Oxysporum Strains Research Articles

Diversity and pathogenicity of the Fusarium fungi occurred in soybean mycobiota

The aim of present study was to reveal the species composition of Fusarium fungi found in the soybean mycobiota from the various origins of Russia, as well as to characterize physiological and biochemical properties of isolates. Identi cation of the taxonomic status of 21 Fusarium strains isolated from seeds, stems and roots of soybeans was clari ed according to data using phylogenetic analysis of the nucleotide sequences of the gene of translation elongation factor 1α. Five fungal species have been identi ed: F. oxysporum (11 strains), F. equiseti (4), F. proliferatum (3), F. solani (2), as well one strain of F. commune, which was identi ed for the rst time in soybean mycobiota in Russia. The morphological and cultural characteristics of the isolates and their pathogenicity to leaves of two soybean varieties in the laboratory conditions were also analyzed. At the cultivation of Fusarium fungi on potato- sucrose agar medium, the optimal temperature range for the growth of all isolates has been established as 25-30 °C, at which the largest colony diameter 68,5-74,0 mm was found in F. equiseti and F. commune strains, and the smallest colonies (49,5-55,8 mm) was detected in F. solani strains. Three F. oxysporum strains and one F. commune strain, isolated from the stems, were characterized by high pathogenicity to the leaves of two soybean varieties. These strains caused the necrosis of leaves of the Isidor variety in the range of average length 16,7-21,7 mm, and the necrosis of leaves of the Selecta 201 variety in the range of 10,7-23,3 mm. At the same time, the most of the analyzed Fusarium strains (52-67 % depending on the soybean variety) were non-pathogenic. A high intraspeci c variability of pathogenicity to soybean leaves was noted among F. oxysporum and F. proliferatum strains

A microbial bioherbicide for Striga hermonthica control: production, development, and effectiveness of a seed coating agent.

Witchweed (Striga hermonthica), also called striga, is a parasitic weed that causes high yield losses in maize on more than 200 000 ha in Kenya alone. A new commercial, biological herbicide developed in Kenya is able to control striga effectively. The product was approved for use by the Pest Control Products Board in Kenya in September, 2021. It is self-produced in villages using a secondary inoculum provided by a commercial company. The formulated product has some disadvantages, which are a complicated production process, a very short shelf life and high application rate. Additionally, the product has to be applied manually and therefore can only be used in manual production, leaving out the opportunity for farmers using mechanization. For this reason, efforts have been made to formulate the active ingredient Fusarium oxysporum f. sp. strigae strain DSM 33471, as a powder and to use it as a seed coating agent. This article deals with the production of the Fusarium spore powder, its properties, its application to the seed, and its herbicidal effect demonstrated in the first two field trials. The F. oxysporum strain was originally isolated from a wilting striga plant in Kenya. The strain was virulence enhanced to over produce the amino acids leucine, methionine and tyrosine. These amino acids are responsible for a second mode of action apart from the wilting causing effect of the fungus on striga. Whereas leucine and tyrosine have a herbicidal effect, ethylene from methionine triggers the germination of striga seeds in the soil. Additionally, the strain has been improved to be resistant to the fungicide captan, which is commonly used to treat maize seed in Kenya. Seed coating tests conducted on 25 striga-infested small holder farms spread out in six counties of western Kenya reported yield increases of up to 88%. A second trial carried out by the Kenyan Agricultural and Livestock Research Organization showed a 93% reduction of emerged striga plants. © 2023 Society of Chemical Industry.

Induced Expression of CYP51a and HK1 Genes Associated with Penconazole and Fludioxonil Resistance in the Potato Pathogen Fusarium oxysporum.

