Nonpathogenic Strains Of Fusarium Oxysporum Research Articles

The Impact of a Non-Pathogenic Strain of Fusarium Oxysporum on Structural and Biochemical Properties of Flax Suspension Cultures.

Flax (Linum usitatissimum L.) is an important crop plant with pharmaceutical significance. It is described in pharmacopoeias (the United States Pharmacopeia and the European Pharmacopoeia), which confirms that it (especially the seeds) is a valuable medicinal product. Similar to flax seeds, which accumulate bioactive compounds, flax in vitro cultures are also a rich source of flavonoids, phenolics, lignans and neolignans. In the present study, flax suspension cultures after treatment of the non-pathogenic Fusarium oxysporum strain Fo47 were established and analyzed. The study examined the suitability of Fo47 as an elicitor in flax suspension cultures and provided interesting data on the impact of these endophytic fungi on plant metabolism and physiology. Two flax cultivars (Bukoz and Nike) and two compositions of media for flax callus liquid cultures were tested. Biochemical analysis revealed enhanced levels of secondary metabolites (total flavonoid and total phenolic content) and photosynthetically active pigments in the flax callus cultures after treatment with the non-pathogenic fungal strain F. oxysporum Fo47 when compared to control, untreated cultures. In cultures with the selected, optimized conditions, FTIR analysis was performed and revealed changes in the structural properties of cell wall polymers after elicitation of cultures with F. oxysporum Fo47. The plant cell wall polymers were more strongly bound, and the crystallinity index (Icr) of cellulose was higher than in control, untreated samples. However, lignin and pectin levels were lower in the flax callus liquid cultures treated with the non-pathogenic strain of Fusarium when compared to the untreated control. The potential application of the non-pathogenic strain of F. oxysporum for enhancing the synthesis of desired secondary metabolites in plant tissue cultures is discussed.

Endophytic non-pathogenic Fusarium oxysporum reorganizes the cell wall in flax seedlings.

Flax (Linum usitatissimum) is a crop producing valuable products like seeds and fiber. However, its cultivation faces challenges from environmental stress factors and significant yield losses due to fungal infections. The major threat is Fusarium oxysporum f.sp lini, causing fusarium wilt of flax. Interestingly, within the Fusarium family, there are non-pathogenic strains known as biocontrols, which protect plants from infections caused by pathogenic strains. When exposed to a non-pathogenic strain, flax exhibits defense responses similar to those seen during pathogenic infections. This sensitization process activates immune reactions, preparing the plant to better combat potential pathogenic strains. The plant cell wall is crucial for defending against pathogens. It serves as the primary barrier, blocking pathogen entry into plant cells. The aim of the study was to investigate the effects of treating flax with a non-pathogenic Fusarium oxysporum strain, focusing on cell wall remodeling. The infection's progress was monitored by determining the fungal DNA content and microscopic observation. The plant defense response was confirmed by an increase in the level of Pathogenesis-Related (PR) genes transcripts. The reorganization of flax cell wall during non-pathogenic Fusarium oxysporum strain infection was examined using Infrared spectroscopy (IR), determination of cell wall polymer content, and analysis of mRNA level of genes involved in their metabolism. IR analysis revealed reduced cellulose content in flax seedlings after treatment with Fo47 and that the cellulose chains were shorter and more loosely bound. Hemicellulose content was also reduced but only after 12h and 36h. The total pectin content remained unchanged, while the relative share of simple sugars and uronic acids in the pectin fractions changed over time. In addition, a dynamic change in the level of methylesterification of carboxyl groups of pectin was observed in flax seedlings treated with Fo47 compared to untreated seedlings. The increase in lignin content was observed only 48 hours after the treatment with non-pathogenic Fusarium oxysporum. Analysis of mRNA levels of cell wall polymer metabolism genes showed significant changes over time in all analyzed genes. In conclusion, the research suggests that the rearrangement of the cell wall is likely one of the mechanisms behind flax sensitization by the non-pathogenic Fusarium oxysporum strain. Understanding these processes could help in developing strategies to enhance flax's resistance to fusarium wilt and improve its overall yield and quality.

