Composition and Antifungal Activity of the Alkaloidal Fraction of Lupinus mirabilis Leaves: A Biochemometrics-Based Exploration

Lupinus plants are well-recognized due to their significant alkaloid content, which has made them the subject of several studies. However, the lack of chemical and biological information on the Colombian Lupinus species remains a fact. Therefore, the alkaloidal fractions from the leaves of L. mirabilis obtained by conventional solvent and ultrasound-assisted extraction (CSE and UAE, respectively) at different time frames were analyzed. Sparteine (2) was the main component in all cases; however, its relative abundance showed large variability, ranging from 64.7% to 80.6%. Minor constituents were also affected by the extraction conditions. In general, prolonged times gave a higher proportion of alkaloids under CSE, while only a slight decrease was observed under UAE. Both the method and extraction time appeared to equally affect the ratios of particular alkaloids, leading to variations in their effect on the mycelial growth of Fusarium oxysporum. Holistic analysis through multiple-covariate statistical methods as an approach to integrating chemical and bioactivity datasets allowed inferring the compounds most likely responsible for the changes in mycelial growth inhibition. 13α-Hydroxylupanine (12) might represent a promising compound to be included in further studies against this phytopathogen.

First Report of Fusarium Wilt of Industrial Hemp (Cannabis sativa L.) Caused by Fusarium oxysporum in the Northeast China

Industrial hemp (Cannabis sativa L.) is an ancient and economically important crop used in food, medicine, textile, and paper industries (Chandra et al. 2017). In July 2021, an estimated 30% of the industrial hemp plants showed wilted leaves and root rot in the greenhouse at the Modern Agriculture Demonstration Area Management Center, Harbin City, Heilongjiang Province, China. Initially, the diseased plants exhibited green and reversible wilting of lower canopy leaves. Upon progression the plants showed irreversible wilting. The epidermal tissue of root and rhizome showed slight cracks and the vascular bundle exhibited light brown discoloration, and then died. Six randomly selected disease plants were collected. Small fragments (5 mm) were cut from the infected roots, surface-sterilized with 70% ethanol for 30s and 1% sodium hypochlorite for 5 min and rinsed three times in sterile H2O. Then the small pieces were embedded on potato dextrose agar at 25℃ for 4 days and sub-cultured by hyphal tipping to isolate the fungus. A single-spore culture was obtained by monosporic isolation. The colonies were characterized by an abundant white cottony mycelium, which became gray or purple with age. The macroconidia were transparent, short to medium in length, straight to slightly curved, septate 0 to 4, 16.8 to 26.6 µm long × 3.5 to 4.1 µm wide. The apical cells were long and tapering to a point and the basal cells were notched. Microconidia were elliptic or kidney-shaped, and septate 0 to 4. The conidia were 4.2 to 11.3 µm long × 3.5 to 5.5 µm wide (n = 50). The morphological characteristics were very similar to those of Fusarium oxysporum (Leslie and Summerell 2006). For molecular identification, the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF1) and RNA polymerase II beta subunit (RPB2) genes were amplified and sequenced with the primers ITS1/ITS4, EF-1/EF-2 (Uwaremwe et al. 2020), and 5f2/7c (O'Donnell et al. 2010). The 520 bp (ITS), 948 bp (TEF1), and 861 bp (RPB2) sequences were deposited in GenBank with acce. nos. MZ722998, OK180473 and OK180474, respectively. NCBI BLAST analysis showed 98 to 100% similarity with the sequences of F. oxysporum. Moreover, the sequences alignment similarity for the six isolates were 100%. Based on the morphological and molecular characteristics, the isolates were identified as F. oxysporum. For the pathogenicity test, 20 seedlings were inoculated 30 ml of a conidial suspension (106 conidia/ml) using the root dip method. Another set of 20 seedlings were inoculated with the same quantity of sterile distilled water as the controls. After inoculation, all seedlings were maintained in a greenhouse at 25°C ± 2, with a relative humidity of 60 to 70% and a 16 h light/8 h dark cycle. This test was repeated twice. The leaves of the inoculated seedlings gradually became yellow and exhibited wilting within 15 to 20 days, the epidermal tissue of root showed light brown discoloration. Eventually the plants were dead within 40 to 50 days after inoculation. The control seedlings did not show any wilt symptoms. F. oxysporum was re-isolated from the infected root tissues to fulfill the Koch's postulates. In addition to F. oxysporum, F. brachygibbosum, Pythium aphanidermatum, F. solani, and F. equiseti have also been reported to cause wilt symptoms of industrial hemp (Zamir et al. 2018). To our knowledge, this is the first report of Fusarium wilt on C. sativa caused by F. oxysporum in the Northeast China.

Potential of biosynthesized zinc oxide nanoparticles to control Fusarium wilt disease in eggplant (Solanum melongena) and promote plant growth

In this study, a novel, non-toxic, eco-friendly zinc oxide nanoparticles (ZnO-NPs) was used instead of the synthetic fungicides widely used to control the destructive phytopathogenic fungus Fusarium oxysporum, the causative agent of wilt disease in Solanum melongena L. Herein, the biosynthesized ZnO-NPs was carried out by Penicillium expansum ATCC 7861. In vitro, mycosynthesized ZnO-NPs exhibited antifungal activity against Fusarium oxysporum. In vivo, ZnO-NPs suppressed Fusarium wilt disease in cultivated Solanum melongena L. by decreasing the disease severity with 75% of plant protection. Moreover, ZnO-NPs stimulated the recovery of eggplant as an indicated by improving of morphological and metabolic indicators including plant height(152.5%), root length(106.6%), plant fresh biomass (146%), chlorophyll a (102.8%), chlorophyll b (67.86%), total soluble carbohydrates (48.5%), total soluble protein (81.8%), phenol (10.5%), antioxidant activity and isozymes compared with infected control. Therefore, this study suggests using mycosynthesized ZnO-NPs as an alternative to synthetic fungicides not only to eradicate the Fusarium wilt disease in cultivated eggplant (Solanum melongena) but also to promote the growth parameters and metabolic aspects.

First report of leaf spot disease caused by Fusarium oxysporum on Litsea cubeba in China

Litsea cubeba, an important industrial plant species that originated in China, produces fruit essential oil extensively applied in the chemical industry (Xiang et al. 2020). In July 2020, a large-scale outbreak of leaf spot disease on Litsea cubeba was first observed and then monitored over time in Yueyang (29°37'N; 113°13'E) and Changsha (28°06'N; 113°02'E), Hunan province, China. Symptoms of this disease consisted of round-shaped lesions that initially appeared as small light-brown spots. With the increase in number, these small spots coalesced into larger, dark-brown lesions leading to yellowing and abscission of the leaves. To identify the causal agent this disease, the pathogen was isolated with a tissue separation method (Gao et al. 2020). The infected leaf tissues surface-disinfected with 75% ethanol and 0.1% HgCl were aseptically cut into small pieces (11 cm) and then placed onto potato dextrose agar (PDA) medium with cephalothin (0.2 mg/ml) and incubated at 28°C for 3-5 days. The purified colonies on PDA exhibited fluffy white hyphae, secreted a dark red pigment that had been observed in previous studies (Xiao et al. 2015) and produced microconidia and macroconidia. The microconidia were single-celled, non-septate, ovoid, and ranged from 3.08 to 13.89 μm long and 2.17 to 3.62 μm wide (n=50). Macroconidia were three to five-septate, slightly curved, and ranged from 11.77 to 26.85 μm long and 3.31 to 4.50 μm wide (n=50). These morphological features suggested that theisolates were most likely Fusarium oxysporum (Savian et al. 2021). To further confirm the identity of this pathogen (designated as Fox-1), the TEF-1a gene (Genbank accession No. OM281065) and rDNA ITS region (Genbank accession No. OM250084) were cloned and then sequenced (Cui et al, 2021). Sequence alignments indicated that the ITS and TEF-1a sequences shared 99.8% (504/505) and 99.7% (665/667) similarities with that of F. oxysporum (Genbank accession No. MF667966, KT230848), respectively. Both of the morphological characteristics and molecular data were used to identify this pathogen as F. oxysporum Schltdl.: Fr. 1824. To further verify whether these isolates of F. oxysporum can cause leaf spot disease, Koch's postulates were tested (Gradmann 2014). The purified pathogens were inoculated on artificial wounds of detached Litsea cubeba leaves and the leaves on the field plants of Litsea cubeba, respectively. The wounds of leaves were inoculated with sterile distilled water as negative controls. The experiment was performed independently three times, each with three leaves and three inoculated wounds on each leaf. All pathogen-inoculated wounds developed dark brown or black lesions on detached leaves within 3 days and on leaves on plants within 9 days, whereas the controls showed no symptoms. Re-isolations from infected leaves confirmed that the re-isolated pathogens possessed identical morphological characteristics to those of the original pathogens. To our knowledge, this is the first report of leaf spot infection of Litsea cubeba caused by F. oxysporum in China. This disease severely delays plant development and significantly decreases the yield of essential oil of Litsea cubeba. Our results laid a foundation for the subsequent research into pathogenic mechanisms drug sensitivity tests, which will contribute to the prevention and cure of leaf spot disease of Litsea cubeba. References: Cui, L. X., et al. 2021. Plant Dis. 105:7. Gao, W., et al. 2020. Plant Dis. 105:501. Gradmann. 2014. J. Microbes Infect. 16:885-892. Savian, L. G., et al. 2021. Plant Dis. 104:1870. Xiang, Y. J., et al. 2020. J. Chin. Cereals Oils Assco. 35:186-195. Xiao, J. L., et al. 2015. Hunan Agric. Sci. 4:105-108.

