bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunological Methods for the Detection of a Coryneform Isolated from Ratoon Stunted Sugarcane
Authors: Oellermann R. A. , Pillay D.
Published: May 2008

A coryneform bacterium, isolated from ratoon stunted sugarcane, has been obtained in pure culture. Its identification by immunological means was investigated. Optimum conditions for the light microscopic observation of bacterial agglutination by specific antiserum, immunofluorescence and the microcapillary haemagglutination of IgG‐sensitized erythrocytes by the bacterium were established. All three assay procedures are simple and rapid. By comparison, more samples can be handled at any one time bythe microcapillary haemagglutination method. Based on bacterial agglutination, the antiserum is specific for the coryneform isolated from ratoon‐stunted sugarcane.
Comparison of a Filter Paper Immunobinding Assay, Western Blotting and an Enzyme Linked Immunosorbent Assay for the Detection of Wheat Streak Mosaic Virus
Authors: Sherwood J. L.
Published: May 2008

The adaptation and improvement of serological assays for the detection of plant viruses has steadily developed. A filter paper immunobinding assay, Western blotting and the double sandwich ELISA were compared for the detection and quantification of wheat streak mosaic virus. ELISA was a more quantitative assay, but the filter paper immunobinding assay and Western blotting were more conservative of antiserum when only a few assays were required and could be run in a shorter period of time.
The Development of an In Vitro Host‐Pathogen System Consisting of Maize Seedling Segments Infected with Ustilago maydis
Authors: Hausen G. , Beiderbeck R.
Published: May 2008

The nodal segments of 7‐day‐old seedlings of maize were inoculated with sporidia of Ustilago maydis. At different times after inoculation (day 0 to day 9), the nodal segments were explanted to tissue culture media containing Benomyl. On one of the media, segments explanted at day 1 or later responded with the formation of galls carrying roots. In such galls Ustilago could complete its life cycle and form teliospores. Explantation at day 0 never led to gall or teliospore formation. Thefindings are discussed with respect to the possible presence of mycoboethins.
Relation Entre la Teneur en Sucres Réducteurs des Tissus du Tournesol (Helianthus annuus L.) et leur Invasion par Macrophomina phaseolina (Tassi) Goid.
Authors: Davet P. , Serieys H.
Published: May 2008

Relation between the amount of reducing sugars in sunflower tissues and their invasion by Macrophomina phaseolina (Tassi) Goid.

Reducing sugars (R.S.) were measured with Bernfeld colorimetric method. In the roots, the amount of R.S. increased up to a maximum, then decreased from the beginning of flowering, and remained constant, at a very low level, from the outset of seed maturation. The same evolution was observed, with a delay of one week, in stem bases, but the amounts of R.S. were a little higher. Roots, and thereafter, stems, were invaded by Macrophomina phaseolina only after the minimum level of R.S.was reached.

Varietal differences were observed, in a collection of sunflower hybrids, in response to invasion by M. phaseolina. R.S. levels in stem bases were higher in the resistant than in the susceptible hybrids.
A Threshold Value for Cutting Intensity in Relation to Fusarium Root Rot of Red Clover (Trifolium pratense L.)
Authors: Rufelt S.
Published: May 2008

Although cutting the foliage is known to increase Fusarium root rot severity in red clover (Trifolium pratense L.), no quantitative relationship has so far been determined. In this study, results from a number of greenhouse experiments, where plants were artificially inoculated with Fusarium avenaceum (Corda ex Fr.) Sacc., show a linear relationship between cutting intensity and Fusarium root rot in red clover, cv. ‘Hermes II’ an increased cutting intensity giving an increased root rot severity. Theoretically, a threshold value can be calculated beyond which no increase in root rot severity, compared to an uncut plant, should be expected.
Determination of Resistance or Susceptibility of Soybean Genotypes to Soybean Cyst Nematode, Heterodera glycines, Race 3
Authors: Al‐Jalili A. S. , Sapra V. T. , Pacumbaba R. P.
Published: May 2008

Resistance and/or susceptibility of several soybean genotypes to soybean cyst nematode (SCN), Heterodera glycines, race 3 was investigated. Three, 11, and 4 soybean genotypes were identified as resistant, moderately resistant, and susceptible, respectively. Resistant plants had fewer cysts on the roots and more root nodules, with the converse in susceptible plants. Reduction in yield of six extensively grown soybean cvs in Alabama was from 10 to 56% compared with the north Alabama average; resistant cv. ‘Bedford’ showed a yield loss of 10%. Cyst numbers were negatively correlated with nodule numbers and other agronomic characters. Nodules and other yield components were positively correlated except for non‐correlation of nodules and number of pods with plant height in the 1980 experiment.
A Method for Selection of Tolerance to African Cassava Mosaic Virus
Authors: Pacumbaba R. P.
Published: May 2008

Detopping hastened the appearance of mosaic symptoms in shoots of cassava cuttings infected with African cassava mosaic virus (ACMV). The degree of plant recovery from severe mosaic after each detopping was the basis for evaluation of ACMV tolerance. In field‐screening, detopping of cassava shoots infected with ACMV is recommended for selection of tolerance to the virus. One detopping of ACMV‐infected shoots was sufficient to analyze tolerance level reliably. Out of 521 lines only one was found tobe tolerant, while 144 lines were found to be moderately tolerant. These included the lines ‘Gimbi MA 235’, (02945S × 3119)S MA 219, and ‘Kadanga Malombe’ previously described as resistant to ACMV.
Vergleich eines “glatten” und eines “rauhen” Stammes von Pseudomonas syringae pv. phaseolicola
Authors: Gerwe P.‐G. , Rudolph K. , Köhn S.
Published: May 2008

Comparison of a “smooth” and a “rough” isolate of Pseudomonas syringae pv. phaseolicola

The “smooth” (S) wild strain of Pseudomonas syringae pv. phaseolicola was compared with a “rough” (R) variant of low virulence. Both strains grew nearly equally well on a sucrose containing medium with yeast extract and casamino acids, and the strains did not differ markedly in the quantity of produced EPS (= extracellular polysaccharides). Principally the same results were obtained for high and medium concentrations of sucrose, or when sucrose was replaced by glucose or fructose. However, on glucose and fructose considerably lower quantities of EPS were produced.

