bluuebunny/crossref_metadata_2025 huggingface dataset:
Crassulacean Acid Metabolism in Two Species of Orchids Infected by Tobacco Mosaic Virus‐orchid Strain and/or Cymbidium Mosaic Virus
Authors: Izaguirre‐Mayoral Maria Luisa , De Uzcategui Rafaela C. , Carballo O.
Published: May 2008

The effect of viral infections on the Crassulacean Acid Metabohsm (CAM) was determined in two orchid species. Plants of a Sophrolaeliocattleya (SLC) commercial hybrid were inoculated with either the orchid strain of the Tabacco Mosaic Virus (TMV‐O), with Cymbidium Mosaic Virus (CybMV) or with a mixture of both viruses. Plants of Epidendrum elongatum, a wild terrestrial orchid, were inoculated either with TMV‐O or with TMV‐O and CybMV simultaneously. Virus infected plants started to show a systemic mosaic on the leaves 3 to 4 years after inoculation, the symptoms being more appreciable in SLC than in E. elongatum. Double inoculation with TMV‐O and CybMV proved to the lethal for the SLC plants. TMV‐O infection caused 58 % and 24 % reduction in nocturnal leaf titratable acidity (TA) in SLC and E. elongatum, respectively. TMV‐O also changed the daily pattern of leaf nonstructural carbohydrates typical of CAM plants. A 50 % decrease in TA at dawn and a mid‐morning peak of sugar accumulation were measured in leaves of doubly inoculated E. elongatum plants. In SLC CybMV infection inhibited CAM and induced an accumulation of glucans in the leaves. Cytoplasmic agglomerations of CybMV, but not of TMV‐O, were detected in SLC mfected cells, whereas TMV‐O particles were clearly observed in the cytoplasm of E. elongatum. Infection by TMV‐O or CybMV in SLC caused an increase in chloroplasts volume and distortion of the grana due to high glucan accumulation. In contrast, TMV‐O infection in E. elongatum induced a lesser degree of damage in the cell ultrastructure.
Germination of Teliospores of Tilletia bardayana, the Causal Agent of Kernel Smut of Rice, in Relation to Some Physical Factors
Authors: Ghahal S. S. , Aulakh K. S. , Mathur S. B.
Published: May 2008

Teliospores of Tilletia harclayana germinated equally well on the surface of 2 % water agar, soil extract agar and in cavities made in water agar. Maximum germination occurred at 29 °C under 12 h photoperiod with artificial daylight (cool fluorescent light). There was marked increase in germination when the teliospores in bunted grains were pre‐treated for 30 min at 60 °C. Seventeen‐week‐old tehospores did not germinate while 73 week‐old‐tehospores showed retention of good germinability. Teliospores buried at 2 mm depth showed no germination whereas those at the moist surface germinated to produce sporidia. Implications of these results in the disease development are discussed.
Enantioselective Antiphytoviral Activity of l‐(α‐carboxyalkyl)‐4,5‐dimethyl imidazol‐3‐oxides in Systemically Infected Host Plants
Authors: Bauer Ute , Kluge S. , Nuhn P. , Stengerand P. , Lettau H.
Published: May 2008

l‐(α‐carboxyalkyl)‐4,5‐dimethyl imidazol‐3‐oxides were tested as D forms, L forms and racements to their antiviral activity to red clover mottle virus (RCMV) and alfalfa mosaic virus (AMV) in systemically infected host plants. A high enantioselective activity of antiphytoviral compounds was detected.

While the D forms reduce the virus content by more than 90 %, the L forms do no show any antiviral activity. With a virus‐inhibiting activity of 40 to 50 %, the racemates are in between these two forms and similar to Virazole. The optimal effective dose is 10–2 mol × 1–1 for the D forms. Reduced virus concentrations were observed in the systemically infected hosts more than six weeks after application of the compounds. The growth reduction of pea plants caused by the virus infection could be partially abolished by the viral inhibiting activity of the compounds.
Differential Screening in a cDNA‐Library from Spruce for Clones Associated with Forest Decline Reveals Accumulation of Ribulose‐l,5‐Bisphosphate Carboxylase Small Subunit mRNA
Authors: Etscheid M. , Buschmann K. , Köhler R. , Köster S. , Riesner D.
Published: May 2008

In this work we identified mRNA species in spruce (Picea abiesL., Karst), which are expressed in altered concentration if the symptoms of forest decline are present. A cDNA library was constructed and ‘damage‐associated’ clones were identified by differential screening. A procedure for polyA+‐RNA preparation from needles of spruce was established which yielded a RNA fraction of sufficient purity for gel electrophoresis, hybridization and most importantly, for reverse transcription and the consecutive steps of molecular cloning. RNA isolated from a symptomless and a damaged tree was combined and a cDNA library in phageλgt 10 was constructed. Three series of differential screening were carried out. In the first series radioactively labeled cDNA samples were prepared from poly A+‐RNA from a symptomless tree and a damaged tree. Differential hybridization of 10,000 cDNA clones with the two different samples yielded 37 cDNAs with different levels of hybridization signals. In a second series samples for hybridization tests were prepared from a symptomless and from a damaged tree at three different seasons, July, September, and December. These six different samples were used to search for significant hybridization differences in 2,000 clones. Five clones could be identified which showed hybridization differences independent of the annual season. In a third series, we tried to differentiate between genetic variations of individual trees and differences solely induced by the damage. Two mixed samples were prepared, one from an ensemble of 10 symptomless and one of 10 damaged trees. Six cDNA clones could be identified, which exerted clear differences with the mixed probes from the symptomless ensemble and the damage ensemble, respectively. In Northern hybridizations the cDNA clones could be attributed to mRNAs of well defined length.

