Some Aspects of the Biology of Fusarium oxysporum Schl. in Soil

From either a mycelial or a conidial inoculum the fungus survivedin soil as inactive chlamydospores. The level of its soil populationat equilibrium was too low to be studied by dilution plating.Plant materials placed on or beneath the surface of inoculatedsoil were colonized deeply by the fungus, which produced conidiaon them. Dispersal of conidia can occur with water movementin soil, and at right angles to, as well as in the directionof, that movement. No evidence was found of dispersal of thefungus in soil by continuous growth, even over continuous stretchesof organic matter. This finding was related to the inabilityof the fungus to colonize those organic materials that werepreviously colonized by other organisms from the soil, unlessits inoculum potential were greatly augmented. The fungus isthus seen to be a pioneer fungus. The strain used here grewoutwards a short distance from colonized organic food basesin the soil, leaving in the soil resting spores which couldcolonize fresh pieces of organic material subsequently addedthere. The organism could thus spread by discontinuous growthon successively available, fresh, organic materials.     

胡麻专化型尖孢镰刀菌ISSR-PCR最佳反应体系的建立

采用正交试验设计原理,对尖孢镰刀菌ISSR-PCR反应体系中的5种主要因素进行优化筛选,确立了适合尖孢镰刀菌ISSR分析的反应体系,即25μL PCR反应体积中合有20 ng模板DNA、1 U Taq酶、0.4 μmol/L引物、0.2 mmol/LdNTPs、4.0 mmol/L Mg2+和2.5 μL 10 × buffer.PCR反应最佳退火温度根据引物而定,在此基础上筛选出12条扩增稳定、多态性丰富的ISSR引物.此研究为今后利用ISSR技术分析尖孢镰刀菌遗传多样性和群体结构奠定了基础.     

The Saprophytic Status of Fusarium oxysporum Schl: Causing Vascular Wilt of Oil Palm

The droplet plating method described, especially when used inconjunction with a baiting technique, facilitates the demonstrationof Fusarium oxysporum in soil. This fungus was present in soilfrom wilt-free areas of oil palm plantations as well as in soilabout wilt-diseased palms. Hyphal fusions between soil isolatesand isolates from wilted palms could be demonstrated. The funguspersisted for periods of at least ¹ year in naturally infestedsoils under a variety of moisture conditions; it also survivedin inoculated alien soil forms of Ieast ¹year. Soil forms ofthe fungus had a high competitive saprophytic ability, competitivelycolonizing sterilized soils and sand, and organic materialsadded to soils and mixed cultures. The pathogenic isolate, aswell as the soil isolates, exhibited characters belonging tosoil-inhabiting fungi, namely continued persistance in soil:tolerance, in respect of growth and reproduction, to antagonism:and the ability competitively to colonize dead organic materialin soils. The pathogenic form is considered to be a soil inhabitant.     

Comparison of Fusarium oxysporum and Fusarium oxysporum var. redolens by Analyzing the Isozyme and Serological Patterns

Extracts from Fusarium oxysporum (F.o.) and F. oxysporum var. redolens (F.o.r.) isolates were compared by means of electrophoresis and crossed immunoelectrophoresis. The polymorphism of five isozyme systems allowed a distinction between F.o. and F.o.r. isolates. The isozyme patterns of three other isozyme systems did not allow this distinction between F.o. and F.o.r. to be made. Both fungi appeared almost identical serologically. Relative amounts of their corresponding proteins differed but the qualitative patterns of the proteins were nearly the same with the anti-F.o.r. serum, only one specific antigen was detected in the extracts from F.o.r., isolates. Although the results obtained indicate a strong similarity between F.o. and F.o.r., they are not sufficient for an unequivocal statement that the fungi belong to the same species.     

The cell wall of Fusarium oxysporum.

