Einfluss Der Gründüngung Auf Das Auftreten Der Fusarium-Welke An Baumwolle In Gefässversuchen

Zusammenfassung 1. Durch Gründüngung mit Hafer, Senf oder Ackerbohnen kann der Befall der Baumwolle durchFusarium oxysporum f.vasinfectum in Gefäßversuchen wesentlich vermindert werden. Die Befallsreduktion beträgt bis zu 80%.2. Durch die Gründüngung wird die Zahl der gegen den Erreger antagonistischen Actinomyceten im Boden erheblich gesteigert. Die Zunahme erreicht etwa 4 Wochen nach Unterbringung des Pflanzenmaterials ihren Höhepunkt. Gleichzeitig wird die fungistatische Potenz des Bodens eindeutig erhöht.3. Andererseits wird, unabhängig von der Infektion, die Entwicklung der Baumwollpflanzen durch Gründüngung stark gefördert. Die Gründe hierfür sind unbekannt.4. Eine bloße Zumischung entsprechender Mengen von Pflanzenmaterial zum Boden hat etwa dieselben Wirkungen wie die eigentliche Gründüngung. Daraus folgt, daß der Gründüngungseffekt ausschließlich von Enbringung und Abbau der Pflanzenmasse, nicht aber vom vorausgehenden Wachstum abhängig ist.5. Von den untersuchten Pflanzen übt Senf in jeder Hinsicht die deutlichsten Wirkungen aus, obwohl er die geringste Massenentwicklung aufzuweisen hat. Der Einfluß des Hafers ist am schwächsten, während Ackerbohnen in der Regel eine Mittelstellung einnehmen.6. Die erhaltenen Ergebnisse werden im Hinblick auf ihre praktische Bedeutung diskutiert.

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Incidence of fusarium with in cotton as influenced by green-manuring in pot trials

Summary 1. The occurrence ofFusarium oxysporum f.vasinfectum in cotton plants has been reduced up to 80% by green-manuring with oats, mustard or broad beans in pot trials.2. The number of actinomycetes antagonistic against the pathogen increased considerably in the soil by green-manuring. The highest number has been found approximately 4 weeks after the admixture of the plant material to the soil. At the same time the fungistatic potency of the soil also increased considerably.3. Green-manuring, on the other hand, stimulated the growth and development of cotton plants, independently from the existence of infections. The reasons for this effect are unknown at the present time.4. Simply adding corresponding amounts of plant material to the soil had about the same effect as the actual green-manuring with plants raised in the same soil. It is concluded that the effect of green-manuring depends exclusively on the addition and subsequent desintegration of plant material and not on the preceding growth of plants in the soil.5. Of the plants investigated mustard had the most distinct effects in each respect, although it produced the smallest amount of organic matter. Broad beans showed only a moderate and oats the smallest effect.6. The results are discussed with regard to their practical significance and application.

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(With a summary)     

Fusarium oxysporum Forms Heterokaryons with Fusarium redolens

Vegetative compatibility among three isolates of Fusarium oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens from diseased lupins was investigated. Pairings between five mutants originated from each isolate revealed two compatibility groups. The first VCG comprised race 1 of F. oxysporum f. sp. lupini and one isolate of F. oxysporum var. redolens; the second VCG comprised race 2 of F. oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens. Heterokaryon formation was observed in many pairings involving mutants of both taxa. These findings provide evidence of the conspecificity of these two taxa and they support Gordon 's classification (1952) according to which F. redolens is actually F. oxysporum.     

Optimization of RAPD-PCR Fingerprinting to Analyse Genetic Variation Within Populations of Fusarium oxysporum f.sp. cubense