After sequence analysis of the cDNA clones and homology search in a gene data bank two sequences could be identified. One clone codes for the small subunit of ribulose‐l,5‐bisphosphate carboxylase (Rubisco SS) and another for the subunit II of photosystem I. By quantitative Northern
Systemic Induction of Resistance in Phaseolus vulgaris L. to Tobacco Necrosis Virus (TNV) by Uromyces phaseoli (Pers.) Wint.
Authors: Kutzner B. , Hellwald K. ‐H. , Buchenauer H.
Published: May 2008

Preinoculation of primary half leaves or whole primary leaves of bean plants (Phaseolus vulgaris, cv. Pinto) with Uromyces phaseoli induced resistance against tobacco necrosis virus (TNV) in the opposite half leaves and in the trifoliate leaves, respectively. For expression of systemically induced resistance an interval of at least 4 days between primary and challenge inoculation was required. The most pronounced effectiveness was found after an induction period of 6 days.

Preinfectional treatment with intercellular washing fluids extracted from rust infected bean leaves (IWF‐R) also reduced disease incidence of TNV. Extracts taken 6 days after rust inoculation induced the most pronounced effect on resistance. For induction of resistance an interval of at least three days between application of IWF‐R and TNV‐inoculation was necessary. IWFs from healthy leaves (IWF‐H) did not induce resistance to TNV. The disease reductions of systemic protection by IWF‐R in the untreated primary half leaves and in the trifoliate leaves averaging 50%. The IWF‐R could be diluted to 1/4 of its original concentration without appreciable loss of the resistance‐inducing capacity.

Besides the resistance inducing effects, the IWF‐R and in addition IWF‐H showed virus inactivating activity; this effect was restricted to the treated leaf area. When IWFs were applied at short time intervals either (0–8 h) before or (0–4 h) after TNV inoculation, the number of local lesions was markedly reduced. Increasing the pre‐ or postinfectional time intervals (0.5–2 dai or 6–8 hpi) diminished the activity significantly. The effectiveness of IWF‐R increased at prolonged preinfectional time intervals (e.g. 3 and 4 dai) while extracts of healthy plants were ineffective. The biphasic pattern of activity indicates that IWF‐R contains ingredients reducing virus infectivity and inducing resistance to TNV.

When the transcription inhibitor actinomycin D and the translation inhibitor cycloheximide were applied simultaneously with IWF‐R 3 dai the resistance inducing effect of IWF‐R was prevented. In preliminary ultrafiltration experiments, the molecular size of the inducing ingredients of IWF‐R could be limited to 10–20 kd and those of the virus inactivating compounds to 1–5 kd.
Scanning Electron Microscopy of Olive and Oleander Leaves Colonized by Pseudomonas syringae subsp. Savastanoi
Authors: Surico G.
Published: May 2008

Leaves of olive and oleander were sprayed with suspensions of their homologous strains (PVBa230 and ITM519, respectively) of Pseudomonas syringae subsp. savastanoi and examined by SEM. It was found that both strains multiplied on the lower surface of the leaves of both species. Preferred sites for survival and multiplication were the shields of peltate hairs on olive and the stomatal pits on oleander. The findings suggest that, at least in olive leaves, some bacteria entered the leaf tissue through the stornata but that this was not important since cells which entered the host did not cause any disease symptoms. Cells of both strains were agglomerated and cells of ITM519 were further attached to the surface of the leaf hairs on oleander by fibrillar material.

Inoculated leaves did not show any disease symptoms except at leaf abscission scars on olive plants where leaves had been excised prior to inoculation. It is suggested that on both olive and oleander preexisting wounds are necessary for symptoms to develop.
Restriction Fragment Length Polymorphisms of Mitochondrial and Nuclear DNAs among Korean Races of Magnaporthe grisea
Authors: Ko Jong Hyun , Hwang Byung Kook , Hwang Byung Gap
Published: May 2008

Three KJ‐races of Magnaporthe grisea (virulent to only japonica type rice cultivars) and seven KI‐races (virulent to either indica or japonica type cultivars) isolated from various rice‐growing areas of Korea were assayed for restriction fragment length polymorphisms (RFLPs) in mitochondrial and nuclear DNAs of the fungus. The size of mitochondrial DNA of M. grisea was estimated to be approximately 39. 8 kb. No RFLP in the mt DNA was detected among the 10 Korean races, indicating an extensive conservation in the gene composition of mt DNA without sequence variation. The identical restriction patterns of mt DNA also suggest that mt DNA of M. grisea may not be responsible for pathotypic diversity and variability. Southern blot analysis with five single‐copy DNA probes showed considerable polymorphisms. Much diversity was detected in the three KI‐races predominated during 1978–1985 in Korea. In contrast, no genetic variation was detected between other four KI‐races and three KJ‐races. RFLPs in nuclear DNA were correlated to some extent with the prevailing races in Korea. However, relationship between RFLPs in nuclear DNA and virulence of M. grisea races was inconclusive.
Comparison of the Wheat Brown and Yellow Rusts for Monocyclic Sporulation and Infection Processes, and their Polycyclic Consequences
Authors: Sache I. , De Vallavieille‐Pope C.
Published: May 2008

Sporulation capacity and infection efficiency of wheat brown and yellow rusts were measured daily in favourable controlled conditions. Monocyclic sporulation capacity for a single lesion of yellow rust was 9 times greater than for an isolated lesion of brown rust, and 40 times greater than for a lesion of brown rust at medium infection density. Infection efficiency fluctuated and reached about 40 % for brown rust but remained under 5% for yellow rust. For both fungi, sporulation capacity and infection efficiency compensated for each other, but their product, the daily multiplication factor, was greater for yellow rust than for brown rust. Progeny/parent ratio was 3 times greater for yellow rust. Effect of daily multiplication factor variations on epidemic progress was simulated using a simple matrix model. Increase in number of lesions was faster in brown rust than in yellow rust because of a latent period shorter by 2 days. Semi‐systemic growth of yellow rust fungus reduced, however, the difference between both fungi when sporulating surface was calculated.
Compatibility of Erysiphe graminis Hybrids f. sp. secalis X f. sp. Tritici with Wheat Lines Involving Resistance Genes from Rye
Authors: Oku Takashi , Tsuchizaki Tsuneo
Published: May 2008