Preventing antifungal resistance development and identifying pathogens with high, medium, and low risk of resistance development to a particular fungicide or fungicide class is crucial in the fight against phytopathogens. We characterized the sensitivity of potato wilt-associated Fusarium oxysporum isolates to fludioxonil and penconazole and assessed the effect of these fungicides on the expression of fungal sterol-14-α-demethylase (CYP51a) and histidine kinase (HK1) genes. Penconazole stunted the growth of F. oxysporum strains at all concentrations used. While all isolates were susceptible to this fungicide, concentrations of up to 1.0 μg/mL were insufficient to cause a 50% inhibition. At low concentrations (0.63 and 1.25 μg/mL), fludioxonil stimulated growth in F. oxysporum. With an increase in the concentration of fludioxonil, only one strain (F. oxysporum S95) exhibited moderate sensitivity to the fungicide. Interaction of F. oxysporum with penconazole and fludioxonil leads to respective elevated expressions of the CYP51a and HK1 genes, which upsurge with increasing concentration of the fungicides. The data obtained indicate that fludioxonil may no longer be suitable for potato protection and its continuous use could only lead to an increased resistance with time.

Genome Sequence Resource of Fusarium oxysporum Strain PkF01: The Causative Agent of Rhizome Rot of Polygonatum kingianum

Fusarium oxysporum strain PkF01 is the causal agent of Polygonatum kingianum rhizome rot. Here, we report, for the first time, the genome assemblies of the F. oxysporum strain PkF01 using the PacBio Sequel system. We obtained a total base number of 51.27 Mb in 87 contigs. The number of scaffolds and scaffold N50 were 86 and 2.46 Mb, with a 47.55% GC content. The number of coding sequences was 17,265, with total length of 36.61 Mb, average length of 1.77 kb, and a gene density of 0.34 kb. A total of 11,447, 14,734, 10,759, and 4,434 genes were annotated using the Pfam, COG, GO, and KEGG databases, respectively. A total of 764, 335, 1,572, 216, 4,245, 1,591, 2,242, and 1,926 genes were annotated using the CAZy, CYP450, DFVF, CARD, PHI, SignalP, TCDB, and TMHMM databases, respectively. Collinearity analysis showed that the PkF01 genome shared more homologous genomic regions with F. oxysporum f. sp. lilii strain Fol39 than with F. oxysporum f. sp. lycopersici strain Fol4287, indicating that the PkF01 genome is more closely related to the Fol39 rather than the Fol4287 genome. The high-quality genome sequences of PkF01 will provide a valuable resource for not only investigating both the pathogenicity mechanism and host specificity in F. oxysporum but also exploring disease control measures. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Fungal species characterization associated with vanilla root rot in the Totonacapan, Veracruz, Mexico

Vanilla (Vanilla planifolia) is a crop of great biocultural importance in the Totonacapan region in Mexico; however, producers face various phytosanitary problems that decrease production. The main one being crop loss caused by the fungus, Fusarium oxysporum f. sp. vanillae, a pathogen that causes a disease whose symptomatology is root rot that in severe cases causes the death of plants. Therefore, the study of the pathogen is crucial, due to the scarcity of genetic variability of vanilla, a condition that makes the crops equally susceptible to the pathogen. The present work aimed to generate and molecularly and pathogenically characterize a fu-ngal isolates collection obtained from V. planifolia with root rot. Roots with rot were collected in six municipalities of the Totonacapan region, for fungal isolation, a semiselective culture medium was used, later, the molecular characterization was carried out through the amplification and sequencing of the partial region of the translational elongation factor 1α gene (TEF1). The pathogenic characterization was carried out on vanilla leaves in a humid chamber, inoculating medium discs with mycelium, and making observations for 18 days every 48 h. As results, 94 strains were obtained, of which 81 belong to the genus Fusarium (42 F. oxysporum strains), eight to Colletotrichum, three to Trichoderma and two it was not possible to identify them, only 23 Fusarium oxysporum strains showed to be pathogenic on vanilla leaves with different degrees of virulence. The results of the molecular and pathogenic characterization will be crucial for further studies of comparative genomics of Fusarium oxysporum.

Differential Colonization of the Plant Vasculature Between Endophytic Versus Pathogenic Fusarium oxysporum Strains.

