Forms Of Fusarium Oxysporum Research Articles

Fusarium oxysporum f. sp. niveum Molecular Diagnostics Past, Present and Future.

Watermelon is an important commercial crop in the Southeastern United States and around the world. However, production is significantly limited by biotic factors including fusarium wilt caused by the hemibiotrophic fungus Fusarium oxysporum forma specialis niveum (Fon). Unfortunately, this disease has increased significantly in its presence over the last several decades as races have emerged which can overcome the available commercial resistance. Management strategies include rotation, improved crop resistance, and chemical control, but early and accurate diagnostics are required for appropriate management. Accurate diagnostics require molecular and genomic strategies due to the near identical genomic sequences of the various races. Bioassays exist for evaluating both the pathogenicity and virulence of an isolate but are limited by the time and resources required. Molecular strategies are still imperfect but greatly reduce the time to complete the diagnosis. This article presents the current state of the research surrounding races, both how races have been detected and diagnosed in the past and future prospects for improving the system of differentiation. Additionally, the available Fon genomes were analyzed using a strategy previously described in separate formae speciales avirulence gene association studies in Fusarium oxysporum races.

Mass Spectrometry-Based Metabolomics Reveals a Concurrent Action of Several Chemical Mechanisms in Arabidopsis-Fusarium oxysporum Compatible and Incompatible Interactions.

Fusarium oxysporum is a destructive root-infecting plant pathogen that causes significant yield losses in many economically important crop species. Hence, a deeper understanding of pathogen infection strategies is needed. With liquid chromatography-tandem mass spectrometry and gas chromatography-time of flight mass spectrometry platforms, we analyzed the metabolic changes in a time-course experiment with Arabidopsis accessions either resistant (Col-0) or susceptible (Ler-0) to isolates of Fusarium oxysporum forma specialis matthioli infection. We showed a concurrent effect of Fusarium-derived polyols and the mycotoxin beauvericin in the suppression of the immune response of susceptible hosts. A significant increase in oxidized glutathione in the resistant host was probably associated with effective reactive oxygen species-mediated resistance responses. Through a combination of targeted and untargeted metabolomics, we demonstrated the concurrent action of several Arabidopsis defense systems as well as the concurrent action of several virulence systems in the fungal attack of susceptible Arabidopsis.

Influence of different biological control agents and compost on total and nitrification-driven microbial communities at rhizosphere and soil level in a lettuce - Fusarium oxysporum f. sp. lactucae pathosystem.

The response of rhizosphere and bulk soil indigenous microbial communities focusing on nitrifiers was evaluated after the application of different biological control agents (BCAs; Bacillus, Trichoderma, Pseudomonas) and compost in controlling lettuce Fusarium wilt. Experiments were conducted 'insitu' over two lettuce cropping seasons. Total fungal, bacterial and archaeal populations and the nitrifiers were analysed using quantitative polymerase chain reaction method. The pathogen, Fusarium oxysporum forma specialis lactucae (FOL), Bacillus, Trichoderma and Pseudomonas and three antifungal genes (chiA, 2,4-diacetylphloroglucinol - phlD and HCN synthase - hcnAB genes) were also assessed. Quantitative data were corroborated with disease severity (DS), potential nitrification activity and soil chemical parameters. The application of BCAs and compost resulted in the disease reduction by as much as 69%, confirmed by significant negative correlations between Bacillus subtilis, Trichoderma and Pseudomonas sp. abundances and DS. The FOL presence in the untreated control resulted in the nitrifiers niche differentiation. The used treatments were efficient against Fusarium wilt and did not influence negatively the nontarget microbial communities. The use of BCAs and compost appears as an effective and safe strategy to implement sustainable agricultural practices.

STUDIES ON CHEMICAL COMPOSITION AND ANTIMICROBIAL ACTIVITIES OF BIOACTIVE MOLECULES FROM DATE PALM (PHOENIXDACTYLIFERA L.) POLLENS AND SEEDS.