Compatibility of hybrid cultures Erysiphe graminis ff. sp. secalis (SI) ×tritici (t2) was tested in the laboratory with wheat cultivars involving different resistance genes and with two rye cultivars. Segregation was observed on wheat without resistance gene and with resistance genes Pm1, Pm3b and Pm3c compatible with t2, but not on wheat with resistance gene Pm2, Pm 3a, Pm 4a and Pm 5 incompatible with t2, nor on rye. It was obvious that S1 involves avirulence genes to Pm1, Pm2, Pm 3a, pm 3b, Pm 3c, Pm 4a, Pm 5. Segregation was found on wheat cultivars involving rye resistance genes Pm 7 (Transfed) and Pm 8 (Kavkaz), but cv. Transec (Pm7) was incompatible with all cultures used, because Transec involves another gene for resistance. The results indicate that hybridization between formae speciales secalis and tritici of the fungus can be a source of fungus compatibility with wheat with rye resistance, even in field conditions.
Virus Diseases of Pepper (Capsicum annuum L.) in Ethiopia
Authors: Agranovsky A. A.
Published: May 2008

Viruses occurring in hot pepper (Capsicum annuum L.) in Ethiopia during 1984–1986 were identified and their symptomatology, host range, serology, morphology and transmission described. Potyviruses were found to cause severe infections of pepper wherever the crop was observed. Disease incidence and yield loss in most surveyed areas were estimated at 40–100 % and 15–50 %, respectively. Besides potato Y and pepper veinal mottle viruses, a new potyvirus with distinctive properties was found widely distributed in Shewa and Welega Provinces. The virus, tentatively designated Ethiopian pepper mottle virus (EPMV), was shown to have an unusually narrow experimental host range and filamentous particles about 700–750 nm in length, and to be nonpersis‐tently transmitted by aphids but not transmissible through pepper seeds. Cucumber mosaic virus was detected in some locations, but appeared to be of minor significance.
Studies on Plant Viruses‐soil Colloids Interactions
Authors: Piazzolla P. , Buondonno A. , Palmieri F. , De Stradis A.
Published: May 2008

Stability and infectivity of cucumber mosaic virus, strain D (CMV‐D), associations with kaolinite and montmorillonite were determined, as affected by: i) nature of clay minerals; ii) nature of clay saturating cations; iii) exposure to dissociating salt solutions (2 M LiCl).

Infectivity experiments carried out with sediments following centrifugation of the virus‐clay mixtures (sd fractions), showed that, in absence of LiCl, the highest values were obtained with kaolinite, in the order Li+= K+ > NH4+= Mg++ > Na+ > Ca++ clay saturating cations, ranging between 91 and 30 % of the untreated control, whereas comparable montmorillonite fractions gave infectivity values with all cations about 10–15 % of the control.

In presence of 2 M LiCl, montmorillonite preserved infectivity of the same fraction (Lsd fraction), which, in the case of Li+‐ or Ca++ ‐saturated samples, was higher when compared with the corresponding sd values, thus revealing for these cations an amplifying effect on infection. This did not occur with kaolinite which, however, gave a Lsd fraction more infectious than the other clay.

The results confirmed that clay minerals preserve infectivity of virus preparations exposed to critical conditions, thus providing an explanation for the persistence in soil of infectivity of viruses which are normally not soil‐borne. Under appropriate soil conditions these viruses may form complexes with clay minerals thus retaining an infectivity which may be enhanced by addition of cations as those contained in fertilizers.
The Hypersensitive Reaction of Soybean Cultivars to Tobacco Necrosis Virus Does Not Induce Systemic Resistance but Inhibits Plant Growth
Authors: Pennazio S. , Roggero P.
Published: May 2008

With soybean cultivars belonging to different maturation groups, the hypersensitive reaction to mechanically inoculated tobacco necrosis virus (TNV) did not induce systemic resistance against challenging viruses that infect locally (TNV) or systemically (alfalfa mosaic virus, AMV; soybean mosaic virus, SbMV). No form of resistance was found when resistance was tested by measuring the area and antigen content of necrotic local lesions induced by challenging TNV, or when it was tested by determining chlorophyll content and viral antigen in tissues systemically infected with AMV or SbMV.

Growth of shoots was partially inhibited by the hypersensitive reaction produced by inoculation of TNV in primary soybean leaves. This inhibition was transient and did not appear to be due to stress ethylene produced by the inoculated leaves during lesion development. It was probably a consequence of nutrient depletion due to collapse of primary leaves following virus infection.
The Ability of Aphis craccivora, A. gossypii and A. citricola to Transmit Single and Mixed Viruses to Cowpeas
Authors: Roberts Julia M. F. , Thottappilly G. , Hodgson C. J.
Published: May 2008

The ability of populations of adult apterous Aphis craccivora, A. gossypii and A. citricola to transmit the cowpea aphid‐borne virus (CAMV) and cucumber mosaic virus (CMV) to cowpea was investigated. CMV was more readily transmitted than CAMV by all three aphid species, but was most readily transmitted by A. craccivora and A. citricola, with transmissions ranging from 64–71 %. With CAMV, the infection level with A. gossypii was higher than with A. craccivora and both were more efficient than A. citricola, although the differences were not significant. With mixed infections of CAMV and CMV, there was a higher level of CAMV transmission using A. craccivora from sequential feeding when CMV‐infected plants were fed on first followed by CAMV‐infected plants, suggesting that cowpea plants were more prone to infection by CAMV when already infected by CMV.
Coumarin Utilization Patterns of Pathogenic Races of Fusaarium oxysporum Causing Vascular Wilt of Cotton
Authors: Rutherford M. A. , Paterson R. R. M. , Bridge P. D. , Brayford D.
Published: May 2008

