Interaction of Fusarium Oxysporum f.sp. Cubense with Pseudomonas Fluorescens Precolonized to Banana Roots

Effect of precolonization of banana cv Neeypovan roots with Pseudomonas fluorescens on infection with Fusarium oxysporum f.sp. cubense was studied. Under in vitro conditions Pseudomonas fluorescens clearly inhibited Fusarium oxysporum f.sp. cubense. Fluorescein isothiocyanate-tagged antibodies raised in a rabbit system for Pseudomonas fluorescens and Fusarium oxysporum f.sp. cubense separately were used to study the spread of both organisms in banana root. It was observed that precolonization with Pseudomonas fluorescens could reduce Fusarium oxysporum f.sp. cubense colonization by 72%, and also correlated with a number of structural changes in the cortical cells, mainly with densely stained amorphous material and polymorphic wall thickenings as revealed by light and electron microscopic studies. Massive depositions of unusual structures at sites of fungal entry was also noticed, which clearly indicated that bacterized root cells were signalled to mobilize a number of defence structures for preventing the spread of pathogen in the tissue. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of flavonoids on the development of Fusarium oxysporum f. sp. lycopersici

Abstract

In the present study the effect of flavonoid compounds on the germination and fungal growth of the soil-borne tomato pathogen Fusarium oxysporum f. sp. lycopersici was studied. Out of 12 flavonoid compounds only myricetin and luteolin exhibited a low stimulating activity on microconidia germination of Fusarium oxysporum f. sp. lycopersici, whereas the other flavonoids tested were inactive when applied at five different concentrations. In our study the tested flavonoids affect fungal growth differently to microconidia germination. Individual flavonoid concentrations resulted in a small increase of fungal growth, but the lowest flavonoid concentrations showed an inhibiting effect on fungal growth for all flavonoids tested. There is evidence to suggest, that low flavonoid concentrations exhibit slight antimicrobial properties against Fusarium oxysporum f. sp. lycopersici.     

Virulence and Vegetative Compatibility of Dutch and Italian Isolates of Fusarium oxysporum f. sp. lilii

The virulence and vegetative compatibility of eight Dutch and four Italian isolates of Fusarium oxysporum obtained from lily were compared. The virulence was tested by determination of the specific interaction between the Fusarium isolates and eight lily cultivars. A specific interaction was not found, so the existence of races was not demonstrated. Six of the twelve isolates turned out to be non-pathogenic for lily. The pathogenic isolates fell in four vegetative compatibility groups. No vegetative compatibility was found between isolates of F. oxysporum f. sp. lilii and those of f. sp. gladioli.     

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.     

Biocontrol efficacy of Trichoderma spp. against sesame wilt caused by Fusarium oxysporum f. sp. sesami

Sesame (Sesamum indicum L.) is one of the most important oilseed crops in Egypt and worldwide. It is being infected with many pathogens, among these pathogens Fusarium oxysporum f.sp. sesami (Zap.) Cast is causing severe economic losses on sesame. In this study, antagonistic capability of 24 isolates of Trichoderma spp. was assessed in vitro against F. oxysporum f.sp. sesami. Two strains; T. harzianum (T9) and T. viride (T21) were revealed to have high antagonistic effect against F. oxysporum f.sp. sesami in vitro with inhibition percentage about 70 and 67%, respectively. These two isolates proved to have high ability to control Fusarium wilt disease under greenhouse conditions. The highest reduction in disease severity was achieved with T. viride followed by T. harzianum with reduction in disease severity about 77 and 74%, respectively. This study revealed that the time of application of bioagents is a decisive factor in determining the efficacy of Trichoderma isolates to control Fusarium wilt of sesame. It was revealed that the highest reduction in the disease severity was achieved when either Trichoderma viride or T. harzianum were applied 7 days before challenging with the F. oxysporum f.sp. sesami.     