Sugar analysis of isolated cell walls from three formae speciales of Fusarium oxysporum showed that they contained not only glucose and (N-acetyl)-glucosamine, but also mannose, galactose, and uronic acids, presumably originating from cell wall glycoproteins. Cell wall glycoproteins accounted for 50-60% of the total mass of the wall. X-ray diffraction studies showed the presence of alpha-1, 3-glucan in the alkali-soluble cell wall fraction and of beta-1, 3-glucan and chitin in the alkali-insoluble fraction. Electron microscopy and lectin binding studies indicated that glycoproteins form an external layer covering an inner layer composed of chitin and glucan.     

Characteristics of Inhibition of a Taiwanese Soil Suppressive to Fusarium oxysporum f. sp. raphani

Germination of nutrient-amended chlamydospores of the three formae speciales of Fusarium oxysporum tested were inhibited in a suppressive soil collected from central Taiwan. The suppressive soil released a volatile substance when moistened with alkaline solution. The inhibition spectrum of the volatile substance was different from that of the suppressive soil. The inhibitory effect of the suppressive soil was greatly reduced when it was heat-treated for 30 min at 40°C or higher. The inhibitory effect of the heat-treated suppressive soil was restored after infestation with 1% conducive or suppressive soil for 14 days. However, infestation of heat-treated conducive soil even with 1% suppressive soil did not render it suppressive. Amendment of suppressive soil with rose bengal, streptomycin or Rubigan completely or partially reduced the inhibitory effect. Increasing the total population of indigenous microorganisms in conducive soil by amendment with rice germ or soybean meal to about the same level as that in suppressive soil did not render it suppressive. Results suggest that a combination of biotic and abiotic factors is responsible for the inhibitory effect of the suppressive soil.     

Regulation of pyruvate kinases from Fusarium oxysporum.

Two types of pyruvate kinases were found in Fusarium oxysporum. One type (inducible) was present mainly during the early stages of growth on glucose or sucrose and displayed Michaelis-Menten kinetics with respect to phosphoenolpyruvate and adenosine diphosphate. The major type (constitutive) was present under all conditions of growth and displayed in the absence of potassium ions, a sigmoidal substrate saturation curve when phosphoenolpyruvate was used as the variable substrate. In the presence of potassium ions the saturation curve for phosphoenolpyruvate exhibits a plateau at half-maximal velocity. The effects of various metabolites on the activity of the inducible and constitutive kinases were also studied. Fructose-1,6-diphosphate, cyclic AMP, acetyl CoA, tryptophan, and phenylalanine had no effect on the activity of the enzymes. Citrate was a potent inhibitor of the constitutive pyruvate kinase activity and increased the sigmoidicity of the saturation curve for phosphoenolpyruvic acid. In the presence of K+, the bimodal plot observed in the absence of citrate gradually changed to a hyperbolic shape as the concentration of citric acid was increased. In the presence of K+ and ADP as the variable substrate citric acid converted the hyperbolic plot to a sigmoidal one. Citrate had no effect on the inducible enzyme.     

Antagonistic Effect of Nonpathogenic Fusarium oxysporum Fo47 and Pseudobactin 358 upon Pathogenic Fusarium oxysporum f. sp. dianthi