Fifty‐six isolates of Fusarium oxysporum from wilted cotton plants were characterized by (a) hydrolysis of aesculin and (b) utilization of the products glucose and aesculetin. Aesculin and aesculetin agars provided a simple in vitro test that enabled differentiation of pathogenic races of the cotton wilt pathogen.
The Use of Ergosterol as a Quantitative Measure of the Resistance of Cultured Tissues of Brassica napus ssp. oleifera to Leptosphaeria maculans
Authors: Gretenkort Marie A. , Ingram D. S.
Published: May 2008

A simplified method for the quantitative assessment of the fungal lipid ergosterol was used to assess the levels of infection in tissue cultures of oilseed rape (Brassica napus ssp. oleifera) inoculated with Leptosphaeria maculans. The growth of L. maculans in liquid culture throughout a 36‐day period correlated well (r = 0·92) with the amount of ergosterol extracted from the mycelium. There were significant differences (P < 0·05) in the amount of ergosterol extracted from infected thin cell layer (TCL) explants and callus tissue of two resistant and three susceptible cultivars of oilseed rape. Amounts of ergosterol extracted from resistant cultivars were < 100 (g and from susceptible > 100 (g. The mean amounts of ergosterol extracted from shoot cultures of two resistant and four susceptible cultivars were similar to those for TCL explants and callus tissue, although the values obtained were variable. This technique can be used in in vitro breeding programmes to accurately assess the resistance of tissue cultures of B. napus to L. maculans and could also have value in conventional breeding programmes.
Host Genetic Analysis by Using Puccinia recondita tritici Induced Mutants for Increased Virulence
Authors: Saione H. A. , Favret E. A. , Franzone P. M. , Sacco F.
Published: May 2008

Monogenic lines derived by recombination from Buck Manantial wheat, a cultivar which has durable resistance, were used as hosts to detect Puccinia recondita tritici induced mutants for increased virulence. After treatments with ethyl methane sulphonate on clone 66 of P. recondita 9 types of mutants were obtained at approximate frequencies of 1 × 10−4 and host lines were grouped in 6 classes, No increase virulence was obtained against B. Manantial after 2 cycles of treatments, but different combinations of virulences were observed on monogenic lines derived from it. Simultaneity of occurrence of some mutational events suggests complexity of virulence genes in the pathogen. At least 4 genes for incompatibility are present in B. Manantial when confronted with clone 66 and 4 to 7 mutational points are recognized in the pathogen. The specific relationships tending to equate the number of genes in both organisms would not be a general rule. Durable resistance can be explained by a combination of several specific disease reaction genes for which the pathogen population has not been able to accumulate all the corresponding alleles for virulence.
Quantification of Infection by Alternaria cassiae Using Leaf Immuno‐Autoradiography and Radioimmunosorbent Assays
Authors: Sharon Amir , Amsellem Ziva , Gressel Jonathan
Published: May 2008

The severity of fungal infection is usually estimated visually as a rating of injury. A more quantitative method was needed to ascertain the effect of additives used to enhance the virulence of mycoherbicidal preparations. A sensitive and accurate serological method is presented for quantitative measurement of Alternaria cassiae infection of Cassia obtusifolia. An antiserum was prepared against a homogenate of mycelium of A. cassiae. A fast and simple procedure of leaf immuno‐autoradiography was developed for the visualization of A. cassiae mycelium on inoculated leaves. A radioimmunosorbent assay (RISA) was developed for quantification of the extent of fungal infection. As little as 1. 6 ng/ ml dry weight equivalent of mycelium could be detected by RISA. There was a linear relationship between the logarithm of the RISA values and the logarithm of fungus concentration up to 300 ng/ml. Reduced sensitivity of the assay was pronounced in extracts containing 400 μ g/ml or more fresh weight of leaves. There was 30–40 % cross‐reactivity of the antiserum with two other species of Alternaria, as well as with Monilinia fructicola, and almost no reactivity was found with three other fungi tested.
Effects of Ozone Exposure on Resistance of Wheat Genotypes to Pyrenophora tritici‐repentis
Authors: Sah D. N. , Tiedemann A. V. , Fehrmann H.
Published: May 2008

Three spring wheat genotypes, susceptible, moderately resistant or resistant to Pyrenophora tritici‐repentis (tan spot fungus) were exposed to charcoal‐filtered air and to approx. 80, 160, 240 (g m−3 ozone for five consecutive days (7 h per day). Visible leaf injury on seedling plants (three‐leaf stage) was only observed after fumigation with 160 or 240 (g m−3 O3. Amount of injury was four‐fold and 10‐fold on the susceptible genotype when compared to resistant or moderately resistant genotype at the two highest concentration of ozone, respectively. Genotypic differences to O3 tolerance were detected at the seedling growth stage (three‐leaf stage) and flowering stage but not at the stem elongation stage. A significant increase in tan spot lesion area was observed only on O3 predisposed second top most leaves of the susceptible genotype at all the three levels of ozone. Predisposition did not enhance tan spot development in resistant and moderately resistant genotypes. In a test with 12 wheat genotypes, a highly significant positive correlation (r = 0· 986, p < 0· 0001) was observed between ozone sensitivity (percent leaf area damaged due to 240 (g m−3 ozone exposure) and tan spot development (mm2 lesion area) following inoculation with P. tritici‐repentis. It indicates that wheat genotypes resistant to the tan spot fungus might be tolerant to ozone damage.
Interactions Hôte‐Parasite Entre Solanum gilo Raddli et Stemphylium floridanum Hannon et Weber: Aspects Ultrastructuraux
Authors: Clerivet A.
Published: May 2008

La penetration et la colonisation des feuilles de Solanum gilo par Stemphylium floridanum sont etudiees sur des plants infectes experimentalement.

