Stem canker and wilt of delphinium caused by Fusarium oxysporum f. sp. delphinii in Japan

Stem canker and severe wilt were observed on delphinium plants (Delphinium elatum) in Aomori Prefecture, Japan, in 2008. The fungus isolated from the diseased crown was identified as Fusarium oxysporum f. sp. delphinii on the basis of morphological characteristics, nucleotide sequences, and host range. The isolate induced similar stem canker and wilt symptoms in inoculated delphinium plants. We propose the name “stem canker and wilt” for the disease.     

Physiological races and soil population level of fusarium wilt of watermelon

Results of a comparative test oflocal isolates ofFusarium oxysporum f. sp.niveum with isolates from abroad indicate the existence of a highly virulent race of this fungus in Israel. All these isolates were found also pathogenic to resistant cultivars from the U.S.A. When inoculum density was tested, a one-hundredfold higher fungus population was required for extensive wilt of watermelon seedlings in freshly infested sterilized soil compared with the same soil kept dry for three months. In naturally infested soil, where almost 100% of the plants were infected toward the end of the season, the lowest count of the fungus population (400 propagules/g soil) was comparable to the inoculum density required for total wilt of watermelon seedlings in infested sterilized soil.     

Comparative proteomic analysis of cucumber roots infected by Fusarium oxysporum f. sp. cucumerium Owen

Cucumber Fusarium wilt (CFW), caused by the soil-borne fungus Fusarium oxysporum f. sp. cucumerium, is a serious disease in cucumber (Cucumis sativus) production worldwide. For the efficient control of the pathogenic fungi, a better understanding of its interaction and associated resistance mechanisms at the molecular level is required. Here, we report a comparative proteomics analysis of total root protein isolated from infected cucumber root of susceptible bulk (SB) and resistant bulk (RB) of cucumber generation F2. Two-dimensional gel electrophoresis (2-DE) coupled with MS/MS approaches identified 15 over-accumulated proteins from the RB plants. Identified proteins are mainly involved in defense and stress responses, oxidation reduction, metabolism and transport and other process. These proteins are likely to be a part of resistance-related protein network, playing different roles in cucumber disease resistance. Three vital clues regarding wilt resistance of C. sativus are gained from this study. First, jasmonic acid and redox signaling components were found in response to F. oxysporum infection in resistant plants. Second, the LRR family protein may play an important role in the defense reaction against CFW. Third, biotic and abiotic stress-related proteins were induced by the CFW fungus F. oxysporum, indicating the activation of common stress pathway.     

Quantification of Root and Stem Colonization of Watermelon by Fusarium oxysporum f. sp. niveum and Its Use in Evaluating Resistance

ABSTRACT Colonization of watermelon root and stem tissues by Fusarium oxysporum f. sp. niveum race 1 and its relationship to the apparent resistance to Fusarium wilt was investigated. In each of 2 years, 17 differentially susceptible watermelon cultivars and one accession were tested in the greenhouse, and 7 cultivars also were tested in the field. Colonization by a chlorate-resistant marked isolate of the fungus was assayed by plating homogenized tissue samples on a selective medium. Six days after inoculation, seedlings of highly resistant, moderately resistant, and susceptible cultivars had F. oxysporum f. sp. niveum race 1 CFU counts in the lower stems of 10(2), 10(3), and 10(4) CFU/g of fresh tissue, respectively. Percent wilt (Y) of the seedlings was positively correlated with colonization (X) by F. oxysporum f. sp. niveum race 1 in roots (Y = 21.2 ln [X + 1] - 140.7, R(2) = 0.85) or lower stems (Y = 17.3 ln [X + 1] - 78.6, R(2) = 0.86). Percent wilt (Y) also was correlated with the ratio (X(r), 0 to 1 values) of lower stem to root colonization (Y = 34 ln X(r) + 112, R(2) = 0.36). Field evaluations confirmed these relationships, and a link between cultivar resistance and a reduced rate of spread of the fungus in primary stems during a season was observed. Fruit yield decreased with increased tissue colonization at linear rates of 9.9 to 12.7 t/ha per ln (CFU/g + 1) (R(2) >/= 0.58). The greenhouse seedling stem colonization assay described may be utilized as a collaborative method to quantify Fusarium wilt resistance in watermelon.     

