Tomato Wilt Disease Research Articles

Compatibility between Pseudomonas fluorescens and Trichoderma harzianum in disease control of Fusarium tomato wilt under greenhouse condition .

This study was conducted to evaluate the efficacy of 6 isolates of Pseudomonas fluorescens and Trichoderma harzianum and there combination against Fusarium tomato wilt disease caused by Fusarium oxysporum F.sp. Lycopersisi under green house condition .The isolates of bacteria (B3) and Trichoderma (T1) were found to be highly effective in reducing the disease incidence to 13.3% , 21% respectively , compared to control treatment (40%).Furthermore, disease severity was reduced to 28 and 30% respectively in comparison to control (90%) .Colonization of the roots (cfu /g fresh root weight )by the two isolates whether alon or together was extremely high . The combination treatment had a high ability in reducing disease incidenece and severity to 10,3 , 16% respectively compared to control (36.3% , 88 % respectively), and highly effective in increasing some growth parameters .

Compatibility between Pseudomonas fluorescens and Trichoderma harzianum in disease control of Fusarium tomato wilt under greenhouse condition .

This study was conducted to evaluate the efficacy of 6 isolates of Pseudomonas fluorescens and Trichoderma harzianum and there combination against Fusarium tomato wilt disease caused by Fusarium oxysporum F.sp. Lycopersisi under green house condition .The isolates of bacteria (B3) and Trichoderma (T1) were found to be highly effective in reducing the disease incidence to 13.3% , 21% respectively , compared to control treatment (40%).Furthermore, disease severity was reduced to 28 and 30% respectively in comparison to control (90%) .Colonization of the roots (cfu /g fresh root weight )by the two isolates whether alon or together was extremely high . The combination treatment had a high ability in reducing disease incidenece and severity to 10,3 , 16% respectively compared to control (36.3% , 88 % respectively), and highly effective in increasing some growth parameters .

INF1 Elicitin Activates Jasmonic Acid‐ and Ethylene‐mediated Signalling Pathways and Induces Resistance to Bacterial Wilt Disease in Tomato

Abstract Phytophthora infestans, the cause of potato and tomato late blight disease, produces INF1 elicitin, a 10 kDa extracellular protein. INF1 induces a hypersensitive response (HR) and systemic acquired resistance in species of the Nicotiana genus and a few other genera. We analysed the response of tomato to INF1 and INF1S3, which has a Cys to Ser substitution at position 3 of the processed protein and therefore lacks HR induction activity in tobacco. No HR cell death was induced in either INF1‐ or INF1S3‐treated tomato leaves. The expression of salicylic acid (SA)‐responsive PR‐1a(P6) and PR‐2a genes was not induced by treatment with either INF1 or INF1S3. However, the expression of jasmonic acid (JA)‐responsive PR‐6 encoding proteinase inhibitor II, LeATL6 encoding ubiquitin ligase E3, and LOX‐E encoding lipoxygenase, was up‐regulated in tomato leaves treated with INF1 but not in those treated with INF1S3. Their induction was completely compromised in INF1‐treated jai1‐1 mutant tomato, in which the JA signalling pathway is impaired. The accumulation of ethylene (ET) and the expression of ET‐responsive genes were also induced in tomato by INF1 but not INF1S3 treatment. The activation of JA and ET‐mediated signals but not the SA‐mediated signalling in INF1‐treated tomato was also demonstrated by global gene expression analysis. INF1‐treated tomatoes, but not those treated with INF1S3, exhibited resistance to bacterial wilt disease caused by Ralstonia solanacearum. Thus, INF1 seems to induce resistance to bacterial wilt disease in tomato and activate JA‐ and ET‐mediated signalling pathways without development of HR cell death.