Les examens en microscopie electronique montrent que le parasite penetre par les stomates des feuilles puis envahit le parenchyme chlorophyllien. La desorganisation des tissus colonises et de ceux situes a distance du parasite est importante et l'ultrastructure cellulaire profondement modifiee. L'hote parait construire des barrieres a la progression du parasite par la creation de territoires necrotiques, la synthese de composes phenoliques et de callose.
Detection of Australian Field Isolates of Citrus Tristeza Virus by Double‐Stranded RNA Analysis
Authors: Habili Nuredin
Published: May 2008

Double‐stranded RNA analysis indicated that widespread latent infection by citrus tristeza virus (CTV) occurs naturally in a citrus variety collection at Merbein, Australia. Detection was based on the presence of the putative replicative form (RF) of the virus (ca 19. 5 kilobase pairs) and the presence or absence of three previously known putative subgenomic dsRNAs with molecular sizes of ca 3. 1,1.7 and 0.8 kilobase pairs. With the exception of some citrus relatives normally used as rootstocks, the dsRNAs were readily detectable in all the trees tested. Variability was noticed among the dsRNAs profiles of individual seedling trees of Microcitrus australasica var. sanguinea. By contrast, dsRNA patterns of trees of open‐pollinated Ellendale tangor were indistinguishable. A number of dsRNA bands found in West Indian lime infected with CTV were not detected when this isolate was graft‐inoculated to healthy sweet orange seedlings. A simple method for enhancing the sensitivity of detection of the CTV dsRNA bands by silver staining is described which involves incubating the gels in RNase A prior to staining; this allowed detection of the putative CTV RF in only 40 mg of green hark material.
Effects of Temperature on Viability of Pathogenic Fusarium Species
Authors: Kováčiková Eva
Published: May 2008

The viability of three species of Fusarium pathogenic to winter cereals was differently affected by temperature. F. culmorum survived in vitro in soil for 4 months at 8, 20 and 30 °C, the number of colony forming units (CFU) recorded at these temperatures after incubation being 125, 185 and 624 % respectively when compared with the number present at the beginning of the experiment. F. avenaceum and F. heterosporum barely survived at 8 °C after incubation for 4 months but at 20 °C the numbers of CFU were 314 and 380 % respectively, while at 30 °C the corresponding number tor each of these species was 200 %.

At natural soil temperatures in winter, the number of CFU of F. culmorum after 4.5 months decreased to 60, 70 and 87 % of the number present at the beginning of this experiment when infested soil was buried at depths of 7–10, 15—20 and 30 cm respectively. In the upper soil layer where winter temperatures were lowest, survival of F. avenaceum and F. heterosporum did not occur. Survival rates for these two species at a depth of 15—20 cm were 20 and 5 % respectively. In the deepest layer of soil (30 cm) survival of these two species was 30 % for F. avenaceum and 10 % for F. heterosporum of the number present at the beginning of this experiment.

These results demonstrate that during the early spring stages of growth of winter wheat, inoculum of F. culmorum, unlike that of F. avenaceum and F. heterosporum, is also a source of infection in the top soil layer in our climatic conditions.
Characterization of Peanut Mottle Virus in Cote d'Ivoire
Authors: Samad Abdul , Thouvenel J.‐C. , Dubern J.
Published: May 2008

A virus, hitherto unreported in Cote d'Ivoire, was detected in groundnut plant (Arachis hypogaea) from the northern parts of the country. Infected plants showed mottling, interveinal depression, and very prominent light and dark green patches on leaves. The causal agent was characterized as a strain of peanut mottle virus, a member of the potyvirus group, on the basis of its host range, mode of transmission, physical properties, particle morphology and on the basis of its serological properties studied in comparison with these of other groundnut viruses.
Purification and Characterization of an Isolate of Apple Mosaic Virus from Rose in the USA
Authors: Wong Sek‐Man , Horst R. Kenneth
Published: May 2008

An isolate of apple mosaic virus, designated ApMV‐J, was isolated from rose cv. Sweet Surrender in New York State, USA. Mechanical transmission of ApMV‐J from rose to cucumber was facilitated by preparing inocula with 0.03 M sodium phosphate buffer containing 0.02 M 2‐mercap‐toethanol and 1 % polyvinylpyrolidone. Catharanthus roseus cv. Little Linda was a good virus maintenance host and Cucumis sativus cv. Lemon a good propagation host. Contaminating host proteins were substantially reduced by including polyethylene glycol in the purification protocol. Purified virus had high A260/280 nm values and contained virus particles of c 25—26 nm in diameter; most particles were isometric but a few were bacilliform. The M.Wts. of the four nucleic acids of ApMV‐J, determined in non‐denaturing and denaturing agarose gels, were estimated at 1.16, 0.98, 0.68 and 0.35 × 106 and 1.0, 0.91, 0.66 and 0.35 × 106, respectively. The viral coat protein M. Wt. was estimated to be 27 kDa.
Further Evidence for the Inclusion of Barley Mild Mosaic Virus (BaMMV) in the Baymovirus Group
Authors: Andersen J. F. , Davies J. W. , Coutts R. H. A.
Published: May 2008

Barley mild mosaic virus (BaMMV) has been purified by a new procedure and some molecular characteristics of the RNA studied. Results summarized in this paper suggest that, although BaMMV and barley yellow mosaic virus are different viruses, they share many features in common. BaMMV should, therefore, be classified in the baymovirus group of the Potyviridae.
Partial Characterization of Nasturtium Mosaic Potyvirus
Authors: Da Graça J. V. , Budnik K.
Published: May 2008

