bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Transmission, Purification and Properties of an Isolate of Maize Stripe Virus from Venezuela
Authors: Lastra R. , Carballo O.
Published: May 2008

A Venezuelan isolate of maize stripe virus (MStpV) was successfully transmitted mechanically and by the leafhopper Peregrinus maidis from field infected plants to sweet cv. Iochief. After purification of maize infected with MStpV, fine spiral filamentous particles about 4 nm in diameter and with variable lengths were consistently associated with a nucleoprotein band present in CsCl or Cs2SO4 isopycnic gradients. Purified preparations exhibited a typical nucleoprotein absorption spectrum with a maximum at 260–263 nm and a minimum at 240–243 nm and a 260–280 ratio of 1.38. The density of the nucleoprotein in CsCl gradients was estimated at 1.29 g/ml. The sedimentation coefficient was calculated at 62 S. The nucleoprotein consisted of 5 % single stranded RNA and a capsid protein of molecular weight 33.500 daltons. Large quantities of non‐capsid proteins were isolated from infected tissue with a molecular weight of 17.500 and 16.500 daltons. Peregrinus maidis, injected with purified MStpV preparation failed to transmit the disease to healthy plants. However, they were infectious when injected with clarified infected plant sap. Antisera against capsid and non‐capsid proteins from MStpV‐Florida strain reacted positively with the Venezuelan antigens.
Mycoplasma‐Like Organisms in Clove Trees Affected by Sudden Death Disease in Zanzibar and Pemba
Authors: Dabek A. J. , Jones P. , Martin P. J.
Published: May 2008

Mycoplasma‐like organisms were seen in eight of twenty trees affected by sudden death disease from the islands of Zanzibar and Pemba. Vesicular bodies were also seen in the phloem of a further six affected trees but did not possess all the characteristics of mycoplasma‐like organisms. No virus‐like particles were found in any of the twenty sudden death trees examined.
An Isolate of Cucumber Mosaic Virus from Fluted Pumpkin in Nigeria
Authors: Atiri G. I.
Published: May 2008

The properties of a virus isolated from fluted pumpkin (Telfairia occidentalis) was investigated. It produced symptoms in some members of the Solanaceae and Leguminosae, and was transmitted nonpersistently by the aphid, Aphis spiraecola. On the basis of these alone, it is distinct from another previously described virus, Telfairia mosaic virus, which neither caused symptoms in members of these families nor was it transmitted by insects.

Furthermore, the virus in crude sap or purified preparations reacted with antiserum to cucumber mosaic virus (CMV), but not with antisera to several common viruses in Nigeria. Electron microscopic examination revealed isometric particles of 29 × 1 nm in diameter. These properties confirmed that the virus is an isolate of CMV, and closely resembles the Y‐strain in causing systemic mosaic symptoms in Vigna unguiculata. From infectivity and pathogenicity tests, it is concluded that it is the main cause of mosaic disease in fluted pumpkin.
Phytotoxity and pathogenicity of Fusarium nivale towards cereal seelings
Authors: Mańka Matgorzata , Chelkowski J.
Published: May 2008

Strong phytotoxic activity towards whew seedling has been derected in culatural extracts of 12 Fusarium nivale strains.

The exmined isolates have been found strong pathogens of rye. triticale and wheat seedlings. However, their phytotoxity was not corrclued with their pathogenicity.
Nucleic Acid Content in Leafblight disease of Brassica oleracea var. botrytis caused by Alternaria brassicicola (Schw.) Wiltshire
Authors: Maitra S. , Samajpati N.
Published: May 2008

The effect of Alternaria brassicicola (Schw.) Wiltshire infection on the changes of nucleic acids of Brassica oleracea var. botrytis was studied. An increase in vocal nucleid adds (57%), DNA (44%) and RNA (150 %) in infected leaves was found. The increase in RNA content was due to an increase of all the four nucleotide contents. Guanylic acid increased significantly more than the other three nucleotides. The increase in G/C ratio was also due to an increase in guanylic acid.
Three Types of Sensitivity to Metalaxyl in Plasmopara viticola
Authors: Herzog J. , Schüepp H.
Published: May 2008

The sensitivity of Plasmopara‐isolates to metalaxyl was determined by a leaf disc test. For the first time this permitted the distinction and clear characterization of not only sensitive and resistant isolates but also of isolates belonging to a third type of sensitivity, termed the reduced sensitive type.
Effect of Seed‐Borne Fusarium Species on the Physico‐Chemical Properties of Rapeseed Oil
Authors: Ashraf S. S. , Chaudhary K. C. Basu
Published: May 2008

Fusarium oxysporum, F. moniliforme and F. semitectum isolated from Brassica campestris var. dichotoma seeds were grown on autoclaved seeds and after several weeks of incubation the oil was analysed. All the three Fusarium species reduced oil content and altered its colour. The infested oil emitted mouldy odour and the refractive index increased. The free fatty acid content increased progressively. The saponification value increased but the iodine value decreased.
Effects of Infection by Plasmodiophora brassicae on Root Anatomy of Rape
Authors: Gustafsson M. , Liljeroth E. , Gunnarsson Marie , Lundborg T.
Published: May 2008

The anatomy of five‐week old roots of rape (Brassica napus L.) infected by Plasmodiophora brassicae Wor. was studied and compared with corresponding non‐infected roots using light microscopy and scanning electron microscopy techniques. The club‐root gall was characterized by atypically initiated vascular strands separated by large, proliferating parenchymatic cells originating from secondary tissues and infected by the parasite. Similarities in the anatomy of the club‐root gall and storage roots of Brassica are discussed together with aspcets of the pathogen control of the host anatomy.
Ricerche sperimentali nell' Oltrepò Pavese (Valle Padana) sugli aspetti epidemiologici delle ruggini del frumento
Authors: Di Fogliani G. , Caffarri E.
Published: May 2008

Experimental researches in Oltrepò Pavese (Padana Valley), on wheat rust epidemiological aspects related to the climatic conditions

Our experimental researches began in 1976 in Oltrepò Pavese, one of the most important seedwheat growing environment in the Padana Valley.