Biocontrol Activity of Nonpathogenic Strains of Fusarium oxysporum: Colonization on the Root Surface to Overcome Nutritional Competition.

Fusarium oxysporum is a soil-borne fungal pathogen that causes vascular wilts in a wide variety of crops. Certain nonpathogenic strains of F. oxysporum are known to protect crops against F. oxysporum pathogens. We assessed the biocontrol activities of nonpathogenic mutants of F. oxysporum ff. spp. melonis and lycopersici generated by disruption of the FOW2 gene, which encodes a Zn(II)2Cys6-type transcriptional regulator essential for their pathogenicity. Pre-inoculation of melon or tomato roots with strain ΔFOW2 conidia markedly reduced disease incidence caused by the parental wild-type strain in a concentration-dependent manner of conidial suspensions of ΔFOW2 strains. The biocontrol effect caused by the ΔFOW2 pre-inoculation lasted for at least 7 days. Pre-inoculation of melon roots with the wild-type or ΔFOW2 strain of F. oxysporum f. sp. lycopersici and nonpathogenic F. oxysporum strain also led to biocontrol activity against F. oxysporum f. sp. melonis, indicating that the biocontrol activity of ΔFOW2 strains is due to its nonpathogenic nature, not to the FOW2 disfunction. Conidial germination and hyphal elongation of only the wild-type strain were inhibited on melon root surface pre-inoculated with conidia of strains nonpathogenic to melon plants. Expression of defense-related genes was not significantly induced in roots and aboveground parts of melon seedlings preinoculated with ΔFOW2 conidia. Carbon source competition assay showed that nonpathogenic strains competed with the wild-type strain for a carbon source in soil. Strain ΔFOW2 also competed with the oomycete pathogen Pythium aphanidermatum for carbon source and protected melon plants from P. aphanidermatum. Our results suggest that the biocontrol activity of the nonpathogenic F. oxysporum strains used in this study mainly depends on their extensive colonization of the root surface and outcompeting pathogens for nutrients.

A non-pathogenic strain of Fusarium oxysporum and grape marc compost control Verticillium wilt of olive

Verticillium wilt of olive (VWO), caused by the widespread soil-borne fungus Verticillium dahliae Kleb., is currently the most serious disease affecting olive trees (Olea europaea L.) in all production areas. An integrated management strategy using eco-friendly approaches such as genetic resistance and biological control is considered the most advisable approach for controlling the disease in commercial olive orchards. This study evaluated a non-pathogenic strain of F. oxysporum (FO12) and the grape marc compost CGR03 for reducing inoculum density of V. dahliae and the disease progress in two olive cultivars with different VWO resistance levels. The experiment was conducted under semi-controlled conditions, using a naturally infested soil with two inoculum densities of V. dahliae. The biocontrol treatments (FO12 and CGR03) were previously selected out of 220 natural products as two of the most effective treatments against the pathogen. FO12 and CGR03 treatments significantly reduced pathogen inoculum density in comparison with that of the control (P = 0.05), with minimum microsclerotium amounts of 0.13 g-1 for FO12 and 0.53 g-1 for CGR03, during the experimental period. CGR03 reduced the progression of the disease compared with that in the control (P = 0.05), and FO12 achieved complete control of VWO, since no plants treated with this biological control strain developed VWO symptoms. This study highlights the effectiveness of these biocontrol treatments, and the potential use of eco-friendly approaches for control of VWO.

Biological control of Verticillium wilt of olive in the field

Verticillium wilt of olive (VWO) caused by Verticillium dahliae is considered one of the most serious diseases in olives. Effective control of this disease requires an integrated management strategy in which implementing biological control is a potential tool. Thus, the aim of this study was to evaluate the effect of 16 natural biological compounds, including biological control agents, organic amendments and one essential oil, under field conditions. The compounds were selected out of 220 treatments previously evaluated against V. dahliae under controlled conditions in both in vitro and in planta experiments. Three experiments were conducted under three different scenarios for the natural infection of V. dahliae in the Andalusian Region (southern Spain): under semi-controlled conditions on potted plants grown with naturally infested soil (Experiment I); new plantation in a field with high inoculum density (ID) of V. dahliae in the soil (Experiment II); replanting a commercial olive orchard affected by Verticillium wilt with 1 or 30 year-old trees (Experiment III). In the Experiment I, the non-pathogenic strain of Fusarium oxysporum (FO12) and a commercial essential oil from Thymus sp. were the most effective treatments, achieving a total reduction of the ID two months after planting. In Experiment II, the grape marc compost (CGR03) was the most effective treatment in reducing the ID of the pathogen in soil up to 100%. In Experiment III, both FO12 and CGR03 treatments reduced significantly the disease incidence in both 1 or 30 year-old olive plants in comparison with the untreated control plants (P = 0.05). This work provides a practical basis for the use of these selected treatments and a useful methodology for the establishment of future field experiments for research on the biological control of VWO.

