Formae Speciales Of Fusarium Oxysporum Research Articles

Secreted in Xylem (SIX) Gene SIX9 Is Highly Conserved in Fusarium oxysporum f. sp. vasinfectum Race 4 Isolates from Cotton in the United States

Many Fusarium oxysporum formae speciales produce small, infection-dependent effector proteins called “secreted in xylem” (SIX) proteins. These proteins are secreted into the xylem of a plant during the infection process and are thought to promote virulence. In this study, a collection of Fusarium oxysporum isolates composed primarily of different races of Fusarium oxysporum f. sp. vasinfectum (FOV) was screened for the presence of 14 SIX effector genes ( SIX1 to SIX14). Our results showed that some of the most virulent FOV races, FOV4 and FOV7, share a common SIX effector: SIX9. This effector is largely absent in other FOV races in North America, making SIX9 a potential target for rapid detection of these highly virulent FOV strains and enabling race-specific FOV quantification in infected host plants. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The elusive bio-stimulatory function of Cladophialophora chaetospira SK51 to alleviate Fusarium wilt of strawberry

The highly virulent Fusarium oxysporum formae speciales (f.sp.) fragaria causes Fusarium wilt and significant losses in the strawberry agroindustry. The effective control strategies for this phytopathogen have yet to be developed. We aimed to evaluate the bioefficacy of root-colonizer dark septate endophytic fungi (DSEs) in controlling Fusarium wilt in simultaneous with biostimulation activities. Three out of nineteen tested isolates were selected because of their superior bioefficacy in regulating disease suppression and growth promotion. Notably, the highest level of disease suppression was marked at 90.48%, followed by 85.71% and 61.90% with the inoculation of these three selected isolates i.e., SK51, SK47, and SK48, respectively. The fungal isolates were identified based on partial SSU, LSU, and ITS as DSE fungus Cladophialophora chaetospira strain SK51, Exophiala sp. strain SK47, and E. pisciphila strain SK48. Our findings showed that C. chaetospira SK51 exhibited significant potential in promoting plant growth and suppressing diseases. It significantly enhanced various plant growth factors, such as the total plant biomass, the content of chlorophyll (SPAD), the formation of flower buds, and the development of fruits compared to both non-inoculated control and the other two DSE-inoculated plants. Our study provides new findings and perspectives on the use of the DSE, particularly C. chaetospira SK51 as a bioprotectant and biostimulant for enhancing the development, flower bud formation, and fruit development in strawberry plants.

An Interactive, Online Web Map Resource of Global Fusarium oxysporum ff. spp. Diversity and Distribution.

An Interactive, Online Web Map Resource of Global Fusarium oxysporum ff. spp. Diversity and Distribution.

Detection and Quantification of Fusarium oxysporum f. sp. niveum Race 1 in Plants and Soil by Real-time PCR.

Fusarium wilt caused by Fusarium oxysporum f. sp. niveum (Fon) is the most serious soil-borne disease in the world and has become the main limiting factor of watermelon production. Reliable and quick detection and quantification of Fon are essential in the early stages of infection for control of watermelon Fusarium wilt. Traditional detection and identification tests are laborious and cannot efficiently quantify Fon isolates. In this work, a real-time polymerase chain reaction (PCR) assay has been described to accurately identify and quantify Fon in watermelon plants and soil. The FONRT-18 specific primer set which was designed based on identified specific sequence amplified a specific 172 bp band from Fon and no amplification from the other formae speciales of Fusarium oxysporum tested. The detection limits with primers were 1.26 pg/μl genomic DNA of Fon, 0.2 pg/ng total plant DNA in inoculated plant, and 50 conidia/g soil. The PCR assay could also evaluate the relationships between the disease index and Fon DNA quantity in watermelon plants and soil. The assay was further used to estimate the Fon content in soil after disinfection with CaCN2. The real-time PCR method is rapid, accurate and reliable for monitoring and quantification analysis of Fon in watermelon plants and soil. It can be applied to the study of disease diagnosis, plant-pathogen interactions, and effective management.