Back to the roots: Understanding banana below-ground interactions is crucial for effective management of Fusarium wilt

Global banana production is affected by Fusarium wilt, a devastating disease caused by the soilborne root-infecting fungus, Fusarium oxysporum f. sp. cubense (Foc). Fusarium wilt is notoriously difficult to manage because infection arises through complex below-ground interactions between Foc, the plant, and the soil microbiome in the root–soil interface, defined as the rhizosphere. Interactions in the rhizosphere play a pivotal role in processes associated with pathogen development and plant health. Modulation of these processes through manipulation and management of the banana rhizosphere provides an auspicious prospect for management of Fusarium wilt. Yet, a fundamental understanding of interactions in the banana rhizosphere is still lacking. The objective of this review is to discuss the state-of-the-art of the relatively scant data available on banana below-ground interactions in relation to Fusarium wilt and, as a result, to highlight key research gaps. Specifically, we seek to understand (a) the biology of Foc and its interaction with banana; (b) the ecology of Foc, including the role of root-exuded metabolites in rhizosphere interactions; and (c) soil management practices and how they modulate Fusarium wilt. A better understanding of molecular and ecological factors influencing banana below-ground interactions has implications for the development of targeted interventions in the management of Fusarium wilt through manipulation of the banana rhizosphere.     

Suppressive effect of secondary metabolites from Streptomyces plumbeus isolate F31D against Fusarium oxysporum f. sp. lycopersici,the causal agent of Fusarium wilt of tomato

Journal of General Plant Pathology - Fusarium wilt of tomato, a disease caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici, causes major losses to tomato production. Chemical...     

Molecular diversity in <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> isolates from common bean fields in Brazil

The common bean (Phaseolus vulgaris L.) is widely cultivated in Brazil and is known as a very important crop for families in this country. Fusarium wilt severely harms common beans and has become a big issue for this crop. In order to assist the breeding programs that target resistance to this disease, the evaluation of genetic diversity of the pathogen and its molecular characterization are crucial. Thus, the present goal was to identify Fusarium isolates obtained from several places in Brazil using molecular tools; select molecular markers for these isolates; and analyze their diversity. All of isolates were molecularly identified as Fusarium oxysporum f. sp. phaseoli (Fop). By using seven selected SSR markers, the results of diversity obtained by the dendrogram and the Bayesian analysis formed four groups where a large diversity of this fungus was found within each state. However, the groups were more homogenous according to the collection source and the pathogenicity test. More specifically, group 2 was composed of the most virulent strains and originated from Minas Gerais State – UFV, and group 3 was mostly composed by isolates from Goias state. Group I was also more diverse in terms of location and virulence. The overall results indicated a positive correlation between Fusarium diversity and its virulence to common bean. Furthermore, the use of these markers was effective in molecular identification and in detecting polymorphism within F. oxysporum f. sp. phaseoli.     

Detection and quantification of Fusarium oxysporum f. sp. cucumerinum in environmental samples using a specific quantitative PCR assay

The rapid and reliable identification and quantification of pathogens is essential for the management of economically important plant diseases. Fusarium oxysporum f. sp. cucumerinum is the soil borne fungus responsible for Fusarium vascular wilt of cucumber. In this study, we report the development of a specific and reliable real-time quantitative PCR assay and the development of an ultra-sensitive diagnostic pseudo-nested PCR assay. The capacity of the PCR assays to accurately identify and quantify Fusarium oxysporum f. sp. cucumerinum was experimentally tested by the development of standard curves from serial dilutions of copy numbers in a range of complex environmental DNA samples. The amplification efficiency, sensitivity and reproducibility of the qPCR assays were not significantly affected by the presence of any of the non-target background DNA tested. In quantitative real-time PCR, as few as 100 copies could be reliably quantified, and in simple and pseudo-nested PCR as little as 10 pg and 10 fg, respectively, could be detected. This rapid and sensitive qPCR method can be used to facilitate investigations into plant–pathogen interactions, epidemiology, and disease management practices.     

Development of a loop-mediated isothermal amplification assay for rapid and sensitive detection of Fusarium oxysporum f. sp. cubense race 4

Fusarium wilt (Panama disease), caused by the fungus Fusarium oxysporum f. sp. cubense race 4 (Foc race 4), is one of the most destructive diseases affecting banana (Musa). Early and accurate detection of Foc race 4 is essential to protect the banana industry. We developed a novel and highly specific loop-mediated isothermal amplification (LAMP) assay for the detection of Foc race 4 based on a SCAR marker sequence. The detection limit for this assay was 10 fg per 25 μl reaction in pure culture and DNA amplification was completed within 60 min. The assays detected 69 different isolates of Foc race 4 from geographically distinct counties in China, and no cross-reaction was observed with other fungal pathogens. When 26 infected and eight healthy looking but infested banana samples naturally from different fields were examined, the detection rate of LAMP was 100 %. The LAMP assay developed in this study was simple, fast, sensitive, and specific, and can be used in the field to detect Foc race 4 in infected banana plant tissue in resource-poor settings.     

