wilt. In susceptible cv. Lena, fusarium wilt is suppressed by antagonism by WCS417r, that is most effective at pH 7.5. In the moderately resistant cv. Pallas, fusarium wilt is suppressed by both antagonism and induced resistance by WCS417r. The latter is also effective at lower pH.
Characterization of an Isolate of Tobacco Necrosis Virus From Zucchini
Authors: Roggero P. , Lisa V.
Published: May 2008

Tobacco necrosis virus (TNV) was isolated from glasshouse zucchini plants in Liguria, northern Italy, showing yellow spots on young leaves and necrotic symptoms on older leaves, petioles and stems. No other viruses were present in these plants. Experimentally, the virus systemically infected zucchini seedlings grown in naturally infected soil but only local infections were induced when leaves and roots were mechanically inoculated. The virus was identified as serotype D, devoid of satellite particles. This appears to be the first report of TNV in zucchini. Three ELISA procedures for field detection of TNV using polyclonal antibodies for serotype D were compared. Antibodies were conjugated with I) alkaline phosphatase (AP‐AB);2) N‐Hydroxy‐succinimid obiotin (BNHS‐Ab); 3) N‐biotinyl‐6‐aminocaproic hydrazide (BACH‐Ab). The procedure using BNHS‐Ab detected the lowest concentration of the homologous virus, followed by BACH‐Ab and AP‐Ab. Only with biotinylated antibodies. TNV serotype A was also detected.
Differential Susceptibilities between Leaf Disks and Plants in the Transmission of Tomato Spotted Wilt Virus by Frankliniella occidentalis to TSWV Hosts and Transgenic Plants
Authors: Wijkamp J. , Goldbach R. , Peters D.
Published: May 2008

The efficiency by which tomato spotted wilt virus (TSWV) was transmitted to plants and leaf disks by the vector Frankliniella occidentalis, was analysed. The virus was efficiently transmitted to Datura stramonium, Impatiens sp. and tobacco plants, i.e. 60–100% of the plants became infected when 1–3 viruliferous thrips were confined per plant for a period of 3 days. However, lettuceexhibited a lower susceptibility since only 25% of the test plants were infected when challenged by 10 viruliferous thrips per plant for 3 days. In contrast, complete resistance was found when transgenic tobacco plants, expressing the nucleocapsid protein of TSWV, were challenged with up to 10 viruliferous thrips per plant, whereas all non‐transgenic control plants were infected when 5 viruliferous thrips per plant were used. To improve and accelerate the tramission studies, the applicability of leaf disks in these studies was tested. Leaf disks of 16 different plant species appeared to be highly susceptible. Infection ratings ranging from 51.6 to 95.0% were obtained when one viruliferous adult was placed singly on these leaf disks for a period for 24 h. The leaf disk assay was also employed to screen resistance of transgenic plants expressing the nucleocapsid protein of TSWV. One transgenic tomato line displayed complete immunity whereas a second line appeared to be susceptible. For the transgenic tobacco line, positive ELISA reactions were found for a few leaf disks (7.5%) suggesting that some virus replication did occur. However, the ELISA readings for these disks were significantly lower than those for leaf disks of non‐transgenic controls. Finally, the significance of the use of the leaf disks and test plants in virus‐vector studies is discussed.
Occurrence of Pseudomonas syringae pv. Tomato race 1 in Italy on Pto Gene‐Bearing Tomato Plants
Authors: Buonaurio R. , Stravato V. M. , Cappelli C.
Published: May 2008

Bacterial speck symptoms on leaves of the tomato cultivar Erminia Fl (Petoseed), heterozygous for the Pto resistant gene, were observed in June 1995 in Northern Italy. Using individual‐lesion isolation, 8 bacterial isolates were obtained from the affected leaves, which were identified as Pseudomonas syringae pv. tomato by biochemical, physiological, nutritional and pathogenicity tests. When the differential cultivar Ontario 7710, homozygous for the Pto gene, was inoculated with the bacterial isolates, 4 of them provoked the typical bacterial speck symptoms and therefore belonged to race 1. This is the first occurrence of P. syringae pv. tomato race 1 in Italy and the first time this race has been isolated on a Pto gene‐bearing tomato cultivar grown in open field.
The Influence of Polyacetylenes on the Susceptibility of Carrots to Storage Diseases
Authors: Olsson Kerstin , Svensson Rita
Published: May 2008