Control of Bacterial Wilt Disease of Tomato Through Integrated Crop Management Strategies

Tomato cultivation is severely affected by bacterial wilt disease caused by the soilborne pathogen Ralstonia solanacearum (previously known as Pseudomonas solanacearum Smith). Effects of rotation of tomato (Lycopersicon esculentum Mill.) with other crops on soil populations of R. solanacearum and on bacterial wilt disease incidence of tomato were evaluated in the field. Monocropped Cassava (Manihot esculenta Crantz), Mucuna puriens L., Crotalaria juncea L., and intercrops of Cassava/Crotalaria, Cassava/Mucuna, and a natural grass mix (control) were rotated with the tomato cvs. Mira, Ronita, Roma VFN, and Ibadan Local. Monocropped Mucuna significantly reduced soil population of R. solanacearum by the end of the rotation period, whereas the natural grass rotation had the highest population of the pathogen. Other crops with the exception of monocropped cassava also reduced the pathogen soil population. The incidence of wilt was delayed in cvs. Mira, Roma VFN, and Ronita compared to ‘Ibadan Local’, but all were 80% or more infected after 8 weeks.

Involvement of jasmonic acid signalling in bacterial wilt disease resistance induced by biocontrol agent Pythium oligandrum in tomato

When the biocontrol agent Pythium oligandrum (PO) colonizes the rhizosphere, it suppresses bacterial wilt disease in tomato (Solanum lycopersicum cv. Micro‐Tom) caused by Ralstonia solanacearum, and a homogenate of its mycelia exhibits elicitor activity, inducing an ethylene (ET)‐dependent defence response in Micro‐Tom. Since salicylic acid (SA) and jasmonic acid (JA) play an important role in plant defence responses to pathogens, the involvement of SA‐ and JA‐dependent signal transduction pathways in resistance to R. solanacearum was investigated in tomato roots treated with a mycelial homogenate of PO. Bacterial wilt disease was also suppressed in tomato cv. Moneymaker treated with the PO homogenate. However, the SA‐inducible PR‐1(P6) gene was not up‐regulated in either Micro‐Tom or Moneymaker. SA did not accumulate in homogenate‐treated roots in comparison with distilled water‐treated controls, even 24 h after inoculation. Induced resistance against R. solanacearum was not compromised in SA‐non‐accumulating NahG transgenic plants treated with the PO homogenate. On the other hand, the expression of the JA‐responsive gene for the basic PR‐6 protein was induced in both tomato cultivars treated with the PO homogenate. Furthermore, quantitative disease assays showed that the induced resistance against R. solanacearum was compromized in PO homogenate‐treated jai1‐1 mutant plants defective in JA signalling. These results indicated that the JA‐dependent signalling pathway is required for PO‐induced resistance against R. solanacearum in tomato.

Tomato Transcriptional Changes in Response toClavibacter michiganensissubsp.michiganensisReveal a Role for Ethylene in Disease Development

Clavibacter michiganensis subsp. michiganensis (Cmm) is a gram-positive actinomycete, causing bacterial wilt and canker disease in tomato (Solanum lycopersicum). Host responses to gram-positive bacteria and molecular mechanisms associated with the development of disease symptoms caused by Cmm in tomato are largely unexplored. To investigate plant responses activated during this compatible interaction, we used microarray analysis to monitor changes in host gene expression during disease development. This analysis was performed at 4 d postinoculation, when bacteria were actively multiplying and no wilt symptoms were yet visible; and at 8 d postinoculation, when bacterial growth approached saturation and typical wilt symptoms were observed. Of the 9,254 tomato genes represented on the array, 122 were differentially expressed in Cmm-infected plants, compared with mock-inoculated plants. Functional classification of Cmm-responsive genes revealed that Cmm activated typical basal defense responses in the host, including induction of defense-related genes, production and scavenging of free oxygen radicals, enhanced protein turnover, and hormone synthesis. Cmm infection also induced a subset of host genes involved in ethylene biosynthesis and response. After inoculation with Cmm, Never ripe (Nr) mutant plants, impaired in ethylene perception, and transgenic plants with reduced ethylene synthesis showed significant delay in the appearance of wilt symptoms, compared with wild-type plants. The retarded wilting in Nr plants was a specific effect of ethylene insensitivity, and was not due to altered expression of defense-related genes, reduced bacterial populations, or decreased ethylene synthesis. Taken together, our results indicate that host-derived ethylene plays an important role in regulation of the tomato susceptible response to Cmm.

