bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenicity Process of Pseudomonas fuscovaginae, the Causal Agent of Sheath Brown Rot of Rice
Authors: Jaunet T. , Notteghem J. L. , Rapilly F.
Published: May 2008

Sheath brown rot of rice caused by Pseudomonas fuscovaginae has been described in areas where low temperatures occur during the rice booting and heading stages. To analyse the relationship between pathogenicity of P. fuscovaginae and low temperatures, pathogenicity process in rice at booting stage was studied in a growth chamber at midrange and low temperatures. Analysis performed at 13°C, 18°C and 23°C in two rice cultivars showed that pathogenicity of P. fuscovaginae was explained by the general model of the independent action. The inoculum dose necessary to obtain 50% of diseased sheaths decreased with increase of temperature Analysis of planta bacterial population dynamics and mean response time pointed out that low temperatures affected pathogen multiplication in host before and after symptoms development. In consideration of our results, it was concluded that low temperatures acted negatively on the pathogenicity process of P. fuscovaginae. Therefore, occurrence of P. fuscovaginae in areas where rice cultivation is restricted by low temperatures can not be explained by a direct effect of temperatures on pathogenicity.
A 4‐Year Study of the Association Between Gibberella Ear Rot Severity and Deoxynivalenol Concentration
Authors: Reid L. M. , Stewart D. W. , Hamilton R. I.
Published: May 2008

To determine the association between visual disease severity and deoxynivalenol (DON) concentration in Fusarium graminearum silk‐inoculated maize ears, 23 Ontario hybrids were assessed in 1989, 1991, 1992, and 1993. The relationship was exponential and consistent between years. Ears with more than 25% of the kernels visibly infected could have very high concentrations of DON. Both temperature and rainfall in July and August influence the level of disease severity and the subsequent DON accumulation. Visual disease severity ratings should be sufficient for the selection of more resistant genotypes in corn improvement programs during routine screenings. Thus, mycotoxin analyses can be reserved for initial selection of parental material and final verification of developed inbreds or hybrids. No relationship was found between hybrid maturity and disease severity or DON concentration.
Induction to Resistance to Crown Rust in Oat
Authors: Sebesta J. , Epstein A. H. , Formanova M.
Published: May 2008

Induction of resistance to crown rust, caused by Puccinia coronata Cda. var, avenae Frazer et Led., occurred in seedlings of three genetic lines of oats (Avena sativa L.) inoculated sequentially with one of three inducer‐challenger combinations of the pathogen. There was significant reduction in both the number of pustules per leaf and the weight of urediospores harvested in all three host genotypes tested. There were highly significant differences between individual spore harvests correlated with age of the pustules. Development of telia by the challenger was found to occur considerably later, and was less intense, when the challenger was inoculated alone in contrast to treatments in which the challenger followed pre‐inoculation with the inducer. There was no correlation between the numbers of resistant and susceptible lesions within the range of inoculum density used in these experiments.
Leaf Spot of Mangoes Caused by Cylindrocladium scoparium in Central Brazil
Authors: Tozetto L. , Ribeiro W. R. C.
Published: May 2008

A leaf spot disease of mango (Mangifera indica) caused by Cylindrocladium scoparium was found in central Brazil in 1994. Pathogenicity tests and re‐isolations from artificially‐inoculated leaves confirmed that C. scoparium was the incitant. This is believed to be the first report of the fungus attacking mango leaves.
Sequence Analysis of the Genomic RNA 3′‐terminal Region of a Potyvirus from Brachiaria spp. Related to Gulneagrass Mosaic Virus
Authors: Morales F. J. , Ospina M. D. , Castano M. , Calvert L. A.
Published: May 2008

The 3'terminal region of the genomic RNA of a potyvirus isolated from Brachiaria spp. which is related to guinea grass mosaic virus (GGMV), was compared to that of members of the sugarcane mosaic subgroup of poty viruses. Reverse transcription‐polymerase chain reaction (RT‐PCR) of total nucleic acid extracted from infected B. brizantha resulted in the amplification of a DNA product of c. 0.9 kb. This product was cloned and sequenced, it has an open reading frame of 149 amino acid residues, and a 3'untranslated region (UTR) of 474 nucleotides. Optimal alignments of the 3'UTRs of the Brachiaria potyvirus and members of the sugarcane mosaic subgroup of potyviruses showed that it has nucleotide sequence similarities of c. 42. 46, 46, and 46% to maize dwarf mosaic virus strain A, sugarcane mosaic virus strains SC and MDB, and sorghum mosaic virus strain SCH, respectively. It had higher nucleotide sequence similarities of c. 88, 89, and 92% with Johnsongrass mosaic virus (JGMV) strains MDO, MDKSl and JG, respectively. Analyses of the deduced amino acid sequence of the Brachiaria potyvirus coat protein fragment revealed a 97.3% similarity to the JG strain of JGMV to which it is scrologically related. We propose that the Brachiaria potyvirus now be considered a strain of JGMV (designated JGMV‐Brac).
Effects of Essential Oils on Phytopathogenic Fungi In Vitro*
Authors: Zambonelli A. , D'Aulerio A. Zechini , Bianchi A. , Albasini A.
Published: May 2008

The essential oils of Thymus vulgaris L., of Lavandula R.C. hybrid and Mentha piperita L. were tested in vitro against the pathogenic fungi Rhizoctonia solani Kühn, Pythium ultimum Trow var. ultimum, Fusarium solani (Mart.) Sacc, Colletotrichum lindemuthianum (Sacc. & Magn.) Briosi & Cav. All the oils tested inhibited fungal growth. The most effective oil was that of thyme, with a fungicidal activity attributable to thymol, found in a concentration of 50.06% in the oil tested. SEM observations revealed that these oils cause degeneration of the fungal hyphae which appeared emptied of their cytoplasmic content.
Antiviral Activity of the Glucan Lichenan (Poly‐β(l→3, 1→4)D‐anhydroglucose)
Authors: Stübler D. , Buchenauer H.
Published: May 2008