Background:Natural resources have been the crucial origin of chemical elements. They have been used in many traditions as alternative medicines. The chemical profiling of some plant extracts and essential oils related to different plants were followed to unveil their most active components. In this paper, Phoenix dactilyfera L was selected as a host plant to investigate the composition of different organs with different cultivars.Materials and method:The antibacterial and antifungal activities of the extracts have been tested using different techniques, including optical density and GC/MS analyses of the natural extracts.Results:GC/MS analysis revealed the presence of abundant oleic (36.69%) and lauric (20.49%) acids in date seeds. However, the pollen contains a high amount of palmitic (22.27 %), linoleic (33.4%) and linolenic (17.055%) acids. Moreover, the largest inhibition zone is obtained with the organic extract of Deglet Nour which showed a strong antibacterial activity against Escherichia coli and pollen extract showed also a strong inhibition against Escherichia coli, Staphylococcus aureus, S. aureus MRSA and Enterococcus faecalis. Aqueous extracts of date palm seeds of and pollen seem to have a fongitoxique activity from a concentration of 6 mg.mL-1 and 12mg.mL-1 of cyanidine; as well as the organic extracts of pollen with a concentration of 90 μg.mL”1 induce an inhibition to the growth of five special forms of Fusarium oxysporum.Conclusion:The bioactive compounds of date palm can be used for drug development and in the food industry.

Antimicrobial Activity of Potato Rhizospheric Pseudomonas chlororaphis subsp. aureofaciens from Sétif Algeria

Aims: This study was assessed to demonstrate the antimicrobial activity in vitro of an identified fluorescent Pseudomonas strain characterized for its capacity to produce phenazine compounds. Methodology: First Pseudomonas chlororaphis subsp aureofaciens was inoculated on Nutrient Broth supplemented with Yeast Extract (NBY) and with glucose at a final concentration of 2%, after incubation the filtered culture was acidified with HCl to pH 2. The solution was extracted twice with the same volume of ethyl-acetate. The organic supernatants were combined, dried over anhydrous Na2SO4, and evaporated to dryness. The crude extract was resuspended in methanol and tested for antimicrobial activity. Antimicrobial activity was determined (i) by disc diffusion technique for bacteria and (ii) using serial dilution technique in soft PDA for fungi. Secondly the antifungal activity of the bacterial strain was tested against several phytopathogenic fungi in dual culture. Results: The studied strain has an important activity against the phytopathogenic bacteria and fungi tested. Among the tested fungi Fusarium oxysporum f. sp. albedinis is the most sensitive to the actions of this Pseudomonas, where the inhibition rate reached 77.78%. The less sensitive one was Pythium ultimum with a rate of 55.56%. While for pathogenic bacteria only Salmonella enteridis was sensitive to the tested strain. Conclusion: Pseudomonas chlororaphis subsp aureofaciens showed appreciable antagonistic activity, in vitro, against special forms of Fusarium oxysporum and the tested phytopathogenic bacteria.

Arabidopsis thaliana RESISTANCE TO FUSARIUM OXYSPORUM 2 Implicates Tyrosine-Sulfated Peptide Signaling in Susceptibility and Resistance to Root Infection

In the plant Arabidopsis thaliana, multiple quantitative trait loci (QTLs), including RFO2, account for the strong resistance of accession Columbia-0 (Col-0) and relative susceptibility of Taynuilt-0 (Ty-0) to the vascular wilt fungus Fusarium oxysporum forma specialis matthioli. We find that RFO2 corresponds to diversity in receptor-like protein (RLP) genes. In Col-0, there is a tandem pair of RLP genes: RFO2/At1g17250 confers resistance while RLP2 does not. In Ty-0, the highly diverged RFO2 locus has one RLP gene conferring weaker resistance. While the endogenous RFO2 makes a modest contribution to resistance, transgenic RFO2 provides strong pathogen-specific resistance. The extracellular leucine-rich repeats (eLRRs) in RFO2 and RLP2 are interchangeable for resistance and remarkably similar to eLRRs in the receptor-like kinase PSY1R, which perceives tyrosine-sulfated peptide PSY1. Reduced infection in psy1r and mutants of related phytosulfokine (PSK) receptor genes PSKR1 and PSKR2 shows that tyrosine-sulfated peptide signaling promotes susceptibility. The related eLRRs in RFO2 and PSY1R are not interchangeable; and expression of the RLP nPcR, in which eLRRs in RFO2 are replaced with eLRRs in PSY1R, results in constitutive resistance. Counterintuitively, PSY1 signaling suppresses nPcR because psy1r nPcR is lethal. The fact that PSK signaling does not similarly affect nPcR argues that PSY1 signaling directly downregulates the expression of nPcR. Our results support a speculative but intriguing model to explain RFO2's role in resistance. We propose that F. oxysporum produces an effector that inhibits the normal negative feedback regulation of PSY1R, which stabilizes PSY1 signaling and induces susceptibility. However, RFO2, acting as a decoy receptor for PSY1R, is also stabilized by the effector and instead induces host immunity. Overall, the quantitative resistance of RFO2 is reminiscent of the better-studied monogenic resistance traits.