Bacillus subtilis as an alternative biologically based strategy for controlling Fusarium wilt disease in tomato: A histological study

The employment of formulateBacillus subtilis as a biocontrol agent successfully controlledFusarium oxysporum f.sp.lycopersici within tomato seedlings (in vivo). B. subtilis was able to proted cortex and vascular tissues of tomato against progression of the wilt pathogen. No changes were observed in tomato tissues due to application ofB. subtilis except for hypertrophy and elongation of cortex tissues, which indicates the production of plant growth hormones byB. subtilis.

Phenotypic characterization of Pseudomonas fluorescens PfG32R and its spontaneous gacS mutants and biocontrol activity against bacterial wilt disease of tomato

Pseudomonas fluorescens strain PfG32R actively suppresses the occurrence of bacterial wilt disease of tomato caused by Ralstonia solanacearum. To determine the characteristics affected by spontaneous mutations in the gacS gene, three spontaneous mutants NR1, NR9, and ASW6 were tested for production of several enzymes, antimicrobial activity, and biocontrol activity against bacterial wilt disease of tomato in a greenhouse. Production of biosurfactant and of enzymes such as Tween-80 lipase, gelatin protease, and lecithinase; swarming activity; and antifungal activities against Fusarium oxysporum f. sp. radicis-lycopersici and F. graminearum were inactivated by mutations in the gacS gene, indicating that they are under the regulation of the GacS/GacA two-component regulatory system. Levan production, swimming, antifungal activity against Magnaporthe grisea, and antibacterial activity against R. solanacearum and Erwinia carotovora ssp. carotovora were not controlled by the GacS/GacA system. Biocontrol activities of the three spontaneous mutants varied from strain to strain, indicating that the biocontrol activities of PfG32R are influenced not only by the GacS/GacA system but also by other complex factors, which may not be regulated by the system.

Biocontrol potential of salinity tolerant mutants of Trichoderma harzianum against Fusarium oxysporum

Exposing a wild-type culture of Trichoderma harzianum to gamma irradiation induced two stable salt-tolerant mutants (Th50M6 and Th50M11). Under saline conditions, both mutants greatly surpassed their wild type strain in growth rate, sporulation and biological proficiency against Fusarium oxysporum, the causal agent of tomato wilt disease. Tolerant T. harzianum mutants detained a capability to grow and convinced sporulation in growth media containing up to 69 mM NaCl. In comparison with their parent strain, characterization of both mutants confirmed that they have reinforced contents of proline and hydroxyproline, relatively higher sodium content compared to potassium, calcium or magnesium contents, higher level of total phenols. Electrophoretic analysis of total soluble proteins in the salt tolerance mutant Th50M6 showed different bands accumulated in response to 69 mM NaCl. Data also showed that mutants produce certain active metabolites, such as chitinases, cellulases, b-galactosidases, as well as, some antibiotics i.e., trichodermin, gliotoxin and gliovirin. Trichoderma mutants significantly reduced wilt disease incidence and improved yield and mineral contents of tomato plants under both saline and non-saline soil conditions, as well as, under infested and natural conditions. T. harzianum mutants were also more efficient in dropping the F. oxysporum growth in rhizosphere compared to the wild type strain. Population density of both mutants in rhizosphere far exceeded that of T. harzianum wild type strain.