Overexpression of the Potato Monosaccharide Transporter StSWEET7a Promotes Root Colonization by Symbiotic and Pathogenic Fungi by Increasing Root Sink Strength

Root colonization by filamentous fungi modifies sugar partitioning in plants by increasing the sink strength. As a result, a transcriptional reprogramming of sugar transporters takes place. Here we have further advanced in the characterization of the potato SWEET sugar transporters and their regulation in response to the colonization by symbiotic and pathogenic fungi. We previously showed that root colonization by the AM fungus Rhizophagus irregularis induces a major transcriptional reprogramming of the 35 potato SWEETs, with 12 genes induced and 10 repressed. In contrast, here we show that during the early colonization phase, the necrotrophic fungus Fusarium solani only induces one SWEET transporter, StSWEET7a, while represses most of the others (25). StSWEET7a was also induced during root colonization by the hemi-biotrophic fungus Fusarium oxysporum f. sp. tuberosi. StSWEET7a which belongs to the clade II of SWEET transporters localized to the plasma membrane and transports glucose, fructose and mannose. Overexpression of StSWEET7a in potato roots increased the strength of this sink as evidenced by an increase in the expression of the cell wall-bound invertase. Concomitantly, plants expressing StSWEET7a were faster colonized by R. irregularis and by F. oxysporum f. sp. tuberosi. The increase in sink strength induced by ectopic expression of StSWEET7a in roots could be abolished by shoot excision which reverted also the increased colonization levels by the symbiotic fungus. Altogether, these results suggest that AM fungi and Fusarium spp. might induce StSWEET7a to increase the sink strength and thus this gene might represent a common susceptibility target for root colonizing fungi.

Genomic and Experimental Analysis of the Biostimulant and Antagonistic Properties of Phytopathogens of Bacillus safensis and Bacillus siamensis

The B. safensis RGM 2450 and B. siamensis RGM 2529 strains were isolated from the rhizosphere of plants presenting resilience to abiotic and biotic stress conditions. To understand the implications of bacteria in resilience, a genomic and experimental analysis was carried out on their biostimulant and phytopathogenic antagonist properties. Genome analyses of both strains indicated that they have the potential to synthesize bioactive compounds such as the battery of non-ribosomal peptides, polyketides, extracellular enzymes and phytohormones. These results were consistent with the antagonistic activities of both strains against the phytopathogens Botrytis cinerea, Colletotrichum acutatum, Fusarium oxysporum and Phytophtora cinnamomi. They also showed the capacity to solubilize phosphorus, fix nitrogen and produce indole acetic acid. This was observed in tomato seedlings grown from seeds inoculated with the mixture of strains which presented significantly greater length as well as wet and dry weight in comparison with the treatments individually inoculated with each strain and the control. Accordingly, the combination of B. safensis RGM 2450 and B. siamensis RGM 2529 showed synergistic biostimulant activity. These findings contribute new knowledge of the genomic and metabolomic properties taking part in the symbiotic interactions between these strains and the plants and uphold the combined use of both strains as a biostimulant.

First report of Fusarium oxysporum causing root rot of Gentiana scabra bunge (Adenophora capillaris) in China

Gentiana scabra bunge (Adenophora capillaris) is a traditional Chinese medicine crop in the northeast China. In July 2019, the root rot symptoms of A. capillaris were observed in its production field (approximately 1.3 hectares) iningyuan Manchu Autonomous County (41º47'28" N, 124º21'35" E), Fushun City in Liaoning province, China. Typical symptom included wilting, darkening, and rotting of the root collar and vascular bundle, leading to plant defoliation and death. Approximately 25% of the plants in the field showed the symptoms, with 2-year-old plants having more severe symptoms. Root tissue samples were collected from the diseased plants, surface-sterilized with 75% ethanol for 30 s, followed by 2% NaClO for 5 min, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). After 3 days of incubation at 25 °C, white Fusarium-like colonies grew out from the symptomatic root tissue pieces. Five single-spore isolates were obtained from 10-day-old cultures using single-spore isolating technique. The fungus produced many macroconidia with the typical macroconidia of Fusarium spp. on carnation leaf agar (CLA) after 18 days of incubation at 26°C. They were falculate, slender and slightly curved, and their cells at both ends were sharp. Macroconidia had 3 to 5 septa, measuring 24.8 to 48.6 × 3.5 to 6.4 μm (n=50). Microconidia had 1 to 2 septa, elliptical, rounded tip, measuring 6.7 to 22.5 × 2.4 to 5.5 μm (n=5). Morphologically, the isolates were identified as Fusarium oxysporum (Leslie and Summerell 2006). For molecular identification, the internal transcribed spacer (ITS) region of rDNA and the translation elongation factor-1a (TEF-1α) of Isolate LD528-1 were amplified with the general primer ITS1/ITS4 and TEF-1α primer EF-1/EF-2 (O'Donnell et al. 1998). The resulting sequences were deposited in GenBank (acc. nos. MW418098 and MW423622). BLASTn analysis of the ITS sequence (KU939043) and TEF sequence (MW423622) revealed 99.06% sequence identity with F. oxysporum (KU939043) and 100% with F. oxysporum (MN892354), respectively. For pathogenicity test, a pot experiment was conducted in a greenhouse with 22 to 28°C and 65 to 90% relative humidity. Roots of A. capillaris were dipped in a spore suspension (1×107 conidia/ml) of Isolate LD528-1 for approximately 5 min, and then planted into the pots filled with sterilized field soil. Root dipped in sterilized water served as the controls. There were five pots for the inoculation treatment and three pots for the control treatment. All treated pots were placed and maintained in the greenhouse. After 15 days, 80% of inoculated plants were infected, with the symptoms similar to those observed in the field. The plants in the control treatment did not develop any symptoms. The same fungus was re-isolated from the diseased root tissue and confirmed by morphological and molecular assays as described above. This is the first report of F. oxysporum causing root rot of gentiana scabra bunge in China. This disease can become one of most important diseases in gentiana scabra bunge in China. References: Leslie, J. F., and Summerell, B. A. 2006. The Fusarium Laboratory Manual. Blackwell Publishing Ltd, Iowa, USA. O'Donnell, K., et al. 1998.PNAS, 95:2044. Funding: This work was supported by the Grant of China Agriculture Research System (CARS-21-06).

Novel fabrication of SiO2/Ag nanocomposite by gamma irradiated Fusarium oxysporum to combat Ralstonia solanacearum

The bacterial wilt is a global destructive plant disease that initiated by the phytopathogenic Ralstonia solanacearum. This study display a novel biofabrication of silica/silver nanocomposite using Fusarium oxysporum-fermented rice husk (RH) under solid state fermentation (SSF). The biofabricated nanocomposite was characterized by XRD, UV–Vis. spectroscopy, DLS, SEM, EDX elemental mapping, and TEM analyses as well as investigated for anti-R. solanacearum activity. Response surface methodology was also processed for optimizing the biofabrication process and improving the anti-bacterial activity of the fabricated nanocomposite. Maximum suppression zone of 29.5 mm against R. solanacearum was reached at optimum RH content of 6.0 g, AgNO₃ concentration of 2.50 mM, reaction pH of 6.3, and reaction time of 2 days. The anti-R. solanacearum activity of the fabricated nanocomposite was further improved by exposing the F. oxysporum strain to a gamma irradiation dose of 200 Gy. In conclusion, RH recycling under SSF by F. oxysporum could provide an innovative, facile, non-expensive, and green approach for fabricating SiO₂/Ag nanocomposite that could be applied efficiently as an eco-friendly antibacterial agent to combat R. solanacearum in agricultural applications. Moreover, the developed method could serve as a significant platform for the designing of new nanostructures for broad applications.

Biofabricated SiO₂/Ag nanocomposite by gamma irradiated-F. oxysporum under SSF.

Statistical optimization and complete characterization of SiO₂/Ag nanocomposite.

Application in agriculture for combating the wilt causing R. solanacearum.