Lichenan is a linear glucan of (1→3, 1→4)‐β‐glycosidic bonds in a ratio cf 1:2 that originates from the lichen Cetraria islandica. Lichenan at 5–1000 μg/ml exhibited antiviral activity against mechanically‐transmitted viruses of different taxonomic groups. The antiviral activity was demonstrated by the inhibition of symptom development and virus accumulation in greenhouse‐grown Nicotiana tabacum (four cultivars), N. benthamiana and N. glutinosa. In plants of N. tabacum cv. “Xanthi‐nc”, which react hypersensitively in response to TMV infection, lichenan reduced the number, but not the size, of necrctic lesions both, when added to purified virions or naked viral RNA. Partly hydrolized lichenan representing different degrees of polymerization (DP) of 6–30, 30–60, 60–190, and > 190, reduced the number of local and systemic infections to the same degree as the unchanged glucan. The antiviral effect of lichenan was restricted to the leaf‐area of application. Depending on the time of application, the strongest effect was achieved when lichenan was added directly to the inoculum. Post‐infectionally, it was inhibitory only up to 3 h post‐inoculation, indicating that early events of virus replication were affected. Viral inhibition caused by lichenan results frotn a plant‐specific protection, which does not function in N. rustica.

Although less inhibitory than lichenan, there were other mixed‐linkage β‐glticans (schizophylian, pacbytnan, laminaran, barley‐β‐glucan) causing antiviral effects. In contrast, pustulan as well as glucans of the a‐coniiguration (amyiose, dextran, nigeran, puUulan) were ineffective.
Antiviral Activity of the Glucan Lichenan (Poly‐β(→ 3,1 → 4)D‐anhydroglucose)
Authors: Stüobler D. , Buchenauer H.
Published: May 2008

Lichenan a β(1→ 3,1→ 4)β‐glucan exhibited a broad antiviral activity against mechanically transmitted viruses of different taxonomic groups in different Nicoliana spp. As shown for tobacco mosaic virus in vitro. lichenan did not interfere with cell‐free protein synthesis programmed with naked RNA or virus particles cotranslationally disassembled. Thus, inhibition of virus replication by lichenan is probably not attributed to direct interaction of lichenan and viral structural components, but rather to reduced sensitivity of the host tissue. Treatment of a suspension of cultured cells of Nicotiana tabacum with lichenan was accompanied by a slight increase in phenylalanine ammonia‐lyase (PAL) activity. However, lichenan applied to leaf tissue did not significantly stimulate PAL‐activity, therefore, antiviral action apparently did not depend on the induction of the phenylpropanoid pathway. According to experiments with lichenan and digitonin (used as a callose elicitor) restriction of viruses to initially‐infected cells by means of callose deposition also appears to be an improbable mechanism of viral inhibition. In cell suspensions treated with lichenan, slight changes in the extracellular concentration of free K+ were observed that did not reflect a marked K+ leakage, as caused by digitonin. This finding requires further examination. According to the present results, it is likely that lichenan affects the early virus‐cell interactions that occur after virus disassembly.
Differential Induction and Accumulation of β‐1,3‐Glucanase and Chitinase Isoforms in the Intercellular Space and Leaf Tissues of Pepper by Xanthomonas campestris pv. vesicatoria Infection
Authors: Lee Yeon Kyeong , Hwang Byung Kook
Published: May 2008

The virulent strain Ds 1 of Xanthomonas campestris pv. vesicatoria multiplied in pepper (cv. Hanbyul) leaves better than did the avirulent strain 81–23, which formed localized necrosis at the onset of pathogenesis. Infection of pepper leaves by X. campestris pv. vesicatoria induced the synthesis and accumulation of β‐1,3‐glucanase and chitinase in the intercellular space and leaf tissue of pepper plants. In the uninoculated controls, the two hydrolases remained at a very low level. High levels of the two enzymes were found in an incompatible interaction of pepper leaves with X. campestris pv. vesicatoria. In particular, chitinase activity in the intercellular washing fluids (IWF) was higher in the incompatible than in the compatible interactions. The direct detection of acidic β‐1,3‐glucanases on 10% native PAGE gels revealed only two isoform bands (Ga 1 and Ga 2). Isoelectric focusing identified two acidic β‐1,3‐glucanase isoforms with pl 5.0 and 5.2, and four basic isoforms with pl 7.1, 7.4, 7.9, and 8.8 in the IWF and extracts of infected leaf tissues. Some of the isoforms disappeared during pathogenesis and the others appeared during symptom expression. The acidic chitinase isoforms (Ca 1, Ca 2, and Ca 3) were located primarily in the intercellular spaces. Synthesis of high levels of the acidic isoform Ca 3 in infected pepper leaves was seen. Several basis chitinase isoforms accumulated only in diseased leaf tissue, and especially more in the incompatible than the compatible interaction. By using isoelectric focusing, the three acidic and seven basic chitinase isoforms in the IWF and leaf extracts were detected on chitin overlay gels.
Differences Between Barley, Oats and Wheat in the Occurrence of Deoxynivalenol and Other Trichothecenes in Norwegian Grain
Authors: Lanoseth W. , Elen O.
Published: May 2008