The biological activity of S‐EPS was higher than that of R‐EPS. This difference between the EPS preparations was not as marked as leaf inoculation with both bacterial isolates. After prolonged bacterial culture the EPS‐production increased further, so that the differences between both strains decreased.

A different EPS type was produced on the glycerol containing medium of KING B. Variations in the composition of this medium resulted in different morphology of the agar grown cultures, and the relative differences between S and R bacteria changed.

When 62 different physiological tests for both bacterial strains were compared, the “rough” bacteria revealed a lowered range of positive reactions, with a few exceptions. However, it appeared unlikely that the reduced virulence of the “rough” bacteria was due to these differences. Obviously, defects in the extracellular products, but not in levan, were responsible for the reduction of virulence.
Mycorrhizal Fungi Prevent Disease in Stressed Pine Seedlings
Authors: Chakravarty P. , Unestam Torgny
Published: May 2008

The common rhizospheric fungus Cylindrocarpon destructans caused severe root damage leading to mortality in light‐starved, stunted seedlings of Pinus sylvestris. This effect was, however, almost fully prevented by the presence of mycorrhizal fungi; i.e. Laccaria laccata, Pisolithus tinctorius, or unidentified species present in small amounts of conifer soil. Protection took place even before visible mycorrhizae were found on the roots. This is the first time that protection ofstressed plants against non‐parasitic (non‐invasive) pathogens has been reported. The results indicate that root protection by mycorrhizal fungi may not only be effective inside the root but probably also extends out into the rhizoplane or rhizosphere.
Characterization of Caper Latent Virus
Authors: Gallitelli D. , Di Franco A.
Published: May 2008

A virus with filamentous particles c. 662 nm in length, distantly serologically related to HelVS was isolated from caper (Capparis spinosa) in Southern Italy and characterized as a member of the carlavirus group. Virus particles have asedimentation coefficient of 168 S and a buoyant density in CsCl of 1.31 g × cm−3. They are constituted by a single protein species with a molecular weight of 35.700 which encapsidates a single species of single stranded RNA with the apparent size of 9100 nucleotides. This RNA was infectious constituting the whole viral genome. Virus particles either scattered or in aggregates but no specific cytopathological alterations were seen in infected cells. This carlavirus proved to infect caper symptomlessly and was often isolated in nature from plants without apparent signs of infection. For this reason, the name of caper latent virus (CapLV) is suggested for it. It is also suggested that CapLV be identical with caper vein banding virus, a tentative, member of the carlavirus group superficially described in 1970 from Southern Italy.
Biological Control of Phoma and Pythium Damping‐Off of Sugar‐Beet with Pythium oligandrum
Authors: Walther D. , Gindrat D.
Published: May 2008

Flooding freshly harvested oospores in sterile distilled water (SDW) for several days enhanced germination in 3 out of 4 isolates of Phythium oligandrum. Treatment of SDW‐flooded oospores with myo‐inositol increased germinability during the first 20 days of storage at 15°C. Seed dressing with oospores of P. oligandrum controlled pre‐ and post‐emergence damping‐off of sugar‐beet caused by soil‐borne P. ultimum and seed‐borne Phoma betae. For some isolates, flooded oospores in SDW and treatment with myo‐inositol increased efficacy of the seed dressing. However, no significant control of damping‐off caused by Rhizoctonia solani was observed.

On corn‐meal agar, P. oligandrum coiled around and penetrated hyphae of P. ultimum and R. solani, but did not interfere with Ph. betae.
Detection of Avocado Sunblotch Viroid in Spain by Double Polyacrylamide Gel Eletrophoresis
Authors: López‐Herrera C. , Pliego F. , Flores R.
Published: May 2008

Avocado sunblotch viroid (ASBV) was detected in samples of young leaves and flowers of the avocado cultivars ‘Hass’ and ‘Fuerte’ grown in southern Spain. Partially purified nucleic acid preparations, obtained by cellulose chromatography, were analyzed by double polyacrylamide gel electrophoresis. This technique, consisting of two consecutive electrophoresis cycles under nondenaturing and denaturing conditions, followed by silver staining of the gel, allowed the selective and sensitive identification, of ASBV. This is the first report on the occurrence of the causal agent of avocado sunblotch in Spain.
Soil Suppressiveness to Fusarium Wilt of Melon, Induced by Repeated Croppings of Resistant Varieties of Melons
Authors: Sneh B. , Pozniak D. , Salomon D.
Published: May 2008

A field soil, artificially infested with pathogenic isolates of Fusarium oxysporum f. sp. melonis was continuously used for screening resistant varieties of melon to Fusarium wilt. After 9–10 years of continuous cropping with resistant varieties, the soil had developed induced suppressiveness. Seven to 9 experimental replantings of the induced suppressive soil with the susceptible cultivar of melon, ‘Ein‐Dor', nullified its suppressiveness. This was expressed by 90 % disease incidence. Only 2 replantings were required to obtain the same disease incidence in an adjacent field of a conducive soil. Nonpathogenic isolates of F. oxysporum, isolated from the rhizospheres of melon seedlings, induced various degrees of soil suppressiveness when added to soil at various ratios to the pathogenic isolate.
Ultrastructure and Development of Sclerotia of Botrytis cinerea Pers. in vitro
Authors: Nair N. G. , Martin A. B.
Published: May 2008

The development of sclerotia of Botrytis cinerea was examined at four stages during their maturation. The surface structure developed a network of profusely branched hyphae through their coalescence to a compact sclerotial body which was maturated by the deposition of melanin pigment.