Genetic variation among 11 isolates of Fusarium oxysporum f.sp. cubense (FOC) was analysed by random amplification of polymorphic DNA using the polymerase chain reaction (RAPD-PCR). The isolates represented three of the four FOC races and the seven vegetative compatibility groups (VCGs) known to occur in Australia. Isolates of F. oxysporum f.sp. cubense were also compared to isolates of F. oxysporum f.sp. gladioli, F. oxysporum f.sp. zingiberi, F. oxysporum f.sp. lycopersici, F. moniliforme, Aspergillus niger and Colletotrichum gloeosporioides. DNA was extracted from fungal mycelium and amplified by RAPD-PCR using one of two single random 10-mer primers; the primer sequences were chosen arbitrarily. The RAPD-PCR products were separated by polyacrylamide gel electrophoresis producing a characteristic banding pattern for each isolate. The genetic relatedness of the F. oxysporum f.sp. cubense isolates was determined by comparing the banding patterns generated by RAPD-PCR. This RAPD-PCR analysis revealed variation at all five levels of possible genetic relatedness examined. F. oxysporum f.sp. cubense could very easily be distinguished from the other fungi, and the three races and five VCGs of F. oxysporum f.sp. cubense could also be differentiated. Within F. oxysporum f.sp. cubense, each isolate was scored for the presence or absence of each band (50 different bands were produced for primer SS01 and 59 different bands for primer RC09) and these data were clustered using the UPGMA method (unweighted pair-group method, arithmetic average). UPGMA cluster analysis of the data generated by primer SS01 revealed two distinct clusters. One cluster contained race 4 isolates (VCGs 0120, 0129 and 01211) and the other cluster contained both race 1 (VCGs 0124, 0124/5 and 0125) and race 2 isolates (VCG 0128). Similar results were obtained with primer RC09. The banding patterns for each isolate were reproducible between experiments. These results indicated that RAPD-PCR was a useful method for analysing genetic variation within F. oxysporum f.sp. cubense. Some of the advantages of this technique were that it was rapid, no sequence data were required to design the primers and no radioisotopes were required.     

Biological Control Activity of Three Trichoderma Isolates Against Fusarium Wilts of Cotton and Muskmelon and Lack of Correlation with their Lytic Enzymes

The enzymatic activity and the biocontrol ability of two new isolates of Trichoderma spp. (T-68 and Gh-2) were compared in laboratory and glasshouse experiments with a previously studied T. harzianum strain (T-35). In dual culture tests with Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. vasinfectum, isolates T-68 and Gh-2 overgrew the colonies of Fusarium, whereas T-35 failed to parasitize both wilt pathogens. Under glasshouse conditions, the three isolates of Trichoderma were effective in controlling Fusarium wilt of cotton but only T-35 was effective against F. oxysporum f. sp. melonis on muskmelon. When the three Trichoderma isolates were grown on liquid media containing laminarin, colloidal chitin or F. oxysporum f. sp. melonis cell walls as sole carbon sources, maximum β-1,3-glucanase and chitinase specific activity in the culture filtrates of all fungi was reached after 72h of incubation. When culture filtrates of the three Trichoderma isolates were incubated with freeze-dried mycelium of F. oxysporum f. sp. melonis or F. oxysporum f. sp. vasinfectum, different concentrations of glucose and N-acetyl-D-glucosamine were released. Overall no correlation was found between enzymatic activity and the biocontrol capability against Fusarium wilt on muskmelon and cotton.     

Über das Formunterscheidungsvermögen der Schmeißfliege Calliphora erythrocephala

Zusammenfassung Mit Alternativwahlversuchen wird nachgewiesen, daß folgende Formmerkmale die Zielorientierung (= Telotaxis) von laufenden, männlichen Schmeißfliegen (Calliphora erythrocephala) stimulieren: 1. Dunkle Kontrastflächen (Abb. 1); 2. Vertikale Kontrastgrenzen (Abb. 2-6); 3. Figurengliederung (Abb. 3f und 4).

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On the pattern discrimination of the blow fly Calliphora erythrocephala

Summary Experiments on binary choices of walking male blow flies (Calliphora erythrocephala) demonstrate the stimulatory value of the following pattern characteristics on the targed orientation (= telotaxis): 1. Dark contrasting area (Fig. 1). 2. Vertical edge of contrast (Fig. 2–6). 3. Disruption of shape (Fig. 3f and 4).

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Mit Unterstützung der Deutschen Forschungsgemeinschaft (SFB 45).     