Frp1 is a Fusarium oxysporum F‐box protein required for pathogenicity on tomato

Fusarium oxysporum f. sp. lycopersici is the causal agent of tomato wilt disease. In order to identify genes involved in its pathogenicity, we performed insertional mutagenesis. Mutant N40 had lost its pathogenicity completely, when tested in bioassays with tomato seedlings. Molecular characterization of mutant N40 revealed that the plasmid insertion had occurred in a gene that codes for a 60.2 kDa protein containing an F-box motif. The gene was therefore designated as FRP1 (F-box protein required for pathogenicity). Targeted FRP1 disruptants had lost their pathogenicity completely, and became fully virulent again upon re-introduction of the FRP1 gene. This confirmed that the FRP1 gene is required for pathogenesis. In a yeast two-hybrid assay Frp1 interacts with Skp1, suggesting involvement of an SCF ubiquitin ligase complex in pathogenicity. FRP1 is constitutively expressed during infection and under different culture conditions. Although growth, spore formation and germination on artificial media were not impaired, confocal laser scanning microscopy of a GFP-marked mutant N40 and a GFP-marked targeted FRP1 disruptant revealed that they were unable to colonize the roots.

Nitric oxide-overproducing transformants of Pseudomonas fluorescens with enhanced biocontrol of tomato bacterial wilt

The relation between nitric oxide (NO) production and the protective ability of Pseudomonas fluorescens T5 against bacterial wilt disease in tomato was examined. The endogenous nitric oxide reductase gene of T5 was disrupted by homologous recombination using a suicide plasmid. Three disruptants were obtained, and all had higher levels of NO production. Infection with Ralstonia solanacearum was reduced in tomato plants treated with the NO-overproducing transformants compared with the wild type. These results suggest that the modification of pseudomonads to increase their level of NO production is a new approach to enhancing their biocontrol efficacy.

Tomato Fusarium wilt and its chemical control strategies in a hydroponic system

Tomato ( Lycopersicon esculentum Mill.) was cultivated in a hydroponic system with unlimited growth cultivation mode by using a deep flow technique. The identified wilt pathogen Fusarium oxysporum Klotz. was used to infect the plants. Seven fungicides, prochloraz, carbendazim, thiram, toclofos-methyl, hymexazol, azoxystrobin and carboxin, were tested in vitro for their inhibitory activities against the pathogen by mycelial growth inhibition with median effective concentration (EC 50) values of 0.019, 0.235, 26.292, 53.606, 69.961, 144.58 and 154.03 μg/ml separately. Prochloraz and carbendazim were the most effective fungicides in inhibiting mycelial growth. The preventive effect was 69.6% after 0.4 μg/ml prochloraz was added to the liquid media for 2 weeks with a curative effect of 50.0%. The preventive effect was 87.0% after 5 μg/ml carbendazim was added to the liquid media for 2 weeks with a curative effective of 34.4%. It was observed that tomato wilt disease could be well controlled by low toxicity and systemic fungicides added in a hydroponic system at their appropriate concentration.

Effects of Varying Environmental Conditions on Biological Control of Fusarium Wilt of Tomato by Nonpathogenic Fusarium spp.