A characteristic feature of the hyphal cells of B. cinerea during the later stages of development was the presence of paramural bodies (plasmalemmasomes and lomasomes). Electrondense bodies with a limiting double‐membrane congregated against the transverse septa of hyphal cells as sclerotia matured and may migrate from cell to cell through septal pores. We suggest that these and the lipid bodies found in hyphal cells may have a storage function in the resting sclerotia.
Tetracycline Therapy of Clove Trees affected by Sudden Death Disease in Zanzibar
Authors: Dabek A. J. , Martin P. J.
Published: May 2008

Repeated trunk injections of tetracycline hydrochloride and oxytetra‐cycline over a 27 month period, retarded the rate at which clove trees in Zanzibar, died from sudden death (SD) disease. This result provides additional support for an MLO aetiology for SD, but indicates that the tetracycline formulations and method of application, as described here, is not a feasible method of SD control in the field. Bioassay of leaf discs and root sections using agar plates seeded with Bacillus subtilis, at various times after injection, indicated that antibiotic distribution to the canopy was extensive, but that down to the roots was minimal. The proportion of leaf discs showing tetracycline activity declined over a 54 day period post‐injection, from 75,% to 17%. Mean tetracycline levels in leaves per tree peaked at 2.4 μg/ml, 21 days after injection. The highest individual leaf disc level was 7 μg/ml. Most trees maintained concentrations of tetracycline inhibitory to B. subtilis growth for 2,1–41 days.
Isolation and Characterization of a Geminivirus Causing Yellow Mosaic Disease of Horsegram (Macrotyloma uniflorum [Lam.] Verdc.) in India*
Authors: Muniyappa V. , Rajeshwari R. , Bharathan N. , Reddy D. V. R. , Nolt B. L.
Published: May 2008

Horsegram yellow mosaic disease was shown to be caused by a geminivirus; horsegram yellow mosaic virus (HYMV). The virus could not be transmitted by mechanical sap inoculation. Leaf dip and purified virus preparations showed geminate virus particles, measuring 15‐18 * 30 nm. An antiserum for HYMV was produced and in enzyme‐linked immunosorbent assay (ELISA) and immunosorbent electron microscopy (ISEM) tests HYMV was detected in leaf extracts of fieldinfected bambara groundnut, french bean, groundnut, limabean, mungbean, pigeonpea and soybean showing yellow mosaic symptoms. Bemisia tabaci fed on purified HYMV through a parafilm membrane transmitted the virus to all the hosts listed above but not to Ageratum conyzoides, okra, cassava, cowpea, Croton bonplandianus, Lab‐lab purpureus, Malvastrum coromandalianum and tomato. No reaction was obtained in ELISA and ISEM tests between HYMV antibodies and extracts of plants diseased by whitefly‐transmitted agents in India such as A. conyzoides yellow mosaic, okra yellow vein mosaic, C. bonplandianus, yellow vein mosaic, M. coromandalianum yellow vein mosaic, tomato leaf curl and cassava mosaic. HYMV was also not found to be related serologically to bean golden mosaic, virus.
Production and Regeneration of Protoplasts from Pseudocercosporella herpotrichoides (Fron) Deighton
Authors: Hocart M. J. , Lucas J. A. , Peberdy J. F.
Published: May 2008

This paper describes the development of a system for protoplast isolation from this pathogen using the commercially available, hydrolytic enzyme preparations Rhozyme HP150, Driselase and Cellulase CP. An analysis of the active components of these enzymes believed to be involved in protoplast release has been made. Factors affecting protoplast release including mycelial age, enzyme concentration and choice of osmotic stabilizer have been optimised, and conditions for high frequency protoplast regener, ation have been determined. The possible significance of the interaction of the several components of each enzyme is discussed. The developments described in this paper can now be exploited in genetic studies in this imperfect fungus.
Studies on the Extracellular Polysaccharides (EPS) Produced in vitro by Pseudomonas phaseolicola
Authors: Gross M. , Rudolph K.
Published: May 2008

Native EPS produced by Pseudomonas syringae pv. phaseolicola in vitro was separated by ion exchange chromatography on DEAE fractogel into three different polysaccharide fractions.

A neutral polysaccharide eluting with the void volume yielded only fructose upon hydrolysis and exhibited an IR spectrum similar to authentic levan. At about 300 mM KCl a mannuronan eluted. Comparison with authentic alginate by IR spectroscopy, elution behaviour during DEAE‐fractogel column chromatography, and monomer composition (mannuronic acid and traces of guluronic acid) confirmed the identity of this fraction as a bacterial alginate. It contained about 56 mol% acetyl groups. A third polysaccharide eluted at about 160 mM KCl. Its monomeric composition (rhamnose, fucose, glucose, and amino sugars), elution behaviour upon DEAE‐fractogel column chromatography, and TLC patterns, closely resembled the sugar moiety of lipopolysaccharides (LPS) from, Pseudomonas syringae pv. phaseolicola.