The amount of the Fusarium toxins deoxynivalenol (DON). 3‐acety‐DON. ivalenol and fusarenon × have been determined in about 3000 samples of barley, oats and wheat grown in Norway. The samples were collected in the period 1988–1994. and grouped according to grain species, year of production, district and sample category. The DON content was found to be significantly higher in oats than both barley and wheat in grain produced by ordinary grain producers in Norway. Of samples collected from grain silos. 68.7% of the barley. 97.1% of the oats and 66.3% of the wheat samples were found to contain 30 mg/kg of DON or more. The proportion containing 1000 μg kg or more was 2.1.13.4and0.0% in burley, oats and wheat, respectively. However, these variations in contamination level were not reflected in the results from two field trials, where the grain species were grown side‐by‐side in the same fields. The differences in contamination level between the grain species seem to be due partly to edaphic and agrotechnical factors and partly to variation in the susceptibility to different Fusarium species in interaction with climatic factors. Nivalenol(≥ 50 μg/kg) was detected in 8.3% of the barley samples. 8.2% of the oats and 0.4% of the wheat samples. Samples collected at the grain silos were then not included.
The Influence of pH on Biodeterioration of a Tropical Timber Exposed to Mixed Cultures of Biocontrol and Wood‐Rot Fungi
Authors: Ejechi B. O. , Obuekwe C. O.
Published: May 2008

A laboratory investigation of the decay control potentials of Trichoderma viride and Penicillium sp. on the deterioration of obeche wood (Triplochiton scleroxylon). buffered at various pH. by wood‐rot fungi (Gloeophyllum sp. and Gloeophyllum sepiarium), was carried out. Biomass determinations in carboxylmethyl cellulose broth at various pH showed that the biocontrol fungal strains exployed grew better as the pH approached neutral while the reverse was true for the wood‐rot fungi. Deterioration of wood (buffered at various pH) simultaneously inoculated with the biocontrol and wood‐rot fungi was more markedly reduced towards neutral pH than at lower pH values. Decay begun in wood initially infested with rot fungi before inoculation with biocontrol fungi was virtually halted at neutral pH. which was not the case in lower pH (2 and 3) buffered wood simultanecously inoculated with biocontrol and wood‐rot fungi. A killing effect was indicated when the rot fungi failed to appear on potato–dextrose agar from interior sections of the wood blocks. Manipulation of pH may prove important in biological control of wood decay.
Suppression of Pythium Root Rot of Cucumber by a Fluorescent Pseudomonad s Related to Reduced Root Colonization by Pythium Apbanidermatum
Authors: Moulin F. , Lemanceau P. , Alaboutte C.
Published: May 2008

Root colonization of cucumber with P aphanidermatum OP4 was examined in the absence and in the presence of either fluorescent pseudomonad strain CH31 or strain CHI. Quantification was performed by antigen‐coated plate enzyme‐linked immunosorbent assay (ACP‐ELISA) using an antiserum obtained from a rabbit immunized with zoospore cysts: this antiserum did not cross‐react with non‐infested roots of cucumber, or with the fluorescent pseudomonads CH31 and CHI. Application of the previously developed biotest enabled us to assess the ability of the two strains of fluorescent pseudomonad to suppress root rot caused by P. aphanidermaium OP4.

At all bacterial densities tested, the fluorescent pseudomonad CH31 led to a significant reduction of both the root colonization of cucumber with P aphanidermatum OP4 and the severity of Pythium root rot. In contrast, the fluorescent pseudomonad CHI had no effect on either root colonization oe disease sevenity.
A Rapid Tomato Seedling Assay for Verticillium Wilt
Authors: Madhosingh C.
Published: May 2008

A rapid (10‐min) tomato seedling assay was developed for determining the wilt‐capacity of cell‐free culture filtrates of race 1 and race 2 isolates of Verticiilium dahliae. The assay also rapidly determined the differences in wilt resistance between tomato cultivars. Rapidity was attained by manipulating incubation conditions to promote rapid wilting. These included inducing elongated stems in the susceptible cv. Bonny Best seedlings by growth of plants in subdued light (2.2 × 102 lux) and by concentrating two‐fold the cell‐free culture filtrates of the pathogen. Further, rapid uptake of the wilt factors in the culture filtrates was facilitated during incubation by increasing transpiration with bright light (23.8 × 103 lux), a wind stream (125–150 metres/min) across the assay seedlings, low relative humidity (28%) and a relatively high assay temperature (30 C). When necessary, these conditions were altered to extend the assay times. This assay system was used to determine optimal incubation time, temperature and medium for obtaining culture filtrates with increased wilt capacities. The assay also determined the relative wilt capacities of races 1 and 2 and the comparative resistance of four tomato cultivars to wilt caused by races 1 and 2.
Identification of a Potential Source of Complete Resistance to Soilborne Wheat Mosaic Virus in a Wheat‐Thinopyrum Intermedium Addition Line
Authors: Rumajun A. , Jahter J. , Trottet M. , Lapierre H.
Published: May 2008

Soilborne wheat mosaic virus (SBWMV) is a Furovirus transmitted by the plasmodiophoraceous fungus, Polymyxa graminis. Resistant cultivars of wheat (Triticum aestivum) to SBWMV have already been described. The resistance encountered mostly includes root infection without viral migration to foliage. In this study, the reaction of addition lines (L1, LIS, L2, L3, L4, L7), and the partial amphiploid derived from wheat (Vilmornn 27) and Thmopyrum intermedium has been evaluated. Lines L1. L3. L7. L1S and cultivar Vilmorin 27 are susceptible to SBWMV. Lines L4 and TAF 46 are root infected only. Chromosome 4Ag in L4 is thought to have an equivalent reaction to that one found in the mostly encountered resistance. Another type of resistance in a wheat line (1.2) with the added chromosome 3Agi of Th. intermedium has been characterized. In this line, L2, no SBWMV particles were detected on their roots by enzyme‐linked immunosorbent assays. Contrary to observations made on lines L1, LIS, L3, L4, L7, amphiploid TAF 46. and the wheat cultivars (Festival. Fandango, Vilmonn 27), no resting spores of P. graminis were found on roots of L2 2 months post inoculation. It is suggested that the disomic addition line L2 is immune to SBWMV.
Suppressiveness to Clubroot, Pea Root Rot and Fusarium Wilt in Swedish Soils
Authors: Worku Y. , Gerhardson B.
Published: May 2008