Presence of Fusarium oxysporum f. sp. melonis Race 1 in Soils Cultivated with Melon in the State of Colima (Mexico)

During years 2001, 2002 and 2003 the gravity of the Fusarium wilt in 1000 hectares of melon culture was evaluated in Colima (Mexico). In spite of the soil disinfections with methyl bromide, the losses could reach 25% of the final production. The analysis of 4 soil samples from the fields with ill plants, in a selective medium for Fusarium, allowed to detect the presence of F. oxysporum. By means of the presented technique “soil phytopathometry”, 31 isolates of F. oxysporum f. sp. melonis were obtained from the soil samples. The isolates were inoculated on melon plants to evaluate their pathogenicity. The 31 isolates inoculated, produced the symptoms of chlorosis and wilting, in melon cultivars that allowed us to affirm that all isolates were race 1 of F. oxysporum f. sp. melonis. Being this the first news of the presence of F. oxysporum f. sp. melonis in the state of Colima (Mexico).     

A simple and rapid technique for fluorescence staining of fungal nuclei

A technique for staining fungal nuclei using fluorescence stain Hoechst Dye 33258 in McIlvaine standard buffer of pH 7.26–7.44 is reported. It is a broad-spectrum fungal nuclear staining tool found to be effective onAgaricus bisporus, Alternaria helianthi, Fusarium oxysporum f. sp.lini, Penicillium binellum, Pythium ultimum, Rhizoctonia solani, andSaccharomyces cerevisiae. Conidial nuclei ofAlternaria helianthi, Fusarium oxysporum f. sp.lini, andPenicillium binellum also stained well.     

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.     

Fungus gnats vector Fusarium oxysporum f.sp. radicislycopersici1

Fungus gnat adults transported Fusarium oxysporum f.sp. radicis-lycopersici from Petri dish culture and infected host plants to the roots and hypocotyls of healthy tomato and bean plants. The source of the fungus did not affect the ability of fungus gnats to transport the fungus to healthy hosts. The presence of fungus gnat larvae in media in which young tomato plants were grown did not increase the incidence of plant infection by the pathogen. Fungus gnat adults appear to aid in the dissemination of F. oxysporum f.sp. radicis-lycopersici.     

Modulation des Réactions de Défense du Palmier a Huile Contre le Fusarium oxysporum f. sp. elaeidis (Schlecht) Toovey: Applications: Prémunition et Stimulation Chimique

Defence reactions of palm trees to Fusarium oxysporum f. sp. elaeidis (Schlecht) Toovey Cross protection and stimulation of inhibitory substances In palm tree genetic characters of tolerance to Fusarium oxysporum f. sp. elaeidis are correlated with synthesis of fungal inhibitors in infected tissues. Individual variation of synthesis level is also observed among plants of a same line. Defence reactions are triggered by pre-inoculation of an avirulent strain of Fusarium oxysporum. Similar results are obtained by application of analogs of fungal elicitors like arachidonic acid. Quite the contrary, treatment of plants with a competitive inhibitor of PAL downs natural barriers and in a same way the effects of cross protection and arachidonic treatment. Seven phenolic compounds, mainly benzoic acid derivatives, inhibit in vitro the growth of pathogen like spores germination. The variability of the host reaction and its stimulation by elicitors could be used to improve the resistance.     

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.     

Induction of defence-related enzymes in onion by combined application of fungal and bacterial biocontrol agents against Fusarium oxysporum f. sp. cepae

Basal rot disease of onion is a major problem in different onion growing regions of Tamil Nadu, India. Fungal and bacterial cultures were isolated and tested their efficiency against Fusarium oxysporum f. sp. cepae under in vitro conditions. Effective bacterial and fungal antagonists were tested alone and in combinations for the control of F. oxysporum f. sp. cepae in glasshouse experiments. Defence-related enzymes such as peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase were induced and accumulated in onion treated with fungal and bacterial antagonists. Defence-related enzymes were significantly higher in onion pretreated with consortial formulation of Pf12 + Pf27 + TH3 at 5 days after the challenge inoculation with F. oxysporum f. sp. cepae and gave resistance to onion against basal rot disease.     

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.     