Plant xylem colonization is the hallmark of vascular wilt diseases caused by phytopathogens within the Fusarium oxysporum species complex. Recently, xylem colonization has also been reported among endophytic F. oxysporum strains, resulting in some uncertainty. This study compares xylem colonization processes by pathogenic versus endophytic strains in Arabidopsis thaliana and Solanum lycopersicum, using Arabidopsis pathogen Fo5176, tomato pathogen Fol4287, and the endophyte Fo47, which can colonize both plant hosts. We observed that all strains were able to advance from epidermis to endodermis within 3 days postinoculation (dpi) and reached the root xylem at 4 dpi. However, this shared progression was restricted to lateral roots and the elongation zone of the primary root. Only pathogens reached the xylem above the primary-root maturation zone (PMZ). Related to the distinct colonization patterns, we also observed stronger induction of callose at the PMZ and lignin deposition at primary-lateral root junctions by the endophyte in both plants. This observation was further supported by stronger induction of Arabidopsis genes involved in callose and lignin biosynthesis during the endophytic colonization (Fo47) compared with the pathogenic interaction (Fo5176). Moreover, both pathogens encode more plant cell wall-degrading enzymes than the endophyte Fo47. Therefore, observed differences in callose and lignin deposition could be the combination of host production and the subsequent fungal degradation. In summary, this study demonstrates spatial differences between endophytic and pathogenic colonization, strongly suggesting that further investigations of molecular arm-races are needed to understand how plants differentiate friend from foe. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Gliocladium catenulatum саңырауқұлақтан алынған экстракттың Botrytis cinerea және Fusarium оxysporumфитопатогендерінеантифунгалдық әсері

This article discusses the antifungal property of the Gliocladium catenulatum extraction on widespread phytopathogenic fungi of agricultural crops in Northern Kazakhstan as Botrytis cinerea and Fusarium Oxysporum. As a result of studies, this micromycete-antagonist isolated from the root of healthy strawberry Gliocladium catenulatum showed high antifungal activity, supressio zone 35±0.05 mm. It was revealed that Fusarium Oxysporum strains are more sensitive compared to Botrytis cinerea. For example, with optimal dilution of the extract 30 times, on average the suppression zone in Fusarium Oxysporumshowed 26±0.03 mm, whereas in Botrytis cinerea 24±0.03 mm.The optimal condition (nutrient medium, temperature, carbohydrate use, pH medium) for intensive growth and development of Gliocladium catenulatum producer by surface cultivation method was determined.The aim of the research is to evaluate the fungicidal property of Gliocladium catenulatum against Botrytis cinerea and Fusarium оxysporum and further use this micromycete as a biological preparation against phytopathogenic fungi to increase crop yields.

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.

Physiological race characterisation of Fusarium oxysporum strains infecting tomato employing candidate pathogenicity genes and host resistance.

Physiological races of 14 strains of Fusarium oxysporum f.sp. lycopersici were established by PCR profiling SIX gene expressions. No amplification of the SIX4 (Avr1) gene was observed in any of the 14 strains. Based on amplification of the SIX3 (Avr2) gene, 6 strains were distinguished as race 2. Race 2 strains are known to contain identical SIX3 sequences and differ from race 3 strains by single point mutations. Hence, based on polymorphic amplicons of the SIX3 gene detected by stringent PCR conditions, 8 strains were identified as race 3. The identity of the physiological races of the strains was validated by inoculating on three germplasm lines, EC-814916, FEB-2 and Pusa Rohini carrying I-2, I-3 and no I gene, respectively. The race 2 and race 3 strains were avirulent on EC-814916 and FEB-2 lines, respectively. All the 14 fungal strains were pathogenic on Pusa Rohini, the Fusarium wilt susceptible cultivar lacking R genes and exhibited different levels of virulence. In evaluating two other potential pathogenicity genes, Fow1 and Fow2 as markers for virulence, their expressions were observed among both the races of the Fol strains, and hence are not potential candidates for physiological race discrimination. However, strong expressions of the genes in the root tissues inoculated with the highly virulent strain, TOFU-IHBT in comparison to the uninoculated control indicated their roles in fungal pathogenicity. To understand the role of these pathogenicity genes in countering the host defence mechanisms, their expressions in response to ROS and phenolics, the earliest known defence mechanisms of host plants were assessed. In H2O2, the Fow2 gene expressed 1.4-fold greater than that of the control. On the contrary, in relation to the control, the expressions of Fow1 were strongly repressed exhibiting 0.7-to 0.8-fold lesser at 0.1 mM through 3 mM concentrations than that of the control indicating that the gene is modulated by the phenolic acid indicating the roles of Fow2 and Fow1 in alleviating oxidative stress and targeted by the phenolic acid, respectively.