Antifungal activity of an artificial peptide aptamer SNP-D4 against Fusarium oxysporum

Fusarium oxysporum f. sp. cubense (FOC4) is a pathogen of banana fusarium wilt, which is a serious problem that has plagued the tropical banana industry for many years. The pathogenic mechanism is complex and unclear, so the prevention and control in agricultural production applications is ineffective. SNP-D4, an artificial peptide aptamer, was identified and specifically inhibited FOC4. To evaluate the efficacy of SNP-D4, FoC4 spores were treated with purified SNP-D4 to calculate the germination and fungicide rates. Damage of FOC4 spores was observed by staining with propidium iodide (PI). Eight proteins of FOC4 were identified to have high affinity for SNP-D4 by a pull-down method combined with Q-Exactive mass spectrometry. Of these eight proteins, A0A5C6SPC6, the aldehyde dehydrogenase of FOC4, was selected as an example to scrutinize the interaction sites with SNP-D4. Molecular docking revealed that Thr66 on the peptide loop of SNP-D4 bound with Tyr437 near the catalytic center of A0A5C6SPC6. Subsequently 42 spore proteins which exhibited associations with the eight proteins were retrieved for protein-protein interaction analysis, demonstrating that SNP-D4 interfered with pathways including 'translation', 'folding, sorting and degradation', 'transcription', 'signal transduction' and 'cell growth and death', eventually causing the inhibition of growth of FOC4. This study not only investigated the possible pathogenic mechanism of FOC4, but also provided a potential antifungal agent SNP-D4 for use in the control of banana wilt disease.

The Protein Phosphatase GhAP2C1 Interacts Together with GhMPK4 to Synergistically Regulate the Immune Response to Fusarium oxysporum in Cotton

The plant mitogen-activated protein kinase (MAPK) cascade plays an important role in mediating responses to biotic and abiotic stresses and is the main pathway through which extracellular stimuli are transduced intracellularly as signals. Our previous research showed that the GhMKK6-GhMPK4 cascade signaling pathway plays an important role in cotton immunity. To further analyze the role and regulatory mechanism of the GhMKK6-GhMPK4 cascade signaling pathway in cotton resistance to Fusarium wilt, we functionally analyzed GhMPK4. Our results show that silencing GhMPK4 reduces cotton tolerance to Fusarium wilt and reduces the expression of several resistance genes. Further experiments revealed that GhMPK4 is similar to GhMKK6, both of whose overexpression cause unfavorable cotton immune response characteristics. By using a yeast two-hybrid screening library and performing a bioinformatics analysis, we screened and identified a negative regulator of the MAPK kinase-protein phosphatase AP2C1. Through the functional analysis of AP2C1, it was found that, after being silenced, GhAP2C1 increased resistance to Fusarium wilt, but GhAP2C1 overexpression caused sensitivity to Fusarium wilt. These findings show that GhAP2C1 interacts together with GhMPK4 to regulate the immune response of cotton to Fusarium oxysporum, which provides important data for functionally analyzing and studying the feedback regulatory mechanism of the MAPK cascade and helps to clarify the regulatory mechanism through which the MAPK cascade acts in response to pathogens.

Fusarium oxysporum causes black gill disease in narrow-clawed crayfish Pontastacus leptodactylus

Morphological and molecular analyses were carried out to determine the causative agent of black gill disease in narrow-clawed crayfish Pontastacus leptodactylus specimens collected from 6 lakes (Taşkısığı, Beyşehir, Karaidemir, Karataş, Manyas, and Gölhisar) in Turkey. Fungi were isolated from the tissues of crayfish displaying putative black gill disease symptoms. Morphological evaluation was conducted, and the isolates were determined to be similar to Fusarium oxysporum. Subsequent molecular cloning of the ITS region of nrDNA by PCR confirmed species identification; DNA sequences from all 6 isolates were 99% similar to those of F. oxysporum. An experimental infection trial was conducted in triplicate using 1 of the 6 isolates to fulfill Koch's postulates. Three groups of crayfish were used: (1) wounded and contaminated (WC), (2) wounded and not contaminated (WNC), and (3) non-wounded and contaminated (NWC). On Day 3, one individual died in the WC group. Throughout the total 74 d monitoring period, no other mortality was recorded. On Day 14, all crayfish in the WC group showed blackened gills, whereas all crayfish in the NWC displayed partial blackening and all crayfish in the WNC group displayed normal gill coloration. F. oxysporum was re-isolated in pure culture from the WC and NWC groups; thus, the disease was confirmed. Our results indicated that F. oxysporum causes black gill disease in P. leptodactylus crayfish. Moreover, we demonstrated that F. oxysporum can also infect non-wounded crayfish.

festucae symbiosis and Fusarium oxysporum pathogenesis

Phosphoinositides (PI) are essential components of eukaryotic membranes and function in a large number of signaling processes. While lipid second messengers are well studied in mammals and yeast, their role in filamentous fungi is poorly understood. We used fluorescent PI-binding molecular probes to localize the phosphorylated phosphatidylinositol species PI[3]P, PI[3,5]P₂, PI[4]P and PI[4,5]P₂ in hyphae of the endophyte Epichloë festucae in axenic culture and during interaction with its grass host Lolium perenne. We also analysed the roles of the phosphatidylinositol-4-phosphate 5-kinase MssD and the predicted phosphatidylinositol-3,4,5-triphosphate 3-phosphatase TepA, a homolog of the mammalian tumour suppressor protein PTEN. Deletion of tepA in E. festucae and in the root-infecting tomato pathogen Fusarium oxysporum had no impact on growth in culture or the host interaction phenotype. However, this mutation did enable the detection of PI[3,4,5]P₃ in septa and mycelium of E. festucae and showed that TepA is required for chemotropism in F. oxysporum. The identification of PI[3,4,5]P₃ in ΔtepA strains suggests that filamentous fungi are able to generate PI[3,4,5]P₃ and that fungal PTEN homologs are functional lipid phosphatases. The F. oxysporum chemotropism defect suggests a conserved role of PTEN homologs in chemotaxis across protists, fungi and mammals.

Biological control of Fusarium tomato-wilt disease by cyanobacteria Nostoc spp

This study investigated the effect of foliar application of extract and culture of Nostoc calcicola and Nostoc linckia on the Fusarium oxysporum f. sp. lycopersici (FOL) that infects tomatoes (Solanum lycopersicum) plant in vitro and in vivo. Cyanobacterial isolates were isolated from saline soils at El-Hamoul and Seidy Salem locations Kafr Elsheikh, Egypt, and identified to be N. calcicola and N. linckia Bioactive compounds of extract were analyzed by Gas chromatography-mass spectrometry (GC-MS). Dry weight, carotene, chlorophyll content, and total phenolic compounds of isolates were measured. Plant height, dry weight, fruit number, and fruit weight of tomatoes were estimated. GC/MS analysis showed 49 and 35 bioactive compounds in extracts of N. calcicola and N. linckia, respectively. N. calcicola possesses the highest values of chlorophyll a, carotenoid, and total phenol contents in dry weight compared with N. linckia. After 100 days of tomato growth, the results showed the highest yield of tomato fruits with the application of N. calcicola and N. linckia compared with the untreated plants and the plants which were infected with Fusarium, suggesting that N. calcicola and N. linckia can serve as a new bioagent for biological control of the soil fungus Fusarium oxysporum f. sp. lycopersici (FOL).

Quinolizidine-Based Variations and Antifungal Activity of Eight Lupinus Species Grown under Greenhouse Conditions

Fusarium oxysporum is an aggressive phytopathogen that affects various plant species, resulting in extensive local and global economic losses. Therefore, the search for competent alternatives is a constant pursuit. Quinolizidine alkaloids (QA) are naturally occurring compounds with diverse biological activities. The structural diversity of quinolizidines is mainly contributed by species of the family Fabaceae, particularly the genus Lupinus. This quinolizidine-based chemo diversity can be explored to find antifungals and even mixtures to address concomitant effects on F. oxysporum. Thus, the antifungal activity of quinolizidine-rich extracts (QREs) from the leaves of eight greenhouse-propagated Lupinus species was evaluated to outline promising QA mixtures against F. oxysporum. Thirteen main compounds were identified and quantified using an external standard. Quantitative analysis revealed different contents per quinolizidine depending on the Lupinus plant, ranging from 0.003 to 32.8 mg/g fresh leaves. Bioautography showed that all extracts were active at the maximum concentration (5 µg/µL). They also exhibited >50% mycelium growth inhibition. All QREs were fungistatic except for the fungicidal QRE of L. polyphyllus Lindl. Angustifoline, matrine, 13α-hydroxylupanine, and 17-oxolupanine were ranked to act jointly against the phytopathogen. Our findings constitute reference information to better understand the antifungal activity of naturally afforded QA mixtures from these globally important plants.