The Role of Volatile Organic Compounds and Rhizosphere Competence in Mode of Action of the Non-pathogenic Fusarium oxysporum FO12 Toward Verticillium Wilt.

Verticillium wilts caused by Verticillium spp. are among the most challenging plant diseases to control and affect numerous hosts worldwide. Due to the lack of effective, conventional control methods, integrated control strategies provide a promising approach to manage these diseases. The non-pathogenic Fusarium oxysporum strain FO12 was reported in previous studies to be an effective biocontrol agent against Verticillium dahliae, however, its mode of action remains to be elucidated. In this study, complementary in vitro and in vivo experiments were conducted in order to explore the implications of inhibitory substances and rhizosphere competence in antagonistic effects of FO12 against V. dahliae and V. longisporum. Volatile organic compounds and soluble substances produced by FO12, which caused significant inhibition of mycelial growth and microsclerotia viability in the two tested Verticillium species, were identified by means of gas and liquid chromatography-mass spectrometry. We showed that the antagonistic effect of F. oxysporum FO12 is partially due to the production of bioactive compounds such as 3-methyl-1-butanol and 2-methyl-1-butanol, among others. Several metabolic pathways of FO12 were altered upon contact with V. dahliae ELV22 volatiles. The reduced production of alpha, alpha-trehalose, a metabolite used in starch and sucrose metabolism, suggests that the biocontrol agent activates its stress response in the presence of the phytopathogen. Microscopic analysis using sGFP-tagged FO12 on oil seed rape as a model plant suggests that the biocontrol strain is an efficient root colonizer, which could compete with V. dahliae in the same ecological niche. The findings obtained in this study provide new insights into the mode of action of this potential biocontrol agent, which are relevant for controlling Verticillium wilt through an ecologically friendly approach.

A non-pathogenic strain of Fusarium oxysporum as a potential biocontrol agent against Verticillium wilt of olive

The non-pathogenic Fusarium oxysporum FO12 strain isolated from cork (Quercus suber) was one of the most effective treatments against Verticillium dahliae from among more than 200 natural compounds evaluated in previous studies. Based on the results of previous work, the present study aims to determine the potential of FO12 as a biological control agent against Verticillium wilt of olive (VWO). To this end, several in vitro and in vivo experiments were carried out to evaluate the effectiveness of FO12 against V. dahliae. Dual cultures were conducted, showing a significant reduction in the mycelial growth of V. dahliae. However, inhibition zones were not observed in vitro. Four different culture fractions of FO12 were prepared to evaluate their effect on the reduction of viable propagules of V. dahliae in soil and on the disease progression in inoculated plants. Treatments with crude culture broth of FO12 resulted in a total reduction of the inoculum density of V. dahliae in naturally infested soils as well as in the progression of VWO under controlled conditions. Treatments with conidial suspension or chlamydospores were also effective in reducing the inoculum density in the soil and the disease severity in olive plants. This work provides useful information about the efficacy of several FO12-based culture fractions against VWO under controlled conditions, which could be the basis for the development of effective commercial formulations in the coming future.