The protein component of crude EPS represented a fourth macromolecular fraction. It was not covalently linked to any of the polysaccharides since it could be removed from the EPS by phenol extraction.
Individual and Combined Effects of Certain Pesticides on Rhizoctonia solani, Sheath Blight Pathogen of Rice
Authors: Singh U. D. , Sethunathan N.
Published: May 2008

The effect of different pesticides (fungicide, herbicide and insecticide) on the mycelial growth and formation and germination of sclerotia of sheath blight pathogen of rice, Rhizoctonia solani Kühn was studied in nutrient medium and in natural soil. Among the herbicides and insecticides, fenitrothion (insecticide) and thiobencarb (herbicide) were the most effective in inhibiting the mycelial growth and sclerotial formation. These pesticides effected significant inhibition of both mycelialgrowth and sclerotial formation at 7.5 to 10μg/ml concentration while fungicides carbendazim and tolclofosmethyl effected almost complete inhibition at 2.5 μg/ml. Interestingly, a synergistic increase in the toxicity to mycelial growth, sclerotial formation and sclerotial germination was noticed when the fungicide, mancozeb and the herbicide, thiobencarb were applied at subtoxic concentration in combination. Such synergistic interactions between pesticides in a combination leading to increased toxicity suggest that under the current practice of applying fungicides, herbicides and insecticides either simultaneously or in rotation, certain combinations may help in reducing the dose of a fungicide in disease control.
Interaction of Apple Cultivars with Populations of Cedar‐Apple Rust
Authors: Korban S. S. , Chen H. , Ries S. M.
Published: May 2008

Five physiological populations of Gymnosporangium juniperi‐virginianae Schw. were identified on the basis of pycnial and aecial lesion formation when seven apple cultivars grown in a glasshouse were inoculated with basidiospores of rust populations collected from six locations in the U.S.A. The relationship between cultivars and rust populations was explored quantitatively using the parameters N, D, and DR, where N was the highest number of pycnial lesions on a leaf/plant; D was the largestdiameter measurement of pycnial lesions on a leaf/plant; and DR, the disease rating, was proportional to the diseased area of the leaf and calculated as ND2. Statistically significant differences among cultivars over all rust populations for variables N, D, and DR were obtained, indicating the possible existence of race non‐specific resistance in apple to cedar‐apple rust. Moreover, significant differences among the rust populations over all cultivars for variable N and DR were obtained, confirming the existence of physiologically different rust populations of the pathogen. A change in the pathogenicities of these physiological populations must have occurred over time (10‐year period). A significant interaction between cultivars and rust populations was observed for lesion size (D) only, indicating a probable existence of race specific resistance in apple as well.
Components of Resistance to Bacterial Blight Disease of Rice
Authors: Nayak P. , Rao A. V. Suriya , Chakrabarti N. K.
Published: May 2008

Studies on the genetic variation, correlation, correlated response and path analysis were conducted on 8 rice cultivars to bring out the association and channelling of the pathway of different components of resistance to Xanthomonas campestris pv. oryzae. High genotypic coefficient of variation coupled with high heritability and genetic gain was observed for lesion size (LS) and the area under disease progress curve (AUDPC) indicating the predominance of additive gene effects. There was a strong association among all the components both at genotypic and phenotypic levels. Genotypic correlations were higher than the corresponding phenotypic correlations indicating the modifying effect of environment on association of components at genotypic level. Maximum correlated response and relative selection efficiency on AUDPC was observed through indirect selection for LS followed by the number of bacteria per unit leaf area (NB). Path analysis revealed highest direct effect of LS on AUDPCboth at genotypic and phenotypic levels. Indirect effects of fairly high magnitude were also exerted by incubation period (ICP) and NB towards AUDPC.
Purification of Phytohaemagglutinins from Phaseolus vulgaris and their Interaction with Plant Pathogenic Bacteria
Authors: Castresana M. C. , Serra M. T. , Tejerina G.
Published: May 2008

Erythrocytes and different strains of plant pathogenic bacteria agglutinated with aqueous and saline 1M NaCl extracts from Phaseolus vulgaris L. seeds, which showed similar gel electrophoretic patterns of proteins.

Haemagglutinating activity in aqueous extracts was inhibited by some carbohydrates, especially N‐acetyl‐D‐galactosamine, D‐galactose and lactose. The agglutinin in this extract was purified by utilizing its ability to bind to Pseudomonas pisi cells followed by its removal from the bacteria by 0.3M galactose.

Mitogenic activity of purified agglutinin was calculated as incorporation of 125I‐iododesoxy‐uridine into DNA of lymphocytes in vitro, which gave values between 25 and 50 μg/ml. The molecular weight of the subunits was found to be 31,500, estimated by mobility in SDS‐PAGE.

A solid phase competition‐binding radioimmunoassay for bean agglutinin was developed in order to determine the affinity of this lectin in bean plants to phytopathogenic bacteria. The highest level of affinity was associated with the system formed by, Ps. pisi and lectin from fresh seeds.
Analysis of Virulence in Populations of Wheat Powdery Mildew in Europe
Authors: Limpert E. , Felsenstein F. G. , Andrivon D.
Published: May 2008

Random samples of spores of wheat powdery mildew were collected from the atmosphere by means of a jet spore sampler while driving through selected wheat growing areas in Europe in 1986. Their single colony progenies were tested in the laboratory forvirulence against wheat differential varieties with powdery mildew resistances Pm2, Pm4b, Pm8, Mli and the combinations Pm2+Pm6, Pm4b+Pm8 and Pm2+Pm4b+Pm8. There were regional differences in virulence frequencies. Virulence on Pm2, Pm2+Pm6 and, less expressed, on Pm4b was most frequent in England and decreased mainly to the east, whereas the reverse was true for Pm8. Virulence to Mli was generally high, and to the combined genotypes generally low. The results suggest that large parts of Europe are an epidemiological unit. The data are discussed with respect to selection caused by the varieties grown, as well as to the influence of wind distribution on the composition of the pathogen population.
Demonstration of Levan and Alginate in Bean Plants (Phaseolus vulgaris) Infected by Pseudomonas syringae pv. phaseolicola
Authors: Gross M. , Rudolph K.
Published: May 2008

A simple method for the extraction of extracellular polysaccharides (EPS) from plant tissue was developed. The polysaccharides of bacterial and plant origin present in the crude leaf extracts were separated by column chromatography on DEAE‐fractogel, and the bacterial polymers were identified by IR spectroscopy.