Wheat rust epidemiology, on the cv San Pastore, was studied in relation to the following climatic conditions: temperature and rain. Therefore, after having illustrated the modalities of observation and survey of the three rusts, we studied the infection behaviour on plants in field and hence the infection behaviour on the single leaves. In the end, knowing, by statistical analysis, the relations between infections and climatic parameters, it was possible to define as follows.

By comparing the three rusts infections in our environment, we noted that San Pastore wheat has been more affected by Puccinia striiformis West. with maximum infection points of 26,4 % on the leaves. We noted the greater development of this infection from the fourth to the sixth observation, in correspondence with average values of T° max rising from 23,7° to 26,4°C; in the same period, precipitations varied with a daily average from 3,0 to 1,7 mm.

Both P. striiformis and P. recondita Rob. ex Desm. appeared when the average of the T° max was 20,6°C, and in lack of rain.

P. recondita had a development rising from the fourth to the sixth observation showing, with regard to P. striiformis, lower demands of humidity and relatively greater demands of temperature; in fact, it reached a maximum point of infection of 26,4 % on the leaves, assuming a more gradual development than P. striiformis.

P. graminis Pers. appeared much later, as it needs higher T° max, followed by rains. Indeed, it appeared with average T° max of 23, 8 °C and with average daily rains of 0,4 mm, rising above all at the sixth observation with 26,4° C and 1,7 mm, respectively.

So, we can affirm that the actual experimental investigations point out and confirm what has been already met by other Authors, that is: a) among the three rusts considered, P. striiformis and P. recondita show to begin their development at the same time, in climatic conditions characterized by T° max relatively mild and high environmental humidity; b) P. striiformis shows, afterwards, the highest infections percentages; c) P. graminis appeared much later reaching modest infection percentages.
Occurrence of Erysiphe cichoracearum Perithecia on Wild Lactuca Species
Authors: Lebeda A. , Buczkowski J.
Published: May 2008

Perithecia of Erysiphe cichoracearum (powdery mildew) were found on several, but not all, accessions of Lactuca serriola, L. saligna, L. aculeata and L. serriola × L. sativa hybrid. Their occurrence varied between Lactuca species and different accessions of the same species. Perithecia were globular, had a mean diameter of 125.5 μm and contained an average 13–14 asci. Asci had mean dimensions of 55.0 × 26.1 μm and each contained two ascospores which measured an average 17.4 × 10.6 μm. There were however significant differences in the dimensions of spores and other structures obtained from different Lactuca accessions.
Effects of Inoculation with a Mild Strain of Tomato Aspermy Virus on the Growth and Yield of Tomatoes and the Potential for Cross Protection
Authors: Kuti J. O. , Moline H. E.
Published: May 2008

Mechanical inoculation of seedlings of 26 tomato cultivars with an attenuated strain of tomato aspermy virus (TAV‐M, ATCC # PV361) resulted in development of only mild symptoms, which had largely disappeared by the time the infected plants had begun to set fruit. Yield trials revealed that plants inoculated with TAV‐M when transplanted at the 6–8 leaf stage displayed no delay in fruit set and had yields only slightly less than uninoculated plants. Cross protection studies carried out in the greenhouse revealed that TAV‐M has the potential to interfere with infection of tomato seedlings by a more severe TAV strain (ATCC # PV127). ‘Pik‐Red’ seedlings inoculated with TAV‐M showed a significant reduction in symptom expression when challenged with the Blencowe strain of TAV 21 days after the initial inoculation with TAV‐M; interference was incomplete at 7 and 14 days.
Symptom Regulation Induced by Chicory Yellow Mottle Virus Satellite‐Like RNA
Authors: Piazzolla P. , Vovlas C. , Rubino L.
Published: May 2008

CYMV‐T, CYMV‐C and CYMV‐RS are three strains of CYMV, a nepovirus isolated from chicory in Southern Italy. They are serologically indistinguishable, but display different electrophoretic and analytical ultracentrifugation patterns. In fact the RNAs obtained from CYMV‐T, when analyzed in 2.4% polyacrylamide cylindrical gels, showed the presence of a 170,000 mol. wt. satellite‐like RNA (CYMV‐T Sat RNA) and several other RNAs, whereas CYMV‐RS gave only the genomic RNAs and CYMV‐C, in addition, some ofthe RNAs present in CYMV‐T but not the Sat RNA.

When these three strains were assayed on Nicotiana glutinosa L., CYMV‐C and CYMV‐RS elicited typical necrotic rings, whereas CYMV‐T infections were symptomless. The conclusions were drawn that CYMV‐T Sat RNA is another low mol. wt. RNA able to display viral disease regulation and that CYMV‐T, CYMV‐C and CYMV‐RS could represent an example of natural oscillation among different stages of RNA satellite emergence.
Growth of Foliage of Pigeon pea (Cajanus cajan [L.] Millsp.) and Disease Progress of Alternaria Blight
Authors: Singh U. P. , Zargar G. H. , Fazili M. A.
Published: May 2008