In Planta Gene Expression Analysis and Colonization of Fusarium oxysporum

In planta gene expression analysis and GFP-based confocal microscopy are two powerful techniques that may be coupled to assess the extent and dynamics of plant colonization by a fungal pathogen. Here we describe methods to prepare common bean plants for inoculation with a highly virulent strain of Fusarium oxysporum f. sp. phaseoli, quantify the extent of colonization by RT-qPCR, and visualize the colonized tissues by confocal microscopy.

Endophytic Fusarium oxysporum GW controlling weed and an effective biostimulant for wheat growth

Wheat crop has to compete with several weeds including Avena fatua, a noxious weed that alone is responsible for 30-70% losses in the yield annually. Because of the environmental concerns associated with conventional methods, researchers are on a continuous hunt to find clean alternatives in order to manage weeds. Fungi have shown promising weedicide potential in lab studies. The current study aimed to isolate endophytic fungi from wheat plants which can promote wheat growth and inhibit the growth of common weed, A. fatua. Of several isolates, GW (grayish white) was selected for its promising features, and the strain was identified as Fusarium oxisporum through ITS sequencing technique. This fungus released a number of compounds including Isovitexin, Calycosin, quercetagetin, and dihydroxy-dimethoxyisoflavone that inhibited the growth of A. fatua but did not influence the growth of wheat seedlings. Biomass of this fungus in the soil also reduced growth parameters of the weed and promoted the growth of wheat. For instance, the vigor index of A. fatua seedlings was reduced to only 6% of the control by this endophyte. In contrast, endophyte-associated wheat seedlings showed a higher vigor index than the control. Behind this differential response of the two plants were their contrasting physiological and biochemical status. Lower growth phenotypes of A. fatua seedlings had reduced levels of IAA, GAs, and SA and higher the levels of JA and ABA. Besides, their ROS scavenging ability was also compromised as evident from relatively lower activities of catalase, peroxidase, and ascorbic acid oxidase, as well as higher accumulation of ROS in their leaves. Wheat seedlings response to GW was opposite to the A. fatua. It may be concluded that F. oxysporum GW has the ability to differentially modulate physiology and biochemistry of the two hosts leading to contrasting phenotypic responses.

Control of Fusarium and nematodes by entomopathogenic fungi for organic production of Zingiber officinale

Ginger (genus Zingiber) is widely used as a spice and a medicinal herb worldwide and is the major ingredient of traditional local drinks such as jamu in Southeast Asia. Because ginger is frequently consumed, there is an increasing interest in organic ginger production without the use of synthetic agrochemicals. Recent studies have reported that certain kinds of entomopathogenic fungi (EPF) can establish endophytic- or mycorrhiza-like relationships with plants, thereby promoting plant growth and health, in addition to their typical role in crop protection as biological control agents. In this study, we explored the possibility of non-entomopathogenic effects of EPF Beauveria bassiana and Cordyceps fumosorosea on ginger plants (Zingiber officinale) via antagonism with Fusarium oxysporum or the parasitic nematode Meloidogyne incognita. The two EPF negatively affected the growth of F. oxysporum and survival of M. incognita in vitro. The application of EPF did not have any negative effect on the growth of ginger plants. Soil chemical properties were not different between the plots with or without EPF application, while the diversity of soil bacteria was observed to increase on application of EPF. At least C. fumosorosea appeared to persist in soil during the period of ginger cultivation. Thus, these EPF are potentially useful tools for producing chemical-free ginger.

High-Throughput Screening Assays to Identify Plant Natural Products with Antifungal Properties Against Fusarium oxysporum

Fusarium oxysporum is a cross-kingdom fungal pathogen that not only causes devastating plant vascular diseases but can also opportunistically infect humans. Here we describe two high-throughput screening assays, a resazurin cell viability assay and an optical density assay, to screen natural products from cultured plant cells with antifungal properties against a clinical isolate of F. oxysporum. After elicitation by applying methyl jasmonate or by co-culture with F. oxysporum, as an abiotic elicitor and a biotic elicitor, respectively, we identified three cell lines that produce materials that inhibit fungal growth. Our procedure validates the powerful potential of combining high-throughput methods for the discovery of novel anti-pathogenic leads.

Karyotyping of Fusarium oxysporum by Pulsed-Field Gel Electrophoresis and the Germ Tube Burst Method

In fungi, karyotyping is fundamental to understanding their genome organization. It is also essential to study various genome- or chromosome-related topics such as karyotype polymorphisms and supernumerary or pathogenicity chromosomes. Here, we describe the protocols of pulsed-field gel electrophoresis and the germ tube burst method for molecular and cytological karyotyping of Fusarium oxysporum. The combined use of the two methods is valuable for determining definitive and comprehensive karyotypes of these fungi.

Arbuscular mycorrhizal fungi enhance disease resistance of Salvia miltiorrhiza to Fusarium wilt

Salvia miltiorrhiza Bunge (Danshen in Chinese) is vulnerable to Fusarium wilt, which severely affects the quality of the crude drug. Mycorrhizal colonization enhances resistance to fungal pathogens in many plant species. In this study, pre-inoculation of S. miltiorrhiza with the arbuscular mycorrhizal fungi (AMF) Glomus versiforme significantly alleviated Fusarium wilt caused by Fusarium oxysporum. Mycorrhizal colonization protected S. miltiorrhiza from pathogen infection, thereby preventing a loss of biomass and photosynthesis. There were greater defense responses induced by pathogen infection in AMF pre-inoculated plants than those in non-treated plants. AMF pre-inoculation resulted in systemic responses upon pathogen inoculation, including significant increases in the protein content and activities of phenylalanine ammonia-lyase (PAL), chitinase, and β-1,3-glucanase in S. miltiorrhiza roots. In addition, mycorrhizal pre-inoculation caused upregulation of defense-related genes, and jasmonic acid (JA) and salicylic acid (SA) signaling pathway genes after pathogen infection. The above findings indicate that mycorrhizal colonization enhances S. miltiorrhiza resistance against F. oxysporum infection by enhancing photosynthesis, root structure, and inducing the expression of defense enzymes and defense-related genes on the other hand.

Isolation, Screening and Identification of Native and New Bacillus subtilis with Strong Antifungal Compound against Fusarium oxysporum

The genus Fusarium causes a wide range of infections in human, animals and herbs. The purpose of this research was to investigate and identify the native strains of Bacillus subtilis playing an inhibitory role against Fusarium oxysporum by producing surfactin. B. subtilis was isolated from the soil of various parks in Tehran-Iran, and identified by biochemical tests. Growth inhibition zone, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of B. subtilis were determined. After purification of surfactin, quantitative and qualitative analysis of surfactin conducted using high performance liquid chromatography (HPLC) . Finally, two selected native strains with the highest production rate of surfactin identified using PCR for 16S rRNA and phylogenetic tree was drawn. Sixty strains of B. subtilis were isolated from soil, after identification through phenotypical and biochemical tests, the antagonistic activity of 27 different strains against F. oxysporum by Agar well diffusion assay determined and the highest inhibition zone was 13.66 mm. Six strains showing the best inhibitory effect, were isolated and their metabolite were purified by methanol. MIC and MFC values of different strains were in the range of 0.5-1.6 and 1.6-2.6 mg/mL. Using HPLC, the purified surfactin content in B. subtilis was about 56.7 - 131.9 μg/mL. Based on the curves of the chromatogram, the preferred strains with the highest production of surfactin, by molecular identification, displayed high similarity to B. subtilis. We got a maximum amount of yellow and transparent surfactin from native strains. Furthermore, the selected bacteria can be good candidates for biological control of fungal pathogens.

LAMP Assay for Distinguishing Fusarium oxysporum and Fusarium commune in Lotus (Nelumbo nucifera) Rhizomes

Yields of edible rhizome from cultivation of the perennial hydrophyte lotus (Nelumbo nucifera) can be severely reduced by rhizome rot disease caused by Fusarium species. There is a lack of rapid field-applicable methods for detection of these pathogens on lotus plants displaying symptoms of rhizome rot. Fusarium commune (91%) and Fusarium oxysporum (9%) were identified at different frequencies from lotus samples showing symptoms of rhizome rot. Because these two species can cause different severity of disease and their morphology is similar, molecular diagnostic-based methods to detect these two species were developed. Based on the comparison of the mitochondrial genome of the two species, three specific DNA loci targets were found. The designed primer sets for conventional PCR, quantitative PCR, and loop-mediated isothermal amplification (LAMP) precisely distinguished the above two species when isolated from lotus and other plants. The LAMP detection limits were 10 pg/μl and 1 pg/μl of total DNA for F. commune and F. oxysporum, respectively. We also carried out field-mimicked experiments on lotus seedlings and rhizomes (including inoculated samples and field-diseased samples), and the results indicated that the LAMP primer sets and the supporting portable methods are suitable for rapid diagnosis of the lotus disease in the field. The LAMP-based detection method will aid in the rapid identification of whether F. oxysporum or F. commune is infecting lotus plants with symptoms of rhizome rot and can facilitate efficient pesticide use and prevent disease spread through vegetative propagation of Fusarium-infected lotus rhizomes.