The amounts of the polyacetylenes falcarindiol (heptadeca‐1, 9(Z)‐dien‐4,6‐diyn‐ 3,8‐diol) and falcarinol (heptadeca‐1,9(Z)‐dien‐4,6‐diyn‐3‐ol) were determined in the roots of a number of commercial carrot cultivars in order to study their influence on resistance to storage rots caused by three different fungi. The content of the diol was much higher in periderm/pericyclic parenchyma than in phloem parenchyma and the outer tissues were less susceptible to Mycocentrospora acerina than the inner tissues. A strong and significant negative relationship was found between falcarindiol contents in the periderm/pericyclic parenchyma and susceptibility to Mycocentrospora acerina for 14 of the 16 cultivars tested. The relationship was less noticable for Sclerotinia sclerotiorum and not significant for Rhizoctonia carotae.
In vitro Reaction of Sunflower (Helianthus annuus L.) to the Toxin(s) Produced by Alternaria alternata, the Casual Agent of Brown Leaf Spot
Authors: Kintzios S. , Koliopoulos A. , Karyoti E. , Drossopoulos J. , Holevas C. D. , Grigoriu A. , Panagopoulos C. G.
Published: May 2008

A bioassay system was developed for studying the in vitro reaction of sunflower (Helianthus annuus L. cv. ‘Nanus’) against the toxin produced by the virulent pathotype IMI 366417 (1) of the pathogenic fungus Alternaria alternata. Cotyledons from 2‐week‐old seedlings were cultured on a MS (Murashige and Skoog) medium supplemented with 0.3 μM NAA (α‐napthylacetic acid) and 1.3 μM BA (6‐benzyladenine). Exponentially growing calli were transferred to selective media containing toxin solutions at various concentrations. The fresh weight of the cultured calli was reduced as the toxin concentration increased, although the viability of the cells, expressed as callus dehydrogenase activity, increased. Selection for toxinresistant genotypes was attempted at 30% toxin concentration, which causes a 90% reduction in callus growth. After one month in culture, 18% of the calli demonstrated resistance to the toxin. However, no plants could be regenerated from those calli after transfer onto a MS medium supplemented with 5.4 μM NAA and 4.4 μM BA. The effect of the toxin purification method on toxin yield and biological activity, as well as its possible mode of cellular action are discussed. The results of these experiments may contribute to a better understanding of the disease mechanism and help establish an efficient selection method of resistant sunflower genotypes.
Phoma nigrificans (P. Karst.) Boerema et al., a New Species for Poland
Authors: Marcinkowska J. , De Gruyter J.
Published: May 2008

Phoma nigrificans was isoiated from leaves of Thlaspi arvense. The cultural characteristics are described, and results of comparative pathogenicity tests including Phoma lingam isolates on B. napus var. oleifera and T. arvense are given. This is the first report of P. nigrificans from Poland.
Occurrence of Coated Vesicles and Alterations in Plasmalemma in Tomato Leaf Cells Infected by Phytophthora infestans Mont. (de Bary) After Treatment with Fosetyl‐Al
Authors: Jiang Y.
Published: May 2008

Treatment of tomato (Lycopersicum esculentum Mill. cv. Bonny Best) leaves with the systemic fungicide Fosetyl‐Al (Tris‐o‐ethyl phosphonate aluminium) induced the formation of haustorial encasements or cell wall deposits in the leaf cells infected by Phytophthora infestans Mont (de Bary). Numerous coated vesicles and extremely invaginated, saclike plasmalemma were found in close spatial association with wall deposits in haustorium infected cells. Wall deposits in non‐infected cells bordering degenerated, infected, cells were also accompanied by the presence of coated vesicles. In leaf tissues without treatment with Fosetyl‐Al, no substantial change in the plasmalemma of infected cells was observed and coated vesicles were found only in close contact with large, smooth‐surfaced vesicles. No coated vesicles were found associated with wall deposits in non‐infected, neighbouring cells. The results are discussed in connection with possible functions of both coated vesicles and plasmalemma.
Electrophoretic Analysis of Total and Membrane Proteins of Xanthomonas campestris Pathovars, the Causal Agents of the Leaf Streak of Cereals and Grasses in Iran
Authors: Alizadeh A. , Dechamp‐Guillaume G. , Sarrafi A. , Rahimian H. , Barrault G.
Published: May 2008

Forty‐five Iranian isolates of Xanthomonas campestris obtained from wheat, barley and grasses were compared with reference strains using polyacrylamide gel electrophoresis (PAGE) of the whole‐cell and membrane proteins.