Vanderplank developed a model based on the logistic growth system to calculate the apparent infection rate (r) and to estimate plant disease progress. By estimating his r and p∧ (infection rate corrected for growth) the results were frequently negative. Kushalappa and Ludwig later developed another model for adequately correcting the host growth. The present model is a modification of Kushalappa and Ludwig's model in which the results are positive in case of Alternaria blight of pigeon pea (Cajanus cajan [L.] Millsp.). The disease intensity increased despite host growth resulting into an epidemic. A factor accounting for leaf fall due to blighting has been taken into consideration.
Phenylalanine Ammonia‐Lyase Activity and Anthocyanin Accumulation in Wounded Maize Mesocotyls
Authors: Pascholati S. F. , Nicholson R. L. , Butler L. G.
Published: May 2008

Activity of phenylalanine ammonia‐lyase (E.C. 4.3.1.5) and anthocyanin accumulation were determined in wounded maize (Zea mays L.) mesocotyls. Mesocotyls were wounded with aluminum oxide and were placed in a 15 h light: 9 h dark photoperiod or in the dark. Extractable enzyme activity increased in response to wounding in the photoperiod but not in the dark. Anthocyanin accumulation in mesocotyls placed in the photoperiod decreased in response to wounding. The results are discussed with reference to phenylalanine ammonia‐lyase activity in mesocotyl tissue wounded or inoculated with fungal pathogens.
Diversity of the RNAs in Thirteen Isolates of Beet Necrotic Yellow Vein Virus in Chenopodium quinoa Detected by Means of Cloned cDNAs
Authors: Burgermeister W. , Koenig R. , Weich H. , Sebald W. , Lesemann D.‐E.
Published: May 2008

Complementary deoxyribonucleic acids (cDNAs) to the four ribonucleic acid (RNA) species of isolate YU2 of beet necrotic yellow vein virus (BNYVV) were prepared by reverse transcription. The duplexes of these cDNAs were incorporated in the plasmid pBR322 and cloned into E. coli strain 5K. The insert sizes of the cDNA clones ranged from 280 to 2100 base pairs. In Southern blot hybridizations not all cDNAs specific for a particular RNA of BNYVV cross‐reacted. This suggests that they are complementaryto different regions of the respective RNA. In dot blot hybridization experiments sixteen out of eighteen cDNA clones detected all thirteen BNYVV isolates which were obtained from sugar beets originating from Yugoslavia, Italy, Switzerland, France and various regions in Germany and which were maintained in Chenopodium quinoa. Two cDNA clones specific for RNA‐3 failed to detect one German isolate. Pronounced differences between the thirteen virus isolates were seen when the electrophoretic migration of their RNAs was compared in Northern blot hybridizations. RNA‐1 and RNA‐2 of all isolates had the same sizes of 7100 and 5200 bases, respectively. The size, number and relative concentration of the smaller RNAs, however, varied greatly with different, isolates.
Effect of Co‐infection by Fusarium oxysporum and Cowpea Mosaic Virus on the Growth and Colonization of Cowpea Seedlings (Vigna unguiculata [L.] Walp.)
Authors: Chant S. R. , Gbaja I. S.
Published: May 2008

Combined infection of cowpea seedlings (c. v. ‘California Blackeye”) by cowpea mosaic virus (CPMV) and Fusarium oxysporum induced greater losses in leaf area, fresh and dry weights than infection by either pathogen alone. The growth of seedlings infected by F. oxysporum f. sp. tracheiphilum was less than that of comparable seedlings infected by F. oxysporum f. sp. phaseoli. The virus infectivity of extracts of the trifoliate leaves of dual‐infected plants was significantly higher than that of comparable extracts from the leaves of plants singly infected with CPMV. The nature of the effects of multiple infection in cowpea is discussed.
Iron Bound‐Siderophores, Cyanic Acid, and Antibiotics Involved in Suppression of Thielaviopsis basicola by a Pseudomonas fluorescens Strain
Authors: Ahl P. , Voisard C. , Défago G.
Published: May 2008

A Pseudomonas fluorescens strain (CHAo) involved in suppression of black root rot caused by Thielaviopsis basicola in the field, inhibited T. basicola when colonizing roots grown under sterile conditions or when grown on culture, media. Under these conditions it produced siderophores (iron chelating compounds), cyanic acid, and several antibiotics. Iron‐free siderophores inhibited neither the germination of endoconidia or chlamydospores nor the mycelial growth of T. basicola, but reduced the production of endoconidia. On the contrary, siderophores complexed with Fe3+ strongly inhibited mycelium growth and spore germination; free iron was less toxic than iron‐bound siderophores. Therefore, contrary to what was believed to date, siderophores seem to be toxic not because they deplete iron but because they increase its concentration to the point where it becomes highly toxic. Cyanic acid and the antibiotics also inhibited the growth of T. basicola. Whetherall these compounds are involved in disease control in the soil remains, however, to be determined.
Competition Between Typhula incarnata strains as a Source of Variation of Typhula blight in Winter Barley
Authors: Cavelier M.
Published: May 2008

Several crosses between monokaryotic strains of Typhula incarnata Laschex Fr. have given rise to hypoaggressive dikaryons under laboratory conditions. Winter barley plants, preinoculated in cold chamber by these strains, were, fully protected against the harmful effects of the aggressive strains inoculated 15 days later. The experiments have stressed the role of plant cold‐hardening on their susceptibility to Typhula. Under field conditions, when inoculated to winter barley seedlings, a mixture of aggressive and nonaggressive strains produced an attack which was intermediate between the severe one of the former and the almost indiscernible one of the latter strain.

Moreover, in cold chamber, mixed sclerotia from two equally aggressive strains induced as much damage as each strain inoculated separately.