Natural soil samples, collected from farms in central and southern Sweden, were tested for soil disease‐suppressiveness. The soils were mixed with inocula of either Plasmodiophora brassicae, Aphanomyces euteiches or Fusarium oxysporum. f.sp. spinaciae and disease symptoms were scored on Chinese cabbage, pea and spinach respectively, that were grown in the soil‐inocula mixture under greenhouse conditions. Most field soils limited the development of disease to some degree compared with a commercial Sphagnum‐sand‐soil mixture, and about 10% were strongly suppressive to disease outbreaks caused by either P. brassicae, A. eutheiches. or F. oxysporum f.f.sp. spinaciae. Some tested soils gave higher disease indices of A. euteiches compared with the control growing medium and were regarded disease synergistic. The suppressiveness found was specific for each disease tested and in no case was a soil sample strongly suppressive to two of the diseases tested.
Fungi Associated with Root Rot of Winter Wheat in Alabama
Authors: Chen C. , Collins D. J. , Morgan‐Jones G.
Published: May 2008

Winter wheat plants were sampled during the spring and autumn to identify fungi associated with root rot in Alabama. Samples were taken from 61 fields in the major wheat‐producing areas of the state; 179 fungi were isolated, identified, and tested for pathogenicity. Of the fungi identified, 46 (26%) were Gaeumannomyces graminis var. tritici, 37 (21%) were Cochtiobolus sativus, and 55 (31%) were Fusarium species of which 37 (21%) were Fusarium oxysporum. Other fungi identified that were pathogenic on wheat were Rhizoctonia solani, Sderotium rolfsii, and Pythium spp. G. g. var. tritier was the main pathogen associated with diseased root and lower stem tissue of wheat in Albama.
PassifloraLatent Carlavirus in European Collections of OrnamentalPassiflora
Authors: Hicks R. G. T. , Mohamed M. E. , Blakesley D.
Published: May 2008

Passifloralatent carlavirus (PLV) was detected by PAS‐ELISA in 15 species/hybrids or cultivars ofPassiflorawith mosaic, mottle or blotch leaf symptoms, from botanical and germplasm collections in the UK and The Netherlands surveyed in 1992 and 1993. A single lesion isolate of PLV induced leaf chlorosis in inoculated apparently virus‐freeP. caerulea. This is the first report of PLV in the UK.
Witches'Broom of Rhamnus catharticus: A New Phytoplasma Disease
Authors: Müurer R. , Seemüller E.
Published: May 2008

A lethal witches'broom disease of buckthorn (Rhamunus catharticus) has been observed in south‐western Germany. The disease is associated with the presence of a distinct phytoplasma that is most closely related to the phytoplasmas of the apple proliferation cluster. However, the agent can clearly be distinguished from the other cluster members.
Bacterial Vascular Necrosis and Root Rot Disease of Sugar Beet in Egypt
Authors: Saleh O. I. , Huang P.‐Y. , Huang J.‐S.
Published: May 2008

Five pectolytic bacteria were isolated from roots and petioles of sugar beet exhibiting soft rot and vascular necrosis symptoms that were collected from different fields in El‐Minia Governorate, Egypt. Inoculation of the bacteria into sugar beet roots through wounded crowns or injured lateral roots reproduced soft rot and vascular necrosis symptoms. According to their biochemical and physiological characteristics, pathogenicity tests, fatty acid composition analysis, and electron microscopy, the bacteria were identified as Erwinia carotovora ssp. betavasculorum. This is the first report of the disease in Egypt.
Transmission of Three Strains of Tobacco Streak Ilarvirus by Different Thrips Species Using Virus‐infected Pollen
Authors: Klose M. J. , Sdoodee R. , Teakle D. S. , Milne J. R. , Greber R. S. , Walter G. H.
Published: May 2008

When cucumber seedlings were dusted with tobacco streak ilarvirus (TSV)‐infected pollen and infested with 5–10 thrips (adults and larvae mixed), Thrips tabaci transmitted all three Australian strains of TSV. In similar work, Microcephalothrips abdominalis transmitted both and Frankliniella schultzei one strain, respectively, of two TSV strains tested. Transmission of the Ageratum strain (TSV‐Ag) infecting pollen of Ageratum houstonianum was very efficient (100%) by all three thrips species. However, transmission rates of only 0–28% were achieved using the Ajuga strain (TSV‐A) and the strawberry strain (TSVS) in pollen of other hosts. A fourth thrips species, T. parvispinus, transmitted TSV‐Ag from infected tomato pollen to Chenopodium amaranticolor seedlings. There was, therefore, little or no vector specificity in the thrips transmission of the three strains of TSV, but factors associated with the virus‐infected pollen affected the efficiency of transmission. This is the first report of F. schultzei and T. parvispinus as vectors of TSV.
Cultural Growth Patterns and Incompatibility Reactions in Diaporthe and Phomopsis Populations
Authors: Muntan̄ola‐Cvetković M. , Vukojević J. , Mihaljčević M.
Published: May 2008