Nasturtium mosaic virus, hitherto considered to be a carlavirus, was shown to be a member of the potyvirus group by its morphology, capsid protein size, positive reaction with potyvirus group antiserum and the presence in its host of cytoplasmic inclusions (“pinwheels”). It is serologically unrelated to five other well characterized potyviruses.
Detection of Three Plant Viruses by Dot‐Blot and Tissue‐Blot Immunoassays Using Chemiluminescent and Chromogenic Substrates1
Authors: Makkouk K. M. , Hsu H. T. , Kumari S. G.
Published: May 2008

Detection of bean yellow mosaic virus (BYMV), impatiens necrotic spot virus (INSV) and lily symptomless virus (LSV) by dot‐blot and tissue‐blot immunoenzymatic assay was compared by using either chromogenic or chemiluminescent substrates. Testing was conducted on infected‐leaf extracts and on purified virus preparations. Both types of substrates gave comparable results with leaf extracts. However, with purified virus, the use of chemiluminescent substrates led to a more sensitive detection of the three viruses.
Evaluation of Streptomyces for Biocontrol of Bipolaris sorokiniana and Sclerotinia homoeocarpa on the Phylloplane of Poa pratensis1
Authors: Hodges Clinton F. , Campbell Douglas A. , Christians Nick
Published: May 2008

Several species of Streptomyces were evaluated for their ability to control Sclerotinia homoeocarpa (dollar spot) and Bipolaris sorokiniana (leaf spot) on the phylloplane of Poa pratensis (Kentucky bluegrass). Species evaluated included S. diastaticus (S32), S. galbus (S35), and S. hygroscopicus (isolates S13, S28). All evaluations were conducted on the upper epidermis of intact attached leaves of P. pratensis, and antagonism was measured as the ability of Streptomyces isolates to prevent chlorophyll loss from leaves inoculated with B. sorokiniana or S. homoeocarpa during pathogenesis. Only S. hygroscopicus (S13) effectively prevented infection and subsequent chlorophyll loss from leaves inoculated with B. sorokiniana or S. homoeocarpa. Isolate S28 of S. hygroscopicus showed erratic antagonism of both pathogens, depending upon how the isolate was prepared for use. Streptomyces diastaticus and S. galbus were antagonistic to S. homoeocarpa only in whole culture form.
Interaction between Pseudomonas syringae pv. Pisi and Isolated Pea Mesophyll Protoplasts
Authors: Akpa A. D. , Archer S. A.
Published: May 2008

The interaction between five races of Pseudomonas syringae pv. pisi (PSP) and isolated mesophyll protoplasts obtained from five pea cultivars was studied. There was no trend in the attachment of bacterial cells to surfaces of compatible and incompatible host protoplasts. The viability of protoplasts from compatible and incompatible host‐pathogen interactions did not differ significantly; however, changes in the viability of cultivar Kelvedon Wonder protoplasts, compatible with all five races, was relatively more stable following inoculation with bacteria than those of cultivar Fortune, incompatible with all of the five races. Protoplast cell wall regeneration did not take place until 24–48 h after isolation. It is concluded that the use of pea protoplasts as a model system for studying the pea‐PSP interaction appears to have considerable potential for the future, but more basic research is required.
Fungi in Living Symptomless Needles of Pinus sylvestris with Respect to Some Observed Disease Processes
Authors: KoWalski Tadeusz
Published: May 2008

The mycoflora in living symptomless needles of Pinus sylvestris was investigated in three 5–8 year‐old plantations in Southern Poland from 1987 to 1990. The needles from trees with symptoms of the autumn needle cast and from trees without such symptoms were treated separately. In total 960 of the current year and 720 of the previous year needles were collected. Fungi were isolated from 80.1 % of needles and 3671 cultures belonging to 86 fungal taxa were obtained. Seven species of fungi showed the rate of infection above 5%: Anthostomella formosa, Lophodermium seditiosum, Cydaneusma minus, Cenangium ferruginosum, Lophodermium pinastri, Sclerophoma pythiophila and Anthostomella pedemontana. The frequency of infection of needles by these species depended on needle age, season of the year, calendar year and site. The spread of fungi in needles was not too high. They were found in 35.8 % of needle sections (isolations were made from 10,080 sections). The needle base, middle and top were infected with more or less similar frequency, but the differences were considerable for the individual fungal species. Anthostomella formosa and A. pedemontana generally occurred slightly more frequently on needles of trees without symptoms of the autumn needle cast, while the other four common species (Cenangium ferruginosum, Cyclaneusma minus, Lophodermium pinastri, Lophodermium seditiosum) generally occurred more frequently on needles of trees showing such symptoms. There were considerable differences in this respect among plantations investigated.
Reduced Development of Grey Mould (Botrytis cinerea) in Bean and Tomato Plants by Calcium Nutrition
Authors: Elad Y. , Volpin Hanne
Published: May 2008

Fertilization of bean plants grown in perlite with 1 and 3 mM CaCl2 or Ca(NO3)2 reduced severity of grey mould as compared with control plants or plants fertilized with 5 mM of the compounds. Fertilization with Ca(NO3)2 reduced severity leaf grey mould and fruit ghost spots of tomato plants grown in perlite by 70 and 45%, respectively. The rate of decrease varied with the position of the fruits on the plants. Leaves from plants treated with calcium or otherwise [KNO3, (NH4)2SO4] produced less ethylene than leaves of nontreated plants. Rate of growth of B. cinerea was lower on growth medium prepared from washings from leaves of calcium fertilized plants than from leaves from other treatments. The fertilizer combination Ca(H2PO4)2+ CaSO4 (1 and 3 g/kg soil) applied once to tomato plants grown in soil reduced severity of leaf grey mould by 80 % (significant at P = 0.05) but 1–3 g CaSO4/kg soil only tended to reduce disease severity (30–40 %, not significant) as compared with the control. The compounds CaCl2 and Ca(NO3)2 increased significantly (P = 0.05) the growth of B. cinerea on synthetic medium when applied at rates of 1 0–10.0 mM whereas reduction of growth was observed with 0.1 mM of the compounds and of CaSO4.
Stress Proteins and Isozymology of Acid Phosphatase, Esterase, and Peroxidase in Phaseolus vulgaris Following Peanut Mottle Virus Infection
Authors: Wagih E. E.
Published: May 2008