Insofar as the extent of barley infection by T. incarnata can be measured by the dry weight of the infected plants before stem elongation and by the number of ears at harvest, our results indicate the determinant role of the first infective strain upon the ultimate degree of the attack. The eventual role of crosses between strains is discussed.
Interrelationship between Nutrients, Pathogenicity and Phytoalexin Metabolism of Botrytis cinerea on Clover Leaves
Authors: Macfoy C. A. , Smith I. M.
Published: May 2008

Botrytis cinerea spores suspended in 0.28 M glucose solution caused limited lesions on clover leaves, on which the clover phytoalexins maackiain and medicarpin accumulated to 1028 μg and 856 μg/g fresh wt respectively after 4 days incubation. During this time, little or none of the phytoalexin degradation products were detected. On the other hand, B. cinerea spores in sucrose casamino acids (SCA) liquid medium caused larger lesions than spores in glucose, and less maackiain and medicarpin (298 μg and 95 μg/g fresh wt respectively) and high concentrations of the degradation products were detected. B. cinerea mycelium in SCA also caused large lesions and both the phytoalexins and their degradation products were detected.,Sclerotinia laxa spores in 0.28 M glucose or its mycelium in SCA liquid medium did not cause any lesions apart from a minute necrotic fleck, and although phytoalexins were recovered from leaves inoculated with spores (67 μg and 78 μg/g fresh weight of maackiain and medicarpin respectively after 4 days) and leaves inoculated with mycelium (150 μg and 167 μg/g fresh wt maackiain and medicarpin respectively after 3 days), no phytoalexin degradation products were detected. The implications of, these results in understanding the interrelationship between nutrients, pathogenicity and phytoalexin metabolism are discussed.
Ultrastructure of Laticifers Modifications in Hevea brasiliensis Infected with Root Rot Fungi
Authors: Nicole M. , Geiger J. P. , Nandris D.
Published: May 2008

This paper presents some aspects of latex coagulation inside latice vessels of roots of Hevea brasiliensis infected by two fungi: Rigidoporus lignosus and Phellinus noxius. Three stages are described in latex coagulation: the phase of latex destabilisation characterized by the bursting of vacuoles and lysosomes membranes; the phase of latex coagulation characterized by the fusion of rubber particles and the disorganization of the cytoplasm; the formation of shots of rubber clumps indicating the final stage of coagulation.
Resistenz verschiedener Kultur‐ und Wildtomatenpflanzen (Lycopersicon spp.) gegenüber Botrytis cinerea Pers.
Authors: Urbasch I.
Published: May 2008

Resistance of different cultivated and wild tomato plants (Lycopersicon spp.) to Botrytis cinerea Pers.

20 provenances of different cultivated and wild tomato plants (Lycopersicon spp.) were screened for resistance to Botrytis cinerea Pers. using an in vitro‐leaf necrosis test.

The Botrytis resistance decreased with increasing age of the leaves corresponding to their insertion height (relative youth resistance respectively senescence susceptibility).

The 6 B. cinerea‐isolates used for inoculation differed significantly in virulence. With increasing inoculum age a virulence reduction of the various B. cinerea‐isolates occurred. Within the investigated test plant collection 2 wild species –L. columbianum and L. hirsutum– proved to be resistant in each stage of development to all B. cinerea‐isolates and additionally showed field resistance.
The Effects of Cymbidium Mosaic Virus and Odontoglossum Ringspot Virus on the Growth of Cymbidium Orchids
Authors: Pearson M. N. , Cole J. S.
Published: May 2008

Two cultivars of Cymbidium orchid were mechanically inoculated with Odontoglossum ringspot virus (ORSV) and Cymbidium mosaic virus (CyMV), individually and in combination. ORSV was found to have an infection rate of 70% (as determined by ELISA), but seldom induced easily discernable leaf symptoms. CyMV had an infection rate of only 20%, but infected plants invariably produced a pronounced leaf mosaic either with or without necrotic streaks. Both viruses were found to reduce plant growth, the effects of CyMV being more severe than those of ORSV.
Auswinterungsschäden in Raigras‐Reinbeständen, die Bedeutung pilzlicher Krankheitserreger und ihre mögliche Eindämmung
Authors: Winter W.
Published: May 2008

Winterkilling in puresown ryegrass, the importance of fungal pathogens and possibilities for their control I. Results from field trials with natural infection

Rotten plants, incomplete stands, a reduced number of shoots and a decline in dry matter yield were observed after hibernations of perennial and Italian ryegrass. Isolations from damaged plants showed that the main pathogen was the causal agent of snow mould Monographella nivalis (Schaffn.) E. Müll., asexual stage Gerlachia nivalis (Ces. ex Sacc.) W. Gams et E. Müll., synonym Fusarium nivale Ces. ex Sacc. The following fungi were also isolated: Laetisaria fuciformis(Mc Alp.) Burds., synonym Corticium fuciforme (Berk.) Wakef., Gibberella avenacea Cook, asexual stage Fusarium avenaceum (Fr.) Sacc. and Fusarium culmorum (W. G. Sm.) Sacc.

The field trials were located at 440 and 630 m a.s.l. These elevations correspond to plain and mid‐mountain climates, respectively. The tetraploid varieties ‘Lipo’, ‘Tetila’, ‘Citadel’ and ‘Bastion’ showed a higher level of resistance to snow mould compared to the diploid varieties ‘Ursus’, ‘Lemtal’, ‘Melino’ and ‘Pablo’. Tetraploid ryegrasses contaminated the soil with Gerlachia nivalis to a lesser extend than diploid ryegrasses.