Genetic Diversity of Fusarium oxysporum Populations Isolated from Tomato Plants in Tunisia

Fusarium crown and root rot of tomato (Lycopersicon esculentum) caused by Fusarium oxysporum f. sp. radicis‐lycopersici is a new devastative disease of tomato greenhouse crops in Tunisia. Nothing is known neither about the population of this pathogen in this region, nor about the population of F. oxysporum f. sp. lycopersici the causal agent of Fusarium wilt of tomato. In order to examine the genetic relatedness among the F. oxysporum isolates by intergenic spacer restriction fragment length polymorphism (IGS‐RFLP) analysis and to elucidate the origin of the formae specialesradicis‐lycopersici in Tunisia by looking for genetic similarity of Tunisians isolates with isolates from a foreign source, the genetic diversity among F. oxysporum f. sp. radicis‐lycopersici and F. oxysporum f. sp. lycopersici populations was investigated. A total of 62 isolates of F. oxysporum, obtained from symptomless tomato plants, were characterized using IGS typing and pathogenicity tests on tomato plants. All Fusarium isolates were highly pathogenic on tomato. Fusarium oxysporum f. sp. radicis‐lycopersici isolates were separated into five IGS types. From the 53 F. oxysporum f. sp. radicis‐lycopersici isolates, 34 isolates have the same IGS types (IGS type 25), and the remaining 19 isolates were distributed into four IGS types. However, the only nine isolates of F. oxysporum f. sp. lycopersici have six different IGS types. This difference of diversity between the two formae speciales suggests that F. oxysporum f. sp. radicis‐lycopersici isolates have a foreign origin and may have been accidentally introduced into Tunisia.     

Comparison of two fatty acid analysis protocols to characterize and differentiate Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici

The utility of fatty acid methyl ester (FAME) profiles for characterization and differentiation of isolates of Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici was investigated. Two fatty acid analysis protocols of the normal (MIDI) and a modified MIDI method were used for their utility. Only the modified MIDI method allowed a clear differentiation between F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicislycopersici. FAME profiles using the modified MIDI method gave the most consistent and reproducible analyzed fatty acid data. Evaluation of the FAME profiles based on cluster analysis and principal-component analysis revealed that FAME profiles from tested isolates were correlated with the same vegetative compatibility groups (VCGs) compared to the same races in F. oxysporum f. sp. lycopersici. Results indicated that FAME profiles could be an additional tool useful for characterizing isolates and forma species of F. oxysporum obtained from tomato.     

Chromatographic Characterization and Phytotoxic Activity of Fusarium oxysporum f. sp. albedinis and Saprophytic Strain Toxins

The bayoud disease, vascular fusariosis of date palm tree (Phoenix dactylifera L.), is caused by the pathogenic fungus Fusarium oxysporum f. sp. albedinis. The characteristic symptoms of the bayoud disease were elicited on detached leaves of F. oxysporum f. sp. albedinis‐susceptible cultivars of date palm trees, which were treated either with the F_II (F. oxysporum f. sp. albedinis) fraction purified from the organic extracts of a F. oxysporum f. sp. albedinis liquid culture, or with a solution of fusaric acid. Enniatins, which are secreted by several Fusarium species, were tested at different concentrations and were not capable of inducing symptoms on such detached leaves. The F_II (F. oxysporum f. sp. albedinis) fraction was unable to induce necrosis of potato slices, which indicates that it does not contain significant amounts of enniatins. The high‐performance liquid chromatography (HPLC) profiles of the F_II (F. oxysporum f. sp. albedinis) fraction showed toxic peaks different from fusaric acid. A fraction, named F_II (AZ₄), was obtained from culture filtrates of a saprophytic Fusarium strain maintained in the same cultural conditions as for the F. oxysporum f. sp. albedinis. The HPLC profile of the F_II (AZ₄) fraction did not show the characteristic phytotoxic peaks present in the F_II (F. oxysporum f. sp. albedinis) fraction. This finding well agrees with the fact that the F_II (AZ₄) fraction is not toxic to detached date palm leaves. Moreover, the HPLC profiles of F_II fractions obtained from other special forms of F. oxysporum are different the F_II (F. oxysporum f. sp. albedinis) profile. The phytotoxic compounds purified from the F_II (F. oxysporum f. sp. albedinis) fraction are probably new molecules that may help in understanding the pathogenesis of bayoud disease.     