In extracts from infected leaves as well as in exudates (ooze) from leaf axils, alginate (an acetylated mannuronan) and levan (β‐2,6‐fructofuranan) were detected as the major components amounting up to 80% of the crude extracts. A race‐1 isolate of P. phaseolicola synthesized both levan and alginate in about equal amounts in planta, whereas a race‐2 strain produced EPS composed almost solely of alginate.

Extraction of healthy leaves yielded low amounts of complex polysaccharides. These consisted mainly of galactose, arabinose, and galacturonic acid. Neither fructose nor mannuronic acid were detected.

Kinetic studies indicated that the main production of bacterial EPS in planta was correlated with the appearance of the water‐soaked symptom in leaves. However, before water‐soaking became apparent, alginate was detected in infected leaves (1, day after inoculation). The high amount of extractable material (ca. 50 mg levan plus alginate per g of dry weight of diseased tissue) suggests that the bacterial EPS is responsible for the typical water‐soaked appearance of lesions after bacterial infection.

Since alginate was predominantly synthesized by the more virulent race‐2 isolate, this component of bacterial EPS was suspected to be a decisive factor of virulence of P. phaseolicola. A possible function of alginate during pathogenesis is discussed.
Observation of Flagellate Protozoa (Phytomonas sp.) in Cocos nucifera, Cecropia palmata and Euphorbia hirta
Authors: Leeuw G. T. N. De , Kastelein P.
Published: May 2008

Trypanosomatid flagellates (Phytomonas sp.) were detected in the sieve tubes of ‘hartrot'‐diseased coconut palms (Cocos nucifera) and in the laticifers of Cecropia palmata and Euphorbia hirta plants occurring as weeds in and around coconut plantations with diseased palms. The possible interrelationship and transmission by insect vectors of these protozoa is discussed.
Independent Inheritance of Genes Governing Virulence and the Production of a Polypeptide in Ustilago hordei*
Authors: Thomas P. L. , Kim W. K. , Howes N. K.
Published: May 2008

Detergent soluble polypeptides from teliospores of Ustilago hordei were examined by two‐dimensional isoelectric focusing‐polyacrylamide gel electrophoresis. A relatively prominent polypeptide (M.W. 28,000, P1 6.8) was found in extracts of teliospores from two isolates that were avirulent on the barley cultivar ‘Plush’ but was not detected in extracts from two isolates that were virulent on this cultivar. The polypeptide was also detected in extracts from teliospores of an F1, hybrid between one of the virulent and one of the avirulent isolates. Haploid cultures from five meiotic tetrads, isolated from the F1 hybrid, were backcrossed to haploids from the virulent parent to determine the pathogenicity of each strain. The polypeptide segregated among the 20 progeny as if under the control of a single, dominant allele. The gene governing virulence on ‘Plush’ was not linked to the gene governing the segregating polypeptide.
Increase of Fusarium Rot in Stored Citrus Fruit
Authors: Schiffmann‐Nadel Mina , Chalutz E. , Waks J. , Lomaniec Ella , Yoffe A. Z.
Published: May 2008

In recent years the incidence of Fusarium spp. isolated from Stem End Rot (SER) and Internal Core Rot (ICR) of grapefruit and oranges has increased markedly.

Fusarium spp. were isolated from apparently healthy green buttons and from the tissue underneath the button of healthy fruits.

Of all the SER‐ and ICR‐rotted fruit, the incidence of Fusarium spp. alone and of Fusarium spp. with Alternaria citri was between 75 and 100%.

Fusarium was also found to be the single causal agent of ICR of oranges and grapefruit.

Species of Fusarium isolated from Stem End Rot and Internal Core Rot of citrus fruit were F. oxysporum, F. moniliforme and recently also F. culmorum.
Characterization of Potyvirus Isolates from West African Yams (Dioscorea spp.)
Authors: Porth A. , Lesemann D.‐E. , Vetten H. J.
Published: May 2008

In comparative studies on potyviruses from West African yams (Dioscorea spp.) the following isolates were used: Dioscorea greenbanding mosaic virus (DGMV) and a Nigerian yam virus (YV‐N), both isolated from Dioscorea rotundata, and a beet mosaic virus isolate from D. alata (BtMV‐Y) formerly designated Dioscorea alata ring mottle virus. Naturally infected D. alata containing very few particles of BtMV‐Y, contained primarily particles of a second potyvirus (Dioscorea alata virus, DaV) which could not be transmitted but which was included in these studies wherever possible.