The Use of Natural Products Against Fusarium oxysporum: A Review

: Currently, numerous researchers have focused their attention on the use of natural products from plants and microorganisms, or compounds derived from these organisms to protect crops from various diseases, thus reduce the negative effects on human health and environmental safety. Fungal diseases cause a considerable loss of crop yields in agricultural industries worldwide. Fusarium oxysporum comprises a multitude of formae speciales that cause vascular wilt diseases of economically important crops. This review presents an overview of researches realized on natural products tested against Fusarium oxysporum formae speciales phytopathogens for the period (2017-2020). This review aims to collect major research works of the antifungal compounds against these fungi and up-dates information on their developments and approaches that have been rapidly taking place in recent years so that further novel researches can be envisaged. Discussion of these studies by analyzing different sources for antifusariosis treatment, evaluation of testing methods, and information on their advantages and limitations and to determine those with real efficacy. Despite the important number of natural products with remarkable in vitro efficiency, the limiting point is their in vivo application for soil microorganisms (in this case: Fusarium oxysporum). Therefore, more advanced researches are needed to solve this problem.

English

Secreted fungal effector proteins and their host targets are good examples to understand the mechanism of host-pathogen co-evolution with genes involved in the interaction undergoing positive selection. SIX genes (secreted in xylem) are obtained via horizontal transfer and can be found within the formae speciales of Fusarium oxysporum. SIX6 and SIX9 of F. oxysporum f. spp. cubense (Foc) are predicted to play a role as effectors. However, their involvement in the pathogenicity of Foc in banana plants has not been determined yet. In the susceptible banana cultivar, we found that the SIX6 and SIX9 genes of Foc TR4 were highly expressed in roots, but not in corms or leaves. The host, however, expressed the pathogenesis-related (PR) genes, PR-1 and PR-3, in corms earlier than in the roots. Phylogenetic analysis on SIX6 and SIX9 genes of F. oxysporum has revealed the separation of SIX6 and SIX9 of Foc from other formae speciales. This leads to detecting genes under positive selection using the ratio nonsynonymous to synonymous substitution rates (Ka/Ks). SIX6 of Foc showed an increase in diversity, but insufficient to drive positive selection. Conversely, SIX9 of Foc showed no divergence in the dN/dS ratio distribution, indicating purifying selection. © 2021 Friends Science Publishers

Underlying Mechanism of Wild Radix pseudostellariae in Tolerance to Disease Under the Natural Forest Cover.

Replanting disease caused by negative plant-soil feedback in continuous monoculture of Radix pseudostellariae is a critical factor restricting the development of this common and popular Chinese medicine, although wild R. pseudostellariae plants were shown to grow well without occurrence of disease in the same site for multiple years. Therefore, we aimed to identify the changes in microbial community composition in the rhizosphere soil of wild R. pseudostellariae thus providing a potential method for controlling soil-borne diseases. We analyzed differences in soil physicochemical properties, changes in soil microbial community structure, and root exudates of wild R. pseudostellariae under different biotopes. And then, simple sequence repeats amplification was used to isolate and collect significantly different formae speciales of Fusarium oxysporum. Finally, we analyzed the pathogenicity testing and influence of root exudates on the growth of F. oxysporum. We found that the different biotopes of R. pseudostellariae had significant effects on the soil microbial diversity. The soil fungal and bacterial abundances were significantly higher and the abundance of F. oxysporum was significantly lower under the rhizosphere environment of wild R. pseudostellariae than under consecutive monoculture. The relative abundances of most genera were Penicillium, Aspergillus, Fusarium, Nitrobacter, Nitrospira, Streptomyces, Actinoplanes, and Pseudomonas. Venn diagram and LEfSe analyses indicated numerously specific microbiome across all the samples, and the numbers of specific fungi were higher than the shared ones in the four biotopes. Eight types of phenolic acids were identified across all the rhizosphere soils. Mixed phenolic acids and most of the examined single phenolic acids had negative effects on the growth of isolated pathogenic F. oxysporum strains and promoted the growth of non-pathogenic strains. Similarly, correlation analysis suggested that most of the identified phenolic acids were positively associated with beneficial Pseudomonas, Nitrobacter, Nitrospira, Streptomyces, and Bacillus. This study suggested that wild R. pseudostellariae was able to resist or tolerate disease by increasing soil microbial diversity, and reducing the accumulation of soil-borne pathogens.