First Record of Fusarium Wilt of Tobacco in Greece Imported as Seedborne Inoculum

Leaf yellowing and brown discoloration was observed in tobacco plants cv. Burley TN97 in tobacco fields of central Greece in 2002. Fusarium oxysporum f. sp. nicotianae was isolated from symptomatic plants and Koch's postulates were fulfilled. The pathogenicity of the isolated fungus was examined on five tobacco cultivars (Burley TN97, BurleyB21, VirginiaBE9, Virginia Niki and Anatolika KE26/2). The pathogen was present in tobacco seed batches imported in 2000 and 2001, which indicates that the infected seed is most probably the primary source of the disease in Greece. As Fusarium oxysporum f. sp. vasinfectum can also cause vascular wilt in tobacco, the hypothesis that the isolated F. oxysporum strain belongs to f. sp. vasinfectum was excluded by a pathogenicity test to cotton cv. Acala SJ‐2. This is the first report of F. oxysporum f. sp. nicotianae in Greece and the second in the European Union, although the seedborne nature of the pathogen has not been previously reported in Europe.     

Host-specific Fusarium oxysporum Causes Wilt of Jojoba

Jojoba [Simmondsia chinensis (Link) Schneider] plantations in Israel originated from vegetative propagation, planted during 1991–92, have shown symptoms of wilting and subsequent death. Verticillium dahliae was only rarely isolated from these plants and artificial inoculation showed only mild disease symptoms. Fusarium oxysporum caused severe chlorosis, desiccation, defoliation and wilt in leaves of jojoba plants, resulting in plant death. Recovery of the fungus from artificially inoculated stem cuttings and seedlings showed for the first time that F. oxysporum was the primary pathogen. Inoculated cuttings exhibited wilt within 3 weeks, while in seedlings wilt occurred 10–24 weeks after inoculation. Seedlings and cuttings of jojoba which were inoculated with other Fusarium isolates originating from different crops (F. oxysporum f. sp. vasinfectum from cotton, F. oxysporum f. sp. dianthi from carnation, F. oxysporum f. sp. lycopersici from tomato and F. oxysporum f. sp. basilicum from basil) did not develop symptoms. Moreover, cotton, tomato, melon and cucumber seedlings inoculated with several virulent F. oxysporum isolates from jojoba did not show any symptoms of wilt or defoliation. These results indicate a high degree of specificity of the Fusarium isolates from jojoba; therefore, it is suggested that this isolate be defined as F. oxysporum f. sp. simmondsia.     

Über Fibrillärstrukturen im Nebennierenmark von Haus und Wildmeerschweinchen (Cavia aperea f. porcellus L. und Cavia aperea tschudii Fitzinger)

Zusammenfassung Im Nebennierenmark von adulten Wildmeerschweinchen (Cavia aperea tschudii) und Hausmeerschweinchen (Cavia aperea f. porcellus) werden bisher unbekannte intrazelluläre Fibrillenstrukturen nachgewiesen. Licht- und elektronenmikroskopische Befunde zeigen, daß in bestimmten Markzellen Filamentbündel in Gruppen auftreten, die durch das Perikaryon bis zur Zellperipherie zu verfolgen sind. Sie fasern in der Nähe des Plasmalemms auf und bilden desmosomenähnliche Kontaktflächen. Die Einzelfilamente sind ca. 70–100 Å dick. Beim Chinchilla konnten im Mark keine Filamentstränge festgestellt werden, beim Haus- und Wildmeerschweinchen kommen sie in unterschiedlicher Häufigkeit vor.

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Intracellular fibrils in the adrenal medulla of domesticated and wild guinea pigs (Cavia aperea f. porcellus L. and Cavia aperea tschudii fitzinger)

Summary By light and electron microscopic observations intracellular fibrils were found in the adrenal medulla of adult wild (Cavia aperea tschudii) and domesticated guinea pigs (Cavia aperea f. porcellus). In certain cells of the adrenal medulla bundles of filaments can be traced from the perinuclear region into the periphery of the cells. Near the plasma membrane they split apart and attach to the desmosome-like regions. The individual filaments are about 70–100 Å in diameter. In adrenal medullary cells of chinchilla no fibrillar strands were observed, in wild and domesticated guinea pigs they occur in different numbers.