Routine mapping of Fusarium wilt resistance in BC1 populations of Arabidopsis thaliana

BackgroundSusceptibility to Fusarium wilt disease varies among wild accessions of Arabidopsis thaliana. Six RESISTANCE TO FUSARIUM OXYSPORUM (RFO) quantitative trait loci (QTLs) controlling the resistance of accession Columbia-0 (Col-0) and susceptibility of Taynuilt-0 to Fusarium oxysporum forma specialis matthioli (FOM) are detected in a recombinant population derived from a single backcross of the F1 hybrid (BC1). In particular, the RFO1 QTL appears to interact with three other loci, RFO2, RFO4 and RFO6, and is attributed to the gene At1g79670.ResultsWhen resistance to FOM was mapped in a new BC1 population, in which the loss-of-function mutant of At1g79670 replaced wild type as the Col-0 parent, RFO1’s major effect and RFO1’s interaction with RFO2, RFO4 and RFO6 were absent, showing that At1g79670 alone accounts for the RFO1 QTL. Resistance of two QTLs, RFO3 and RFO5, was independent of RFO1 and was reproduced in the new BC1 population. In analysis of a third BC1 population, resistance to a second pathogen, F. oxysporum forma specialis conglutinans race 1 (FOC1), was mapped and the major effect locus RFO7 was identified.ConclusionsNatural quantitative resistance to F. oxysporum is largely specific to the infecting forma specialis because different RFO loci were responsible for resistance to FOM and FOC1. The mapping of quantitative disease resistance traits in BC1 populations, generated from crosses between sequenced Arabidopsis accessions, can be a routine procedure when genome-wide genotyping is efficient, economical and accessible.

Molecular markers reflect differentiation of Fusarium oxysporum forma speciales on tomato and forma on eggplant

Selective pressure induces pathogens to change their method of infection and, sometimes, causes species to become infectious. Pathogenic fungi must differentiate different morphological and physiological properties during the process of host specialization in their life cycle. In the present study, we conducted a genetic investigation and compared similarities within a generation of Fusarium oxysporum forma speciales (f. sp.) infecting tomato and forma (f.) infecting eggplants using selected ISSR and RAPD markers, two horticultural commodities belonging to the same taxon of the Solanaceae. Interestingly, genetic data showed that fungi belonging to F. oxysporum f. sp. infecting tomato have a close genetic relationship with the fungi f. infecting eggplant. Furthermore, F. oxysporum f. sp. infecting tomato showed less genetic variation than F. oxysporum f. melongenae, suggesting that it could be developed more recently during host adaptation. On the other hand, the gene sequence of inter-simple sequence repeat (ISSR) markers resulting in high polymorphism showed matches with gene sequences encoding specific proteins related to pathogenicity of F. oxysporum species. These findings support the notion that selected ISSR markers can be used to follow host-associated divergence of F. oxysporum species infecting tomato and eggplant and that differentiation of their specific genes can also be related to pathogenicity and development as predictive studies before initiating detailed sequencing analysis.

Fusarium oxysporum Strains as Potential Striga Mycoherbicides: Molecular Characterization and Evidence for a new forma specialis