Pathogenicity study of Rhizoctonia solani and its integrated management on different crop species in Morocco

In this work, we aimed to develop an ecofriendly strategy to manage the R. solani damping-off incidence of Moroccan strains. After the assessment of damping-off incidence on different crops, a greenhouse experiments were carried out to assess the efficiency of chemical and biological agents on plant growth and damping-off control. Results revealed that R. solani MN191236 strain was the most virulent as it dramatically increased severity indexes and reduced root length and pods number by 23% and 58% respectively. On R. solani-infested bean seedlings, Trichoderma asperellum increased pods number by 169% and reduce the severity index up to 1.33. However, the Tolclofos-methyl and the hypovirulent F. oxysporum strain came in second place. The efficiency of chemical or biological agents was significantly related to the interaction ‘pathogenic strains*fungicide or biological agents’. These results are promising in term of integrally and eco-friendly management of R. solani damping-off.

Surveillance, Diversity and Vegetative Compatibility Groups of Fusarium oxysporum f. sp. vasinfectum Collected in Cotton Fields in Australia (2017 to 2022)

Cotton (Gossypium hirsutum) is a billion-dollar crop in regional New South Wales (NSW) and Queensland, Australia. Fusarium wilt (FW) caused by Fusarium oxysporum f. sp. vasinfectum (Fov) is an economically important disease. Initial disease losses of up to 90% when the disease was first detected resulted in fields being taken out of cotton production. The disease is now well-managed due to the adoption of highly resistant varieties. However, annual disease surveys recently revealed that the disease dynamic has changed in the past few seasons. With relatively mild and wet weather conditions during the 2021/22 growing season, FW was detected in eight surveyed valleys in NSW and Queensland, with the disease incidence as high as 44.5% and 98.5% in individual fields in early and late seasons, respectively. Fov is genetically distinct and evolved from local Fusarium oxysporum strains. Additionally, the pathogen was reported to evolve rapidly under continuous cotton cropping pressure. However, our knowledge of the genetic composition of the prevailing population is limited. Sequences of the translation elongation factor alpha 1 (TEF1) revealed that 94% of Fusarium isolates recovered from FW-infected cotton were clustered together with known Australian Fov and relatively distant related to overseas Fov races. All these isolates, except for nine, were further confirmed positive with a specific marker based on the Secreted in Xylem 6 (SIX6) effector gene. Vegetative compatibility group (VCG) analyses of 166 arbitrarily selected isolates revealed a predominance of VCG01111. There was only one detection of VCG01112 in the Border Rivers valley where it was first described. In this study, the exotic Californian Fov race 4 strain was not detected using a specific marker based on the unique Tfo1 insertion in the phosphate (PHO) gene. This study indicated that the prevalence and abundance of Fov across NSW and Queensland in the past five seasons was probably independent of its genetic diversity.

Untargeted 1 H-NMR Metabolome of Celery During Fusarium Wilt: Implications for Vegetable Quality.