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Die Untersuchung wurde mit dankenswerter Hilfe der Deutschen Forschungsgemeinschaft durchgeführt.     

Weitere Untersuchungen zur Resistenz vonMedicago-arten gegenPseudopeziza medicaginis (Lib.) Sacc.

Zusammenfassung Durch Infektionsversuche an 44Medicago-Arten und-Varietäten mit den f. sp.medicaginis sativae undmedicaginis lupulinae vonPseudopeziza medicaginis sowie mitP. meliloti wurden die Kenntnisse über das Resistanzverhalten der GattungMedicago erweitert und frühere Ergebnisse bestätigt.

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Further investigations on the resistance ofMedicago species toPseudopeziza medicaginis (Lib.) Sacc.

Summary Experimental infections of 44 species and varieties ofMedicago with the f. sp.medicaginis sativae andmedicaginis lupulinae fromPseudopeziza medicaginis and withP. meliloti have broadened the knowledge on resistance behavior of the genusMedicago and confirmed earlier results.

     

Pathogenicity of Fusarium oxysporum Isolates from Malaysia and F. oxysporuin f. sp. elaeidis from Africa to Seedlings of Oil Palms (Elaeis guineensis)

Pathogenicity tests with Fusarium oxysporum isolated form Malaysian oil palm were made with oil palms seedlings raised form Malaysian seed as well s with wilt-susceptible seedlings gown from African seed. Oil palm seedlings grown form Malaysian seed were also inoculated with African isolates of F. oxysporum f. sp. elaeidis and F. oxysporum var. redolens. The experiments were made under normal soil moisture conditions and under water stress. F. oxysporum f. sp. elaeidis isolates form Africa were pathogenic to oil palm seedlings from Malaysian seeds but the Malaysian F oxysporum isolates were non-pathogenic to plams grown from Malaysian seed or the wilt-susceptible palms from African seed. Seedlings from Malaysian seed proved to be highly susceptible to the vascular wilt disease caused by F. oxysporum f. sp. elaeidis as 75–90% of the palms were infected. The susceptibility of the palms from Malaysian seed varied with different African isolates tested. The Yaligimba isolate from Zaire which was found to be F. oxysporum var. redolens was the most virulent. Disease was more severe when oil palm seedlings were subjected to a period of water stress. The incidence of death in the seedlings under stress conditions was 45% as compared with only 15% for palms grown under normal conditions.     

Akustische Barrieren beim Waldbauml?ufer (Certhia familiaris)?

Zusammenfassung Waldbaumläufer besitzen je nach geographischer Herkunft deutlich verschiedene Reviergesangs-Strophen. Zusammenfassen lassen sich jene aus Mittel- und W-Europa (Certhia familiaris macrodactyla, mWb;C. f. britannica undC. f. corsa), aus dem weiteren Himalaya-Gebiet (Nepal,C. f. mandellii, nWb; und SW-China,C. f. khamensis, cwb) und als weitere Gruppe die aus Japan (C. f. orientalis, jWb). Differenzen im Gesang bestehen hinsichtlich der Zahl der Elemente in der Strophe, Frequenzumfang der Strophe, Frequenzverlauf der Elemente und deren Frequenzumfang. Der nWb reagiert nicht auf Gesang des mWb, umgekehrt besteht hohe Reaktionsfreudigkeit des mWb auf Str. des nWb. Freiland-Experimente mit unveränderten, gekürzten und künstlichen Str. aus gereihten Einzel-El. zeigen, daß bestimmter Frequenz-Verlauf der El. die Reaktion hervorruft. Es sind solche El. des nWb, die beim mWb in ähnlicher Form auftreten. Vielfach sind es aber El., die zwar vordergründig geringe oder keine Übereinstimmungen aufweisen, in einzelnen El.-Abschnitten jedoch erkennbare Frequenz-Entsprechungen besitzen. Einzelne dieser El. von mWb und nWb sind als homolog zu betrachten. In den meisten Fällen kann über die mögliche Homologie nicht entschieden werden, denn über El.-Veränderungen in der Evolution akustischer Signale ist bei Baumläufern zu wenig bekannt.