The influence of the date of cutting and of nitrogen fertilization in autumn on snow mould was also tested. Lowest values at both locations were observed when the last cutting occurred at the end of October. Severity was higher when the last cutting, took place earlier (mid September, end of September, mid October). Since parts of stands of the last cutting were strongly damaged by the cold, last cutting should take place in the middle of October, although infection with snow mould will not be as much reduced as if the last cutting was done at the end of October. The plant rotting caused by Gerlachia nivalis was increased with 80 kg N/ha in autumn compared with 40 kg N/ha.
The Influence of Plant Extracts on Phytotoxin Production and Growth Rate of Alternaria helianthi
Authors: Robeson D. J. , Strobel G. A.
Published: May 2008

When liquid cultures of Alternaria helianthi were supplemented with aqueous extracts of leaf tissue of its host plant (sunflower), pronounced effects on both growth and production of the toxin deoxyradicinin were apparent. Very low levels of leaf extract stimulated toxin production but did not significantly affect growth, while higher levels markedly stimulated mycelial growth and at the same time toxin production was greatly suppressed. Leaf extracts of non‐host plant species were also stimulatory to phytotoxin biosynthesis.
Microwave Treatment to Eradicate Seed‐borne Pathogens in Cassava True Seed
Authors: Lozano J. C. , Laberry R. , Bermudez A.
Published: May 2008

A high percentage of cassava seeds, collected from five different edapho‐climatic zones, were found infected by several fungal and bacterial pathogens. The incidence and severity of seed infections were not correlated with the climatic conditions at, harvest. These pathogens were eradicated from seeds by a microwave oven treatment (1400 W heating power, 2450 MHz) for 120 s. The effectiveness of this treatment depended on reaching an optimum temperature of 77°C. Several factors, such as container capacity, water volume and seed number can affect the time required to reach 77°C. An Arasan dust treatment after microwave exposure, reduced seed re‐infestation.
Observations on the Effect of Inoculating Cassava (Manihot esculenta) Plantlets with Fluorescent Pseudomonads
Authors: Hernandez J. M. , Laberry R. , Lozano J. C.
Published: May 2008

Some 136 isolates of fluorescent pseudomonads were isolated from the rhizosphere of plants growing in 5 different ecosystems. Thirty‐four percent of these isolates inhibited the causal agent of cassava stem rot, Erwinia carotovora pv. carotovora, in vitro. One month old plantlets, produced by rooting the shoots of 4 cultivars in distilled water, were inoculated with a suspension (1.1 × 109 cells/ml) of each pseudomonad. Some isolates increased root weight by 95% over uninoculated controls two months after planting when inoculated at planting, and 15, and 30 days afterwards. Inoculated plants were free from symptoms of root pathogens and roots filled earlier than controls. Taxonomic studies showed that these bacterial isolates, were either Pseudomonas putida (90%) or P. fluorescens (10%).
Effect of NH3 on Chlamydospore Formation of Fusarium oxysporum f. sp. dianthi in an NH3‐Flow System
Authors: Löffler H. J. M. , van Dongen M. , Schippers B.
Published: May 2008

Conidia of Fusarium oxysporum on membrane filters on a sand bed saturated with a TRIS‐buffer in Conway vessels were exposed to different concentrations of NH3. NH3 was generated by bubbling air through NH4OH‐containing cylinders and pumped through the Conway vessels. Low concentrations of NH3 (15 ppm) stimulated chlamydospore formation in both germinated and ungerminated conidia. Higher concentrations of NH3 (150 ppm) inhibited chlamydospore formation. Ammonia had no apparent effects on the quality of the produced chlamydospores as measured by determining the persistence in soil.
Mycoplasma‐like Organisms Associated with Little Leaf Disease of Eucalyptus microtheca Muell.
Authors: Dafalla G. A. , Theveu E. , Cousin M. T.
Published: May 2008

A little leaf disease has been observed in several plants of Eucalyptus microtheca Muell. grown in Wad Medani area, Sudan. The disease is characterized by general plant stunting, reduction in diameter and height of trunks of affected trees, yellowing and reduction in leaf size, shortening of internodes together with excessive proliferation of axillary shoots. Electron microscope observations on ultrathin sections have revealed the presence of pleomorphic bodies in the sieve elements of diseased but not of healthy plants. These bodies possess DNA strands, ribosome‐like granules and a three‐layered unit membrane well defined at high magnifications (> 100,000) suggesting a mollicute nature of these bodies. Studies using semi‐thin sections revealed the absence of helical forms. Thus, a mycoplasma‐like organism (MLO) is suspected to be the agent responsible for the disease. The results are discussed with reference to the economic and environmental importance of this tree species in the Sudanand, the possible threat of the disease to its cultivation.
Host‐Parasite Relationship in a Susceptible and a Resistant Rose Cultivar Inoculated with Sphaerotheca pannosa.
Authors: Conti G. G. , Bassi M. , Maffi D. , Bocci A. M.
Published: May 2008

Young leaves of two rose cultivars, one susceptible (rose Cardinal) and the other moderately resistant (rose Q. Elizabeth) to mildew infection, were either inoculated with Sphaerotheca pannosa or wounded with glass or metal needles. At different times after these treatments the presence of callose, lignin and phenolics in the infected or wounded cells was revealed by histochemical reactions. After either treatment no difference was found between the cultivars in the amount or earliness of deposition of callose or lignin, while phenolics were present in far larger amounts in the resistant cultivar. It is therefore suggested that one of the factors of rose resistance to powdery mildew might be the capacity to synthesize large amounts of phenolic compounds, also in view of the fact that the vacuoles of healthy epidermal cells are strongly electron opaque in rose Q. Elizabeth, while they are much more transparent in rose Cardinal.
Elicitation and Suppression of Phytoalexin and Isoflavone Accumulation in Cotyledons of Cicer arietinum L. as Caused by Wounding and by Polymeric Components from the Fungus Ascochyta rabiei
Authors: Kessmann H. , Barz W.
Published: May 2008

Shortly after sowing cotyledons of chickpea (Cicer arietinum) start to accumulate the isoflavones biochanin A and formononetin together with their 7‐0‐glucosides and their 7‐0‐glucoside‐6″‐malonates. The additional accumulation of the pterocarpan phytoalexins medicarpin and maackiain can be induced by wounding of the cotyledons. Treatment of sliced cotyledons with a crude elicitor fraction obtained from the growth medium or the mycelium of the chickpea pathogenic fungus Ascochyta rabiei (Pass.) Lab. leads to a dramatic increase in the level of numerous aromatic compounds, especially of the isoflavone aglyca and the phytoalexins. Accumulation of isoflavone conjugates is not altered by elicitor treatment as shown by time course studies, and dose‐response curves.