ABSTRACT The influence of varying environmental and cropping conditions including temperature, light, soil type, pathogen isolate and race, and cultivar of tomato on biological control of Fusarium wilt of tomato by isolates of nonpathogenic Fusarium oxysporum (CS-20 and CS-24) and F. solani (CS-1) was evaluated in greenhouse and growth chamber experiments. Liquid spore suspensions (10(6)/ml) of the biocontrol isolates were applied to soilless potting mix at the time of tomato seeding, and the seedlings were transplanted into pathogen-infested field soil 2 weeks later. Temperature regimes ranging from 22 to 32 degrees C significantly affected disease development and plant physiological parameters. Biocontrol isolate CS-20 significantly reduced disease at all temperature regimes tested, yielding reductions of disease incidence of 59 to 100% relative to pathogen control treatments. Isolates CS-24 and CS-1 reduced disease incidence in the greenhouse and at high temperatures, but were less effective at the optimum temperature for disease development (27 degrees C). Growing plants under shade (50% of full light) versus full light affected some plant growth parameters, but did not affect the efficacy of biocontrol of any of the three bio-control isolates. Isolate CS-20 effectively reduced disease incidence (56 to 79% reduction) in four different field soils varying in texture (sandy to clayey) and organic matter content (0 to 3.2%). Isolate CS-1 reduced disease in the sandy and loamy soils (49 to 66% reduction), but was not effective in a heavy clay soil. Both CS-1 and CS-20 were equally effective against all three races of the pathogen, as well as multiple isolates of each race (48 to 66% reduction in disease incidence). Both isolates, CS-1 and CS-20, were equally effective in reducing disease incidence (66 to 80% reduction) by pathogenic races 1, 2, and 3 on eight different tomato cultivars containing varying levels of inherent resistance to Fusarium wilt (susceptible, resistant to race 1, or resistant to races 1 and 2). These results demonstrate that both these Fusarium isolates, and particularly CS-20, can effectively reduce Fusarium wilt disease of tomato under a variety of environmental conditions and have potential for further development.

Specific Detection of Tomato Pathotype of Verticillium dahliae by PCR Assays

Klebahn is the causal agent of tomato wilt disease. Isolates of V. dahliae can be classified based on pathogenicity to tomato, but the pathotypes are indistinguishable in morphology. We designed PCR primers for specific detection of isolates pathogenic to tomato (tomato pathotype) from the sequences of a pathotype-specific gene, vdt1. With the primer pair Tg5/Tc3, a PCR product (approximately 3.2 kb) specific to tomato pathotype was amplified from the genomic DNA of isolates. Using the primer pair, a tomato pathotype isolate was specifically detected from hypocotyls of inoculated tomato and eggplant. On the other hand, no amplification was observed from non-tomato pathotype isolates of V. dahliae, some other wilt pathogens of tomato and a healthy host plant. Therefore, the primer pair can be useful for pathotype-specific detection of V. dahliae as well as for diagnosis of wilt disease of tomato plant.

Systemic Resistance to Fusarium Wilt in Tomato Induced by Phytopthora cryptogea

AbstractUnder climate chamber conditions, suppression of tomato wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL) was obtained by spraying a suspension of Phytophthora cryptogea (Pc) zoospores on the green parts of two tomato cultivars, Danish Export (susceptible) and Elin F1 (moderately resistant). Direct competitive or antagonistic interaction between Pc and FOL in the soil or on the root surfaces was ruled out, but not interaction within the stems of plants. After Pc application followed by FOL inoculation, the two cultivars showed no wilt disease symptoms during the 50 days following FOL inoculation, whereas the FOL‐control plants were destroyed by wilt within about 40 days. Over a period of 7 weeks, both Pc and FOL were detected inside the stems of plants, for all treatments. Pc and FOL were also found inside the petioles of plants, except for one treatment, Pc application followed by challenge inoculation with FOL. Systemic induced resistance was assumed to be responsible for the observed elimination of disease incidence. It was concluded that, under climate chamber conditions, Pc application to the green parts of tomato plants is a viable alternative for control of disease incidence caused by FOL.

Induction of an acidic isozyme of peroxidase and acquired resistance to wilt disease in response to treatment of tomato roots with 2-furoic acid, 4-hydroxybenzoic hydrazide or salicylic hydrazide

Thirty nine derivatives of salicylic acid, nicotinic acid or furoic acid were tested for their ability to induce cell wall bound peroxidase activity in an attempt to identify inducers of acquired resistance. The activity of cell wall bound peroxidase in tomato hypocotyls was enhanced by treatment of roots with 4-hydroxybenzoic hydrazide (4HBHZ), salicylic hydrazide (SHZ), or 2-furoic acid (2FA). Isoelectric focusing revealed that an acidic isozyme (pI 4.6) of peroxidase was induced specifically by treatment with these compounds. The isozyme was induced independently to wounding or pathogen infection. Dipping roots in solutions of these compounds at concentrations of 0.1 μm4HBHZ, 1.0 μmSHZ and 10 μm2FA also induced resistance against the tomato wilt disease caused byFusarium oxysporumf.sp.lycopersici.