The Effectiveness of a Dark Septate Endophytic Fungus, Cladophialophora chaetospira SK51, to Mitigate Strawberry Fusarium Wilt Disease and With Growth Promotion Activities.

Strawberry Fusarium wilt, caused by the virulent fungus Fusarium oxysporum formae speciales fragariae (Fof) is a devastating soil-borne disease that causes severe production losses worldwide, including Japan. Fof is one of the top 10 fungal pathogens that threaten global crop security, and a method to effectively control this pathogen has yet to be found. This study aimed to investigate the effectiveness of dark septate endophytic (DSE) fungi against Fof to develop an efficient, effective, and environmentally friendly approach to improve plant health and fitness. A total of 19 fungal isolates were assessed, out of which three (SK47, SK48, and SK51) were selected based on their effectiveness in disease suppression in controlled growth chamber conditions using a soil system. Isolates SK47, SK48, and SK51 suppressed disease severity by 85.71, 61.90, and 90.48%, respectively. Molecular identification based on highly conserved small subunit (SSU), internal transcribed spacer (ITS), and large subunit (LSU) nrRNA regions identified these isolates as DSE Exophiala sp., Exophiala pisciphila, and Cladophialophora chaetospira, respectively. The sequences were deposited under accession numbers MN811693–MN811695 in the GenBank database. Notably, our results revealed that isolate C. chaetospira SK51 possessed superior growth promotion activities as well as disease suppression by significantly increased plant growth parameters (shoot and root dry mass, chlorophyll content, flower bud initiation, and number of fruit) in comparison to control plants and other two fungal candidates. Root colonization by C. chaetospira SK51 was visualized, and it was confirmed that the symbiosis with strawberry plants occurred successfully. Our results provide new insights in the application of DSE fungus C. chaetospira SK51 as a biocontrol agent on strawberry plants could promote plant growth, flower bud initiation, and fruit formation. C. chaetospira SK51 exhibited remarkable beneficial traits for the host plant, and it can potentially be applied in the development of new, safe, and effective treatments as an alternative to chemical fertilizers and fungicides for sustainable crop protection.

MOLECULAR CHARACETIZATION OF TOMATO YELLOW LEAF CURL VIRUS AND FUSARIUM OXYSPORUM FORMAE SPECIALES AND RACES OF TOMATO AREAS IN NORTHERN CYPRUS

Fusarium oxysporum (FO) and viruses have caused wilt, root, crown rots, mosaic, yellowing and curling on tomato plants and have resulted economic yield losses on tomato production areas at Northern Cyprus (NC) in 2011–2015 years. Typical FO symptoms showing greenhouse and open field areas used for collecting 62 plants and suspected Tomato yellow leaf curl virus (TYLCV) of 76 tomato plants have been studied respectively. In the researches, four different primers (uni, sp 13, sp 23, sprl) were used to determine the formae speciales and races of 62 isolates of FO isolates from different locations. PCR analyse studies have revealed that 81% of collected samples were Fusarium oxysporum f.sp. lycopersici (FOL) and 19% of them were Fusarium oxysporum f.sp. radicis-lycopersici (FORL). Additionally, further PCR analyses have identified that 37% of FOL samples were race 1, 15% were race 2 and 29% were race 3 identified respectively. The different samples of 76 tomato plants were tested with specific primers in PCR amplifications. Their results determined that the strains TYLCV-Israel, TYLCV-Sicilia, TYLCV-Mild of TYLCV found. The molecular techniques have suggested that Israel, Sicilia and Mild strain of TYLCV were present in the tomato production areas at NC. The TYLCV races with single or mixed infections and Fusarium oxysporum formae speciales and races are able to identify in molecular techniques in not only accurately but also reliably.