Celery is a vegetable widely consumed as a condiment to prepare diverse dishes around the world. Nevertheless, this plant is susceptible to the attack of several phytopathogens including those of the Fusarium genus which is translated into devastating losses for the production chain. Herein we report on the metabolic changes produced during the celery wilt caused by Fusarium oxysporum which was determined through untargeted 1 H-NMR metabolomics. The changes in the metabolite content of celery were measured at 16, 24, and 32 days post-inoculation using viable conidia obtained from the native F. oxysporum strain FO3. Our results demonstrated that the parasitic activity of the fungus reduced the endogenous levels of free sugars (fructose, galactose, glucose isomers, mannose, Myo-inositol, mannitol, and sucrose) amino acids (alanine, aspartate GABA, glutamate, glutamine, histidine, isoleucine, leucine, methionine, proline, threonine, tyrosine, and valine), nucleosides (adenosine, cytidine, guanosine, and uridine) and organic acids (citric acid, fumaric acid, malic acid, and succinic acid). Interestingly, the levels of tyrosine and tryptophan were triggered as a consequence of F. oxysporum infection. This tendency was correlated with an increase in the levels of chlorogenic acid, apiin, and apigenin derivatives, suggesting their involvement in the chemical defense of celery against fungal colonization. According to principal component analysis (PCA) and Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) methanol was the main differential metabolite and it was considered as a new chemical marker associated with F. oxysporum infection. Our results demonstrate that infected celery plants dramatically reduced their nutritional and nutraceutical contents during Fusarium wilt after 32 days post-inoculation. However, these findings also suggest that the phenylpropanoid pathway is strongly related with the chemical defense of celery against F. oxysporum.

Fusarium oxysporum f. sp. ginseng, a new forma specialis causing Fusarium root rot of Panax ginseng

Panax ginseng is a valuable medicinal plant which is affected by many diseases during its long cultivation period. Ginseng root rot, caused by Fusarium oxysporum, has become severe in China. This soilborne pathogen comprises many formae speciales based on host specificity. Ten representative isolates from diseased ginseng rot root showed pathogenicity on ginseng. To identify the forma specialis of the F. oxysporum strains, host range tests of three representative isolates were carried out on nine plant species. All three isolates caused severe symptoms only on ginseng, but only slight or no visual symptoms on the other eight hosts, indicating that the strains were host-specific to ginseng. Phylogenetic trees were constructed based on sequences of the translation elongation factor 1-α (EF-1α) gene, two endopolygalacturonase genes (Pg1, Pg5) and two exopolygalacturonase genes (Pgx1 and Pgx4). The ten F. oxysporum isolates from ginseng clustered into a unique group clearly separated from other formae speciales already described. Based on the host range tests and phylogenetic analyses, the isolates of F. oxysporum derived from ginseng have been identified as a new forma specialis, designated Fusarium oxysporum f. sp. ginseng. This is the first report of forma specialis of F. oxysporum on ginseng.

Invasion and Colonization of Pathogenic Fusarium oxysporum R1 in Crocus sativus L. during Corm Rot Disease Progression.

The corm rot of saffron caused by Fusarium oxysporum (Fox) has been reported to be the most destructive fungal disease of the herb globally. The pathogen, Fusarium oxysporum R1 (Fox R1) isolated by our group from Kashmir, India, was found to be different from Fusarium oxysporum f.sp. gladioli commonly reported corm rot agent of saffron. In the present study, Fox R1 was further characterized using housekeeping genes and pathogenicity tests, as Fusarium oxysporum R1 f.sp. iridacearum race 4. Though Fox R1 invaded the saffron plant through both corm and roots, the corm was found to be the preferred site of infection. In addition, the route of pathogen movement wastracked by monitoring visual symptoms, semi-quantitative PCR, quantitative-PCR (q-PCR), real-time imaging of egfp-tagged Fusarium oxysporum R1, and Fox R1 load quantification. This study is the first study of its kind on the bidirectional pathogenesis from corm to roots and vice-versa, as the literature only reports unidirectional upward movement from roots to other parts of the plant. In addition, the colonization pattern of Fox R1 in saffron corms and roots was studied. The present study involved a systematic elucidation of the mode and mechanism of pathogenesis in the saffron Fusarium oxysporum strain R1 pathosystem.