The PAGE profiles of the whole‐cell and membrane proteins of the Iranian isolates obtained from barley, with the exception of IBLS 11 and IBLS 12, were identical and clearly distinguishable from those of the other isolates. The barley group isolates, which were pathogenic only to barley, were similar to UPB 458 (NCPPB 2389), the reference strain of pathovar hordei. The isolates obtained from wheat and grasses, as well as IBLS 11 and IBLS 12, which can infect wheat, barley and some wild grasses, had similar banding patterns: only IBLS 40 isolated from Hordeum sp. displayed the same profile as the barley group. Reference strains UPB 443 (NCPPB 2821) and UPB 513, which correspond to pathovars undulosa and translucens, respectively, were related to the wheat group. IBLS45, isolated from Bromus sp., had a banding pattern that differed from those observed for strains of the barley and wheat groups.

The results suggest that this method can be useful for discriminating different pathovars of X. campestris attacking cereals and grasses, and sodium dodecyl sulphate (SDS)‐PAGE of membrane proteins was not more sensitive than SDS‐PAGE of total proteins for differentiating the isolates.
Biological and Serological Properties of Strains of Barley Mild Mosaic Virus
Authors: Nomura K. , Kashiwazaki S. , Hibino H. , Inoue T. , Nakata E. , Tsuzaki Y. , Okuyama S.
Published: May 2008

The biological and serological properties of two Japanese barley mild mosaic virus (BaMMV) strains (BaMMV‐Kal and BaMMV‐Nal) and a German BaMMV strain (BaMMV‐M) were compared. Mechanical inoculation experiments showed that these three strains differed from one another in their ability to infect specific barley cultivars. BaMMV‐Kal and BaMMV‐M caused similar symptoms, but BaMMV‐Nal clearly differed from them in its symptoms on some barley cultivars. The three BaMMV strains efficiently infected barley plants at 15°C, whereas at 20°C BaMMV‐Kal and BaMMV‐M also infected many plants but BaMMV‐Nal infected only a few. BaMMV‐Kal and BaMMV‐M were indistinguishable by ELISA, while BaMMV‐Nal was distinguished from both. The biological and serological variability reported shows that BaMMV occurs as two distinct strains in Japan.
Pseudomonas syringae pv. coriandricola, Incitant of Bacterial Umbel Blight and Seed Decay of Coriander (Coriandrum sativum L.) in Germany
Authors: Toben H.‐M. , Rudoph K
Published: May 2008

Since 1987 a devastating disease has occurred in coriander in Germany, characterized by dark‐brown discoloration of blossoms and umbels. water‐soaked and brown spots on leaves and stems, seed decay and willing. Infected tissue always contained large quantities of Gramnegative, rod‐shaped, motile bacteria with few polar flagella. Tests for LOPAT reactions showed the bacteria to be positive for levan‐production and tobacco hypersensitivity reaction but negative for oxidase reaction, rot of potato slices and arginine dihydrolase. The bacteria failed to produce fluorescent pigment on King's medium B but revealed a blue fluorescence after growing in a liquid medium without Fe, According to further standard nutritional, biochemical and physiological tests the coriander pathogen belongs to Pseudomonas group la. i.e. Pseudomonas syringae. Also, the fatty acid composition revealed a very close similarity to Pseuodomonas syringae. On Biolog plates the coriander strains showed a uniform metabolic pattern and could clearly be distinguished from other Pseudomonas syringae pathovars.

Typical hosts of Pseudomonas syringae pv. syringae were not infected by the coriander pathogen. Also, most tested umbelliferae species reacted resistant towards the pathogen. Typical disease symptoms, such as persistent water‐soaked lesions, were incited only a Coriandrum saticum Animi majus and Levisticum offieinale. The studies revealed that the pathogen described is a separate pathovar of Pseudomonas syringae not included in the approved list of P. syringae pathovars. The name Pseudomonas syringae pv. coriandricola is proposed. Strain GSPB 1965 has been deposited in the NCPPB as pathotype strain (no. 3781).
Sequence Analysis and Detection Using Immunocapture‐PCR of Cymbidium Mosaic Virus and Odontoglossum Ringspot Virus in Hawaiian Orchids
Authors: Barry K. , Hu J. S. , Kuehnle A. R. , Sughii N.
Published: May 2008