The normal lengths of DGMV, YV‐N, DaV, and BtMV‐Y were 754, 772, 805, and 812 nm, respectively. All viruses induced cytplasmic inclusions of the pinwheel type and laminated aggregates. In addition, the nucleoli of BtMV‐Y infected cells contained characteristic electron dense inclusions. The buoyant density of purified DGMV and BtMV‐Y in CsCl was 1.336 g/cm3 and 1.321 g/cm3, respectively. The sedimention velocities (Srel) of DGMV, YV‐N, and BtMV‐Y were 156, 158, and 162 Srespectively. In SDS‐polyacrylamide gel electrophoresis the coat protein of purified DGMV and YV‐N all migrated as a single band with an apparent molecular weight of 36 kd. Coat protein of purified DaV showed up to 5 bands with molecular weights of 36 to, 32 kd. Polypeptides of purified BtMV‐Y had an estimated molecular weight of 35 kd but those from infected plant extracts had a molecular weight of 36 kd. DGMV, YV‐N, and BtMV‐Y particles contained a single nucleic acid with an apparent molecular weightof 3.2, 3.2, and 3.1 Md, respectively. Using λ‐DNA digested with Hind III as a marker, the molecular weight of DGMV and BtMV‐Y nucleic acid was calculated to be 3.6 Md ± 10%. The nucleic acid was determined to be single‐stranded RNA by enzymatic digestion and by staining with acridine orange.

In serological studies using immunoelectron microscopy (IEM), electro‐blot immunoassay (EBIA), and enzyme‐linked immunosorbent assay (ELISA), DGMV and YV‐N were closely related. Strong serological reactions were also obtained in IEM and EBIA when DGMV and YV‐N were tested with antiserum to yam mosaic virus (YMV). Antisera against DGMV, YV‐N, and YMV also reacted strongly with DaV antigen. Serological reactions between these viruses and BtMV‐Y were usually not found or were weak. A very close serological relationship could be detected between BtMV‐Y and beet mosaic virus isolated from beet (BtMV); both isolates were also very similar in host range, symptomatology, and cytopathology.
A Field and Storage Rot of Onion (Allium cepa L. var. cepa) Caused by Pseudomonas cepacia in Lowland Papua New Guinea
Authors: Tomlinson D. L.
Published: May 2008

A bacterium consistently isolated from rotting onions in the field and in storage was shown by biochemical and pathogenicity tests to be Pseudomonas cepacia. In experiments to determine the mode of entry of the pathogen only injured bulbs developed a soft rot after a 10 min soak in a suspension of P. cepacia (approx. 108 cfu/ml).
Effects of Two Carboxylic Acid Anilide Fungicides on Pustule Development and Carbohydrate Movement and Metabolism in Barley Leaves Infected by Brown Rust (Puccinia hordei Otth.)
Authors: Whipps J. M. , Roderick H. W. , Clifford B. C. , Lewis D. H.
Published: May 2008

The effects of two concentrations of two carboxylic acid anilide fungicides (benodanil and oxycarboxin) on fungal growth, carbohydrate movement and metabolism in barley leaves infected with Puccinia hordei were investigated using radiological, biochemical and histological techniques. At the higher concentration, both fungicides killed the fungus and prevented normal movement of carbohydrate to the pustules and accumulation of fungal carbohydrates. Autoradiography showed that small amounts ofassimilates accumulated at infection sites when leaves or leaf segments were treated with the lower concentration that allowed slight fungal growth. Associated biochemical changes were monitored. Possible mechanisms involved in the alterations caused bythe fungicides are discussed.
Occurrence of Malformin‐like Substances in Seedlings of Mango (Mangifera indica L.)*
Authors: Singh Zora , Dhillon B. S.
Published: May 2008

The ether soluble extracts from stem and root tissues of malformed seedlings of mango showed four malformin‐like substances on chromatograms in the corn root curvature test at Rf 0–0.1 (M1), 0.1–0.2 (M2), 0.8–0.9 (M9) and 0.9–1.0 (M10). M10 was identified as a malformin A‐like substance(s). Stems and roots of malformed seedlings contained high levels of malformin A‐like substance(s) (42.0 μg/g and 41.0 μg/g) respectively, which were absent in stems and roots of healthy seedlings.
The Role of White Mold‐Infected White Bean (Phaseolus vulgaris L.) Seeds in the Dissemination of Sclerotinia sclerotiorum (Lib.) de Bary
Authors: Tu J. C.
Published: May 2008

Sclerotinia sclerotiorum survived in infected seeds of white beans as dormant mycelium in testa and cotyledons. The rate of survival averaged 85 to 89% and did not change appreciably over a 3‐year period. When the infected bean seeds were sown in soil or sand, 88 to 100% failed to germinate. The seeds that failed to germinate, depending on the severity of seed infection, were rotted by S. sclerotiorum. In place of each seed, 3 to 6 sclerotia were formed. A low percentage of these sclerotia germinated carpogenically with or without preconditioning, (2.5 and 11.5% respectively). Myceliogenic germination of sclerotia with and without preconditioning was 35.5% and 70.5% on water agar and 81.0% and 93.0% on glucose agar, respectively. Both, preconditioning and nonpreconditioned sclerotia which were scattered on soil surface could germinate myceliogenically and infect bean leaves by contact. It is therefore, concluded that dormant mycelia in the infected seeds play an important role notonly in dissemination of the fungus but also in epidemiology of the disease.
Seed Transmission of Telfairia Mosaic Virus in Fluted Pumpkin (Telfairia occidentalis Hook f.) in Nigeria
Authors: Anno‐Nyako F. O.
Published: May 2008

Telfairia mosaic virus (TeMV) was transmitted through seeds of four highly susceptible cultivars of fluted pumpkin (Telfairia occidentalis Hook f.) in a screenhouse experiment.