Genome-wide annotation, comparison and functional genomics of carbohydrate-active enzymes in legumes infecting Fusarium oxysporum formae speciales

ABSTRACTFusarium wilt caused by soil borne ascomycetes fungi Fusarium oxysporum which has host-specific forms known as formae speciales (ff. spp.), apparently requires plant cell wall degrading enzymes (PCWDE) for successful invasion. In this study, 12 F. oxysporum ff. spp. were taken for genome-wide annotation and comparative analysis of CAZymes, with an assessment of secretory PCWDE and orthologues identification in the three legumes infecting ff. spp. Further, transcriptomic analysis in two legumes infecting ff. spp. using publically available data was also done. The comparative studies showed Glycoside hydrolase (GH) families to be abundant and Principle Component Analysis (PCA) formed two distinct clusters of ff. spp. based on the CAZymes modules and families. Nearly half of the CAZymes in the legumes infecting ff. spp. coded for signal peptides. The orthologue clusters of secretory CAZymes common in all the three legume infecting ff. spp. mostly belonged to families of AA9, GH28, CE5 and PL1 and the expression analysis revealed the abundant PCWDE were differentially expressed in these legumes infecting ff. spp. Therefore, this study gave an insight into the distribution of CAZymes especially extracellular PCWDE in legumes infecting ff. spp. with further shedding light onto some of the key PCWDE families through differential expression analysis.

Molecular characterization by PCR-ITS technique of Fusarium oxysporum isolated from tomato in Baghdad city

The present study aimed to estimate the pathogenesis of Fusarium oxysporum isolates and identify them by molecular technique Polymerase Chain Reaction-Internal Transcript Spacer (PCR-ITS). A total of thirty Fusarium oxysporum isolates were isolated from infected tomato plants and diagnosed depending on 'morphological characteristics. The pathogenicity test was performed for thirty Fusarium oxysporum isolates. So it was procedure
 steps that Genomic DNA was extracted from seven F. oxysporum isolates according to pathogenicity test by using'' ZR Fungal/Bacterial DNA'' MiniPrep™ kit. Seven F. oxysporum isolates showed high pathogenicity. The concentration and purity of the DNA extracted from the seven F. oxysporum isolates was (150 – 201) ng/µl and (1.4 -1.9) respectively. ITS gene was amplified by using PCR-ITS The sequencing results of amplified product of ITS gene from Fusarium oxysporum isolates indicated that all the seventh sequenced isolates where from one Formae speciales of Fusarium oxysporum as Fusarium oxysporum f. sp. Lycopersici. These results have been devoted to study genetic variability among the species involved in study. Molecular markers are highly important'' to focus on F. oxysporum isolates below'' the species level therefore, the DNA array containing "genus, species'' and forma specialis specific" detector'' for the detection and identification ''of F. oxysporum. Also, Cluster analysis and phylogenetic tree depending on genetic distance revealed the genetic relationship between the thirteen F. oxysporum isolates and confirmed sequencing analysis.

Characterization and sequence analysis of potential biofertilizer and biocontrol agent Bacillus subtilis strain SEM-9 from silkworm excrement.

Fusarium wilt is a devastating soil-borne disease caused mainly by highly host-specific formae speciales of Fusarium oxysporum. Antagonistic microorganisms play a very important role in Fusarium wilt control, and the isolation of potential biocontrol strains is becoming more and more important. We isolated a bacterial strain (SEM-9) from the high-temperature stage of silkworm excrement composting, which had a marked ability to solubilize phosphorus, promote the growth and increase the yield of the small Chinese cabbage, and which also exhibited considerable antagonistic effect towards Fusarium sambucinum and other fungi. The result of physiological and biochemical analyses, as well as genome sequencing, showed that SEM-9 was a strain of Bacillus subtilis. Through genome annotation and analysis, it was found that SEM-9 contained genes related to the regulation of biofilm formation, which may play an important role in colonization, and gene clusters encoding the biosynthesis of antimicrobials, such as surfactin, bacilysin, fengycin, and subtilosin-A. The production of such antifungal compounds may constitute the basis of the mode-of-action of SEM-9 against Fusarium spp. These data suggested that the SEM-9 strain has potential as both a biofertilizer and a biocontrol agent, with the potential to manage Fusarium wilt disease in crops.