Molecular Characterization of Fusarium and Screening of Cowpea [Vigna unguiculata (L.) Walp.] Germplasms against Fusarium Wilt (Fusarium oxysporum f. sp. Tracheiphilum)

Background: Fusarium wilt caused by fungal pathogen, Fusarium oxysporum is one of the soil-borne diseases that cause 30 to 100% yield reduction with high plant mortality and severe problem in cowpea production. Methods: The Fusarium spp. isolate was obtained from infected cowpea plants and morphological and molecular characterization were done using universal primers. Similarity and phylogenetic evolutionary relationship analysis were performed with database. The fusarium wilt symptoms occurrence in each germplasm were scored using disease rating scale by artificial inoculation of 10% culture. Result: Isolated Fusarium spp. was an anamorphic species with medium growth rate (5 mm/day), characterised by white cottony to pinkish colonies, aseptate microconidia (12.879×3.570 µm) with false head, septate macroconidia (32.409×5.297 µm) along with chlamydospores. While, 90-100% homology was observed between isolate (Accession no: MZ706473) and fusarium reference database. Phylogenetic evolutionary analysis showed that the isolate was closely related to F. oxysporum (OL679453.1) strain supported by 52% bootstrap. Artificial screening of 115 cowpea germplasm under pot culture, identified 18 resistant lines with 0% symptoms. The wilting intensity was maximum during flowering or pod stage than seedling stage in cowpea. The identified resistant cowpea varieties could be used as donor parent in future resistant breeding programmes.

Fusarium oxysporum effector clustering version 2: An updated pipeline to infer host range.

The fungus Fusarium oxysporum is infamous for its devastating effects on economically important crops worldwide. F. oxysporum isolates are grouped into formae speciales based on their ability to cause disease on different hosts. Assigning F. oxysporum strains to formae speciales using non-experimental procedures has proven to be challenging due to their genetic heterogeneity and polyphyletic nature. However, genetically diverse isolates of the same forma specialis encode similar repertoires of effectors, proteins that are secreted by the fungus and contribute to the establishment of compatibility with the host. Based on this observation, we previously designed the F. oxysporum Effector Clustering (FoEC) pipeline which is able to classify F. oxysporum strains by forma specialis based on hierarchical clustering of the presence of predicted putative effector sequences, solely using genome assemblies as input. Here we present the updated FoEC2 pipeline which is more user friendly, customizable and, due to multithreading, has improved scalability. It is designed as a Snakemake pipeline and incorporates a new interactive visualization app. We showcase FoEC2 by clustering 537 publicly available F. oxysporum genomes and further analysis of putative effector families as multiple sequence alignments. We confirm classification of isolates into formae speciales and are able to further identify their subtypes. The pipeline is available on github: https://github.com/pvdam3/FoEC2.

The secreted FoAPY1 peptidase promotes Fusarium oxysporum invasion.

The secretion of peptidases from several pathogens has been reported, but the biological function of these proteins in plant-pathogen interactions is poorly understood. Fusarium oxysporum, a soil-borne plant pathogenic fungus that causes Fusarium wilt in its host, can secrete proteins into host plant cells during the infection process to interfere with the host plant defense response and promote disease occurrence. In this study, we identified a peptidase, FoAPY1, that could be secreted from F. oxysporum depending on the N-terminal signal peptide of the protein. FoAPY1 belongs to the peptidase M28 family and exerts peptidase activity in vitro. Furthermore, the FoAYP1 gene knockout strain (∆FoAYP1) presented reduced virulence to tomato plants, but its mycelial growth and conidiation were unchanged. Moreover, FoAYP1 overexpression tomato seedlings exhibited enhanced susceptibility to F. oxysporum and Botrytis cinerea strains. These data demonstrated that FoAYP1 contributes to the virulence of F. oxysporum may through peptidase activity against host plant proteins.