A protein preparation (“suppressor”) isolated from the culture filtrate of the same fungus was shown to inhibit the accumulation of isoflavone aglyca, isoflavone conjugates and phytoalexins in the sliced cotyledons.

The possible relevance of elicitor‐suppressor counteraction with regard to the defence mechanisms of the host plant is discussed.
Une phytotoxine de Xanthomonas campestris pv. vasculorum
Authors: Ducourneau C. , Auriol P.
Published: May 2008

A phytotoxin from Xanthomonas campestris pv. vasculorum I. Purification and partial characterization

Xanthomonas campestris pv. vasculorum, the causal agent of sugarcane disease produces, when maintained in pure culture, a host selective phytotoxin. The molecule obtained at a high purity level is a strongly acid polyalcohol.
Seasonal Variation in Sporulation of Phytophthora infestans
Authors: Sujkowski L. S.
Published: May 2008

Sporulation ability of two isolates of Phytophthora infestans maintained on potato tuber slices of a susceptible cv. ‘Bintje’ and on‐rye agar medium was studied for four years (1981–1984). This feature of the fungus was shown to vary in particular seasons during the year.

Significantly higher sporulation density per cm2 of aerial mycelium on potato tuber slices was observed in winter and late autumn while significantly lower sporulation was found in spring. Similar tendencies were observed when one of the isolates was cultivated on rye agar medium under controlled conditions. Positive correlation was found between sporulation patterns of isolates of the fungus maintained on rye agar and on tuber slices. Hypothesis has been proposed that these changes are due, to a biorhythm in the fungus.
Relations Between Biomass Accumulation and Infection by Vesicular‐Arbuscular Mycorrhizal Fungi in Cassava as Affected by Planting Date
Authors: Ayanru D. K. G.
Published: May 2008

Roots of 12, 3‐month‐old, field‐propagated clones of cassava (Manihot esculenta Crantz) were more heavily mycorrhizal in the dry (Jan.–March and Oct.–Dec.) (39–83 %) than in the wet season (April–Sept.) (20–71%). Mean dry weights (biomass) of roots and shoots in the wet season (3.8–7.9 and 9.7–19.1 g/plant) were higher (P = 0.01) than in the dry season (2.1–5.9 and 5.4–12.8 g/plant, respectively). Clones with symptoms of the African cassava mosaic disease (ACMD) were less mycorrhizal, (20–69%) than mosaic symptom‐free clones (51–83%). Higher colonization of roots of the clones by indigenous fungal symbionts and lower biomass accumulation in the dry season are attributed mainly to soil moisture and other effects, while reduced infections in cassava with ACMD symptoms may be due to ACMD‐induced reductions in carbohydrate levels.
Influence of Temperature and Relative Humidity on Germinability of Mucor piriformis Spores
Authors: Bernd Regina B. , Bean G. A. , Conway W. S. , Moline H. E.
Published: May 2008

Studies were conducted to determine the influence of temperature and relative humidity (RH) on germinability and viability of Mucor piriformis spores. Spores did not survive when stored at 35 °C and their survival rate decreased rapidly at 30 °C; however, spores remained viable for more than 1 year at 0 °C. RH also significantly affected spore viability. Spores held at 26 °C and 100% RH no longer germinated after 35 days, while those held at 75 or 90% RH germinated for 65 days. At 20 °C, RH had little effect on spore germinability. The effect of temperature and RH on percentage spore germination also varied. At all temperatures studied, spore viability decreased more rapidly with time at 100% RH than at 75 or 90% RH. The least favorable, temperature‐humidity combination, 30 °C and 100% RH, decreased spore germination from 100% to less than 1% in 14 days.
Restriction Digest Patterns of Total DNA from Different Races of Fusarium oxysporum f. sp. pisi– an Improved Method for Race Classification
Authors: Coddington A. , Matthews P. M. , Cullis C. , Smith Karen H.
Published: May 2008

Seven isolates of Fusarium oxysporum f. sp. pisi were allocated to either race 2 or race 6 by their ability or inability to cause disease on the six host differentials New Season, New Era, Dark Skin Perfection, WSU 28, WSU 23 and Little Marvel. The isolates showed similar colony morphology on various solid media and their growth rates were inhibited to a similar extent by nystatin, cycloheximide and trichodermin when these compounds were included in potato dextrose agar. Total DNA waspurified from each isolate, digested separately with the restriction endonucleases EcoRI, EcoRV, Pstl, BamHl, SmaI and PvuII and the resulting DNA fragments separated by agarose gel electrophoresis. The patterns obtained were indicative of the presenceof repetitive DNA sequences. Moreover, the patterns obtained for the five race 2 isolates were identical for a given enzyme as were the patterns for the two race 6 isolates. Hence classification of isolates into races by their restrictive enzyme digestion, patterns coincided with that according to pathotypes and could be an improved, more reliable and reproducible method of race classification. An eighth isolate, originally classified as race 1, had lost its ability to cause disease on all six host differentials. The restriction digest patterns of its DNA were different from those of the DNA from both the race 2 and the race 6 isolates.
Auftreten der Blattdürre an Winterweizen (Drechslera tritici‐repentis) in Abhängigkeit von der Fruchtfolge und unter dem Einfluß verschiedener Spritzfolge
Authors: Schmitz H. , Grossmann F.
Published: May 2008