Fusarium oxysporum f. sp. lavandulae, a novel forma specialis causing wilt on Lavandula × allardii

Symptoms of a vascular wilt were observed on many plants of Lavandula × allardii (hybrid of Lavandula dentata and L. latifolia) cultivated in a nursery near Albenga, Liguria region, Northern Italy. After identification based on morphological characteristic and ITS sequence analysis, the pathogen was identified as Fusarium oxysporum. Eight single-spore isolates obtained from infected tissues were used for a phylogenetic analysis in order to identify the forma specialis. Translation elongation factor 1-α (EF-1α), intergenic spacer (IGS) and three genes encoding for polygalacturonase genes (pg1, pg5 and pgx1) were amplified by PCR. Gene sequences were aligned with other formae speciales of Fusarium oxysporum obtained from GenBank databases in order to build phylogenetic trees. Results obtained for each genomic region showed a unique group with isolates derived from L. × allardii well separated from the other formae speciales. Results obtained, together with pathogenicity tests, allowed us to introduce a new forma specialis named F. oxysporum f. sp. lavandulae.

Efficiency of Saccharothrix algeriensis NRRL B-24137 and Its Produced Antifungal Dithiolopyrrolones Compounds to Suppress Fusarium oxysporum-Induced Wilt Disease Occurring in Some Cultivated Crops

Saccharothrix algeriensis NRRL B-24137 (SA) is a well-studied actinobacterium strain for its ability to produce numerous bioactive dithiolopyrrolone derivatives with appreciable antifungal properties. Our study aimed to investigate the possible usefulness of SA and its produced compounds to control several formae speciales of Fusarium oxysporum, which affect different important crops. Such is the case of F. oxysporum f. sp. lini (FOLi), F. oxysporum f. sp. lentis (FOLe), F. oxysporum f. sp. ciceris (FOC) and F. oxysporum f. sp. lycopersici (FOLy) which cause devastating wilt to flax, lentil, chickpea and tomato, respectively. Antagonistic properties of the strain SA have been primarily evaluated in vitro. This screening showed the significant antifusarium activity of the actinobacteria strain against FOLi, FOC, FOLe and FOLy. Consecutively, strain SA and FOLi soil development has been assessed. The SA soil treatment permitted an important decrease (threefold) in the FOLi infestation. Moreover, the actinobacteria soil density seemed maintained after 7-week treatment at an appreciable level of 44×106 CFU/gram of dry soil (gds). Through different pot experiments, soil pre-treatment with the SA strain significantly reduced the disease incidence of FOLi, FOLe, FOC and FOLy by 71.0, 73.3, 61.2 and 59.7%, respectively. However, the treatment with pure dithiolopyrrolones appeared less effective with about 50% of FOLi disease impact reduction, which thus suggested the involvement of more than direct antibiosis in the whole SA biocontrol performance. Globally, significant correlation between the in vitro antagonistic properties of SA and its capacity to reduce the disease occurrence (r=0.81, P≤0.05) has been highlighted.

Comparative genomics and prediction of conditionally dispensable sequences in legume-infecting Fusarium oxysporum formae speciales facilitates identification of candidate effectors.