Research of ivermectin influence on Fusarium graminearum and F. oxysporum

Aim. Determination of the ivermectin influence on plant pathogenic species of Fusarium genus; particularly, F. graminearum and F. oxysporum. Methods. The susceptibility of studied strains (F. graminearum F-55756 and F. oxysporum F-54635) to ivermectin was measured in vitro with the agar diffusion method. Ivermectin in concentrations from 0 to 3 mg/ml was poured into the wells made in media for that purpose. Further, mycelial discs of F. graminearum and F. oxysporum strains were placed into the central regions of Petri dishes, which were then maintained in the dark at 25 °C. Ivermectin influence on growth and morphology of studied strains was estimated after the 7 days using the ImageJ software and methods of statistical analysis to determine the most effective concentrations. Results. As the result, it was found that at 1 mg/ml concentration and above the fungistatic effect is observed and the 3 mg/ml concentration appeared to be the most effective one. Thus, the percentage of mycelium area in comparison with control at this concentration was 83,91 % for F. graminearum F-55756 and 69,95 % for F. oxysporum F-54635. Conclusions. The ivermectin effective fungistatic action on the studied strains was observed giving the reason for further analysis of the ivermectin influence on other strains of Fusarium complex species and search of molecular targets of its action.

Fusarium oxysporum Associated with Fusarium Wilt on Pennisetum sinese in China.

Pennisetum sinese, a versatile and adaptable plant, plays an essential role in phytoremediation, soil reclamation, and fodder production. From 2018 to 2021, the occurrence of Fusarium wilt, with symptoms of foliar blight and internal discoloration of the stem, was observed in Chongqing, China. Pathogens were isolated from the symptomatic leaves. Based on morphological characteristics as well as DNA sequences of the 18S ribosomal RNA (SSU), translation elongation factor 1-α (EF1-α), RNA polymerase II subunit 1 (rpb1), and RNA polymerase II second largest subunit (rpb2) genes, the causal agents were identified as Fusarium oxysporum. Phylogenetic analysis of the combined dataset of EF1-α, rpb1 and rpb2 showed that pathogenic isolates clustered with F. oxysporum strains. The pathogen was reisolated from inoculated and diseased tissues; thus, Koch’s postulates were fulfilled. This is the first report of F. oxysporum causing Fusarium wilt on P. sinese in China and worldwide.

Comparative transcriptome analysis reveals that ATP synthases regulate Fusarium oxysporum virulence by modulating sugar transporter gene expressions in tobacco.

Fusarium oxysporum is a main causative agent of tobacco root rot, severely affecting tobacco growth. Here, 200 F. oxysporum strains were isolated and examined for their virulence toward tobacco plants. These strains were divided into disease class 1–3 (weak virulence), 4–6 (moderate virulence), and 7–9 (strong virulence). To understand the virulence mechanism of F. oxysporum, a comparative transcriptome study was performed using weak, moderate, and strong virulence-inducing strains. The results showed that expression levels of 1,678 tobacco genes were positively correlated with virulence levels, while expression levels of 3,558 genes were negatively associated with virulence levels. Interestingly, the expression levels of ATP synthase genes were positively correlated with F. oxysporum virulence. To verify whether ATP synthase gene expression is associated with F. oxysporum virulence, 5 strains each of strong, moderate, and weak virulence-inducing strains were tested using qRT-PCR. The results confirmed that ATP synthase gene expression is positively correlated with virulence levels. Knock-out mutants of ATP synthase genes resulted in a relatively weak virulence compared to wild-type as well as the inhibition of F. oxysporum-mediated suppression of NtSUC4, NtSTP12, NtHEX6, and NtSWEET, suggesting that ATP synthase activity is also associated with the virulence. Taken together, our analyses show that ATP synthases are key genes for the regulation of F. oxysporum virulence and provide important information for understanding the virulence mechanism of F. oxysporum in tobacco root rot.