Fusarium oxysporum isolates (Foxy 2 and PSM197) are potential, highly host specific mycoherbicides for the control of the parasitic weeds Striga hermonthica and S. asiatica. Their target weeds, Striga spp., are major biotic con- straints in cereal and legume production in semi-arid tropical Africa, where they adversely affect livelihood of millions of subsistence farmers. The aim of this study was to characterize and sequence the Striga mycoherbicides Foxy 2 & PSM197 in order to more clearly distinguish them from other morphologically similar pathogenic Fusarium oxysporum strains. The fungal isolates were cultivated on PDA medium and characterized based on the analysis of partial DNA sequence of the internal transcribed spacer (ITS) regions of the nuclear ribosomal RNA gene. Both isolates were identical in their ITS- sequence. The unique and identical ITS-sequence of the two isolates obtained, compared to the sequences of Fusarium oxysporum forma speciales deposited in GenBank along with the host specificity to Striga demonstrated in previous stud- ies, provides strong evidence to propose these pathogens of Striga as a new forma specialis (f. sp. strigae). The possibility to clearly distinguish between the new forma specialis and all pathogenic Fusarium oxysporum strains sequenced so far will facilitate and encourage the acceptance and introduction of Striga-mycoherbicides for practical field application by regulatory authorities and farmers.

RESISTANCE TO FUSARIUM OXYSPORUM 1, a Dominant Arabidopsis Disease-Resistance Gene, Is Not Race Specific

Arabidopsis thaliana ecotypes differ in their susceptibility to Fusarium wilt diseases. Ecotype Taynuilt-0 (Ty-0) is susceptible to Fusarium oxysporum forma specialis (f.) matthioli whereas Columbia-0 (Col-0) is resistant. Segregation analysis of a cross between Ty-0 and Col-0 revealed six dominant RESISTANCE TO FUSARIUM OXYSPORUM (RFO) loci that significantly contribute to f. matthioli resistance in Col-0 relative to Ty-0. We refer to the locus with the strongest effect as RFO1. Ty-0 plants in which only the Col-0 allele of RFO1 (RFO1(Col-0)) was introduced were resistant to f. matthioli. Surprisingly, RFO1(Col-0) also conferred resistance to f. raphani, demonstrating that RFO1-mediated resistance is not race specific. Expression of resistance by RFO2, RFO4, or RFO6 was dependent on RFO1(Col-0). Map-based cloning of RFO1(Col-0) showed that RFO1 is identical to the previously named Arabidopsis gene WAKL22 (WALL-ASSOCIATED KINASE-LIKE KINASE 22), which encodes a receptor-like kinase that does not contain an extracellular leucine-rich repeat domain. Consistent with these results, a Col-0 rfo1 loss-of-function mutant was more susceptible to f. matthioli, f. conglutinans, and f. raphani. Thus, RFO1 encodes a novel type of dominant disease-resistance protein that confers resistance to a broad spectrum of Fusarium races.

Diagnosis and detection of host‐specific forms of Fusarium oxysporum*

Diagnosis and detection of host‐specific forms of Fusarium oxysporum are traditionally based on the combination of diagnostic symptoms on the host with the presence of the fungus in the affected tissues. The classical approach is becoming increasingly problematic because more than one forma specialis may occur on a given host, along with non‐pathogenic strains which are common soil and rhizosphere inhabitants. Neither formae speciales nor pathogenic races within formae speciales can be distinguished morphologically. Although united by joint pathogenicity to a given host, strains belonging to the same forma specialis need not be phylogenetically related. Development of diagnostics for host‐specific groups in F. oxysporum requires monophyletic target groups. Recent studies on gene‐genealogy and AFLP‐based phylogenies show that the majority of formae speciales in F. oxysporum are polyphyletic (unnatural) and do not offer any prospects for the development of molecular diagnostics. In contrast, highly specific PCR primers have been developed for formae speciales (or races) that consist of a single clonal lineage, and for monophyletic groups of lineages within a forma specialis. Among others, specific PCR primers have thus been developed for F. oxysporum f. sp. basilici, specific races in F. oxysporum ff. spp. dianthi and gladioli, and for the EPPO A2 (EU II/A1) quarantine fungus F. oxysporum f. sp. albedinis which can reliably replace conventional isolation and pathogenicity testing procedures.