Tomato Inoculation With a Non-pathogenic Strain of Fusarium oxysporum Enhances Pest Control by Changing the Feeding Preference of an Omnivorous Predator

Mirid predators, a special group of plant-feeding omnivorous predators, have become important biological control agents for pest control in greenhouse cropping systems. Their efficacy and behavior may potentially be affected by microorganisms that induce plant defenses or change plant quality. Here we studied the interaction between a root restricted endophytic non-pathogenic strain of Fusarium oxysporum (Fo162) in tomato plants, the greenhouse whitefly Trialeurodes vaporariorum (Westwood) and the plant-feeding mirid predator Macrolophus pygmaeus (Rambur). In the absence of prey, inoculation of tomato plants with the Fo162 endophyte significantly reduced the reproduction of M. pygmaeus compared to plants without the endophyte. In contrast, the population growth of M. pygmaeus was not affected by the Fo162 endophyte in the presence of whiteflies. Moreover, the combination of the predator and endophyte resulted in lower whitefly densities than the predator alone. Whitefly population development was not different between endophyte-inoculated and untreated plants. Thus, endophyte inoculation of tomato plants seems to shift the feeding preference of this omnivorous predator from plant consumption towards relatively more prey consumption, resulting in enhanced suppression of the herbivore. Moreover, the negative effect of the endophyte on M. pygmaeus reproduction could easily be eliminated by providing decapsulated cysts of Artemia franciscana Kellogg as a supplemental food source. Together, this suggests an overall net positive effect of the Fo162 endophyte on a preventive biological control strategy in tomato using M. pygmaeus. Besides the enhanced whitefly control, endophyte-inoculation of tomato plants both with or without the predator also resulted in a higher yield and a reduced number of fruits with blossom-end rot, a disorder caused by limitations in uptake and transport of calcium to the fruits. This suggests that the Fo162 endophyte is also involved in the acquisition of essential nutrients for the benefit for the plant. Since both the Fo162 endophyte and the predator M. pygmaeus can induce plant defense, further studies need to elucidate the exact mechanisms that occur when both organisms are present. Our findings confirm the importance of studying endophytes and induced plant responses in a multi-trophic context with herbivores and their natural enemies.

Ability of Non-Pathogenic Fusarium oxysporum Strain Fo47 to Suppress Rhizomania Disease of Sugar Beets in Morocco

Rhizomania is one of the most devastating diseases of sugar beet worldwide. The disease poses a serious threat to Moroccan production and it is capable of significantly decreasing quality and yield of sugar beet plantations. The long-term survival of its fungal vector (Polymyxa betae) in soil makes it a very difficult disease to manage. Therefore, this study investigated the potential of a non-pathogenic fungal Fusarium oxysporum strain Fo47 to control Polymyxa betae. This biocontrol agent was applied as soil treatment, seed treatment, or a combination of the both treatments. A bio-test was performed on treated soil. After four weeks of culture, the roots of sugar beet seedlings were retrieved and analyzed by the DAS-ELISA test. Results indicated that F. oxysporium Fo47 reduced the activity and survival of P. betae when compared to a reference biocontrol agent Trichoderma harzianum, which only revealed significant in reducing the viral load of Beet Necrotic Yellow Vein Virus (BNYVV) as seed treatment. The non-pathogenic Fusarium oxysporum Fo47 was more effective as soil treatment and allowed almost the same reduction of BNYVV virus concentration as T. harzianum 908. Therefore, our findings emphasizes that the performance of the biocontrol agent depends on the method of application.

Biosynthesis of Silver Nanoparticles by Pathogenic and Nonpathogenic Strains of Fusarium oxysporum f. sp. lycopersici

N ANOTECHNOLOGY, a highly promising discipline in science and technology, is the emerging and novel trend that will redesign the future of several existing know how which will change every aspect of our lives and leads to the generation of uniqueness in all the streams of technology. Biological synthesis of metal nanoparticles using microbes is gaining momentum due to the ecofriendly nature of the organisms which reduce toxic chemicals. Plant pathogenic fungi produce extracellular degradative enzymes that may be important in pathogenicity. Biosynthesis of silver nanoparticles was investigated using pathogenic Fusarium oxysporum f. sp. lycopersici and nonpathogenic strains of the same fungal species. These silver nanoparticles were characterized by means of UV–vis spectroscopy, transmission electron microscopy (TEM). UV–visible spectrum of the aqueous medium containing silver ion showed a peak at 420 nm corresponding to the Plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) micrograph showed formation of well-dispersed spherical silver nanoparticles with mean sizes 11.20 nm and 15.38 nm for pathogenic and nonpathogenic strains, respectively.