BackgroundSoil-borne fungi of the Fusarium oxysporum species complex cause devastating wilt disease on many crops including legumes that supply human dietary protein needs across many parts of the globe. We present and compare draft genome assemblies for three legume-infecting formae speciales (ff. spp.): F. oxysporum f. sp. ciceris (Foc-38-1) and f. sp. pisi (Fop-37622), significant pathogens of chickpea and pea respectively, the world’s second and third most important grain legumes, and lastly f. sp. medicaginis (Fom-5190a) for which we developed a model legume pathosystem utilising Medicago truncatula.ResultsFocusing on the identification of pathogenicity gene content, we leveraged the reference genomes of Fusarium pathogens F. oxysporum f. sp. lycopersici (tomato-infecting) and F. solani (pea-infecting) and their well-characterised core and dispensable chromosomes to predict genomic organisation in the newly sequenced legume-infecting isolates. Dispensable chromosomes are not essential for growth and in Fusarium species are known to be enriched in host-specificity and pathogenicity-associated genes. Comparative genomics of the publicly available Fusarium species revealed differential patterns of sequence conservation across F. oxysporum formae speciales, with legume-pathogenic formae speciales not exhibiting greater sequence conservation between them relative to non-legume-infecting formae speciales, possibly indicating the lack of a common ancestral source for legume pathogenicity. Combining predicted dispensable gene content with in planta expression in the model legume-infecting isolate, we identified small conserved regions and candidate effectors, four of which shared greatest similarity to proteins from another legume-infecting ff. spp.ConclusionsWe demonstrate that distinction of core and potential dispensable genomic regions of novel F. oxysporum genomes is an effective tool to facilitate effector discovery and the identification of gene content possibly linked to host specificity. While the legume-infecting isolates didn’t share large genomic regions of pathogenicity-related content, smaller regions and candidate effector proteins were highly conserved, suggesting that they may play specific roles in inducing disease on legume hosts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2486-8) contains supplementary material, which is available to authorized users.

Efficacy of dimethyl disulfide (DMDS) against Meloidogyne sp. and three formae speciales of Fusarium oxysporum under controlled conditions

The efficacy of a soil disinfectant, dimethyl disulfide (DMDS), was assessed on known populations of different formae speciales of Fusarium oxysporum: F. oxysporum f. sp. radicis-lycopersici; F. o. f. sp. radicis-cucumerinum and F. o. f. sp. lycopersici and Meloidogyne nematodes. Two trials were carried out over two years (2012–2013), in a greenhouse under semi-controlled environmental conditions and in a growth chamber, in 3-L volume pots filled with sterile vermiculite. Two doses of DMDS (400 L ha−1 and 600 L ha−1) and two plastic covers: VIF (virtually impermeable film) and PE (transparent polyethylene) were tested. The results showed a full nematicidal effect for the two doses, without differences between the two types of plastic. The inoculum density of F. oxysporum was significantly decreased by DMDS, but expression of the disease was not prevented. The assessment of the phytotoxic effect on seed germination of lettuce showed that residual vapors of DMDS have a negative effect on seed germination in vermiculite.

Fusarium oxysporum f. sp. papaveris: a new forma specialis isolated from iceland poppy (Papaver nudicaule)

Symptoms of a new vascular wilt were observed on several plants of Papaver nudicaule cultivated at the Regional Institute for Floriculture in Sanremo and in a nursery near Ventimiglia, Liguria region, Northern Italy. Morphology and ITS sequence analysis characterize the pathogen as Fusarium oxysporum . To identify the forma specialis , eight isolates obtained from infected tissues were used for a phylogenetic analysis based on translation elongation factor 1-α ( EF-1α ) gene and four polygalacturonase genes ( Pg1 , Pg5 , Pgx1 and Pgx4 ). After amplification by PCR, the gene sequences were aligned with corresponding sequences from other formae speciales of Fusarium oxysporum obtained from GenBank databases in order to build phylogenetic trees. Results obtained for each genomic region showed that the isolates derived from P. nudicaule form a unique group well separated from other formae speciales . To our knowledge, this is the first report of F. oxysporum on P. nudicaule and together with the phylogenetic analysis and positive pathogenicity tests permits us to introduce a new forma specialis named F. oxysporum f. sp. papaveris.