VEGETATIVE COMPATIBILITY GROUPS WITHIN KENYAN POPULATIONS OF FUSARIUM OXYSPORUM F. SP. CUBENSE

Fusarium wilt of banana, caused by Fusarium oxysporum forma specialis cubense (Foc), is causing significant losses for small-scale holders in Kenya. The affected cultivars include 'Muraru' (AA?), 'Wang'ae' (AB),'Gros Michel' (AAA), and 'Bluggoe' (ABB). Vegetative compatibility studies involving 135 isolates of Foc have been carried out and compatibility has been recorded with testers from five existing vegetative compatibility groups (VCGs): VCG 01212, VCG 0124, VCG 0125, VCG 0128 and VCG 01220. Some isolates did not show anastomosis with tester strains and may belong to previously unrecognised VCGs. In many cases the isolates showed bridging reactions and were compatible with two or more testers from the 0124/5/8/20 complex. This complex represents a single clonal lineage of Foc and was the predominant and most widespread population in the country. The only other VCG found (01212) forms a second clonal lineage and may be cultivar specific. The distribution of these populations in Kenyan smallholder banana plantations has been determined and will assist in monitoring the occurrence of new strains.

Root and Stem Rot of Cucumber Caused byFusarium oxysporumf. sp.radicis-cucumerinumf. sp. nov.

Root and stem rot of cucumber (Cucumis sativus) caused by a new Fusarium oxysporum forma specialis is reported for the first time. Of 18 cultivated species from six different botanical families that were artificially inoculated, two species of Cucurbitaceae-mdon (C. melo) and sponge gourd (Luffa aegyptiaca)-showed root and stem rot similar to that caused by isolates of F. oxysporum that attack cucumber. Optimum temperature for disease development was close to 17°C. Disease symptoms and pathogenicity tests confirm that a new forma specialis of F. oxysporum is the incitant of the disease. The author proposes to name this forma specialis as F. oxysporum f. sp. radicis-cucumerinum f. sp. nov.

Interaction of Pratylenchus Penetrans and Fusarium Oxysporum Forma Pisi Race 2 and of Rotylenchus Uniformis and F. Oxysporum F. Pisi Race 1 On Peas

Wilting of peas, var. 'Rondo', caused by Fusarium oxysporum forma pisi race 2 was enhanced by Pratylenchus penetrans attack at an initial density of this nematode of about 500 or more nematodes per 500 g soil. Some wilting occurred in the absence of the nematode but none at any nematode density in the absence of the fungus. P. penetrans alone possibly reduced stem and seed weight at initial densities exceeding 20,000 nematodes per 500 g soil. P. penetrans + Fusarium did not reduce stem weight but reduced seed weight below that which occurred at smaller initial densities at about 500 and more nematodes per 500 g soil. Seed weight in pots with P. penetrans + Fusarium at 0 to 500 nematodes per 500 g soil was about 80% of that at the same nematode densities in pots without Fusarium. The presence of the fungus probably reduced the rate of multiplication of P. penetrans at all initial densities of this nematode. Rates of multiplication at high initial densities indicate that the attack by the nematodes reduced the quantity of food available to them by damaging the roots. This damage was not reflected in the weight of the above-ground parts of the plants. At low initial densities the rate of multiplication of the nematode was reduced because of underpopulation. The rate of multiplication of Rotylenchus uniformis on pea (var. 'Rondo') was increased by the presence of F. oxysporum forma pisi race 1.

Effect of mixed inoculations with Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. dianthi on the phenols content of tomato plants

Forms ofFusarium oxysporum specific on hosts other than tomato induce in this plant greater initial increases of the phenols content than the pathogenic f. sp.lycopersici. Mixed inoculations of f. sp.lycopersici and f. sp.dianthi are on the contrary no more effective in inducing the phenol accumulation 24 h after the infection than f. sp.lycopersici alone. This observation suggests that the pathogen can suppress the phenolic response that is typical of the incompatible combinations.

Fusarium oxysporum on the Oil Palm

IN an earlier communication1 I directed attention to the presence of a vascular wilt disease of the oil palm (Elis guineensis) in the Belgian Congo. In so far as mycological studies could be pursued under the conditions of the investigation, the same species of Fusarium was isolated on a number of occasions from discoloured vascular strands. A culture submitted to Dr. S. P. Wiltshire of the Imperial Mycological Institute has now been reported on by Dr. W. L. Gordon of the Dominion Laboratory of Plant Pathology, Winnipeg. The latter, who has been making a special study of this genus, has identified the culture as Fusarium oxysporum forma. The organism isolated from infected vascular strands of the oil palm is thus a strain or form of the comprehensive species to which the other wilt-producing Fusaria belong. Its pathogenicity has, of course, still to be tested.