Comparative studies were carried out with cultures isolated from Phomopsis condiomata and/or Diaporthe ascomata found on naturally‐infected living stems or on overwintered stem fragments of Arctium lappa L., Helianthus annuus L., Glycine max (L.) Merr., and Xanthium italicum Moretti, growing in or nearby the same fields in Vojvodina. Results underscored the heterogeneity of the Phomopsis anamorphs in the D. arctii (Lasch) Trav, complex, Intra‐specific vegetative incompatibility groups were distinguished among Phomopsis and/or Diaporthe populations from A. lappa. More than one phytopathogenic Phomopsis and/or Diaporthe species were identified on X. italicum. P. longicolla Hobbs was isolated for the first time in Yugoslavia from soybean stem debris. The holomorph Diaporthe (Phomopsis) helianthi Muntanola‐ Cvetkovic, Mihaljcevic et Petrov showed distinguishing characteristics with respect to other congeneric fungi.
Rapid Identification of Xanthomonas campestris pv. graminis and X.c. pv. phlei by Fatty Acid Profiling
Authors: Sletten A.
Published: May 2008

Xanthomonas campestris pv. graminis and X. campestris pv. phlei isolated from different grass‐species were analysed for their fatty acid content with a gas‐chromatograph and a commerially‐available software package. The two pathovars could be rapidly and reliably identified and separated from each other with this technique, offering alternative to time‐consuming identification by biochemical and pathogenicity tests.
Identification and Phytotoxicity of 3‐methylthiopropanoic and Trans‐3‐methylthiopropenoic Acids Produced in Culture by Xanthomonas campestris pv. vitians
Authors: Scala F. , Zoina A. , Coppola L. , Capasso R. , Lorito M. , Evidente A.
Published: May 2008

Two phytotoxic metabolites were isolated from culture filtrates of Xanthomonas campestris pv, vitians, the causal agent of lettuce leaf spots and headrot. The two compounds were identified as 3‐methylthiopropanoic (1) and trans‐3‐methylthiopropenoic (2) acids by chemical and spectroscopic methods. Toxic effects of the two compounds on leaf tissues and protoplasts of lettuce and cabbage were investigated. Solutions of 1 and 2 induced chlorosis and necrosis on lettuce leaves at minimum concentrations of 300 and 50 μg/ml, respectively. Infiltration in cabbage leaves did not produce any symptoms. The LD50 values for 1 and 2 against lettuce protoplasts were 15 and 16 μg/ml, respectively. Activity of the two metabolites against cabbage protoplasts was very low (LD50 > 500 μg/ml).
Fungicidal Activity of Two Spermidine Analogues
Authors: Mackintosh C. A. , Walters D. R.
Published: May 2008

The potential use of polyamine analogues as inhibitors of polyamine biosynthesis to control plant pathogenic fungi is well established. However, all of this information relates to the use of putrescine analogues and no data exist for spermidine analogues. In the present work, two spermidine analogues. N1‐ and N8‐acetylspermidine were evaluated against powdery mildew on barley. Post‐inoculation treatments reduced infection by 69.7% and 51.5%. respectively. Since the barley powdery mildew fungus cannot be grown axenically. mode of action studies were undertaken using the oat leaf‐stripe pathogen Pyrenophora avenae. Neither of the analogues had any effect on polyamine biosynthesis in P. avenae grown in vitro. Although the mechanism(s) by which inhibitors affect in vivo fungal growth and in vitro growth may differ, it is unlikely that the antifungal properties of the analogues are the result of a perturbation in polyamine biosynthesis.
Peroxidase Isoenzymes in Strawberry Roots Infected with Binucleate Rhizoctonia spp. and their Implication in Disease Resistance
Authors: Krstiĉ B. , Vico I. , Toˇiĉ M. , Stojanović G.
Published: May 2008

Infection of strawberry plants with binucleate Rhizoctonia spp. results in an increase in peroxidase activity and the appearance of new isoforms of the enzyme. In healthy and diseased roots of two different strawberry genotypes seven peroxidase isoenzymes were found. In healthy strawberry cv. Senga Sengana, which was moderately resistant to infection, four isoenzymes (1, 2, 5, and 6) were found. Moreover the activity of these isoenzymes was increased and three new isoenzymes (3, 4, and 7) were found in infected roots. In the strawberry hybrid 3/2/86/88/R, which is very susceptible to infection, only isoenzyme 2 was present in the roots of healthy plants. Following infection, the activity of isoenzyme 2 was increased and five new isoenzymes (1, 4, 5, 6, and 7) were detectable. The results obtained indicate that strawberry resistance to binucleate Rhizoctonia may be correlated with peroxidase isoenzyme profile with particular reference to isoform 3, which is only present in infected roots of the moderately resistant cv., Senga Sengana.
Evidence for Resistance‐inducing Compounds in Conidia of Erysiphe graminis f.sp. hordei
Authors: Kristensen H. J. , Smedegaard‐Petersen V.
Published: May 2008

Preparations of Erysiphe graminis f.sp. hordei conidia were spray‐applied to the first leaf of barley plants which were subsequently challenge inoculated with virulent powdery mildew. The powdery mildew reducing effect of the preparations was assessed by scoring the outcome of the challenge inoculation. Homogenates of ungerminated conidia, germinated conidia, and methanol‐water extracts of germinated conidia reduced the number of powdery mildew colonies. Cell wall fragments from ungerminated conidia, germinated conidia, and conidial germination fluid obtained from conidia germinated in aqueous suspension did not reduce the number of powdery mildew colonies. Microsconical analysis of the infection course following challenge inoculation indicated that the powdery mildew reducing effect is due partly to induced resistance.
Fusarium Resistance in Gladiolus: The Development of a Screening Assay
Authors: Loffler H. J. M. , Straathof Th.P. , Van Rubroek P. C. L. , Roebroeck E. J. A.
Published: May 2008