Anti-nemic secondary metabolites produced by Fusarium oxysporum f. sp. ciceris

Several nonpathogenic strains of Fusarium oxysporum have been selected as potential biological control agents. Culture filtrate of F. oxysporum f. sp. ciceris was extracted sequentially with ethyl acetate (EtOAc) and n-butanol (n-BuOH). Chromatographic separation of EtOAc concentrate has afforded five compounds, bikaverin (1), 3-O-methyl-8-O-methyl fusarubin (2), 8-O-methyl fusarubin (3), anhydrofusarubin (4) and fusarubin (5). Structures of these compounds were elucidated by detailed NMR and LC/ESI-MS spectra. Anti-nemic activity of the extracts and secondary metabolites were evaluated against root-knot nematode, Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis. EtOAc concentrate was found to be strongly active against M. incognita (LC50 56.2μgmL−1) followed by n-BuOH concentrate (LC50 97.4μgmL−1). However, these concentrates were moderately effective on R. reniformis (LC50 134.5–189.2μgmL−1). Fusarubin (LC50 248.9μgmL−1) was found to be highly active followed by anhydrofusarubin (LC50 257.6μgmL−1) against M. incognita. Structure anti-nemic activity relationship indicated comparatively more polar molecule with naphthoquinone nucleus as most active. Fusarubin analogues could be exploited further to develop standard nematicidal liquid formulation.

Identification of a Novel Small Cysteine-Rich Protein in the Fraction from the Biocontrol Fusarium oxysporum Strain CS-20 that Mitigates Fusarium Wilt Symptoms and Triggers Defense Responses in Tomato.

The biocontrol effect of the non-pathogenic Fusarium oxysporum strain CS-20 against the tomato wilt pathogen F. oxysporum f. sp. lycopersici (FOL) has been previously reported to be primarily plant-mediated. This study shows that CS-20 produces proteins, which elicit defense responses in tomato plants. Three protein-containing fractions were isolated from CS-20 biomass using size exclusion chromatography. Exposure of seedling roots to one of these fractions prior to inoculation with pathogenic FOL strains significantly reduced wilt severity. This fraction initiated an ion exchange response in cultured tomato cells resulting in a reversible alteration of extracellular pH; increased tomato chitinase activity, and induced systemic resistance by enhancing PR-1 expression in tomato leaves. Two other protein fractions were inactive in seedling protection. The main polypeptide (designated CS20EP), which was specifically present in the defense-inducing fraction and was not detected in inactive protein fractions, was identified. The nucleotide sequence encoding this protein was determined, and its complete amino acid sequence was deduced from direct Edman degradation (25 N-terminal amino acid residues) and DNA sequencing. The CS20EP was found to be a small basic cysteine-rich protein with a pI of 9.87 and 23.43% of hydrophobic amino acid residues. BLAST search in the NCBI database showed that the protein is new; however, it displays 48% sequence similarity with a hypothetical protein FGSG_10784 from F. graminearum strain PH-1. The contribution of CS20EP to elicitation of tomato defense responses resulting in wilt mitigating is discussed.

Production of anti-fungal volatiles by non-pathogenic Fusarium oxysporum and its efficacy in suppression of Verticillium wilt of cotton

Aims The study aimed at identifying volatile organic compounds (VOCs) produced by the non-pathogenic Fusarium oxysporum (Fo) strain CanR-46, and to determine the anti-fungal spectrum and the control efficacy of the Fo-VOCs.