Agrobacterium tumefaciens-Mediated Transformation Method for Fusarium oxysporum

Agrobacterium tumefaciens-mediated transformation (ATMT) is becoming a popular effective system as an insertional mutagenesis tool in filamentous fungi. An efficient Agrobacterium tumefaciens-mediated transformation approach was developed for the plant pathogenic fungus, F. oxysporum, the causal agent of Apple replant disease (ARD) in China. Four parameters were selected to optimize efficiencies of transformation. A. tumefaciens concentration, conidial concentration of F. oxysporum, and co-culture temperature and time have a significant influence on all parameters. Transformants emit green fluorescence under fluorescence microscopy. The integration of a mitotically stable hygromycin resistance gene (hph) in the genome is confirmed by PCR. The transformation efficiency can reach up to 300 transformants per 10⁶ conidia under optimal conditions. This ATMT method is an efficient tool for insertional mutagenesis of F. oxysporum.

in Vicia faba L

Out of seven Fusarium spp. isolated from infected faba bean roots, two Fusarium oxysporum were selected and showed faba bean-wilt disease severity with percentages of 68% and 47% under greenhouse conditions. The F. oxysporum showed the highest wilt disease was selected to complete the current study. Three rhizobacterial strains were isolated and identified as Bacillus velezensis Vb1, B. paramycoides Vb3, and B. paramycoides Vb6. These strains showed the highest in-vitro antagonistic activity by the dual-culture method against selected F. oxysporum with inhibition percentages of 59±0.2, 46±0.3, and 52±0.3% for Vb1, Vb3, and Vb6, respectively. These rhizobacterial strains exhibit varied activity for nitrogen-fixing and phosphate-solubilizing. Moreover, these strains showed positive results for ammonia, HCN, and siderophores production. The phytohormones production (indole-3-acetic acid, ABA, benzyl, kinten, ziaten, and GA₃) and secretion of various lytic enzymes were recorded by these strains with varying degrees. Under greenhouse conditions, the rhizobacterial strains Vb1, Vb3, Vb6, and their consortium can protect faba bean from wilt caused by F. oxysporum with percentages of 70, 60, 65, and 82%, respectively. Under field conditions, the inoculation with the rhizobacterial consortium (Vb1+Vb3+Vb6) significantly increases the growth performance of the F. oxysporum-infected faba bean plant and recorded the highest wilt protection (83.3%).

Absolute Configuration Determination of Two Diastereomeric Neovasifuranones A and B from Fusarium oxysporum R1 by a Combination of Mosher's Method and Chiroptical Approach

Endophytic fungi are one of prolific sources of bioactive natural products with potential application in biomedicine and agriculture. In our continuous search for antimicrobial secondary metabolites from Fusarium oxysporum R1 associated with traditional Chinese medicinal plant Rumex madaio Makino using one strain many compounds (OSMAC) strategy, two diastereomeric polyketides neovasifuranones A (3) and B (4) were obtained from its solid rice medium together with N-(2-phenylethyl)acetamide (1), 1-(3-hydroxy-2-methoxyphenyl)-ethanone (2) and 1,2-seco-trypacidin (5). Their planar structures were unambiguously determined using 1D NMR and MS spectroscopy techniques as well as comparison with the literature data. By a combination of the modified Mosher's reactions and chiroptical methods using time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) and optical rotatory dispersion (ORD), the absolute configurations of compounds 3 and 4 are firstly confirmed and, respectively, characterized as (4S,7S,8R), (4S,7S,8S). Bioassay results indicate that these metabolites 1-5 exhibit weak inhibitory effect on Helicobacter pylori 159 with MIC values of ≥16 μg/mL. An in-depth discussion for enhancement of fungal metabolite diversity is also proposed in this work.

Biosolid-Amended Soil Enhances Defense Responses in Tomato Based on Metagenomic Profile and Expression of Pathogenesis-Related Genes

Biosolid application is an effective strategy, alternative to synthetic chemicals, for enhancing plant growth and performance and improving soil properties. In previous research, biosolid application has shown promising results with respect to tomato resistance against Fusarium oxysporum f. sp. radicis-lycopersici (Forl). Herein, we aimed at elucidating the effect of biosolid application on the plant-microbiome response mechanisms for tomato resistance against Forl at a molecular level. More specifically, plant-microbiome interactions in the presence of biosolid application and the biocontrol mechanism against Forl in tomato were investigated. We examined whether biosolids application in vitro could act as an inhibitor of growth and sporulation of Forl. The effect of biosolid application on the biocontrol of Forl was investigated based on the enhanced plant resistance, measured as expression of pathogen-response genes, and pathogen suppression in the context of soil microbiome diversity, abundance, and predicted functions. The expression of the pathogen-response genes was variably induced in tomato plants in different time points between 12 and 72 h post inoculation in the biosolid-enriched treatments, in the presence or absence of pathogens, indicating activation of defense responses in the plant. This further suggests that biosolid application resulted in a successful priming of tomato plants inducing resistance mechanisms against Forl. Our results have also demonstrated that biosolid application alters microbial diversity and the predicted soil functioning, along with the relative abundance of specific phyla and classes, as a proxy for disease suppression. Overall, the use of biosolid as a sustainable soil amendment had positive effects not only on plant health and protection, but also on growth of non-pathogenic antagonistic microorganisms against Forl in the tomato rhizosphere and thus, on plant-soil microbiome interactions, toward biocontrol of Forl.

Biosynthesis of silver nanoparticles using endophytic Fusarium oxysporum strain NFW16 and their in vitro antibacterial potential

Nanotechnology has provided a platform for altering, modifying, and developing metal properties to nanoparticles with promising applications. This study aimed to produce functionalized and biocompatible silver nanoparticles (AgNPs) using cellular extracts of endophytic Fusarium oxysporum-NFW16 isolated from Taxus fauna and evaluate its antibacterial potential. Under optimized reaction conditions, well-dispersed and extremely stable AgNPs were synthesized in 1 hr. AgNPs were characterized through UV-visible spectrophotometry (at 423 nm), and scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The obtained AgNPs were spherical, monodispersed, and size was ~30-36.1 nm. Strong peaks of XRD (311), (220), (200), and (111) matched to silver plane's diffraction facets. FTIR spectra at 1,650, 2,950, and 1,400 cm^-1 confirmed the capping of AgNPs with phenolic compounds and compounds having primary amines. The AgNPs showed 100 μg/ml of minimum inhibitory concentration against methicillin-resistant Staphylococcus aureus (MRSA). In addition, AgNPs showed a synergistic effect with both vancomycin and ciprofloxacin against MRSA (25%), Pseudomonas aeruginosa (50%), and pus isolated Escherichia coli (50%). Moreover, AgNPs impregnated cotton and bandage showed in vitro antibacterial potential against American Type Culture Collection and skin-associated clinical pathogenic bacteria. Findings showed that endophytic fungi are the potential source for AgNPs synthesis that are effective against multidrug-resistant bacteria and the development of antimicrobial textile finishes.

Leaf spot of Hosta ventricosa caused by Fusarium oxysporum in China

Leaf spot of Hosta ventricosa is a new disease in China. This disease seriously affects the ornamental value and greening function of H. ventricosa. Identification of the causal agent can prevent and control leaf spot in H. ventricosa and promote the healthy development of the H. ventricosa industry. Known incidents of leaf spot of H. ventricosa occurred in three places, and samples were collected. After the fungus were isolated, its pathogenicity was tested according to Koch's postulates. Isolates ZE-1b and ZE-2b were identified as Fusarium oxysporum based on morphological features and multigene phylogenetic analyses of calmodulin (CMDA), RNA polymerase II subunit A (RPB1), RNA polymerase II second largest subunit (RPB2) and translation elongation factor 1-alpha (TEF1). These results provide a theoretical basis for the control of this disease of H. ventricosa.

dianthi

Rooted cuttings from two carnation (Dianthus caryophyllus L.) cultivars showing contrasting responses to the vascular wilt caused by Fusarium oxysporum f. sp. dianthi (Fod) were inoculated with this phytopathogen, and some of the biochemical responses associated with flavonoid biosynthesis were investigated in the roots. The resistant cultivar ('Golem') showed a significant increase in the levels of phenolic and flavonoid compounds at 48-96 h post-inoculation (hpi) (α = 0.05). LC-MS-based analysis indicated that the flavonoids mainly included flavanol-type glycosides, especially quercetin and kaempferol aglycones. Quantification of the mRNA levels of genes encoding CHS (Chalcone Synthase), CHI (Chalcone Isomerase), FLS (Flavonol Synthase), and the transcription factor MYB11 by using reverse transcription quantitative polymerase chain reaction (RT-qPCR) indicated that the resistant cultivar exhibited higher expression levels of these genes and, therefore, showed more flavonoid accumulation at 96 hpi. The differences in the temporal regulation of the assessed variables during infection support the idea that the early expression of enzymes of the flavonoid biosynthesis pathway in carnation roots is linked to a resistance response to the hemibiotrophic pathogen Fod race 2. The present experimental approach is the first report describing the molecular mechanisms underlying flavonoid biosynthesis in carnation roots during their interaction with Fod.