The present work was undertaken to study soluble protein changes and enzyme alterations in “Topcrop” bean (Phaseolus vulgaris L.) primary leaves following inoculation with peanut mottle virus (PMV) in an attempt to elucidate the biochemical basis of the hypersensitive reaction in this host virus combination. Using the discontinuous polyacrylamide gel electrophoresis (disc‐PAGE) technique, at least four apparently “novel” protein bands at Rf values of 0.80, 0.77, 0.74 and 0.68 were observed in infected tissue. The band at Rf 0.76 seems to be injury related and is shown here to be an isozyme of acid phosphatase. It is believed that these proteins are neither the cause nor the product of necrosis and may thus play a role in the active defense mechanism of the plant. In this virus host combination it was found that heating soluble protein fractions at 55 °C for 10 min before electrophoresis dramatically reduced the background and improved resolution on gels. While the biological function(s) of these proteins needs further investigations it is almost certain that none of them is an isozyme of alkaline phosphatase, acid phosphatase, esterase, or peroxidase. Zymogram analysis has additionally revealed the absence of alkaline phosphatase activity in untreated, abraded and PMV‐infected primary leaves and no qualitative or quantitative changes in esterase isozymes have been observed in primary leaf tissues following abrasion or PMV–infection. By contrast, qualitative alterations in acid phosphatase after PMV‐infection and both qualitative and quantitative changes in peroxidase after mechanical abrasion and PMV‐infection have also been demonstrated.
Some Properties of Singapore Ageratum Yellow Vein Virus (SAYVV)
Authors: Tan H. N. P. , Wong S. M.
Published: May 2008

A whitefly‐transmitted geminivirus was found in a local weed, Ageratum conyzoides L. It caused leaf vein yellowing which developed into a bright yellow mosaic at an advanced stage of infection. The virus could not be transmitted by inoculation with sap, by seed or by dodder. By whitefly transmission, the virus was transmitted to seven species belonging to the families of Compositae, Oxalidaceae and Solanaceae. Generally, symptoms observed were either vein yellowing or leaf curling. Cytopathological studies showed the reduction of chromatin to a few periphery clumps within infected nuclei and the appearance of electron‐dense fibrillar rings within the sieve elements. Both large and small fibrillar rings which are considered as diagnostic features for geminivirus infection were observed.
Identification of Intersterility Groups of Heterobasidion annosum by Restriction Analysis of PCR Products
Authors: Karjalainen R. , Fabritius A. ‐L.
Published: May 2008

Polymerase chain reaction (PCR) was used to amplify ribosomal RNA (rRNA) genes of two isolates belonging to different intersterility groups of Heterobasidion annosum. Amplification of nuclear small rRNA or small mitochondrial rRNA yielded products of similar size in both intersterility groups. Digestion of PCR products with restriction enzymes did not reveal any differences between groups. Amplification of an internal transcribed spacer (ITS) region yielded an 0.3 kb product in both isolates. Digestion of this product with Hha I restriction enzyme revealed an intersterility specific banding pattern. These results indicate that PCR has a considerable potential for the diagnosis and characterization of fungal pathogens which are difficult to identify in conventional ways.
Studies on Particle Components of Cacao Swollen Shoot Virus
Authors: Uhde Christiane , Vetten H. J. , Maiss E. , Adomako D. , Paul H. L.
Published: May 2008

Virions of the cacao swollen shoot virus (CSSV) strain 1A were purified and used for studies of its particle components. CSSV virions had a buoyant density of 1.365 g/cm3 in buffered CsCl. Following SDS polyacrylamide gel electrophoresis (PAGE), CSSV‐specific proteins were identified in electroblot immunoassays (EBIA) with cross‐absorbed polyclonal antibodies and especially well with monoclonal antibodies (MABs) to CSSV‐1A. Based upon EBIA experiments with a selected MAB, CSSV virions appeared to have one capsid protein species with a relative molecular mass (M), of about 43 kd that was shown to be not glycosylated. However, this protein is sensitive to proteolytic degradation as degradation products ranging from 37 to 33 kd were found in addition to the 43 kd protein. Studies on the viral genome of CSSV revealed that CSSV virions contain a DNA of about 7. 5 kbp. Nucleic acid probes obtained by cloning parts of the viral genome yielded specific hybridization reactions with extracts and preparations from plants infected with strain 1A of CSSV but not with those from non‐inoculated plants. One clone of 738 bp was sequenced and shown to contain a motif similar to the putative RNA binding domain of pararetroviruses. Based upon particle morphology and properties of the virion components, CSSV can be grouped with other nonenveloped bacilliform viruses for which the name badnaviruses has been proposed.
Monoclonal Antibodies Specific for Xanthomonas campestris Bacteria Pathogenic on Wheat and other Small Grains, in Comparison with Polyclonal Antisera
Authors: Bragard G. , Verhoyen M.
Published: May 2008

4 hybridoma cell lines (named F1‐AA9‐D9, F1‐AB3‐B6, F1‐BC7‐C1 and F2‐CA7‐F11) secreting monoclonal antibodies to Xanthomonas campestris pv. undulosa were produced by fusing splenocytes from immunized Lou rats with IR983F myeloma cells. Whole cells were used both as immunogen and as antigen in ELISA and indirect immunofluorescence tests.