Pseudobactin production by Pseudomonas putida WCS358 significantly improves biological control of fusarium wilt caused by nonpathogenic Fusarium oxysporum Fo47b10 (P. Lemanceau, P. A. H. M. Bakker, W. J. de Kogel, C. Alabouvette, and B. Schippers, Appl. Environ. Microbiol. 58:2978-2982, 1992). The antagonistic effect of Fo47b10 and purified pseudobactin 358 was studied by using an in vitro bioassay. This bioassay allows studies on interactions among nonpathogenic F. oxysporum Fo47b10, pathogenic F. oxysporum f. sp. dianthi WCS816, and purified pseudobactin 358, the fluorescent siderophore produced by P. putida WCS358. Both nonpathogenic and pathogenic F. oxysporum reduced each other's growth when grown together. However, in these coinoculation experiments, pathogenic F. oxysporum WCS816 was relatively more inhibited in its growth than nonpathogenic F. oxysporum Fo47b10. The antagonism of nonpathogenic F. oxysporum against pathogenic F. oxysporum strongly depends on the ratio of nonpathogenic to pathogenic F. oxysporum densities: the higher this ratio, the stronger the antagonism. This fungal antagonism appears to be mainly associated with the competition for glucose. Pseudobactin 358 reduced the growth of both F. oxysporum strains, whereas ferric pseudobactin 358 did not; antagonism by pseudobactin 358 was then related to competition for iron. However, the pathogenic F. oxysporum strain was more sensitive to this antagonism than the nonpathogenic strain. Pseudobactin 358 reduced the efficiency of glucose metabolism by the fungi. These results suggest that pseudobactin 358 increases the intensity of the antagonism of nonpathogenic F. oxysporum Fo47b10 against pathogenic F. oxysporum WCS816 by making WCS816 more sensitive to the glucose competition by Fo47b10.     

Mineral Uptake in Fusarium oxysporum f. sp. vasinfectum

A method for growing Fusarium oxysporum, a mycelial fungus, and a technique for its use in mineral uptake studies have been described. Some general characteristics of the uptake process were determined. The fungus, grown for 54 hours, was found to take up as much K as 15 to 20 meq/100 g dry weight in 2 to 4 hours from a solution of 5 meq/l KCl. Approximately 3 to 5 meq of this uptake was readily removed by a CaCl₂ rinse. The uptake was only slightly sensitive to pH over the range of 4 to 9. Below pH 4 uptake dropped rapidly. The age of the culture appeared to be the dominant factor in determining the rate of uptake. In contrast to other fungi, the presence of glucose during uptake was detrimental to K uptake. Conditions unfavorable for metabolic activity as low temperature, anaerobiosis, or the presence of DNP markedly reduced the uptake rate. Although the fungus took up Na from single salt solutions nearly as well as K, the latter ion was much preferred in mixtures of the two ions. The organism showed no significant metabolic uptake of Ca or Cl. During uptake from KCl solutions, the organic acid content increased. The increase, chiefly in succinic acid and to a lesser extent in acetic and citric acids, amounted to about half the K uptake. The remainder of the K taken up was correlated with a roughly equivalent efflux of cellular Mg.     

Dispensable chromosomes in Fusarium oxysporum f. sp. lycopersici

The genomes of many filamentous fungi consist of a ‘core’ part containing conserved genes essential for normal development as well as conditionally dispensable (CD) or lineage‐specific (LS) chromosomes. In the plant‐pathogenic fungus Fusarium oxysporum f. sp. lycopersici, one LS chromosome harbours effector genes that contribute to pathogenicity. We employed flow cytometry to select for events of spontaneous (partial) loss of either the two smallest LS chromosomes or two different core chromosomes. We determined the rate of spontaneous loss of the ‘effector’ LS chromosome in vitro at around 1 in 35 000 spores. In addition, a viable strain was obtained lacking chromosome 12, which is considered to be a part of the core genome. We also isolated strains carrying approximately 1‐Mb deletions in the LS chromosomes and in the dispensable core chromosome. The large core chromosome 1 was never observed to sustain deletions over 200 kb. Whole‐genome sequencing revealed that some of the sites at which the deletions occurred were the same in several independent strains obtained for the two chromosomes tested, indicating the existence of deletion hotspots. For the core chromosome, this deletion hotspot was the site of insertion of the marker used to select for loss events. Loss of the core chromosome did not affect pathogenicity, whereas loss of the effector chromosome led to a complete loss of pathogenicity.     