Antifungal Activity against Fusarium oxysporum of Botanical End-Products: An Integration of Chemical Composition and Antifungal Activity Datasets to Identify Antifungal Bioactives

Plants produce various compounds as defensive barriers to naturally control fungal diseases. Among them, vascular wilt caused by Fusarium oxysporum is one of the most destructive diseases in crops, causing relevant economic losses. The application of synthetic fungicides is the most used management for this disease. However, this kind of method also involves adverse environmental impacts. Therefore, alternative methods are continuously being developed as a strategy to be involved in integrated pest management programs. Thus, as part of our research on antifungals of plant origin, a group of botanical extracts was assessed for the respective inhibitory effect on mycelium and conidia of F. oxysporum. Mycelial growth inhibition was measured in 12-well plates containing amended semi-solid medium, whereas conidial susceptibility was determined through microdilution. The identification of the bioactive compounds among test extracts was performed using an indirect approach, consisting of the integration of chemical composition and antifungal activity datasets through single-Y orthogonal partial least squares (OPLS) regression. Results showed that Piper aduncum extract was the most potent mycelial growth inhibitor whereas P. elongatum exhibited the best effect on conidia susceptibility. The active compounds identified through statistical integration and subsequent isolation were piperaduncin C, asebogenin and (-)-methyllinderatin. These findings indicated that the integrative, indirect approach is useful for the identification of bioactive metabolites from botanical extracts to be further used as biological protective agents against this phytopathogen.

Genome-Wide Analysis of Major Facilitator Superfamily and Its Expression in Response of Poplar to Fusarium oxysporum

The major facilitator superfamily (MFS) is one of the largest known membrane transporter families. MFSs are involved in many essential functions, but studies on the MFS family in poplar have not yet been reported. Here, we identified 41 MFS genes from Populus trichocarpa (PtrMFSs). We built a phylogenetic tree, which clearly divided members of PtrMFS into six groups with specific gene structures and protein motifs/domains. The promoter regions contain various cis-acting elements involved in stress and hormone responsiveness. Genes derived from segmental duplication events are unevenly distributed in 17 poplar chromosomes. Collinearity analysis showed that PtrMFS genes are conserved and homologous to corresponding genes from four other species. Transcriptome data indicated that 40 poplar MFS genes were differentially expressed when treated with Fusarium oxysporum. Co-expression networks and gene function annotations of MFS genes showed that MFS genes tightly co-regulated and closely related in function of transmembrane transport. Taken together, we systematically analyzed structure and function of genes and proteins in the PtrMFS family. Evidence indicated that poplar MFS genes play key roles in plant development and response to a biological stressor.

Bright Side of Fusarium oxysporum: Secondary Metabolites Bioactivities and Industrial Relevance in Biotechnology and Nanotechnology

Fungi have been assured to be one of the wealthiest pools of bio-metabolites with remarkable potential for discovering new drugs. The pathogenic fungi, Fusarium oxysporum affects many valuable trees and crops all over the world, producing wilt. This fungus is a source of different enzymes that have variable industrial and biotechnological applications. Additionally, it is widely employed for the synthesis of different types of metal nanoparticles with various biotechnological, pharmaceutical, industrial, and medicinal applications. Moreover, it possesses a mysterious capacity to produce a wide array of metabolites with a broad spectrum of bioactivities such as alkaloids, jasmonates, anthranilates, cyclic peptides, cyclic depsipeptides, xanthones, quinones, and terpenoids. Therefore, this review will cover the previously reported data on F. oxysporum, especially its metabolites and their bioactivities, as well as industrial relevance in biotechnology and nanotechnology in the period from 1967 to 2021. In this work, 180 metabolites have been listed and 203 references have been cited.

Detection and Control of Fusarium oxysporum from Soft Rot in Dendrobium officinale by Loop-Mediated Isothermal Amplification Assays

Soft rot causing Fusarium oxysporum is one of the most destructive diseases of Dendrobium officinale Kimura et Migo in China that reduces D. officinale yield and quality. A key challenge for an integrated management strategy for this disease is the rapid and accurate detection of F. oxysporum on D. officinale. Therefore, a new loop-mediated isothermal amplification (LAMP) assay was developed for this purpose. In this study, the primers were selected and designed using the translation elongation factor-1α (TEF-1α) gene region as the target DNA sequence in order to screen the best system of reaction of LAMP to detect F. oxysporum through optimizing different conditions of the LAMP reaction, including time, temperature, concentrations of MgSO4, and concentrations of inner and outer primers. The optimized system was able to efficiently amplify the target gene at 62 °C for 60 min with 1.2 μM internal primers, 0.4 μM external primers, 7 mM Mg2+, and 5 fg/µL minimum detection concentration of DNA for F. oxysporum. The amplified products could be detected with the naked eye after completion of the reaction with SYBR green I. We were better able to control the effect of soft rot in D. officinale using fungicides following a positive test result. Additionally, the control effect of synergism combinations against soft rot was higher than 75%. Thus, LAMP assays could detect F. oxysporum in infected tissues of D. officinale and soils in field, allowing for early diagnosis of the disease.

NtSWEET1 promotes tobacco resistance to Fusarium oxysporum-induced root rot disease

Sugars Will Eventually be Exported Transporter (SWEET) is a newly characterized family of sugar transporters, which plays critical roles in plant-pathogen interactions. However, the function of SWEET in tobacco and its interaction with Fusarium oxysporum, a causal agent of root rot, remain unclear. This study aimed to dissect the function of NtSWEETs in tobacco root rot using stem bases from tobacco plants inoculated with F. oxysporum. RNA-sequencing (RNA-Seq) analysis was performed, and the results indicated that Sucrose Transporter 4 (NtSUC4), Sugar Transporter 12 (NtSTP12), Hexose Transporter 6 (NtHEX6), NtSWEET1, NtSWEET3b, and NtSWEET12 were downregulated by infection with F. oxysporum. The expression of NtSWEET1, but not of NtSUC4, NtSTP12, NtHEX6, NtSWEET3b, or NtSWEET12, was suppressed at all the time points tested after inoculation with F. oxysporum. The NtSWEET1-green fluorescent protein was localized on the plasma membrane and possessed the ability to transport glucose, fructose and galactose. Compared with the wild-type plants, NtSWEET1 RNAi plants were more susceptible to root rot, indicating that NtSWEET1 positively regulated the defense of tobacco against root rot. This study identified the role of SWEETs in tobacco and their interaction with F. oxysporum. The results might be useful in protecting tobacco plants from root rot.

Tomato Endophytic Bacteria Composition and Mechanism of Suppressiveness of Wilt Disease (Fusarium oxysporum)

Tomato wilt disease, caused by the Fusarium oxysporum is an ever-increasing threat for agricultural production, and unreasonable fertilization and pesticide abuse caused environmental challenge. Increasing evidence suggested that microbiomes or those associated with crops, played key roles on plant health. Plant disease dynamics were affected by multiple biotic and abiotic factors including phytopathogen population density, the genetic type of the pathogen and the host, in particular, the composition and assembly of the host-associated microbiome. However, it was unclear how pathogen invasion interaction and correlate with endophytic bacterial communities in natural field conditions. To study this, we sampled temporally the tomato plants that were exposed to F. oxysporum invasions over one crop season. High-throughput sequencing were performed to explore the correlation between agricultural practice, pathogen invasion, and endophytic microbiota communities. Results showed that pathogen invasion had clear effect on the endophytic and a strong link between increased pathogen densities and reduced abundance of Bacillus sp., which are crucial taxonomy for suppressiveness to F. oxysporum in vitro and in greenhouse condition. In summary, monitoring the dynamics of endophytic bacteria communities and densities of pathogen could thus open new avenue for more accurate disease diagnostics and high-efficiency screening antagonisms methods in the future, and our results will broaden the agricultural view of beneficial microbiota as biological control agents against plant pathogen.