Fusarium oxysporum f.sp. gladioli is a major pathogen of Gladiolus and resistance to this fungus is needed. A standardized screening assay to assess resistance levels in breeding selections must be developed. Corms of cultivars, ranging from susceptible to resistant, were planted either in soil infested with various inoculum levels or incubated in vitro after wound inoculation. The soilgrown corms were rated using relative length of the shoots and average disease rating. In vitro incubated corms were evaluated visually after 6 weeks. All parameters produced similar results. It was concluded that the relative length of shoots of corms after 8 weeks of growing in soil with a high inoculum level combined with the assessment of the average disease rating of the corms after either 8 or 20 weeks is an effective screening assay.
The Effect of Extracts of Some Nigerian Spices on Biodeterioration of Okro (Abelmoschus (L) Moench) by Fungi
Authors: Ejechi B. O. , Ojeata A. , Oyeleke S. B.
Published: May 2008

Aqueous and ethanol extracts of five Nigerian spices (Allium sativum, Zingiber officinale, Aframomum melegueta, Xylopia aetiopica and Monodora myristica) inhibited the growth of fungi (Botryodiplodia theobromae, Aspergillus niger, Aspergillus flavus, Mucor sp., Rhizopus stolonifer, Penicillium sp., Fusarium sp.) isolated from deteriorating okro on agar plate with an average minimum inhibitory concentration of 6.0% (v/v); a marked reduction in weight loss of the challenged extract — impregnated okro fruit was observed with A. sativum and Z. officinale. Reduction in okro carbohydrate was best inhibited by Z. officinale while X. aetiopica best limited the loss of protein. Changes in pH and titratable acidity of challenged okro was inhibited best by A. sativum. Z. officinale and A. melegueta while in all cases. M. myristica showed the least ability to reduce biodeterioration. Of the treatments applied, the combination of mild heat, and mixtures of aqueous Z. officinale and A. melequeta extracts markedly reduced biodeterioration of fresh okro as indicated by the little loss of carbohydrate (1.2%) after 3 months of storage. Spices may be economically important in the application of hurdle technology for preservation of fruits.
Immuno‐capture Polymerase Chain Reaction and Plate‐Trapped ELISA for the Detection of Apple Stem Pitting Virus
Authors: Jelkmann W. , Keim‐Konrad R.
Published: May 2008

Isolates of apple stem pitting (ASP) and pear vein yellows (PVY) were sap transmitted from apple and pear cultivars, respectively, to Nicotiana occidentalis ssp. obliqua. Total nucleic acid extraction, including a proteinase Kdigestion of leaf homogenates prior to phenol/chloroform extraction, was of limited use for RNA template preparation. Amplification products were obtained from N. occidentalis and from apple and pear leaf tissue. Three primer combinations near the viral 3′‐ terminus resulted in amplification products of 264 bp, 610bp and 1548bp. The specificity of the products was confirmed by restriction enzyme digestion. To improve RNA template preparation and the reliability of PCR tests from woody plant tissue, a fusion protein‐specific antiserum 647 was prepared to in vitro expressed viral coat protein. This allowed us effective immunocapture RT‐PCR assays from woody tissue infected with either ASPV and PVYV. Antiserum 647 reacted in an indirect plate‐trapped ELISA with ASPV isolates from N. occidentalis, whereas two antisera prepared previously to a different coat protein fusion construct were not successful in any of the ELISA types investigated. In addition a positive test result was obtained from PVY infected pear but not from apple.
Systemic Infection of Vigna mungo Using the Cloned DNAs of the Blackgram Isolate of Mungbean Yellow Mosaic Geminivirus through Agroinoculation and Transmission of the Progeny Virus by Whiteflies
Authors: Mandal B. , Varma A. , Malathi V. G.
Published: May 2008

Agroinoculation of blackgram (Vigna mungo) by the cloned genomic components (DNA‐A and DNA‐B) of a non‐sap transmissible isolate of mungbean yellow mosaic geminivirus (MYMV) has been demonstrated. It has been shown that MYMV has a bipartite genome. Tandem dimeric constructs of DNA‐A and DNA‐B were infectious when inoculated together and induced systemic yellow mosaic symptoms. Agroinoculation of germinated seeds of blackgram was superior to inoculation of stems of seedlings. Infection of blackgram plants was confirmed by ELISA, dot blot and Southern hybridization. Agroinfected plants contained different forms of DNA characteristic of whitefly transmitted geminiviruses. The virus from agroinfected plants was transmissible by the whitefly Bemisia tabaci.
Characteristics of Pathogenesis‐Related Proteins Induced in Phaseolus vulgaris cv. Pinto Following Viral Infection
Authors: Mohamed F. , Sehgal O. P.
Published: May 2008

Ten acidic and eight basic pathogenesis‐related (PR) proteins were induced in primary leaves of Phaseolus vulgaris cv. Pinto following infection with southern bean mosaic virus (SBMV), a virus that induces circular, brown necrotic local lesions. These PR proteins included: four, 17 kDa, serologically related, acidic proteins of unknown functions; two chitinases, one acidic (29 kDa) and one basic (32 kDa) possessing antifungal activities; and four (21 kDa, 28 kDa, 29 kDa, 36 kDa) serologically related, acidic glucanases. The production of PR proteins was minimal during the period of active SBMV multiplication; greatest increase of PR proteins occurred after SBMV had reached a maximum level. Several of these PR proteins, including the 29 kDa acidic chitinase and two acidic glucanases (21 kDa and 36 kDa) accumulated in the intercellular space fluid. Similar PR proteins were synthesized in Pinto bean primary leaves infects with any of three other viruses that formed lesions of divergent phenotypes. However, the proportion of some of the PR proteins in the various lesion‐types differed considerably. These results indicate that PR proteins play no active role in viral localization or inactivation and that their production is a metabolic adjustment to endogenous stress.
Evaluation of Spring and Winter Wheat Reaction to Fusarium culmorum and Fusarium avenaceum
Authors: Wojciechowski S. , Chelkowski J. , Ponitka A. , ŠLusarkiewicz‐Jarzina A.
Published: May 2008

Winter (37), spring (8) wheat accessions and additionally, 7 double haploid (DH) lines were examined for susceptibility to Fusarium seedling blight after inoculation with F. culmorum and F. avenaceum. Winter accessions exhibited lower susceptibility of about 30% to both pathogens than spring cultivars. Susceptibility of winter cultivars varied from low (22%) to high (97%). Evaluation of the root was found to be more reliable than evaluation of coleoptile necrosis.