Comparative abilities of fungi pathogenic and nonpathogenic to bean (Phaseolus vulgaris) to metabolize phaseollin

The abilities of fungi pathogenic and nonpathogenic to bean (Phaseolus vulgaris) to metabolize the phytoalexin phaseollin were compared when grown in shake cultures containing 12 to 15 μg phaseollin/ml. Under these conditions phaseollin was metabolized by five out of seven pathogens and by three out of five nonpathogens. Disappearance of phaseollin was accompanied by the appearance of metabolic products in cultures ofFusarium solani f. sp.phaseoli, Colletotrichum lindemuthianum, Botrytis cinerea andCladosporium herbarum. The nonpathogenC. herbarum detoxified phaseollin to 1a-hydroxyphaseollone as rapidly as the pathogenF. solani f.sp.phaseoli. Phaseollin was converted to 6a-hydroxyphaseollin by the pathogensB. cinerea andC. lindemuthianum, and this product was further metabolized by the latter fungus. 6a-Hydroxyphaseollin was less fungitoxic toB. cinerea. C. lindemuthianum was equally sensitive to both compounds. Phaseollin was not metabolized by the pathogensFusarium oxysporum f. sp.phaseoli andThielaviopsis basicola.     

Fusarium rosicola sp. nov. causing vascular wilt on Rosa chinensis

Chinese rose (Rosa chinensis) is one of the most popular and widely cultivated flowers worldwide and has extremely high economic and ornamental value. In 2020 wilt disease on R. chinensis was discovered in Pukou District, Nanjing, Jiangsu Province, China. Fungal isolates were obtained from the stems of the rose. According to morphological characteristics and multilocus phylogenetic analyses with the sequences of the rDNA internal transcribed spacer (ITS), translation elongation factor 1-α gene (TEF1-α), and part of the RNA polymerase II gene (RPB2), the isolates YJ1 to YJ4 were determined as a new species of Fusarium solani species complex, and named as Fusarium rosicola sp. nov., which is hereby described and illustrated. Pathogenicity of the isolate YJ1 was verified by Koch's postulates. The fungus was determined as the pathogen causing rose vascular wilt. The isolate YJ1 was labelled with green fluorescent protein (GFP), and roots of R. chinensis were inoculated. The result showed that the fungus infected the vascular tissue of the host plants and caused withering of the above-ground parts, resulting in the death of the whole plant. The GFP-labelled pathogen was reisolated from the stems and foliage, proving that this is a newly emerged systemic disease on R. chinensis in the world.     

A study on the susceptibility of the model legume plant <Emphasis Type="Italic">Medicago truncatula</Emphasis> to the soil-borne pathogen <Emphasis Type="Italic">Fusarium oxysporum</Emphasis>

Fusarium wilt is a soil-borne disease caused by formae specialis of Fusarium oxysporum on a large number of cultivated and wild plants. The susceptibility of the model legume plant Medicago truncatula to Fusarium oxysporum was studied by root-inoculating young plants in a miniaturised hydroponic culture. Among eight tested M. truncatula lines, all were susceptible to F. oxysporum f.sp. medicaginis, the causal agent of Fusarium wilt in alfalfa. However, a tolerant line, F83005.5, and a susceptible line, A17, could be distinguished by scoring the disease index. The fungus was transformed with the GFP marker gene and colonisation of the plant roots was analysed by epifluorescence and confocal microscopy. A slightly atypical pattern of root colonisation was observed, with massive fungal growth in the cortex. Although colonisation was not significantly different between susceptible and tolerant plants, the expression of some defence-related genes showed discrimination between both lines. A study with 10 strains from various host-plants indicated that M. truncatula was a permissive host to F. oxysporum.     