A nonpathogenic Fusarium oxysporum strain enhances phytoextraction of heavy metals by the hyperaccumulator Sedum alfredii Hance

Low biomass and shallow root systems limit the application of heavy metal phytoextraction by hyperaccumulators. Plant growth-promoting microbes may enhance hyperaccumulators’phytoextraction. A heavy metal-resistant fungus belonged to the Fusarium oxysporum complex was isolated from the Zn/Cd co-hyperaccumulator Sedum alfredii Hance grown in a Pb/Zn mined area. This Fusarium fungus was not pathogenic to plants but promoted host growth. Hydroponic experiments showed that 500μM Zn2+ or 50μM Cd2+ combined with the fungus increased root length, branches, and surface areas, enhanced nutrient uptake and chlorophyll synthesis, leading to more vigorous hyperaccumulators with greater root systems. Soil experiments showed that the fungus increased root and shoot biomass and S. alfredii-mediated heavy metal availabilities, uptake, translocation or concentrations, and thus increased phytoextraction of Zn (144% and 44%), Cd (139% and 55%), Pb (84% and 85%) and Cu (63% and 77%) from the original Pb/Zn mined soil and a multi-metal contaminated paddy soil. Together, the nonpathogenic Fusarium fungus was able to increase S. alfredii root systems and function, metal availability and accumulation, plant biomass, and thus phytoextraction efficiency. This study showed a great application potential for culturable indigenous fungi other than symbiotic mycorrhizas to enhance the phytoextraction by hyperaccumulators.

Seedling vaccination by stem injecting a conidial suspension of F2, a non-pathogenic Fusarium oxysporum strain, suppresses Verticillium wilt of eggplant

Several bacterial and fungal strains have been evaluated as biocontrol agents (BCAs) against Verticillium dahliae. In these studies, the BCAs were applied as a root drenching inoculum; however, this application method may have an adverse effect on the native, beneficial for the plants, microbial community. In the present study, it was evaluated whether endophytic application by stem injecting a conidial suspension of the non pathogenic Fusarium oxysporum F2 strain, isolated from a V. dahliae suppressive compost amendment, could reduce significantly Verticillium wilt symptom development in eggplants. It was revealed that stem injection of F2 seven days before transplanting the seedlings to soil infested by V. dahliae microsclerotia resulted in reduced disease severity compared to the control treatment. To visualise F2 ramification into the plant vascular system eggplant stems were injected with an EGFP transformed F2 strain. It was shown that F2 colonises effectively the plant vascular tissues over a long period of time as it was assessed by F2 DNA levels. In parallel, qPCR analysis showed that the application of F2 reduced significantly the amount of V. dahliae DNA in the stem tissues compared to the control treatment.

Induced Resistance in Tomato Plants Against Fusarium Wilt Invoked by Nonpathogenic Fusarium, Chitosan and Bion

The potential of. nonpathogenic Fusarium oxysporum strain Avr5, either alone or in combination with chitosan and Bion, for inducing defense reaction in tomato plants inoculated with F. oxysporum f. sp lycopersici, was studied in vitro and glasshouse conditions. Application Bion at concentration of 5, 50, 100 and <TEX>$500{\mu}g$</TEX>/ml, and the highest concentration of chitosan reduced in vitro growth of the pathogen. Nonpathogenic F. oxysporum Avr5 reduced the disease severity of Fusarium wilt of tomato in split plants, significantly. Bion and chitosan applied on tomato seedlings at concentration <TEX>$100{\mu}g$</TEX> a.i./plant; 15, 10 and 5 days before inoculation of pathogen. All treatments significantly reduced disease severity of Fusarium wilt of tomato relative to the infected control. The biggest disease reduction and increasing tomato growth belong to combination of nonpathogenic Fusarium and Bion. Growth rate of shoot and root markedly inhibited in tomato plants in response to tomato Fusarium wilt as compared with healthy control. These results suggest that reduction in disease incidence and promotion in growth parameters in tomato plants inoculated with nonpathogenic Fusarium and sprayed with elicitors could be related to the synergistic and cooperative effect between them, which lead to the induction and regulation of disease resistance. Combination of elicitors and non-pathogenic Fusarium synergistically inhibit the growth of pathogen and provide the first experimental support to the hypothesis that such synergy can contribute to enhanced fungal resistance in tomato. This chemical could provide a new approach for suppression of tomato Fusarium wilt, but its practical use needs further investigation.