A Hawaiian isolate of Cymbidium mosaic virus (CyMV‐H) was purified from Dendrobium orchid, and a cDNA library was constructed. Clones containing the coat protein (CP) gene and movement protein (MP) gene were identified by colony hybridization and polymerase chain reaction (PCR). The Hawaiian isolate of Odontoglossum ringspot virus (ORSVH) was purified from Cattleya orchid. The CyMV CP gene was PCR amplified from a cDNA done. The ORSV CP and 54 kDa putative replicase genes and CyMV‐MP gene were cloned by RT‐PCR Sequences of these genes of CyMV‐H and ORSV‐H were compared with those of CyMV and ORSV from Singapore, Japan. Korea, and Germany. The high degree of sequence identity (91–99%) at the nucleotide level for all gene sequences analysed, shows that CyMV and ORSV from different countries are closely related. Sequence comparison results show that CyMV strains can be divided into two groups based on differences in amino acid sequences of the coat protein gene: CyMV‐H closely resembles CyMV‐SI while CyMV‐S2 resembles CyMV‐K, A sensitive, rapid, and reliable immunocapture PCR (ICPCR) assay was developed to detect both viruses, CyMV was detected from dilutions equivalent to 100 mg of orchid material and ORSV was detected from dilutions equivalent to 10 μg of orchid material. IC‐PCR was compared with direct binding PCR (DB‐PCR) and ELISA for their sensitivities.
Properties of the Iranian Isolate of Bermudagrass Etched‐line Virus
Authors: Masumi M. , Izadpanah K.
Published: May 2008

The Iranian isolate of bermudagrass etched‐line virus (BELV‐I), purified by low‐pH treatment of infected bermudagrass sap followed by several cycles of differential centrifugation and sucrose density‐gradient centrifugation, formed two components in density‐gradient columns. The top component consisted of empty protein shells. It had a major structural protein of c. 22 kDa and a minor of c. 25 kDa. The weight of the nucleic acid present only in bottom component particles, was calculated to be 1.82 × 106 Da. Only Aconurella prolixa (Leth.) was able to transmit the virus under experimental conditions or contained the virus in natural populations. In ELISA tests the virus titer in the vector increased rapidly between days 14 and 29 after acquisition, results indicating a propagative relationship. BELV‐1 was serologically closely related to the Moroccan isolate of BELV, and related to the American but not to the Costa Rican isolate of maize rayado fino virus (MRFV). Several graminaceous species were found to be experimental or natural hosts of the virus.
Effect of 1,3;1,6‐β‐D‐glucan on Infection of Detached Tobacco Leaves with Tobacco Mosaic Virus
Authors: Reunov A. V. , Lapshina L. A. , Nagorskaya V. P. , Elyakova L. A.
Published: May 2008

Glucan preparations were obtained by transformation of laminaran from the alga Laminaria cichorioides with endo‐β‐1,3‐glucanase from marine mollusks. These preparations, like those of other sources, have an inhibitory effect on tobacco mosaic virus (TMV) infection of detached leaves of local and systemic host tobacco plants.
Serological and Biological Comparisons of Blackeye Cowpea Mosaic and Cowpea Aphid‐borne Mosaic Potyvirus Isolates Seed‐borne in Vigna unguiculata (L.) Walp. Germplasm
Authors: Bashir M. , Hampton R. O.
Published: May 2008

Serological and biological comparisons were made among 45 seed‐borne isolates of blackeye cowpea mosaic (BICMV) and 54 seed‐borne isolates of cowpea aphidborne mosaic (CAbMV) potyviruses derived from cowpea seedlots or young nursery‐grown seedlings comprising 2112 germplasm accessions or pre‐introduction seedlots of Vigna unguiculata. Isolates were identified by DAS‐ELISA using polyclonal immunoglobulin G specific for these viruses. Twenty isolates of BICMV and 32 isolates of CAbMV were also compared by ACP‐ELISA with selected monoclonal antibodies and by SDS‐immunodiffusion. By all approaches, isolates of BICMV were clearly distinguished from CAbMV isolates. Isolate comparisons on selected cowpea genotypes (TVu‐401, TVu‐1582, TVu‐2657, and TVu‐3433) partitioned most isolates into two distinct groups. A few isolates seed‐borne in Indian cv. Pusa Phalguni, however, were clearly BICMV by all serological tests, but behaved as CAbMV in definitive cowpea genotypes. Although BICMV is generally considered to be a ‘new world virus’, both BICMV and CAbMV occurred in V. unguiculata seedlots originating in ‘old‐world regions’, including Afghanistan, Botswana, Nigeria, Senegal, and South Africa. Seedborne CAbMV was isolated from 6 of 155 tested US V. unguiculata Germplasm accessions originating, respectively, in Afghanistan (2), Botswana (2), India (1), and Pakistan (1).
Geminiviruses Associated with Diseased Tomatoes in Cuba
Authors: Zubiaur Y. Martinez , Zabalgogeazcoa I. , De Blas C. , Sanchez F. , Peralta E. L. , Romero J. , Ponz F.
Published: May 2008