Race Differentiation in Fusarium oxysporum f.sp. chrysanthemi

The pathogenicity of different isolates of Fusarium oxysporum obtained from plants of Gerbera (Gerbera jamesonii), Chrysanthemum (Chrysanthemum morifolium), Paris daisy (Argyranthemum frutescens) and African daisy (Osteospermum sp.), all in the family Asteraceae, was tested on different cultivars of these hosts, to assess their pathogenicity. The reactions were compared with those of isolates of F. oxysporum f. sp. chrysanthemi and of f.sp. tracheiphilum obtained from the American Type Culture Collection. We found that isolates of F. oxysporum f. sp. chrysanthemi can be distinguished as three physiological races on the basis of their pathogenicity to the panel of differential cultivars. Sequencing of the intergenic spacer (IGS) region of ribosomal DNA (rDNA) and phylogenetic analysis showed that the Fusarium races fell into three phylogenetic groups, which coincided with those observed in pathogenicity tests. Analysis of the IGS sequences revealed a high degree of similarity among strains from Italy and Spain from different host species, suggesting that recent outbreaks in these ornamentals were probably caused by introduction of infected nursery material from a common origin.     

Chitinous components of the cell wall of Fusarium oxysporum.

The cell wall of Fusarium oxysporum f. sp. lycopersici was digested with chitinase to analyze the structure of its chitinous components. In spite of a similar acetylation degree of the cell wall components to that of 25-35% acetylated chitosan, only N-acetylglucosamine disaccharide [(GlcNAc)2] was obtained from chitinase hydrolyzate of the fungal cell wall by CM-Sephadex C-25 column chromatography, while (GlcNAc)2 and several types of deacetylated chitooligosaccharides were separated from that of 25-35% acetylated chitosan. The results indicate that N-acetylglucosamine residues in the polysaccharide chains of the fungal cell wall are most likely condensed into some region, while acetylated residues are more scattered in 25-35% acetylated chitosan.     

Some Aspects of the Ecology and Biology of Some Small Mammal Fleas from Yorkshire

The Invertebrates R. MCNEILL ALEXANDER 561 pp. London: Cambridge University Press, 1979. £28.00/£7.95. ISBNs 0 521 22120 X/29361 8 Reviewed by Andrew C. Campbell

Lecture Notes on Invertebrate Zoology Second edition M. S. LAVERACK and J. DANDO 194 pp. Oxford: Blackwell Scientific, 1979. £5.50. ISBN 0 632 00325 1 Reviewed by Andrew C. Campbell

An Illustrated Guide to River Phytoplankton H. BELCHER and E. SWALE 64 pp. London: Institute of Terrestrial Ecology/HMSO, 1979. £1.50. ISBN 0 11 886602 8 Reviewed by J. W. G. Lund

The Cell as a Habitat 286 pp. London: The Royal Society, 1979. £8.50. ISBN 0 85403 113 8 H. V. Wyatt

Cell Motility Integrated Themes in Biology H. STEBBINGS and J. S. HYAMS 192 pp. Harlow, Essex: Longman, 1979. £4.95. ISBN 0 582 44380 6 Reviewed by K. R. Tyler

Concepts in Cell Biochemistry W. K. STEPHENSON 221 pp. Chichester, Sussex: John Wiley, 1978. £5.00. ISBN 0 471 03390 1 Reviewed by D. A. Kennedy

The Kindly Fruits of the Earth G. E. HUTCHINSON 264 pp. London: Yale University Press, 1979. £13.35. ISBN 0 300 02272 7 Reviewed by W. H. Dowdeswell

Brain, Behaviour and Evolution D. A. OAKLEY and H. C. PLOTKIN (Ed.) 237 pp. Andover, Hants: Methuen, 1979. £9.00/£4.95. ISBNs 0 416 71260 6/71270 3 Reviewed by W. H. Dowdeswell

Introduction to Evolution F. A. RACLE 162 pp. Hemel Hempstead, Herts: Prentice/Hall, 1979. £5.80. ISBN 0 13 382869 0 Reviewed by J. A. Dawes