Isolation and Identification of Talaromyces sp. Strain Q2 and Its Biocontrol Mechanisms Involved in the Control of Fusarium Wilt

Fusarium wilt is an important disease of many food crops and often causes serious damages to yield and food quality. Consequently, numerous studies mainly focused on exploring the control strategy for Fusarium oxysporum as well as the mechanism of interaction between the F. oxysporum and other beneficial soil microorganisms. In this study, we have screened and identified an efficient biocontrol strain from the soil with infection of F. oxysporum f. sp. momordica (referred to as Fom), Talaromyces purpurogenus Q2 (referred to as TpQ2), which could be effective to reduce relative abundance of the rhizospheric Fom, leading to a significant decrease of Fusarium wilt disease incidence in bitter gourd during the greenhouse and field trails. TpQ2 can reduce the relative abundance of rhizospheric Fom through inhibition of growth and development of Fom. During the co-cultivation of TpQ2 and Fom, we confirmed that TpQ2 could significantly suppress the growth and development of Fom through disturbing the normal hyphae shape and function of the cell walls of Fom via secreting cell wall–degrading enzymes and suppression of the expression of cell wall biosynthesis genes, such as FomCFEM. In the meantime, TpQ2 showed a strong negative correlation with F. oxysporum in soil and positive correlation with beneficial indigenous microorganisms that had significant negative correlation with Fusarium populations, such as Streptomycetes, Lysobacter, and Sphingobium. To summarize, TpQ2 has a good biocontrol efficacy on Fusarium wilt of bitter gourd. The biocontrol mechanisms of TpQ2 on Fusarium wilt are complex and diverse.

Time-Lapse Imaging of Root Pathogenesis and Fungal Proliferation Without Physically Disrupting Roots

Microscopic observation of root disease onset and progression is typically performed by harvesting different plants at multiple time points. This approach prevents the monitoring of individual encounter sites over time, often mechanically damages roots, and exposes roots to unnatural conditions during observation. Here, we describe a method developed to avoid these problems and its application to study Fusarium oxysporum-Arabidopsis thaliana interactions. This method enabled three-dimensional, time-lapse imaging of both A. thaliana and F. oxysporum as they interact via the use of confocal and multi-photon microscopy and facilitated inquiries about the genetic mechanism underpinning Fusarium wilt.

Multi-Pronged Investigation of Volatile Compound-Mediated Interactions of Fusarium oxysporum with Plants, Fungi, and Bacteria

Proteins and many biogenic compounds require water as a medium for movement. However, because volatile compounds (VCs) can travel through the air and porous soils due to their ability to vaporize at ambient temperature, they can mediate diverse intra- and inter-kingdom interactions and perform ecologically functions even in the absence of water. Here, we describe several tools and approaches for investigating how Fusarium oxysporum interacts with plants and other microbes through VCs and how VC-mediated interactions affect its ecology and pathology. We also present a method for capturing F. oxysporum VCs for analysis via gas chromatography linked to mass spectrometry.

lactucae

The use of nanotechnology to suppress crop diseases has attracted increasing attention in agriculture. The present work investigated the antifungal efficacy of copper oxide nanoparticle (CuO NP)-embedded hydrogels, which were synthesized by loading CuO nanoparticles (NPs) in hydrogels formed from cross-linked interaction between chitosan and acrylic acid, against Fusarium wilt of lettuce (Lactuca sativa) caused by Fusarium oxysporum f. sp. lactucae. In comparison with CuO NPs, 7-day Cu dissolution from CuO NP-embedded hydrogels was 34.2-94.8% slower regardless of media type, including water, potato dextrose broth, or a soil extract. In a greenhouse study, upon exposure to CuO NP-embedded hydrogels, CuO NPs, or Kocide 3000 with equivalent amounts of Cu (31 mg/kg), the fresh shoot biomass was significantly increased by 40.5, 26.1 and 27.2%, respectively, as compared to that of the infected control. Notably, CuO NP-embedded hydrogels enhanced uptake of P, Mn, Zn, and Mg and increased the levels of organic acids as compared to the diseased control. Increased salicylic acid (SA) and decreased jasmonic acid (JA) and abscisic acid (ABA) levels with the addition of different forms of Cu may have enhanced disease resistance. Taken together, our findings provide useful information and approach for improving the delivery efficiency of agrichemicals via nanoenabled strategies and an advanced understanding of plant defense mechanisms triggered by Cu-based NPs.

Antifungal Evaluation and Molecular Docking Studies of Olea europaea Leaf Extract, Thymus vulgaris and Boswellia carteri Essential Oil as Prospective Fungal Inhibitor Candidates

Background: The present study investigated the antifungal activity and mode of action of four Olea europaea leaf extracts, Thymus vulgaris essential oil (EO), and Boswellia carteri EO against Fusarium oxysporum. Methods:Fusarium oxysporum lactucae was detected with the internal transcribed spacer (ITS) region. The chemical compositions of chloroform and dichloromethane extracts of O. europaea leaves and T. vulgaris EO were analyzed using GC-MS analysis. In addition, a molecular docking analysis was used to identify the expected ligands of these extracts against eleven F. oxysporum proteins. Results: The nucleotide sequence of the F. oxysporum lactucae isolate was deposited in GenBank with Accession No. MT249304.1. The T. vulgaris EO, chloroform, dichloromethane and ethanol efficiently inhibited the growth at concentrations of 75.5 and 37.75 mg/mL, whereas ethyl acetate, and B. carteri EO did not exhibit antifungal activity. The GC-MS analysis revealed that the major and most vital compounds of the T. vulgaris EO, chloroform, and dichloromethane were thymol, carvacrol, tetratriacontane, and palmitic acid. Moreover, molecular modeling revealed the activity of these compounds against F. oxysporum. Conclusions: Chloroform, dichloromethane and ethanol, olive leaf extract, and T. vulgaris EO showed a strong effect against F. oxysporum. Consequently, this represents an appropriate natural source of biological compounds for use in healthcare. In addition, homology modeling and docking analysis are the best analyses for clarifying the mechanisms of antifungal activity.

Secreted Secondary Metabolites Reduce Bacterial Wilt Severity of Tomato in Bacterial-Fungal Co-Infections

In order to gain a comprehensive understanding of plant disease in natural and agricultural ecosystems, it is essential to examine plant disease in multi-pathogen-host systems. Ralstonia solanacearum and Fusarium oxysporum f. sp. lycopersici are vascular wilt pathogens that can result in heavy yield losses in susceptible hosts such as tomato. Although both pathogens occupy the xylem, the costs of mixed infections on wilt disease are unknown. Here, we characterize the consequences of co-infection with R. solanacearum and F. oxysporum using tomato as the model host. Our results demonstrate that bacterial wilt severity is reduced in co-infections, that bikaverin synthesis by Fusarium contributes to bacterial wilt reduction, and that the arrival time of each microbe at the infection court is important in driving the severity of wilt disease. Further, analysis of the co-infection root secretome identified previously uncharacterized secreted metabolites that reduce R. solanacearum growth in vitro and provide protection to tomato seedlings against bacterial wilt disease. Taken together, these results highlight the need to understand the consequences of mixed infections in plant disease.

Contribution of NADPH-cytochrome P450 Reductase to Azole Resistance in Fusarium oxysporum

Fusarium species exhibit significant intrinsic resistance to most antifungal agents and fungicides, resulting in high mortality rates among immunocompromised patients. Consequently, a thorough characterization of the antifungal resistance mechanism is required for effective treatments and for preventing fungal infections and reducing antifungal resistance. In this study, an isolate of Fusarium oxysporum (wild-type) with broadly resistant to commonly antifungal agents was used to generate 1,450 T-DNA random insertion mutants via Agrobacterium tumefaciens-mediated transformation. Antifungal susceptibility test results revealed one mutant with increased sensitivity to azoles. Compared with the resistant wild-type, the mutant exhibited low MICs to KTZ, ITC, VRC, POS, and PCZ (0.125, 1, 0.06, 0.5, and 0.125μg/ml, respectively). The T-DNA insertion site of this mutant was characterized as involving two adjacent genes, one encoding a hypothetical protein with unknown function and the other encoding the NADPH-cytochrome P450 reductase, referred as CPR1. To confirm the involvement of these genes in the altered azole susceptibility, the independent deletion mutants were generated and the Cpr1 deletion mutant displayed the same phenotypes as the T-DNA random mutant. The deletion of Cpr1 significantly decreased ergosterol levels. Additionally, the expression of the downstream Cyp51 gene was affected, which likely contributed to the observed increased susceptibility to azoles. These findings verified the association between Cpr1 and azole susceptibility in F. oxysporum. Furthermore, this gene may be targeted to improve antifungal treatments.

albedinis

The complete mitogenome of Fusarium oxysporum f. sp. albedinis (FOA), the causal agent of the destructive fusarium wilt in date palm, is sequenced and assembled. The circular mitogenome of isolate Foa44 is 51,601 bp in length and contains 26 transfer RNA (tRNA) genes, one ribosomal RNA (rRNA), and 28 protein-coding genes. A mitogenome-based phylogenetic analysis of Fusarium revealed that FOA is congruent with previous nuclear-gene phylogenetic results.