Tomato plants displaying symptoms of yellowing and leaf curling were analysed for the presence of geminiviruses. Two distinct geminiviruses were present in the plants studied. One had a genome size and coat protein gene sequence similar to the Israeli strain of tomato yellow leaf curl virus (TYLCV), while the other had a smaller genome size than TYLCV that could not be amplified using primers specific for Israeli TYLCV. The presence of the Israeli strain of TYLCV has been reported in other Caribbean islands, but not in Southern Florida (USA) which is close to those islands where TYLCV has been detected. This suggests that the introduction of the Israeli strain of TYLCV to the Caribbean area may have occurred within recent times.
Occurrence of Bacterial Wilt and Soft Rot of Seed Cabbage Plants (Brassica oleracea var. capitata L.) in Yugoslavia
Authors: Arsenuević M. , Obradović A.
Published: May 2008

Soft rot and wilt symptoms were noticed on 2‐year‐old seed cabbage plants grown in field crops. Soft rot Erwinia was isolated from the diseased tissues. Pathogenicity tests showed that the bacterium effectively colonised different vegetable species and sunflower, indicating a wide host range.

Pathogenicity, morphological, biochemical and physiological characteristics showed that the investigated strains are of Erwinia carotovora subsp. carotovora (Jones) Bergey et al.
Assessment of the Resistance to Phytophthora fragariae var. fragariae of the USA and Canadian Differential Series of Strawberry Genotypes
Authors: van de Weg W. E. , Henken B. , Giezen S.
Published: May 2008

The resistance of the USA and Canadian differential series of strawberry (Fragaria sp.) genotypes was assessed against nine USA isolates (A1‐A4, A6‐A10) and three Canadian isolates (NS2‐NS4) of Phytophthora fragariae var. fragariae. The resistance of part of the UK series was also examined. Of the 157 host genotype‐isolate combinations tested, 13 were classified differently from earlier reports. These differences can be explained by the existence of different clones under the same cultivar name (Aberdeen and Perle de Prague), the substitution of Aberdeen by Sparkle, which differ in their resistance, and by the application of different criteria for resistance. Here, incomplete resistance was considered as resistance. The discernment of the US differential series can be improved by including the UK differential Perle de Prague and the Canadian differential Sparkle. The Canadian series can be improved by including Perle de Prague and the US differential Aberdeen. This leads to one unified differential set for North America.The results also allow the proposition of a formal gene‐for‐gene model which, in turn, provides for a universal differential series for this pathosystem.
Resistance to Vanilla Necrosis Potyvirus in Transgenic Nicotiana benthamiana Plants Containing the Virus Coat Protein Gene
Authors: Wang Y. Y. , Gardner R. C. , Pearson M. N.
Published: May 2008

The full‐length vanilla necrosis potyvirus (VNV) coat protein (CP) gene was introduced into Nicotiana benthamiana plants via Agrobacterium tumefaciens‐mediated transformation. Four constructs contained either: sense (+) CP sequence, antisense (‐) CP sequence, sense CP sequence with a Kozak's consensus ATG resulting in a change in the first amino acid, or antisense CP sequence with the Kozak's modification. When mechanically inoculated with a high concentration of VNV, one of the plant lines containing the full‐length sense CP gene was highly resistant to virus infection. Plants from the resistant lines expressed the CP at a relatively low level compared to susceptible lines containing the same construct. Plants containing the other three constructs were either susceptible or showed delayed symptom expression.
Density‐Dependent Growth and Life History Evolution of Polycyclic Leaf Pathogens: A Continuous Time Growth Model
Authors: Damgaard C. , ØStergärrd H.
Published: May 2008