大豆根瘤内抗棉花枯萎病菌株的筛选及其防病试验

【目的】采用优良抗病性内生菌资源来控制棉花枯萎病是一种有效的措施。本研究从大豆根瘤中筛选棉花枯萎病拮抗性内生细菌,探索其对棉花枯萎病菌丝的抑制作用和代表菌株特性,为发掘和应用防病、抗逆优良菌株提供理论基础。【方法】采用对峙法和代谢液培养法对大豆根瘤内生细菌进行棉花枯萎病菌抑菌性筛选,显微观察法研究筛选菌株引起病原菌菌丝变化,通过菌株培养特征、理化特性和16S r DNA序列同源性分析确定菌株系统发育地位,比色法测定DD174耐盐碱性,盆栽试验验证防病效果。【结果】经复筛和代谢液试验有5株拮抗性较强菌株,被作用病原菌菌丝畸形、细胞壁消失、自溶,菌丝基部加粗、分支增多,呈树根状;菌丝被菌苔包埋而溶解、断裂,菌丝末端球形膨大。对棉花枯萎病菌的抑制作用主要通过菌体产生胞外代谢物发挥作用。菌株DD174、DD176和DD179最相似菌株分别为Bacillus oceanisediminis H2T(GQ292772)和B.thuringiensis ATCC 10792T(AF290545),菌株DD165和DD166最相似菌株均为Stenotrophomonas maltophilia LMG 958T(X95923)。DD174能耐受6%盐浓度,p H 10生长良好,具有一定耐盐碱能力。DD174处理组防治效果达76.32%,其他防效均在62%以上,可作为棉花枯萎病的生防菌株资源。【结论】大豆根瘤内存在棉花枯萎病内生拮抗细菌,其中有些菌株具有一定耐盐碱能力,对棉花枯萎病病原菌及病害有一定抑菌和防病作用。     

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.     

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.     

Gerbera jamesonii, Osteospermum sp. and Argyranthemum frutescens: New Hosts of Fusarium oxysporum f. sp. chrysanthemi

The pathogenicity of five isolates of Fusarium oxysporum obtained from infected gerbera (Gerbera jamesonii), chrysanthemum (Chrysanthemum morifolium), Paris daisy (Argyranthemum frutescens) and African daisy (Osteospermum sp.) plants was tested on some varieties of the following Compositae hosts: C. morifolium, G. jamesonii, Argyranthemum frutescens (Paris daisy) and Osteospermum sp. and compared with the host range and pathogenicity of an isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC collection. The results indicated that isolates of F. oxysporum from G. jamesonii as well as those from A. frutescens and Osteospermum sp. belong to the forma specialischrysanthemi. The isolate from gerbera was virulent on all tested varieties of gerbera, C. morifolium, A. frutescens and Osteospermumsp. Similar results were obtained testing the isolates obtained from A. frutescens and Osteospermumsp. The strain from C. morifolium infected cultivar of gerbera, A. frutescens and Osteospermum sp. The pathogenicity of isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC showed a different cultivar range particularly in the case of chrysanthemum and gerbera.     

Antagonistic effects of soil bacteria onFusarium oxysporum Schlecht f. sp.dianthi (Prill and Del.) Snyd. and Hans

Summary Fusarium oxysporum f. sp.dianthi, pathogenic on carnation plants is very sensitive toBacillus subtilis M51 inhibition.Fusarium oxysporum disease (fusariosis) is prevented for a period of two months after treatment of plants withBacillus subtilis M51. The persistence ofB. subtilis M51, marked for selenomycin resistance (MZ51) and inoculated on the roots of carnation cuttings was studied. Soil used was two types: naturally infested withFusarium oxysporum and free from this pathogen. Bacterial cells presence on the roots was detected by direct plating and the presence of the pathogen in the roots was investigated by histological assays. Evidence gathered by these procedures suggest that plant protection is dependent on the physical presence ofB. subtilis M51 cells on the roots.     

Biological control ofFusarium oxysporum f.sp.cubense in banana by inoculation withPseudomonas fluorescens

Native strains ofPseudomonas fluorescens exhibitedin vitro antibiosis towards isolates of races 1 and 4 ofFusarium oxysporum f.sp.cubense, the Panama wilt pathogen of banana. The seedlings ofMusa balbisiana seedlings treated withP. fluorescens showed less severe wilting and internal discolouration due toF. oxysporum f.sp.cubense infection in greenhouse experiments. In addition to suppressing Panama wilt, bacterized seedlings ofM. balbisiana also showed better root growth and enhanced plant height.