Characterization of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">melongenae</Emphasis> isolates from eggplant in Turkey by pathogenicity,VCG and RAPD analysis

Fusarium wilt is an economically important fungal disease of common eggplant (Solanum melongena) cultivated in the eastern Mediterranean region of Turkey. Seventy-four isolates of Fusarium oxysporum isolated from diseased eggplant displaying typical Fusarium wilt symptoms were screened for pathogenicity on the highly susceptible cv. ‘Pala’. All the isolates tested were pathogenic to eggplant and designated as Fusarium oxysporum f. sp. melongenae (Fomg). Genetic diversity among a core set of 20 Fomg isolates that were selected based upon geographic locations, were characterized by using pathogenicity, vegetative compatibility grouping (VCG), and random amplified polymorphic DNA (RAPD) analysis. The area under the disease progress curve (AUDPC) was calculated for each Fomg isolate until 21 days after inoculation (DAI). The most virulent isolate was identified as Fomg10 based on AUDPC, disease severity and vascular discoloration measurements at 21 DAI. At this date, a good correlation was observed between disease severity and AUDPC values for all isolates (r = 0.73). UPGMA (unweighted pair group method with arithmetic average) cluster analysis of RAPD data using Dice’s coefficient of similarity differentiated all the Fomg isolates tested, and indicated considerable genetic variation among Fomg isolates, but isolates from the same geographic region were grouped together. There was no direct correlation between clustering in the RAPD dendrogram and pathogenicity testing of Fomg isolates. Twenty isolates of Fomg were assigned to VCG 0320.     

Genetic variability among breeding lines and cultivars of eggplant against Fusarium oxysporum f. sp. melongenae from Turkey

Seventy isolates of Fusarium oxysporum (Schlechtend: Fr.) f. sp. melongenae Matuo and Ishigami (Fomg), the causal agent of eggplant Fusarium wilt, were tested for their interaction with different lines and cultivars to determine whether there was race-specific interaction. Also, a total of 13 cultivars were tested under greenhouse conditions to evaluate the presence of resistance to Fusarium wilt. The disease severity (%) and the area under disease progress curve (AUDPC) for each of the Fomg isolates were calculated by scale values. Results showed that neither of the resistant lines (LS1934 and LS2436) exhibited wilting symptoms, whereas susceptible local cultivars (cvs. ‘Kemer’ and ‘Hadrian’) displayed severe disease symptoms. There was no significant variation in the virulence, indicating the occurrence of a race or races among 70 Fomg isolates tested on resistant lines and susceptible cultivars. This may indicate a genetically homogeneous population structure of Fomg in Turkey. The eggplant cultivars Amadeo, Anatolia, Angela, Brigitte, Corsica, Hawk, Koksal, Nouma, Sharapova and Yula exhibited various degrees of susceptibility to three virulent Fomg isolates, but disease severity for AGR-703 was significantly different and lower among the tested eggplant cultivars, as well as rootstocks. Therefore, it is considered as the most appropriate for rootstock purposes in eggplant cultivations where Fusarium wilt is present in the soil.     

Physiological races of Fusarium oxysporum f.sp. melonis in Tunisia

Fusarium wilt of melon, caused by Fusarium oxysporum f.sp. melonis (Fom), is an important disease; races of the pathogen were identified by inoculating differential standard host cultivars. A total of ten isolates that were obtained from 23 fields located in four different geographical regions were identified as pathogenic. Results indicate that all four known Fom races, namely, 0, 1, 2 and 1.2, were found in north and middle Tunisia. Race 1.2 was the most prevalent.     

Antifungal activity of pomegranate peel extract against fusarium wilt of tomato

Pomegranate (Punica granatum) is an important source of bioactive compounds and has been used in folk medicine for many centuries. This paper describes the in vitro antifungal activity of pomegranate peel aqueous extract (pae) on the development of Fusarium wilt of tomato caused by Fusarium oxysporum, f. sp. lycopersici. HPLC-DAD-ESI/MS analysis was performed to identify punicalagins and ellagic acid, which are the main antifungal compounds. In vivo tests established the efficacy of pae treatments in controlling Fusarium wilt by evaluating improvements in growth variables of tomato plants. At high concentrations, pae showed allelopathic activity in tomato plants. The germination and the radicle growth of tomato seeds were significantly affected by pae. Increasing the extract concentration led to a progressive decrease in germination and in the length of the radicle. The reduction of the Fusarium population in soil and the increase in number of healthy plants obtained as a result of pae treatments indicate that this plant extract could have an important role in biologically-based management strategies for the control of Fusarium wilt in tomato crops.     