A density‐dependent growth model of a polycyclic leaf pathogen is analysed. Viability and fecundity of the pathogen are regulated by the current population density. Spores are produced continuously from a sporulating infection until death of the infection, and consequently, all age classes of infections are present at a certain point in time. The leaf area of the host varies with time. Evolution of life history strategies are studied by letting different pathogen genotypes compete with each other. Evolution of life history strategies and evolution of impact of disease are discussed in relation to the ecology of the host‐pathogen system. The model is exemplified by Erysiphe graminis f. sp. hordei growing on Hordeum vulgare.
Oligonucleotide Fingerprinting Detects Genetic Variability at Different Levels in Nigerian Mycosphaerella fijiensis
Authors: Müller R. , Pasberg‐Gauhl C. , Gauhl F. , Ramser J. , Kahl G.
Published: May 2008

DNA fingerprinting with synthetic simple repetitive oligonucleotides such as (CA)8 or (CAA)5 detected polymorphisms between various isolates of the ascomycete Mycosphaerella fijiensis, the causal agent of the black Sigatoka disease of Musa. These microsatellite motifs are present at multiple chromosomal locations and in high copy numbers in the Mycosphaerella genome, generating informative fingerprints with low background. Variability exists on a macro‐ as well as a microgeographical scale: it occurred within one lesion, between lesions of one plant, between plants, cultivars, and geographic locations. Mathematical analysis of the data produced dendrograms that demonstrated the presence of different genetically related groups of Mycosphaerella fijiensis in Nigeria.
Toxicity and Occurrence of Fusarium species and Mycotoxins in Late Harvested and Overwintered Grain from Norway, 1993
Authors: Langseth W. , Kosiak B. , Clasen P.‐E. , Torp M. , Gareis M.
Published: May 2008

Samples of grain, harvested in October/November of 1993 or in the spring of 1994 from fields in Norway with overwintered grain, were collected. The presence of Fusarium species and the amount of mycotoxins produced by this genus were determined. The cytotoxic properties of the grain samples were examined with an in vitro methylthiazoltetrazolium (MTT)‐cell culture assay using swine kidney and VERO cells as target cells. The total count of colony forming units of Fusarium species was about the same in the grain harvested in late autumn and in the spring, but the dominant species seemed to vary somewhat between the two groups. F. culmorum was found more in the samples from October/November while F. avenaceum was isolated more in the grain harvested in the spring. Only small amounts of F. sporotrichioides were present in the grain harvested in the autumn, and none was found in the overwintered grain. The deoxynivalenol content was significantly higher in the grain harvested in autumn than in the overwintered grain. Although very small amounts of toxins were detected in the overwintered grain, it was more cytotoxic than the grain harvested in October/November. A significant correlation between the cytotoxicity and the amount of F. avenaceum in the samples was found.
Mycoparasitism of Pythium ultimum by Antagonistic Binucleate Rhizoctonia Isolates in Agar Media and on Capsicum Seeds
Authors: Siwek K. , Harris A. R. , Scott E. S.
Published: May 2008

Hyphal interactions between two antagonistic binucleate Rhizoctonia isolates (BNR) and the seedling dampingoff pathogen, Pythium ultimum var. sporangiiferum, were observed by both light‐and scanning electron microscopy (SEM), on agar media and on capsicum seeds in sterilized potting mix. Both BNR isolates displayed similar mycoparasitic behaviour towards P. u. sporangiiferum on agar media. This included parallel growth along the pathogen hyphae, formation of hook‐shaped hyphal tips and coils on the surface of P. u. sporangiiferum hyphae and penetration and growth within pathogen structures. Disruption of cytoplasmic streaming and disorganisation of pathogen cytoplasm were also observed. SEM observations revealed alterations in P. u. sporangiiferum cell wall structure and the presence of penetration holes apparently due to digestion by the BNR.

P. u. sporangiiferum was also parasitised by both BNR isolates on capsicum seed coats, with parallel growth, hook formation and coils commonly observed. The above observations indicated that mycoparasitism is a possible mode of action of BNR against P. u. sporangiiferum.
Use of a Colonization‐Deficient Strain of Escherichia coli in Strain Combinations for Enhanced Biocontrol of Cucumber Seedling Diseases
Authors: Roberts D. P. , Dery P. D. , Mao W. , Hebbar P. K.
Published: May 2008

Seed treatments containing combinations of Escherichia coli S17R1 and Burkholderia cepacia Bc‐B provided significantly greater (P ≤ 0.05) suppression of cucumber seedling pathogens in a field soil naturally infested with Pythium and Fusarium spp. than seeds treated individually with strains Bc‐B, S17R1, or Enterobacter cloacae 501R3. Although strain S17R1 had no effect on disease severity when applied alone and did not colonize cucumber rhizosphere, it enhanced the biocontrol effectiveness of strain Bc‐B.