F. avenaceum infected mostly root and, to a lesser extent, coleoptile and leaves, with about a three times lower disease score of coleoptile against root. F. culmorum caused a 1.5 higher disease score on root than on coleoptile. Susceptibility of DH lines was different from susceptibility of parental forms. Reaction of individual accessions to F. culmorum and F. avenaceum was different.
Survival, Germinability and Infectivity of Oospores of Peronospora viciae f.sp. fabae
Authors: van der Gaag D. J. , Frinking H. D.
Published: May 2008

A series of experiments was conducted to germinate oospores of Peronospora viciae f.sp. fabae. With rare exceptions, dry‐stored oospores did not germinate in water nor did they infect faba bean seedlings in soil. Long‐term storage, pre‐treatment with KMnO4 or addition of nutrients to the medium did not induce germination. Survival and infectivity of dry‐stored oospores were compared to those of oospores incorporated in a silt loam and a loamy sand soil in the field during 21–22 months. Under dry conditions, the percentage of living oospores did not change as determined by the vital stain tetrazolium bromide. In soil, less than 2% of the oospores had survived after 21 months. Infectivity of oospores was determined by a bioassay 17 and 21 months after oospores had been incorporated in soil. Diseased seedlings were obtained after inoculation of faba bean seeds with oospores extracted from the soil but not with the drystored ones. Soil samples from two field plots naturally infested with oospores 2 and 3 years before the bioassay were infective. Oospores collected with diseased plant material on one of these plots and subsequently stored dry for 3 years were not infective. The results suggested that oospores need a period of natural weathering to become germinable and infective.
Witches'Broom of Sarothamnus scoparius: A New Disease Associated with a Phytoplasma Related to the Spartium Witches'Broom Agent
Authors: Marcone C. , Ragozzino A. , Seemüller E.
Published: May 2008

In southern and central Italy, a witches’broom and decline disease of Sarothamnus scoparius has been observed. In affected plants, phytoplasmas were detected by PCR amplification of ribosomal DNA. Restriction fragment length polymorphism analysis of PCR‐amplified DNA revealed that the diseased plants were infected by a phytoplasma that is closely related to the spartium witches’broom phytoplasma, a member of the apple proliferation group.
Investigations on Adult Plant Resistance of Barley Against Erysiphe graminis f.sp. hordei
Authors: Heitefuss R. , Ebrahim‐Nesbat F. , Ordonez M. T. , Schorn‐Kasten K.
Published: May 2008

Spring barley cultivars and lines were tested for 3 years in field studies for adult plant resistance against Erysiphe graminis f.sp. hordei. The cultivars Osiris and Asse were selected for further detailed cytological studies and compared with the susceptible cultivar Peruvian. Under controlled greenhouse conditions, the percentage of conidia that had formed a functional haustorium and secondary hyphae (infection efficiency) was reduced in fifth leaves of the adult plant resistant cultivars. On fifth and flag leaves of adult plant resistant cultivars, papillae were formed more frequently under primary germ tubes and appressoria, and fungal penetration was prevented more often than on the susceptible cultivar Peruvian. In ultrastructural studies various types of papillae were observed, but could not be strictly correlated with penetration success or failure of the fungus.
Influence of Virus on the Chlorophyll, Carotenoid and Polyamine Contents in Grapevine Microcuttings
Authors: González E. , Mosquera M. V. , San José M. C. , Diaz T.
Published: May 2008

We have studied the effect of different types of virus infections on the content in chlorophylls, carotenoids and free polyamines in shoots of vine cv. Albariño cultured in vitro. The ratio of chlorophyll a/c hlorophyll b was maintained practically constant in the different cases studied. A significant increase was observed in the polyamines, especially putrescine, in shoots infected with the different types of virus, mainly in the cases of grapevine fleck disease+grapevine leafroll disease type I and grapevine stem pitting.
Leaf Disk Inoculation — a Useful Tool for Selecting Infections of Sunflower Downy Mildew at Low Inoculum Concentration, but Inappropriate to Pathotype Characterization
Authors: Spring O. , Rozynek B. , Zipper R.
Published: May 2008

A modified technique for leaf disk inoculation of sunflower with zoosporangia of the downy mildew pathogen Plasmopara halstedii was developed. Infection with low concentrations of inoculum was obtained down to the level of single sporangia. No significant difference in the infection rate was seen between disks from cotyledons and true leaves. This makes leaf disk inoculation particularly suitable for infections at low sporangium density and for the investigation on plant tissue which cannot be infected with whole seedling inoculation. The technique seems, however, to be inappropriate for pathotype characterization using differential host lines.
A Comparison of the Resistance Against Phytophthora fragariae var. rubi, the Causal Agent of a Raspberry Root Rot
Authors: Laun N. , Zinkernagel V.
Published: May 2008