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Acoustic barriers in the Tree Creeper (Certhia familiaris)?

Summary Tree Creepers use according to their distributional origin different territorial songs. Populations with similar songs occur in Central and W Europe (C. f. macrodactyla, mWb;C. f. britannica, C. f. corsa), in Himalayan East Asia (Nepal,C. f. mandellii, nWb; SW China,C. f. khamensis, cWb) and Japan (C. f. orientalis, jWb). Differences in the territorial songs refer to number of elements in the verse, frequency volume of the verse, frequency modulation of the elements and their frequency volume. The Tree Creeper from Nepal (mandellii) does not react on the song of Central European Tree Creepers (macrodactyla), but the latter is very responsive tomandellii verses. Field experiments using unchanged, shortened or artificial verses consisting of one natural element arranged in a row, demonstrate that only certain frequency modulations evoke reactions. Such elements occur at least in similar expression in nWb and mWb as well. Often also such elements are answered which at first sight do not correspond or only to a low degree to mWb elements, but do so in certain small sections of mWb elements. Several of the similar elements in mWb and nWb are to be considered homologous. But in most cases where reaction in field experiments is high, the homology of the elements concerned cannot be substantiated. Changes of element structures in the course of vocal evolution in the [familiaris] superspecies is too poorly known.

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Results of the Himalaya Expeditions ofJ. Martens, No. 146. — For No. 145 see: Stuttgarter Beitr. Naturk., (A) 411: 1–43, 1987. — J. M. sponsored by Deutscher Akademischer Austauschdienst and Deutsche Forschungsgemeinschaft.     

Cross-pathogenicity between Formae Speciales of Fusarium oxysporum, the Pathogens of Cucumber and Melon

The population structure of Fusarium oxysporum f. sp. cucumerinum was studied using the vegetative compatibility grouping (VCG) approach. All 37 of the examined isolates from Israel were assigned to VCG 0180, the major VCG found in North America and the Mediterranean region. Approximately two‐thirds of the tested isolates were pathogenic to both cucumber and melon, but cumulatively they were more aggressive on cucumber, their major host, than on melon. Disease symptoms on melon plants were less destructive and often expressed as growth retardation. Melon cultivars differing in Fom genes for resistance to F. oxysporum f. sp. melonis were inoculated with three isolates of F. oxysporum f. sp. cucumerinum. Results showed that Fom genes do not confer resistance to F. oxysporum f. sp. cucumerinum, although different horticultural types may respond differently to this pathogen. The reciprocal inoculation of F. oxysporum f. sp. melonis on cucumber, using four physiological races, did not result in disease symptoms or growth retardation. It is concluded that cucumerinum and melonis should remain two distinct formae speciales.     

Protein and Esterase Patterns of Pathogenic, Fusarium oxysporum f. sp. elaeidis and F. oxysporum var. redolens from Africa, and Non-Pathogenic K oxysporum from Malaysia

Protein and esterase patterns of eleven isolates of F. oxysporum f. sp. elaeidis, one isolate of F. oxysporum var. redolens pathogenic to oil palm from Africa and six non-pathogenic isolates of F. oxysporum from oil palm soils in Malaysia were studied by vertical disc-electrophoresis and isoelectric focusing, to determine whether the pathogenic and saprophytic forms of F. oxysporum could be distinguished using these two methods. The protein patterns of all the isolates studied by the two methods were almost identical qualitatively and it was impossible to distinguish between the pathogenic isolates of F. oxysporum f. sp. elaeidis and F. oxysporum var. redolens from Africa and saprophytic isolates of F. oxysporum from Malaysia. Esterase zymograms of the isolates produced by the two methods were different. Esterase zymograms produced by vertical disc-electrophoresis showed great variations between and within the African and Malaysian isolates, but the esterase patterns produced by isoelectric focusing were almost identical qualitatively.     