Tissues and Organs: a text-atlas of scanning electron microscopy R. G. KESSEL and R. H. KARDON 317 pp. San Francisco and Reading: W. H. Freeman, 1979. £18.90/£7.00. ISBNs 0 7167 0091 3/0090 5 Reviewed by A. W. Robards

The Cycling Female A. LEIN 135 pp. Reading: W. H. Freeman, 1979. £6.30/£2.90. ISBNs 0 7167 1039 0/1038 2 D. J. Reid

Ecology and Evolution of Animal Behaviour Second edition R. A. WALLACE 284 pp. Hemel Hempstead, Herts: Prentice/Hall, 1979. £7.10. ISBN 0 87620 272 5 Reviewed by Ursula Bowen

Man Against Disease MUIR GRAY 192 pp. Oxford: Oxford University Press, 1979. £2.50. ISBN 0 19 289127 8 Reviewed by H. V. Wyatt

Pollen and Allergy Studies in Biology, No. 107 R. BRUCE KNOX 60 pp. London: Edward Arnold, 1979. £1.75. ISBN 0 7131 2736 8 Reviewed by D. Brookes

Principles of Animal Physiology Second edition J. A. WILSON 890pp. London: Collier Macmillan, 1979. £16.45. ISBN 0 02 428360 6 Reviewed by K. R. Tyler

Morphogenesis of the Vertebrates Fourth edition T. W. TORREY and A. FEDUCCIA 570 pp. Chichester, Sussex: John Wiley, 1979. £11.60. ISBN 0 471 03232 8 Reviewed by F. E. G. Cox

Lizards—A Study in Thermoregulation Studies in Biology, No. 109 R. A. AVERY 56 pp. London: Edward Arnold, 1979. £1.80. ISBN 0 7131 2745 7 Reviewed by Gillian E. Standring

Life at High Altitude Studies in Biology, No. 112 D. HEATH and D. REID WILLIAMS 60 pp. London: Edward Arnold, 1979. £1.80. ISBN 0 7131 2754 6 Reviewed by C. G. Gayford

Seal Cull J. LISTER-KAYE 174 pp. Harmondsworth, Middx: Penguin Books, 1979. 95p. ISBN 0 14052 336 7 Seal Song B. DAVIES and E. PORTER 94 pp. Harmondsworth, Middx: Penguin Books, 1979. £2.50. ISBN 0 1400 4740 9 Reviewed by Ursula Bowen

Fieldwork Projects in Biology M. HINGLEY 170 pp. Poole, Dorset: Blandford Press, 1979. £4.95. ISBN 0 7137 0964 2 Reviewed by Malcolm Watson

Investigative Mycology R. F. SHARP 136 pp. London: Heinemann Educational, 1978. £5.00/£2.20. ISBNs 0 435 60750 2/60751 0 Reviewed by Avice M. Hall

Sexual Incompatibility in Plants Studies in Biology, No. 110 D. LEWIS 60 pp. London: Edward Arnold, 1979. £1.90. ISBN 0 7131 2747 3 Reviewed by David Skibinski

Introduction to the Principles and Practice of Soil Science R. E. WHITE 198 pp. Oxford: Blackwell Scientific, 1979. £8.50. ISBN 0 632 00052 X Reviewed by D. Payne

Bioscience Education in Developing Countries T. RAMASARMA et al. (Ed.) 230pp. Singapore: University of Singapore, 1979 $7.00 Reviewed by Colin Wood-Robinson

Ecology of African Mammals M. J. DELANY and D. C. D. HAPPOLD 434 pp. Harlow, Essex: Longman, 1979. £25.00. ISBN 0 582 44176 5 Reviewed by Colin Wood-Robinson

Modern Biology Made Simple R. BARRASS 304 pp. London: W. H. Allen, 1979. £3.50/£2.25. ISBNs 0491 02452 5/02462 2 Reviewed by John May

Life Science Physics J. W. KANE and M. M. STERNHELM 664 pp. Chichester, Sussex: John Wiley, 1978. £11.00. ISBN 0 471 03137 2 Reviewed by P. Burdett