Ecological fitness of the biocontrol agent Fusarium oxysporum Fo47 in soil and its impact on the soil microbial communities

Some nonpathogenic strains of Fusarium oxysporum can control Fusarium diseases responsible for severe damages in many crops. Success of biological control provided by protective strains requires their establishment in the soil. The strain Fo47 has proved its efficacy under experimental conditions, but its ecological fitness has not been carefully studied. In a series of microcosm studies, the ability of a benomyl-resistant mutant Fo47b10 to establish in two different soils was demonstrated. One year after its introduction at two concentrations in the disinfected soils, the biocontrol agent (BCA) established at similar high population densities, whereas in the nondisinfected soils it survived at lower densities, related to the initial concentrations at which it was introduced. The BCA behaved similarly in the two soils at temperatures ranging from 5 to 25 degrees C and soil water potentials between -0.01 and -1.5 MPa. In addition, terminal restriction fragment length polymorphism analysis of 16S and 18S rRNA showed that the structures of the bacterial and fungal communities evolved with time but were not significantly affected by the introduction of the BCA. Overall, the results showed that Fo47 is potentially a good BCA, able to establish in different soil environments without perturbing the investigated microbial structures.

Mode of action of a non-pathogenic Fusarium oxysporum strain against Verticillium dahliae using Real Time QPCR analysis and biomarker transformation

Verticillium wilt is a devastating disease of a wide range of herbaceous and woody plant hosts. It is incited by the soilborne fungus Verticillium dahliae. Management strategies are mainly focused on preventive measures. In a previous study, the efficacy of a non-pathogenic Fusarium oxysporum strain, designated as F2, isolated from a suppressive compost amendment, has been reported to reduce Verticillium wilt symptom development in eggplants under greenhouse and field conditions; in addition, antibiosis or parasitism were ruled out by using a dual culture test. In the present study, we investigated the mode of action of F2 against V. dahliae. For this purpose, the F2 and V. dahliae strains were transformed with the EGFP and DsRed2 reporter genes respectively, so as to visualize their presence on the root surface of eggplants. In addition, the ramification of both fungi into the plant vascular system was monitored by Real Time QPCR analysis. It was shown that F2 colonizes the root surface along the intercellular junctions excluding V. dahliae from the same ecological niche. In parallel, QPCR analysis showed that application of F2 reduces the levels of V. dahliae vascular colonization along with the disease severity. In a split root experiment it was demonstrated that F2 does not trigger the defense mechanisms of eggplants against V. dahliae. Therefore, it seems that competition for space or nutrients on the root surface are the main mechanism of action of F2 against V. dahliae.

Comparative analysis of PR gene expression in tomato inoculated with virulent Fusarium oxysporum f. sp. lycopersici and the biocontrol strain F. oxysporum Fo47

Non-pathogenic strains of Fusarium oxysporum have the capacity to protect plants against wilt induced by pathogenic strains of F. oxysporum. Among the mechanisms involved in this protection, induced systemic resistance has been demonstrated by using a split-root method. The aim of this study was to follow the accumulation kinetics of transcripts encoding 5 PR proteins in roots and leaves of tomato inoculated with a pathogenic or a protective strain in comparison to non-inoculated control. Moreover quantification of transcripts was assessed by real-time RT-PCR in cell cultures inoculated with the pathogenic or the protective strain. Results showed a lower expression of PR encoding genes in the plants or cells inoculated with the protective strain. These results showing that there is no increased accumulation of PR proteins after inoculation of the protective strain, suggest that accumulation could follow inoculation of the pathogen. Priming the plant defense reaction could be the mode of action of Fo47.

Mutualistic endophytic fungi and in-planta suppressiveness to plant parasitic nematodes

This paper reviews the development of the concept of biological enhancement of plants with mutualistic fungal endophytes for the management of plant parasitic nematodes. The vast majority of the research conducted to date on biological enhancement of plants with fungal endophytes involves the use of nonpathogenic strains of Fusarium oxysporum and, to a lesser extent, species of Trichoderma, for biological control of nematodes. The main crops thus far studied for biological enhancement with endophytes have been banana, tomato and rice. Because the concept of using nonpathogenic fungi that colonize the endorhiza for biological control is still relatively new, information on this subject in the form of published literature is scare, in the form of Ph.D. theses or in unpublished form. Taking this limitation into account, it is nevertheless hoped that this review will be useful to those working or planning to work with mutualistic fungal endophytes for biological enhancement of plants for nematode management.