Incidence of yellow leaf blotch (Drechslera tritici‐repentis) on winter wheat in dependence on crop rotation and under the influence of different spray programs

On winter wheat grown on two experimental fields in different crop rotation programs, a severe incidence of Drechslera tritici‐repentis on the leaves was observed. Monoculture of wheat resulted in a significantly higher attack than growing in rotation with other crops. A distinct relation between different spray programs and disease severity could be found only in isolated cases.
Preparation and Characterization of Membranes from a Coryneform Isolated from Ratoon Stunted Sugarcane
Authors: Oellermann R. A. , Seetal A. , Pillay D. , Roth G.
Published: May 2008

Membranes from the coryneform were prepared by an optimized chemical procedure using EDTA and lysozyme and isolated upon equilibrium sucrose density gradient ultracentrifugation. Four bands, I to IV, of peak densities 1.15, 1.19, 1.21 and 1.245 g. cm−3 respectively, were reproducibly obtained. Immunodiffusion of the isolated membrane bands against bacterial antiserum showed that the immunological integrity of the isolated membranes was retained. Membrane bands I and II had similar precipitin arcs having one major component. A shift towards greater immunological complexity in band IV was observed. Similarly, a change in polypeptide composition established by polyacrylamide gel electrophoresis was found. The major group of polypeptides inband I ranging in size from 39 to 67 kdal were successively reduced in bands II, III and IV whereas the polypeptide of 15.7 kdal and of those in the region of 140 kdal showed respective increases. Transmission electron microscopy revealed similar membrane, structures in all membrane bands with only minor differences between them.
Epidemiology of Maize Root Rot in South Africa
Authors: Chambers K. R.
Published: May 2008

Maize roots were rapidly infected by soil inhabiting fungi as soon as they differentiated. The first tissues to develop were the seminal roots and mesocotyls. As their function became superseded by that of the adventitious roots, they rapidly became, completely rotted. Adventitious root rot developed slower and the roots did not become as severely rotted. Numerous fungi were isolated from the roots. The most frequently isolated were Helminthosporium pedicellatum and Fusarium moniliforme. Trichoderma sp. was the next most frequently isolated fungus; it was, however, significantly less frequently isolated than the above. Young and Kucharek (1977) found that the fungi isolated from maize roots occur in communities associated with certain plant growth stages. This was not clearly evident in this study. Numbers of root lesion nematodes (Pratylenchus species) correlated non‐significantly with fungus frequencies and root rot.
Changes in the Hill Reaction and the Chlorophyll Fluorescence of Chloroplasts Isolated from Wheat Plants Infected with Stem Rust (Puccinia graminis f. sp. tritici)
Authors: Berghaus R. , Reisener H. J. , Arenz H. , Franck U. F.
Published: May 2008

Wheat plants with different resistance to stem rust were inoculated with urediospores of Puccinia graminis f. sp. tritici race 32. By means of isolated chloroplasts Hill activity and chlorophyll fluorescence were measured during the first 8–10 days of the infection.

Highly resistant cultivars (infection type 0) showed no significant differences in Hill activity whereas resistant (infection type 1) and susceptible plants (infection type 4) exhibited a significant decrease in electron transport. This was associated with an apparent reduction of chlorophyll content. In both the incompatible as well as in the compatible interaction an additional factor had an effect on the inhibition of the Hill activity.

Chlorophyll fluorescence was also affected in compatible and in incompatible interactions. However, the two interactions showed different patterns. Whereas the decline in variable fluorescence dominated in resistant varieties, susceptible cultivars showed an additional significant increase in basic fluorescence.

The determination of Hill activity and chlorophyll fluorescence demonstrated that photosynthesis was inactivated in different ways in resistant and in susceptible cultivars.
Isolation of Carnation Italian Ringspot Virus from a Creek in a Forested Area South West of Bonn
Authors: Büttner C. , Jacobi V. , Koenig R.
Published: May 2008

During a survey of plant viruses in small ponds and creeks in a forested area near Bad Münstereifel about 30 km south‐west of Bonn several viruses were isolated. One of these was identified as carnation Italian ringspot virus which previously has been isolated only twice from carnations originating from Italy and USA and which infected carnations only with difficulty. The role of this virus in the forest ecosystem is so far unknown.
Rapid Detection of Potato Spindle Tuber Viroid (PSTV) by Dot Blot Hybridization
Authors: Bernardy M. G. , Jacoli G. G. , Ragetli H. W. J.
Published: May 2008

A PSTV probe of 350 bases, prepared in our laboratory, was used to detect picogram quantities of viroids by a simplified, improved, dot blot, hybridization technique in crude potato and tomato extracts. Optimum conditions for certification of PSTV‐free potato plants were established, involving formamide concentration, washing stringencies, exposure time during autoradiography and method of probe radiolabelling. Ten pg of purified PSTV in water and 50 pg of purified PSTV added to healthy plant extract were detected. Also hybridization signals could be detected from as little as 0.075 mg of infected plant tissue.
Influence of Various Factors on Toxicity of Culture Filtrate of a Drechslera maydis Strain from Costus speciosus
Authors: Shukla R. Sajiwan , Husain Akhtar
Published: May 2008

Drechslera maydis causing severe leaf blight of Costus speciosus, produced toxic matabolites in vitro. Maximum toxin was produced in modified Fries’ medium if its carbon source was substituted with glucose and nitrogen source with asparagine. Highest toxin accumulation was found at 21 days of incubation and with the initial pH 5.0. The toxin was stable in acidic condition (pH 3.5—7.0) but unstable under alkaline conditions.
A Low Temperature Therapy and Meristem‐Tip Culture for Eliminating four Viroids from Infected Plants
Authors: Paduch‐Cichal E. , Kryczyński S.
Published: May 2008