Resistance reaction of Medicago truncatula genotypes to Fusarium oxysporum: effect of plant age, substrate and inoculation method

Fusarium wilt, caused by several formae speciales of Fusarium oxysporum, is an important disease of most crop and pasture legumes, including field pea (Pisum sativum), chickpea (Cicer arietinum), lucerne (alfalfa, Medicago sativa) and barrel medic (M. truncatula). Medicago truncatula is an important pasture legume and a model legume species. Hence, it can be used to increase our knowledge of resistance mechanisms efficient to block F. oxysporum infection if its response to the disease is characterised. We evaluated the physiological and susceptibility responses to the disease of two contrasting M. truncatula genotypes, and the effect of several cultural conditions known to affect the disease incidence, such as plant age at infection time, growth substrate and the method of inoculation. Our results indicated that the A17 accession harbours a moderate level of resistance to the disease. We also showed that the method of inoculation strongly affected development of fusarium wilt disease in this model species, whereas it was not significantly altered by plant age or the inorganic growth substrate tested. In addition, we describe a rapid change in leaf temperature after infection, which can be used as an indirect parameter to confirm fungal infection at a very early stage of the interaction.

Contamination of seeds of Iceland poppy (Papaver nudicaule L.) by Fusarium oxysporum

In 2011, a new Fusarium wilt of Papaver nudicaule was observed in a commercial nursery near Ventimiglia (Imperia province, northern Italy) as well as in the Regional Institute of Floriculture (I.R.F.) of Sanremo (Imperia province, northern Italy). Molecular analysis enabled identification of the causal agent as a new forma specialis called Fusarium oxysporum f. sp. papaveris. The origin of the infection was found on P. nudicaule seeds. However, disinfection with sodium hypochlorite was able to eliminate the pathogen infection. Virulence of ten isolates obtained from seeds was evaluated by pathogenicity assay. The more virulent strains were analyzed by phylogenetic analysis on the basis of the EF-1α, pg1 and pgx4 genes. Sequences obtained by PCR amplification were aligned with other formae speciales of Fusarium oxysporum from the GenBank and used in the construction of the phylogenetic trees. Seed infections have been observed in the case of many vegetable crops; however, this phenomenon has been less studied in the case of ornamental crops. As a consequence of seed exchanges or transmission via infected seeds, new and old pathogenic species of Fusarium are continuously introduced into new areas and production systems.

Production and Characterization of Iturinic Lipopeptides as Antifungal Agents and Biosurfactants Produced by a Marine Pinctada martensii-Derived Bacillus mojavensis B0621A

Bacillus mojavensis B0621A was isolated from a pearl oyster Pinctada martensii collected from South China Sea. While screening for cyclic lipopeptides potentially useful as lead compounds for biological control against soil-bone fungal plant pathogens, three lipopeptides were isolated and purified from the fermentation broth of B. mojavensis B0621A via vacuum flash chromatography coupled with reversed-phase high performance liquid chromatography (RP-HPLC). The structural characterization and identification of these cyclic lipopeptides were performed by tandem mass spectrometry (MS/MS) combined with gas chromatography-mass spectrometry (GC-MS) analysis as well as chemical degradation. These lipopeptides were finally characterized as homologues of mojavensins, which contained identical amino acids back bones of asparagine1, tyrosine2, asparagine3, glutamine4, proline5, asparagine6, and asparagine7 and differed from each other by their saturated β-amino fatty acid chain residues, namely, iso-C14 mojavensin, iso-C16 mojavensin, and anteiso-C17 mojavensin, respectively. All lipopeptide isomers, especially iso-C16 mojavensin and anteiso-C17 mojavensin, displayed moderate antagonism and dose-dependent activity against several formae speciales of Fusarium oxysporum and presented surface tension activities. These properties demonstrated that the lipopeptides produced by B. mojavensis B0621A may be useful as biological control agent to fungal plant pathogens.