Infection was confirmed through visual appraisal and electron microscopy in cvs NHTo 75–10 (14), 54–4 (4), 54–4 (7), and 6–7 (14), to the extent of 20, 10, 6.4 and 6 % respectively.
Rhabdovirus‐Like Particles in Crinkle‐Diseased Strawberries in Germany
Authors: Jelkmann W. , Lesemann D. E. , Casper R.
Published: May 2008

Thin sections of midribs from a Fragaria vesca UC‐5 indicator plant infected by leaf grafting with a German isolate of strawberry crinkle contained typical rhabdovirus‐like particles within cytoplasmic vesicles. Masses of rhabdovirus‐like particles with a dark stained core and a transparent surrounding layer were seen in necrotic cells surrounding the vascular bundle and in necrotic leaf parenchyma.
Multiplication of Pseudomonas solanacearum in Rhizosphere and Root Tissue of Susceptible and Resistant Varieties of Solanum melongena
Authors: Khan A. N. A. , Shetty K. S. , Patil R. B.
Published: May 2008

The population build‐up of Pseudomonas solanacearum in the rhizosphere, and root‐tissues of two egg plant varieties, susceptible and resistant, raised in infested soil was investigated at different stages of plant growth. There was no perceptible difference in the population build‐up of the pathogen in the non‐rhizosphere soils of both the susceptible and resistant plants. However, the soil 3 cm away from the tap root of the susceptible variety contained a higher population of the pathogen compared to the soil similarly drawn from the resistant plants. The pathogen population in the rhizosphere of the susceptible variety increased 1,000‐fold with increasing age of the plant and was highest at flowering. The rhizosphere of the resistant plant, showed only a 10‐fold increase in pathogen population. The trend was similar with the root tissue populations of the pathogen, but the differences in the root tissue populations of the resistant and susceptible plants were more pronounced. Considerable, buildup of the pathogen population in the susceptible variety was also seen in the above ground portions of the plants. Root extracts of the resistant variety had a marked inhibitory effect on the growth of the pathogen.
Occurrence of Southern Bean Mosaic Virus on Cowpea in Senegal
Authors: Gaikwad D. G. , Thottappilly G.
Published: May 2008

For identification of cowpea viruses existing in Senegal, 180 samples collected from 4 different locations were examined. Initially agar gel diffusion tests were employed to identify the viruses present in these samples using antisera to 3 beetle‐transmitted viruses viz. CPMV, SBMV and CMeV. The results indicated the presence of SBMV in 78 samples mostly from Casamance while none of these viruses were detected in the samples collected from northern Senegal. These results were later confirmed by Enzyme‐linked Immunosorbent Assay (ELISA). This is the first report of occurrence of SBMV in Senegal.
A Muslin Wick Culture Technique for Mass Production of Conidia of Venturia inaequalis
Authors: Puttoo B. L. , Basu Chaudhary K. C.
Published: May 2008

For in vitro and glasshouse studies, mass production of conidia of Venturia inaequalis is essential. A wick culture technique utilising ordinary muslin cloth in 250 ml prescription bottles wetted in 4 % malt extract medium and maintained at 18 ± 2°C for 21 days in darkness produced abundant conidia and proved superior to other methods.
Variations of Phenoloxidase Activities as a Consequence of Stresses that Induce Resistance to Fusarium Wilt of Tomato
Authors: Abbattista Gentile I. , Ferraris L. , Matta A.
Published: May 2008

The variations over 7–8 day of peroxidase (PO) and polyphenoloxidase (PPO) activity have been investigated in tomato plants the roots of which had been subjected to stresses (heat, chloroform and a non‐pathogenic form of Fusarium oxysporum) that induce resistance to Fusarium oxysporum f. sp. lycopersici.

All treatments induced increase of PO and PPO activity that reached a maximum 3 days after the treatments in leaves, 4 days in stem and roots and were higher in leaves than in other parts. Activity decreased to levels for the control plants after 8 days.

Inoculation with Fusarium oxysporum f. sp. lycopersici further stimulated PO and PPO activity in all treated plants over that caused by the treatments alone. Again, activity of treated plants was lower than in controls 7 days after inoculation.

It is concluded that 1. increased PO and PPO activity in tomato is a systemic response to cellular injury caused in the root by heat, chloroform and non‐pathogenic Fusarium oxysporum, 2. these treatments do no prevent the pathogen from interacting with the plants and inducing further enzyme increase, 3. treated plants react more strongly to the challenge inoculation than untreated plants.
Relationship of Cyanogenic Capacity (HCN‐c) of the Rubber Tree Hevea brasiliensis to Susceptibility to Microcyclus ulei, the Agent Causing South American Leaf Blight
Authors: Lieberei Reinhard
Published: May 2008

Liberation of HCN from cyanogenic plant tissue depends on cyanogen content (HCN‐potential), cyanogen splitting enzymes, cyanohydrin cleaving activity (hydroxynitrile lyase) and nonenzymatic cyanide detoxifying compounds. The maximal amount of HCN potentially set free is governed by the total cyanogen content, whereas the velocity of HCN liberation depends on enzymatic activities (β‐glucosidase [β‐G], hydroxynitrile lyase [HN]). Plants revealing a high HCN‐potential and a high β‐glucosidase activity generally are susceptible to infection with Microcyclus ulei. Based on the data of HCN‐p and β‐G activity of different Hevea species a proposal for future screening work in Hevea resistance selection is given.
Behaviour of Phytophthora citrophthora and P. nicotianae var. in soil, and Differences in Their Tolerance to Antimicrobial Components of Selective Media Used for Isolation of Phytophthora spp.
Authors: Sneh Baruch , Katz DaniellaA.
Published: May 2008

Phytophthora citrophthora was inhibited to a greater extent than P. nicotianac var. parasitica by chloramphenicol, hymexazol, PCNB and pimaricin at concentrations used in selective media for the isolation of Phytophthora spp. Reduced concentrations of the antimicrobial components of the selective media to tolerant levels for P. citrophthora markedly increased the recovery of the two brown rot pathogens from soil.