The monoclonal antibodies produced reacted positively with X. c. pv. undulosa (38 strains), pv. translucens (3), pv. hordei (3), pv. cerealis (2) and pv. secalis (1).

Strains from other pathovars (X. c. pv. arrhenatheri, pv. graminis, pv. manihotis, pv. oryzicola, pv. poae and pv. pruni) and from other species (X axonopodis, X. ampelina) and genus (Pseudomonas, Erwinia, Clavibacter, wheat saprophytic strains) gave a negative reaction. In comparison, seven polyclonal rabbit antisera showed to be less specific: they reacted with unrelated X. campestris pathovars as well as with Pseudomonas strains. Nevertheless, the use of phenol‐treated cells in Ouchterlony double immunodiffusion could reduce the effect of cross‐reaction for antisera.

The detection of X. c. pv. undulosa by indirect immunofluorescence on infected wheat seed lots has already been applied with success.
Differentiation and Diagnosis of Pseudocercosporella herpotrichoides (Fron) Deighton with Genomic DNA Probes
Authors: Frei U. , Wenzel G.
Published: May 2008

Repetitive genomic clones were used to differentiate between varieties within the species Pseudocercosporella herpotrichoides. From 21 clones tested 13 revealed restriction fragment length polymorphisms among isolates. Cluster analysis was performed based on these data. Differentiation of isolates according to growth speed corresponds better to genetic information than differentiation on the basis of spore morphology. Pathogen‐specific probes can be used in early diagnosis of the pathogen in infected plant material. Furthermore polymorphic pathogen‐specific probes allow varieties to be differentiated directly in infected plant material without isolation and culture of the fungus.
Production and Fungitoxicity of the Terpenoid Phytoalexins in Cotton Inoculated with Fusarium oxysporum f. sp. vasinfectum
Authors: Zhang Jiuxu , Mace M. E. , Stipanovic R. D. , Bell A. A.
Published: May 2008

Four terpenoid phytoalexins, desoxyhemigossypol (dHG), hemigossypol (HG), desoxyhemigossypol‐ 6‐methyl ether (dMHG) and hemigossypol‐6‐methyl ether (MHG), were identified with HPLC analysis of extracts from the moderately Fusarium wilt resistant cotton var. TAMCOT CAMD‐E (Gossypium hirsutum) inoculated with Fusarium oxysporum f. sp. vasinfectum (F. o. v.). Concentrations of dHG, HG, dMHG and MG in stem steles at 10 days after inoculation were 45.1, 175. 0, 38. 3 and 1. 6 (g g–1 fresh tissue, respectively. The bioassays demonstrated that all four phytoalexins were toxic to F. o. v. The ED50's of dHG, dMHG and HG were calculated as 8. 8, 13. 4 and 29. 3 (g ml−1, respectively. The very low solubility of MHG in the standard assay medium prevented the determination of its ED50 value. Only dHG is water soluble at levels that appear necessary to act as an effective phytoalexin. At 30 μg ml−1, dHG kills all conidia and mycelia of F. o. v. Viable propagules of F. o. v. were recovered from the steles of inoculated plants 10 days after inoculation; however, the pathogen was restricted to a zone 15 cm above the hypocotyl inoculation site. Thus, the fungistatic action of dHG appears to contribute to the resistance of cotton to Fusarium wilt by preventing the systemic distribution of F. o. v. propagules.
Histopathological Studies of Resistance of Sunflower (Helianthus annuus L.) to Downy Mildew (Plasmopara halstedii)
Authors: Mouzeyar Saïd , De Labrouhe Denis Tourvieille , Vear Felicity
Published: May 2008

Histopathological studies of the infection of sunflower seedlings by downy mildew (Plasmopara halstedii) have shown that penetration of roots and the lower part of the hypocotyl occurs for both compatible combinations (suseptibility) and incompatible combinations (resistance). After penetrating susceptible genotypes, the parasite develops intercellular hyphae and intracellular haustoria, leading to systemic invasion. In contrast, in resistant plants, as soon as colonization develops, hypersensitive‐like reactions occur in the parenchyma, with the appearance of necrotic zones surrounded by dividing cells. Growth of the parasite is strongly inhibited and most hyphae are blocked before they reach the cotyledonary node.
Mitochondrial and Nuclear DNA Restriction Enzyme Analysis of the Closely Related Phytophthora Species P. infestans, P. mirabilis, and P. phaseoli
Authors: Möller E. M. , De Cock A. W. A. M. , Prell H. H.
Published: May 2008

To determine relatedness of the phytopathogenic fungi Phytophthora infestans, P. mirabilis, and P. phaseoli restriction fragment patterns of mitochondrial DNAs of several isolates and hybridization patterns of nuclear DNAs after Southern hybridization with a specific homologous probe were analyzed.

All but two isolates of P. infestans and P. mirabilis show very similar restriction fragment patterns differing only in the length of one fragment due to small insertion/deletion(s). Two isolates of P. mirabilis have one additional site for Scr FI. On the contrary at least six sites differ in P. phaseoli when compared to the other two species. The mitochondrial genome of P. phaseoli is considerably smaller (approx. 6 kbp) than those of P. infestans and P. mirabilis.

A cloned 430 bp multicopy DNA sequence, derived from P. infestans, hybridized specifically with P. infestans, P. mirabilis, and P. phaseoli out of 61 species of Peronosporales (Phytophthora, Halophytophthora, Pythium, Albugo, Bremia, Peronospora, Plasmopara) tested and therefore has potential as a diagnostic probe. Restriction patterns revealed by this probe are invariant intraspecifi‐cally but differ between the three species.

We consider P. mirabilis a forma specialis of P. infestans because of the very high similarly in its mitochondrial DNA restriction patterns.