Viroid‐free potato and chrysanthemum plants were obtained from meristem‐tips cut from potato spindle tuber viroid‐infected potato plants and from chrysanthemum plants infected with chrysanthemum stunt, chrysanthemum chlorotic mottle or cucumber palefruit viroids after 6 months therapy in a growth chamber at 5 °C and 16 hours daily light of 5.000 lx intensity. Chrysanthemum plants survived quite well the conditions of therapy while potato plants grown from stem cuttings survived these conditions much worse and potato plants grown from tubers did not survive these conditions. PSTV‐free plants were obtained from meristem‐tips cut from sprouts grown from potato tubers infected with severe (s‐PSTV) or mild (m‐PSTV) strains of potato spindle tuber viroid after 6 months therapy at 6–7 °C in the dark. The tubers survived these conditions quite well.

The 3 months therapy period was found too short for any plant material. The efficiency of 6 months therapy in viroid elimination varied for different viroids and different plant material from 18.5 to 80.0 %.
Nachweis von Phytophthora fragariae Hickman in Wurzeln der Erdbeerkultursorte ‘Tenira’ mit Hilfe des enzyme‐linked immunosorbent assay (ELISA)
Authors: Werres S. , Casper R.
Published: May 2008

Detection of Phytophthora fragariae Hickman in roots of strawberry cultivar ‘Tenira’ by enzyme‐linked immunosorbent assay (ELISA)

Phytophthora fragariae Hickman is detected by ELISA in roots of strawberry cv. ‘Tenira’. Because of the high sensitivity of ELISA presence on fungal antigen was demonstrated before symptoms are detected in microscopical investigations.
Hypersensitive Reaction in Petunia
Authors: Nicoud S. , Dumas E. , Gianinazzi S. , White R. F.
Published: May 2008

The hypersensitive reaction of Petunia axillaris cv. ‘M’ to TMV‐SM1 strain is accompanied by the production of 4 unusual proteins in the tissues around the necrotic local lesions.

These proteins called d1, d2, d3 and d4, according to their decreasing electrophoretic mobility, are composed of a monomer of either 27,000 d (d2 and d4), 34,500 d (d3) or 20,000 d (d1). They do not appear to be related to the b1 of the PR (b) proteins synthesized by Nicotiana species in response to TMV infection.
Resistenzinduktion gegen systemische Virusinfektionen durch Kulturfiltrate von Stachybotrys chartarum (Ehrenb. ex Link) Hughes
Authors: Maiss E.
Published: May 2008

Induced resistance in systemic host‐virus combinations by culture filtrates of Stachybotrys chartarum (Ehrenb. ex Link) Hughes

Culture filtrates of the fungus Stachybotrys chartarum sprayed on systemic hosts decreased the development of symptoms of different elongated and isometric viruses. The degree of induced resistance depended on the host‐virus system. An interval of three or five days between application of the filtrate and virus inoculation was sufficient to induce resistance. High inoculum concentration reduced the efficiency of induced resistance in cucumber against CMV. The content of CMV in inoculated andsystemically infected, induced resistant cucumber leaves was decreased. TMV inoculated leaves of induced resistant tobacco plants contained higher, systemically infected leaves lower virus amounts as comparable untreated control leaves. Reduced virus content and distribution in induced resistant plants obviously resulted from inhibition of multiplication and spread of viruses.
Attack of Didymella bryoniae on Roots of Cucumber
Authors: Thinggaard Kirsten
Published: May 2008

Didymella bryoniae is very common in cucumber crops grown in Danish glasshouses and is able to attack all aerial parts of the plant. In October 1984 an attack of D. bryoniae on cucumber roots was observed for the first time. Some of the roots were dark because of pseudothecia containing asci. This fact may have importance for the spread and survival of the disease and for its control.
Geographic Variation of Esterase Isozymes in Populations of Alternaria mali on Apple Leaves
Authors: Hwang Byung Kook , Yun Ju Ho , Kim Zin Suh
Published: May 2008

The 500 monoconidial isolates of Alternaria mali occurring in different locations, Suweon, Cheongju, Kochang, Daegu and Jinju, Korea, in 1983 were used to examine geographic variation of esterase isozymes. The electrophoretic patterns of esterases were qualitatively and quantitatively different between isolates. The 14 different bands were detected on the basis of the decreasing electrophoretical mobility, although all bands were not present in any of the isolates. A comparison of the frequency of esterase isozymes at different bands showed marked variations among the geographic locations. The geographic distance between A. mali populations did not correlate strongly with divergence in esterase isozymes, whereas A. mali populations within a geographic feature were more closely related than populations separated by a mountain range.
Antagonism of Rhizoctonia spp. to Pythium oligandrum and Damping‐Off Fungi
Authors: Walther D. , Gindrat D.
Published: May 2008

In paired cultures on corn‐meal agar, Rhizoctonia solani, R. cerealis and R. fragariae caused vacuolation, disappearance of cytoplasm, and apparent lysis of hyphae of Pythium oligandrum, P. ultimum, and Aphanomyces cochlioides. Hyphae of Phoma betae were not injured by the Rhizoctonia spp. When sugar‐beet seeds dressed with mycelium of R. cerealis, R. fragariae, or an isolate of R. solani nonpathogenic to sugar‐beet were planted in soil naturally infested with P. ul‐timum, the level of biological control of damping‐off was similar to that obtained with captan dressing. In soil artificially infested with P. ultimum, biological dressings were slightly less efficacious than the chemical dressing.