Zoospore encystment, sporulation, oospore formation and detection of Phytophthora fragariae var. rubi, the causal agent of raspberry root rot, on three Rubus genotypes with different levels of resistance were investigated. There were no qualitative or quantitative differences in encystment as determined by scanning electron and fluorescence microscopy. Susceptibility was associated with an extended period of sporulation on roots with a proportion of roots containing oospores increasing continuously until the whole root system was colonised and the fungus could be isolated from the stem bases. Quantitative resistance as found in some raspberry (Rubus idaeus) cultivars was associated with a shorter sporulation period and decreasing proportion of the roots containing oospores due to the strong regeneration of healthy roots and limited spread of the fungus in the root system. Stem bases were consequently not affected. Sporulation was very limited on a blackberry x raspberry hybrid that was almost totally resistant to root rot and sustained infections could not be found.
Immunocapture Polymerase Chain Reaction for the Detection and Characterization of Cacao Swollen Shoot Virus 1 A Isolates
Authors: Hoffmann K. , Sackey S. T. , Maiss E. , Adomako D. , Vetten H. J.
Published: May 2008

Oligonucleotides derived from the flanking regions of the putative coat protein gene of the cacao swollen shoot badnavirus isolate I A (CSSV‐1 A) were able to prime the synthesis of specific products directly from extracts from CSSV‐IA‐infected leaves by immunocapture polymerase chain reaction (IC‐PCR), following trapping of virions with polyclonal antibodies to CSSV‐1 A. CSSV isolates serologically distinct from CSSV‐I A were not detected by IC‐PCR when the CSSV‐I A‐derived primers were used following trapping with homologous antisera. IC‐PCR was at least 100‐fold more sensitive than double antibody sandwich (DAS)‐ELISA in comparative tests on samples from greenhouse‐grown cacao plants. The superior sensitivity of IC‐PCR over DAS‐ELISA was confirmed in attempts to detect and identify CSSV‐I A isolates in field samples and permitted detection of CSSV‐I A isolates even in symptomless leaves from plants showing stem swelling only. The IC‐PCR products obtained from four randomly selected field samples were sequenced and shown to contain a region of the CSSV‐I A genome where ORF X overlaps ORF 3. Analysis of the partial amino acid sequences deduced from ORF 3 and ORF X of the four field isolates revealed a considerable variation in these CSSV‐I A gene products.
Shoot‐feeding Aphids Promote Development of Gremmeniella abietina, the Fungal Pathogen Causing Scleroderris Canker Disease in Conifers
Authors: Virtanen T. , Ranta H. , Neuvonen S.
Published: May 2008

We tested experimentally whether shoot feeding aphids Cinara pinea (Mordv.) can promote the development of Gremmeniella abietina (Lagerb.) Morelet, a fungus which causes Scleroderris canker disease in conifers. Pine seedlings were infested with aphids at two different times, and subsequently inoculated with conidia of G. abietina at two different times. The degree of infestation was classified into three groups based on the number of aphids/seedling: none, one (low level), and three (high level). Because of parthenogenetic reproduction, the number of aphids increased during the summer, so we also used aphid numbers to explain the development of the symptoms. Necrosis caused by G. abietina was more prevalent in seedlings infested by aphids in June, and inoculated with fungus in July. Expressed as percents of the total length of the shoots, the necrosis had advanced 50%, 70%, and 95% with no, low, and high aphid levels, respectively. Canker formation was significantly greater when G. abietina conidia were inoculated in July, compared to August. In August, there were no statistically significant differences in the intensity of disease between aphid infestation levels, but the mean number of aphids was related to disease intensity. In the spring following infection, seedlings with aphids had more dead and fewer healthy terminal buds compared to seedlings without aphids.
Polyacrylamide Gel Electrophoresis (PAGE) and Densitometric Measurement of Enzyme Activity of the Pea Root Pathogen Aphanomyces euteiches in Pea Roots
Authors: Kiøller R. , Rosendahl S.
Published: May 2008

A new method to measure enzyme activity of the fungal root pathogen Aphanomyces euteiches in pea roots is described. The specific enzymes of the fungus and the host were separated by polyacrylamide gel electrophoresis (PAGE) and the activity of fungal Glucose‐6‐phosphate dehydrogenase and Phosphoglucomutase were quantified by densitometry. Fungal activity could be correlated to the percentage infected root length and to the disease symptoms of the plants. The activity of A. euteiches was studied in a time course experiment with increasing levels of zoospore inoculum. The results indicated that an increase in inoculum level resulted in a faster disease development in the plants. The relation between fungal enzyme activity and infection level is discussed.
Occurrence of Fusarium oxysporum f. sp. cumini in the Island of Chios, Greece
Authors: Pappas A. C. , Elena K.
Published: May 2008

A severe disease of cumin causing pre‐mature plant death was observed in the island of Chios, Greece. Disease symptoms included sudden red‐brown shrivelling of the foliage, growth retardation and pre‐harvest plant death. From plants showing early disease symptoms Fusarium oxysporum (F.o.) was consistently isolated. In artificial inoculations, representative isolates from this fungus species were found to be pathogenic on cumin, confirming the belonging to the f. sp. cumini. This is the first report of F.o. f.sp. cumini in Greece.
A Serious Disease of Groundnut Caused by Cowpea Mild Mottle Virus in the Sudan
Authors: El‐Hassan S. M. , Naidu R. A. , Ahmed A. H. , Murant A. F.
Published: May 2008

A serious disease of groundnut (Arachis hypogaea L.) characterized by stunting of plants, downward rolling, mottling, general chlorosis and reduced size of the leaflets was observed in the Sudan. Surveys conducted from 1992 to 1994 showed that this disease was restricted to irrigated groundnut crops grown between the two Niles. The virus had slightly flexuous filamentous particles (626 nm long) and was transmitted by whiteflies. It was identified serologically as cowpea mild mottle virus (CPMMV). This appears to be the first record of natural occurrence of CPMMV on groundnut in the Sudan and the first evidence that it causes a disease of major economic importance.