Mycelium of both Phytophthora spp. survived in air‐dried soil for at least 5 months while mycelium of most Phytophthora spp. do not survive in dry soil. In moist soil, P. nicotianae var. parasitica produced hyphal swellings, sporangia and chlamydospores. P. citrophthora produced hyphal swellings and sporangia, but no chlamydospores. No oospores were produced, even in pairing cultures on agar plates with isolates obtained from several locations of citrus groves andfruits by both species. Sporania were obtained in both species in citrus groves on mycelium mats, in the rhizosphere, in infected leaves and fruits buried at soil depths of 5–35 cm. Numbers of propagules declined during the incubation period, but conside, rable numbers survived throughout the experimental period (6 months). Although P. nicotianae var. parasitica produced chlamydospores while P. citrophthora did not, numbers of surviving propagules recovered from soil after 6 months were comparable with both species. The brown rot pathogens survived in soil both as colonizers of detached leaves and fruits and as parasites in living root tissues.
Development of Infection Structures by the Direct‐Penetrating Soybean Rust Fungus (Phakopsora pachyrhizi Syd.) on Artificial Membranes
Authors: Koch E. , Hoppe H. H.
Published: May 2008

The development of infection structures by the directly infecting soybean rust fungus of different artificial membranes was followed by light and scanning electron microscopy. On water agar uredospores developed germ tubes without appressoria. On dialysis membranes more than 80% of the uredospores formed appressoria. With low frequencies (1–7%) also primary hyphae and/or penetration hyphae were present. When cellulose nitrate membrane filters with pore diameters ≤ 0.2 μm were used, uredospores germinated but showed a strongly reduced appressoria formation. Membranes with pores ≥ 0.1 μm allowed a development of infection structures similar to that on dialysis membranes. In experiments with paraffin oil incorporated into collodion membranes more than 90% of the uredospores formed appressoria, about 50% of the appressoria developed hyphae. Ungerminated spores and germ tubes always contained 2 nuclei. In fully developed appressoria 4 nuclei were present. Compared with stomata entering rust fungi appressoria formation by Phakopsora pachyrhizi occurred more frequently and seemed to be less dependent on specific stimuli. Moreover, in most cases only few of the appressoria formed penetration or primary hyphae. The induction of these structures seemed to be dependent on further unknown stimuli.
Prevention of Bacterial Wilt of Grasses by Phylloplane Bacteria
Authors: Schmidt Dorothea
Published: May 2008

Various chromogenic bacteria were isolated from the mowing site in natural and sown meadows and in pastures. Their ability to protect young ryegrass plants from wilt by simultaneous inoculation with Xanthomonas campestris pv. graminis was tested under low concentrations of the parasite inoculum. From about 200 isolates tested 35% had a very high protective effect, 45% a moderate one, and only 20% had no significant effect. Mixtures of different species of phylloplane bacteria usually gave very good protection. Most of these bacteria live between the leaf‐sheaths. In vitro antagonism of the phylloplane bacteria was not related to their protective effect. Avirulent mutant strains of X. c. pv. graminis and pathovars, of other grass species, e.g. pv. poae, pv. phlei, and pv. arrhenatheri, have the same protecting effect. Heat killed bacteria were no longer effective.

These observations suggest an unspecific reaction of the plant, such as the induction of a general defense mechanism which results in resistance also to the parasite.
Detection of Pseudocercosporella herpotrichoides (Fron) Deighton in Wheat by Indirect ELISA
Authors: Unger J.‐G. , Wolf G.
Published: May 2008

An indirect ELISA for quantitative detection of P. herpotrichoides in fections in wheat is presented. All tested isolates of the virulent varieties P. herpotrichoides var. herpotrichoides, P. h. var. acuformis or the W‐ and R‐type react on a high level in the test, while the less virulent P. anguioides is assessed only with 40% and the avirulent P. aestiva with 20% of the homologous reaction. No crossreactions occur with extracts of 11 other species of in, vitro cultivated fungi nor with plant material infected with other pathogens. The infection profile throughout the leaf‐sheaths was clearly reflected by ELISA. The examination of 24 stembase samples from the field showed that the values assessed by ELISA correlate well also with the disease indices of naturally infected plant material.
Changes in the Lipid Composition of Rhizoctonia solani Infected Groundnut Hypocotyls
Authors: Reddy M. N. , Sujathamma P.
Published: May 2008

Alterations in the total and individual lipids in healthy and Rhizoctonia solani infected groundnut hypocotyl tissues were determined. Infection resulted in an increase in the total as well as individual lipid components at various stages of disease development.
Races of Xanthomonas campestris pv. malvacearum (Smith) Dye, the Causal Organism of Bacterial Blight of Cotton, in Nigeria
Authors: Poswal M. A. T.
Published: May 2008

Races 6, 7 and 10 of Xanthomonas campestris pv. malvacearum (Smith) Dye, the causal organism of bacterial blight of cotton, were identified among twelve isolates of the pathogen from the three cotton growing zones of Nigeria. Races 7 and 10 were, however, predominant. The races were distinguished by inoculation of eight cotton lines known to differentiate through possession of different resistance genes. Further work is necessary, on a much greater number of isolates, to determine therange and distribution of different virulence types in Nigeria.