Warwick Real Time Science Simulations Teacher's Handbook R. A. BEARE £3.00 Eleven biology booklets J. HEWITSON £1.00-1.75. Hatfield, Herts: Association for Science Education, 1978 Reviewed by M. E. Leveridge     

Some pathological aspects of narcissus basal rot, caused by Fusarium oxysporum f. sp. narcissi

Excavations of ridge-grown narcissus showed that most roots were beneath the bulbs and that few extended sideways to the next ridge. Root senescence preceded leaf senescence and moribund roots were available for colonization by Fusarium oxysporum f. 8p. narcissi when soil temperatures became favourable for the pathogen. Inoculation experiments with 1 and 2 yr crops showed that some inoculum is redistributed during the first season to allow increased disease incidence in the second. In 2yr crops, some bulbs rot without trace so that true disease incidence in a stock is greater than is indicated by examination of lifted bulbs.     

Production of Intraspecific Hybrids of Fusarium oxysporum f. sp. radicis-lycoperisici and Fusarium oxysporum f. sp. lycopersici by Protoplast Fusions

The fusion of protoplasts from the cycloheximide-resistant mutant FOL(C) of Fusarium oxysporum f. sp. lycopersici (FOL) and the mycostatin-resistant mutant FORL(M) of F. oxysporum f. sp. radicis-lycopersici (FORL), produced hybrids which expressed significant differences from the parents in their pathogenicity and growth and in the electrophoretic separation patterns of their proteins, enzymes and isoenzymes. The results suggest a transformed genetic basis for these altered expressions and the feasibility of using protoplast fusion technology for examining the biology of pathogenicity genes and for elucidating the disease and virulence potential for new races from within hybridisable taxa of Fusarium spp. Such information would be useful for the design and development of long-term control systems for Fusarium diseases, particularly in breeding programs for disease resistance in crops.     

Sucrose-induced lupine defense against Fusarium oxysporum. Sucrose-stimulated accumulation of isoflavonoids as a defense response of lupine to Fusarium oxysporum.

Defense responses to inoculation with Fusarium oxysporum SCHLECHT f. sp. lupini were studied in embryo axes of Lupinus luteus L. cv. Polo cultured on a medium with sucrose (60 mM) or without it. Exogenous sucrose caused a marked endogenous increase in concentrations of sucrose, glucose and fructose in embryo axes. In axes cultured with sucrose, high performance liquid chromatography (HPLC) revealed generally higher levels of isoflavone glycosides (particularly until 48 h of culture) and free aglycones (genistein, wighteone, luteone). Inoculation resulted in a considerable decline in soluble carbohydrates between 24 and 72 h of culture. Simultaneously, the infection stimulated an increase in the level of free isoflavone aglycones in inoculated embryo axes, as compared to non-inoculated ones. Concentrations of free aglycones (i.e. genistein, wighteone and luteone) after infection were particularly high in inoculated embryo axes fed with sucrose. Genistein was a better inhibitor to F. oxysporum growth than genistein 7-O-glucoside tested. Exogenous sucrose also stimulated the activity of phenylalanine ammonialyase (PAL, EC 4.3.1.5)--an important enzyme initiating phenylpropanoid metabolism. After infection of tissues, a strong increase was observed in the activity of PAL and beta-glucosidase (EC 3.2.1.21)--an enzyme hydrolyzing isoflavone glycosides. Furthermore, the growth of inoculated embryo axes cultured with sucrose was less inhibited as a result of infection than inoculated axes cultured under carbohydrate deficiency conditions. Additionally, it had been reported previously that disease symptoms of embryo axes growing in the presence of sucrose were less intensive [30]. These results suggest that soluble sugars are involved in the mechanism of resistance, as they can stimulate phenylpropanoid metabolism and contribute to the increase in concentration of isoflavonoids, which are important elements of the defense system of legumes.