Further Investigation of the Specificity of Interactions Between Wild Lactuca spp. and Bremia lactucae Isolates from Lactuca serriola

Callus cultures derived from isogenic lines of the tomato cultivars Moneymaker and Craigella, resistant or susceptible to F. oxysporum f. sp. lycopersici, were inoculated with Fusarium oxysporum f. sp. lycopersici race 1. Fungal growth was restricted on callus derived from resistant plants, after inoculation with a conidial suspension, whereas callus derived from susceptible plants was totally overgrown by the fungus within 7 days. The concentration of the phytoalexin rishitin was significantly higher in the callus culture derived from a resistant tomato line compared with the callus culture from a susceptible line, 2 and 3 days after inoculation with mycelium. The results of the experiments were compared with experiments with whole plants. Rishitin production as well as growth of the fungus was comparable with responses in plant-fungus interaction. Therefore callus culture may be useful in studying the interaction between tomato plants and race 1 of F. oxysporum f. sp. lycopersici.     

Phytopathogenic Fusarium oxysporum Schlecht, as a Necrotrophic Mycoparasite

Fusarium oxysporum f. sp. dianthi, f. sp. lycopersici, f. sp. cepae, f. sp. niveum and one unidentified F. oxysporum isolate proved to be active necrotrophic mycoparasites. In dual cultures hyphae of Trichoderma hamatum, T. longibrachiatum, T. pseudokoningii, T. harzianum, Botrytis cinerea and Rhizoctonia solani were parasitized and destroyed by F. oxysporum. One isolate of Phytophthora sp. was not affected. Mutual parasitism between F. oxysporum and T. pseudokoningii and T. longibrachiatum has been observed, too. Details of parasitic hyphal interactions: hyphal coiling, penetration sites, resistance sheat formation, hyphal invasion and internal growing are described. The mycoparasitic feature as well as antimicrobial metabolic production of F. oxysporum is probably a common phenomenon to ensure this important plant pathogenic species to compete successfully against other soil-borne fungal pathogens and saprophytes.     

Impact of biological control agents on fusaric acid secreted from <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">gladioli</Emphasis> (Massey) Snyder and Hansen in <Emphasis Type="Italic">Gladiolus grandiflorus</Emphasis> corms

Fusaric acid (FA) (5-n-butylpuridine 2-carboxyl acid), a highly toxic secondary metabolite produced by Fusarium oxysporum strains, plays a significant role in disease development. The abilities of three F. oxysporum f. sp. gladioli (Massey) Snyder and Hansen isolates (G010; 649-91; and 160-57) to produce FA in infected Gladiolus corm tissues was evaluated in vitro in relation to the presence of two biological control agents, Trichoderma harzianum T22, and Aneurinobacillus migulanus. Pathogenicity tests were used to differentiate between the abilities of the F. oxysporum strains to secrete FA. FA was identified using LC/MS and quantified using HPLC. Isolate G010 was significantly more virulent (P < 0.01) on Gladiolus grandiflorus corms; it secretes 1.8 μM FA/g fresh weight corm into inoculated Gladiolus. Moreover, G010 was the only isolate that produced FA among the three examined isolates. There was a correlation between the corm lesion area and the FA secretion ability of F. oxysporum f. sp. gladioli (P < 0.001; r ² = 0.96). No FA was detected in PDA cultures of F.oxysporum f. sp. gladioli isolates. The presence of T. harzianum T22 appeared to prevent FA secretion into the corms. In the presence of A. migulanus, however, the amount of FA secreted into the corm tissues increased. These results support the use of T. harzianum as an effective biological control agent against F. oxysporum f. sp. gladioli.     

Analysis of genetic variability of Fusarium oxysporum f. sp. cepae the causal agent of basal rot on onion using RAPD markers

Genetic variability among isolates of Fusarium oxysporum f. sp. cepae was obtained from different onion-growing areas of Tamil Nadu, India. Random amplified polymorphic DNA (RAPD) analysis was carried out using 12 random primers, each of them consisting of 10 base pairs. Four out of the 12 primers were differentiated between some of the tested F. oxysporum f. sp. cepae isolates. Analysis of the genetic coefficient matrix derived from the scores of RAPD profile showed that minimum and maximum per cent similarities among the F. oxysporum f. sp. cepae isolates were in the range of 14–85%. Cluster analysis, using the unweighted pair-group method with arithmetic average, clearly separated the isolates into two clusters (A and B) confirming the genetic diversity among the isolates of F. oxysporum f. sp. cepae from onion.