Functional analysis of the G-protein α subunits FGA1 and FGA3 in the banana pathogen Fusarium oxysporum f. sp. cubense

The asexual fungus Fusarium oxysporum f. sp. cubense (Foc) is the causal agent of fusarium wilt in bananas (Musa spp.). This fungus poses a threat to banana production throughout the world. Here, two Foc genes, fga1 and fga3, were functionally characterized. These genes encode proteins homologous to the G-protein α subunits GPA1 from Saccharomyces cerevisiae and MAGC from Magnaporthe grisea, respectively. The deletion of fga1 leads to a phenotypic defect in colony morphology and reductions in vegetative growth, conidiation and pathogenicity against the banana plant (Musa spp. cv. Brazil), which was not observed for the Δfga3 deletion mutant. Intriguingly, both Δfga1 and Δfga3 deletion mutants showed declines in intracellular cyclic AMP levels and increases in heat resistance, suggesting that FGA1 regulates growth, development, pathogenicity, and heat resistance, whereas FGA3 modulates heat resistance, potentially through the cAMP-dependent protein kinase A pathway. These findings offer insights into the roles of the G-protein α subunits in the development and pathogenicity of the fungus Foc.     

The use of GFP<Emphasis Type="Italic">-</Emphasis>transformed isolates to study infection of banana with <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">cubense</Emphasis> race 4

Fusarium oxysporum f. sp. cubense (Foc) is the causal pathogen of Fusarium wilt of banana. To understand infection of banana roots by Foc race 4, we developed a green fluorescent protein (GFP)-tagged transformant and studied pathogenesis using fluorescence microscopy and confocal laser scanning microscopy. The transformation was efficient, and GFP expression was stable for at least six subcultures with fluorescence clearly visible in both hyphae and spores. The transformed Foc isolate also retained its pathogenicity and growth pattern, which was similar to that of the wild type. The study showed that: (i) Foc race 4 was capable of invading the epidermal cells of banana roots directly; (ii) potential invasion sites include epidermal cells of root caps and elongation zone, and natural wounds in the lateral root base; (iii) in banana roots, fungal hyphae were able to penetrate cell walls directly to grow inside and outside cells; and (iv) fungal spores were produced in the root system and rhizome. To better understand the interaction between Foc race 4 and bananas, nine banana cultivars were inoculated with the GFP-transformed pathogen. Root exudates from these cultivars were collected and their effect on conidia of the GFP-tagged Foc race 4 was determined. Our results showed that roots of the Foc race 4-susceptible banana plants were well colonized with the pathogen, but not those of the Foc race 4-resistant cultivars. Root exudates from highly resistant cultivars inhibited the germination and growth of the Fusarium wilt pathogen; those of moderately resistant cultivars reduced spore germination and hyphal growth, whereas the susceptible cultivars did not affect fungal germination and growth. The results of this work demonstrated that GFP-tagged Foc race 4 isolates are an effective tool to study plant–fungus interactions that could potentially be used for evaluating resistance in banana to Foc race 4 by means of root colonization studies. Banana root exudates could potentially also be used to identify cultivars in the Chinese Banana Germplasm Collection with resistance to the Fusarium wilt pathogen.     

Companion cropping with wheat increases resistance to Fusarium wilt in watermelon and the roles of root exudates in watermelon root growth

Pot experiments were performed to investigate the effects of companion cropping with D₁₂₅ wheat on Fusarium wilt in watermelon. Fusarium oxysporum f. sp. niveum (Fon) is responsible for Fusarium wilt in watermelon. Also, the relationship between root exudates of wheat and watermelon growth was estimated. Studies showed that companion cropping with D₁₂₅ wheat reduced the incidence rate of watermelon Fusarium wilt. Companion cropping with D₁₂₅ wheat decreased malondialdehyde content and increased activities of phenylalanine ammonia-lyase and polyphenol oxidase and contents of flavonoid, total soluble phenolics and lignin in watermelon roots after inoculation with Fon compared to monoculture. qRT-PCR showed that the expression levels of six specific genes were higher during the early stage of Fon infection in companion cropping than in monoculture. D₁₂₅ wheat root exudates increased root length, root surface area, root volume, root number, root dry weight, but decreased root mean diameter in watermelon seedlings in the absence of sodium orthovanadate. These results suggest that companion cropping with D₁₂₅ wheat reduced Fusarium wilt in watermelon by promoting the growth of watermelon roots and by triggering gene expression and physiological changes to protect the watermelon from injury.