lycopersici confers resistance against Fusarium wilt in tomato

In the present study, we have explored the potential of the RNAi mediated silencing of genes encoding peroxisomal biogenesis factor and β-1,3-glucanosyltransferase in Fusarium oxysporum f. sp. lycopersici (Fol) to confer resistance to Fusarium wilt in transgenic tomato plants. The partial gene fragments from these genes were utilized independently to generate hairpin RNAi constructs in appropriate silencing vectors and used for Agrobacterium-mediated transformation of tomato. The presence of gene-specific siRNAs was confirmed by stem-loop RT-PCR analysis of selected transgenic tomato lines. Transgenic lines expressing gene-specific dsRNA displayed enhanced resistance to Fol with delayed development of disease symptoms. The survival rate of transgenic tomato lines after fungal infection was higher as compared to that of the untransformed tomato plants.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02973-8.

pisi, growth, yield, physiological and anatomical characteristics of pea plants

Fusarium root rot caused by Fusarium oxysporum is an aggressive disease-causing damping-off, root rot, and vascular wilt in all peas growing fields. The disease can cause 100% yield losses under favorable conditions. The present study aims to control Fusarium root rot using Trichoderma harzianum, Pseudomonas fluorescens, and arbuscular mycorrhizal fungi, singly or in combinations. The results showed that all treatments significantly enhanced not only the plant growth, total phenol, activities of antioxidant enzymes, but also, the yield and seed quality. Several changes in the anatomical, physiological, and characteristics of the treated plants were also recorded. Compared to the untreated control treatment, under greenhouse conditions, the maximum reduction of the disease severity (80%) was achieved by the synergistic triple treatment consists of arbuscular mycorrhizal fungi, Trichoderma harzianum, and Pseudomonas fluorescens, as they gave the best growth and yield parameters. The same combination showed the highest activity of the antioxidant enzyme peroxidase (57.1%), as well as the highest total phenol content (117.7%), over the control. The synergistic triple increased the contents of protein (64.6%), total soluble sugars (48.5%), and total carbohydrate (24.8%) in seeds of pea compared with the control. The synergistic triple treatment led to an increase in the thickness of the root section (25%), the thickness of the cortex (24.8%), the thickness of the vascular cylinder (31.5%), and the diameter of the xylem vessels (81.5%) of the root. Based on their efficiency and eco-safety, this synergistic triple might be very effective for controlling root rot disease of pea caused by F. oxysporum, as well as improve the growth, yield, and seed quality.

Bacillus subtilis HSY21 can reduce soybean root rot and inhibit the expression of genes related to the pathogenicity of Fusarium oxysporum

Soybean root rot occurs globally and seriously affects soybean production. To avoid the many disadvantages of chemical fungicides, the addition of Bacillus is gradually becoming an alternative strategy to tackle soybean root rot. However, the molecular mechanism of phytopathogenic fungi in this process by Bacillus inhibition is rarely reported. In this study, we isolated a strain of B. subtilis HSY21 from soybean rhizosphere soil, which had an inhibition rate of 81.30 ± 0.15% (P < 0.05) against Fusarium oxysporum. The control effects of this strain against soybean root rot under greenhouse and field conditions were 63.83% and 57.07% (P < 0.05), respectively. RNA-seq analysis of F. oxysporum after treatment with strain HSY21 revealed 1445 downregulated genes and 1561 upregulated genes. Among them, genes involved in mycelial growth, metabolism regulation, and disease-related enzymes were mostly downregulated. The activities of cellulase, β-glucosidase, α-amylase, and pectin-methyl- galacturonase as well as levels of oxalic acid and ergosterol in F. oxysporum were significantly decreased after HSY21 treatment. These results demonstrated that B. subtilis HSY21 could effectively control F. oxysporum by inhibiting its growth and the expression of pathogenic genes, thus indicating that this strain may be an ideal candidate for the prevention and control of soybean root rot.

Mixtures of Biological Control Agents and Organic Additives Improve Physiological Behavior in Cape Gooseberry Plants under Vascular Wilt Disease

This study aimed to assess the soil application of mixtures of biological control agents (BCAs) (Trichoderma virens and Bacillus velezensis) and organic additives (chitosan and burnt rice husk) on the physiological and biochemical behavior of cape gooseberry plants exposed to Fusarium oxysporum f. sp. physali (Foph) inoculum. The treatments with inoculated and non-inoculated plants were: (i) T. virens + B. velezensis (Mix), (ii) T. virens + B. velezensis + burnt rice husk (MixRh), (iii) T. virens + B. velezensis + chitosan (MixChi), and (iv) controls (plants without any mixtures). Plants inoculated and treated with Mix or MixChi reduced the area under the disease progress curve (AUDPC) (57.1) and disease severity index (DSI) (2.97) compared to inoculated plants without any treatment (69.3 for AUDPC and 3.2 for DSI). Additionally, these groups of plants (Mix or MixChi) obtained greater leaf water potential (~-0.5 Mpa) and a lower MDA production (~12.5 µmol g^-2 FW) than plants with Foph and without mixtures (-0.61 Mpa and 18.2 µmol g^-2 FW, respectively). The results suggest that MixChi treatments may be a promising alternative for vascular wilt management in cape gooseberry crops affected by this disease.

radicis-lycopersici

Tomatoes (Solanum lycopersicum L.) are the most cultivated and important vegetable crop in the world. These plants can wilt during crop growth due to fusarium wilt (fusariosis), a disease that damages tomato vascular systems. The Fusarium isolated and analyzed in this work correspond to Fusarium oxysporum f. sp. radicis-lycopersici. The isolates were molecularly identified, and analysis was done on the in vitro effects of the nanoemulsions (previously obtained from extracts of Chilean medicinal plants of the genera Psoralea and Escallonia) to inhibit mycelial and conidial germination of the isolates. Subsequently, the nanoemulsions were evaluated under greenhouse conditions for preventive control of fusariosis in the root and crown, with high levels of disease control observed using the highest concentrations of these nanoemulsions, at 250 and 500 ppm.

Enhanced esterase activity during the degradation of dibutyl phthalate by Fusarium species in liquid fermentation

Dibutyl phthalate (DBP) is one of the most abundantly produced and used plasticizers and is incorporated into plastic to make it more flexible and malleable. DBP has been found to be an environmental contaminant and reported as an endocrine disruptor. Therefore, it is crucial to develop ecofriendly alternatives to eliminate phthalate pollution. In the present research, the growth of F. culmorum and F. oxysporum in the presence of DBP was studied in liquid fermentation. The esterase activity, specific growth rate, and growth and enzymatic yield parameters were determined in DBP-supplemented media (1,500 or 2,000 mg/L) and in control medium (lacking DBP). These results show that in general, for both Fusarium species, the highest esterase activities, specific growth rates, and yield parameters were observed in media supplemented with DBP. It was observed that 1,500 and 2,000 mg of DBP/L did not inhibit F. culmorum or F. oxysporum growth and that DBP induced esterase production in both fungi. These organisms have much to offer in the mitigation of environmental pollution caused by the endocrine disruptor DBP. This study reports, for the first time, esterase production during the degradation of high concentrations (i.e., 1,500 and 2,000 mg/L) of DBP by F. culmorum F. oxysporum.

Anaerocolumna chitinilytica sp. nov., a chitin-decomposing anaerobic bacterium isolated from anoxic soil subjected to biological soil disinfestation

An obligately anaerobic bacterial strain (CTTW^T) belonging to the family Lachnospiraceae within the class Clostridia was isolated from an anoxic soil sample subjected to biological or reductive soil disinfestation. Cells of the strain were Gram-stain-positive, short rods with peritrichous flagella. The strain was saccharolytic and decomposed polysaccharides, chitin, xylan and β-1,3-glucan. Strain CTTW^T decomposed cell biomass and cell-wall preparations of an ascomycete plant pathogen, Fusarium oxysporum f. sp. spinaciae. The strain produced acetate, ethanol, H₂ and CO₂ as fermentation products from the utilized substrates. The major cellular fatty acids of the strain were C_16 : 1 ω7c dimethylacetal (DMA), C_16 : 0 DMA and C_18 : 1 ω7c DMA. The closely related species of strain CTTW^T based on the 16S rRNA gene sequences were species in the genus Anaerocolumna with sequence similarities of 95.2-97.6 %. Results of genome analyses of strain CTTW^T indicated that the genome size of the strain was 5.62 Mb and the genomic DNA G+C content was 38.3 mol%. Six 16S rRNA genes with five different sequences from each other were found in the genome. Strain CTTW^T had genes encoding chitinase, xylanase, cellulase, β-glucosidase and nitrogenase as characteristic genes in the genome. Homologous genes encoding these proteins were found in the genomes of the related Anaerocolumna species, but the genomic and phenotypic properties of strain CTTW^T were distinct from them. Based on the phylogenetic, genomic and phenotypic analyses, the name Anaerocolumna chitinilytica sp. nov., in the family Lachnospiraceae is proposed for strain CTTW^T (=NBRC 112102^T=DSM 110036^T).