Allosteric Regulation of Cell Wall-bound Peroxidase and Induction of Acquired Resistance to Tomato Wilt Disease by 4-hydroxybenzoic Hydrazide.

Resistance-inducing compounds, 4-hydroxybenzoic hydrazide (4HBHZ), salicylic hydrazide (SHZ) and 2-furoic acid (2FA) inhibited tomato cell wall-bound peroxidase and horse radish peroxidase (HRP) activities. However, salicylic acid (SA), a non-inducer of resistance against Fusarium wilt did not inhibit peroxidase activity. HRP was allosterically regulated by the substrate. These resistance-inducing compounds acted as inhibitory effectors of HRP. On the contrary, 4-coumaric acid (4CA) and salicylhy-droxamic acid (SHAM) acted as stimulatory effectors. Among these compounds, 4HBHZ and SHZ were bound to compound III, an inactive intermediate of peroxidase. Furthermore, 4HBHZ weakly activated compound III and acted as a cofactor of the NADH-dependent peroxidase reaction as did 4CA and SHAM.

The I2C family from the wilt disease resistance locus I2 belongs to the nucleotide binding, leucine-rich repeat superfamily of plant resistance genes.

Characterization of plant resistance genes is an important step in understanding plant defense mechanisms. Fusarium oxysporum f sp lycopersici is the causal agent of a vascular wilt disease in tomato. Genes conferring resistance to plant vascular diseases have yet to be described molecularly. Members of a new multigene family, complex I2C, were isolated by map-based cloning from the I2 F. o. lycopersici race 2 resistance locus. The genes show structural similarity to the group of recently isolated resistance genes that contain a nucleotide binding motif and leucine-rich repeats. Importantly, the presence of I2C antisense transgenes abrogated race 2 but not race 1 resistance in otherwise normal plants. Expression of the complete sense I2C-1 transgene conferred significant but partial resistance to F. o. lycopersici race 2. All members of the I2C gene family have been mapped genetically and are dispersed on three different chromosomes. Some of the I2C members cosegregate with other tomato resistance loci. Comparison within the leucine-rich repeat region of I2C gene family members shows that they differ from each other mainly by insertions or deletions.

Effects of Streptomyces corchorusii, Streptomyces mutabilis, pendimethalin, and metribuzin on the control of bacterial and Fusarium wilt of tomato

Two Streptomyces spp. and two herbicides were used to control the pathogens of tomato wilt disease in vitro and in vivo. In vitro studies showed inhibitory effects of Streptomyces corchorusii against Fusarium oxysporum f.sp. lycopersici (Sacc.) and inhibitory effects of Streptomyces mutabilis against Pseudomonas solanacearum. In cultures amended with pendimethalin or metribuzin, the growths of P. solanacearum and F. oxysporum were inhibited. The degree of growth inhibition was proportional to the herbicide concentration, with pendimethalin being more effective than metribuzin, and maximum inhibition was at 2.0 × 10−3 M. The growth of S. corchorusii and S. mutabilis was slightly inhibited or enhanced by the herbicides. Supplementation of the herbicides to culture media of the antagonistic Streptomyces spp. increased their inhibitory effects against P. solanacearum and F. oxysporum that were proportional to the herbicide concentrations. Soaking seeds of tomato in the herbicides prior to sowing in sterilized and raw soils and applying S. corchorusii and (or) S. mutabilis to the soils artificially infested with P. solanacearum and (or) F. oxysporum f.sp. lycopersici (Sacc.) 40 days after transplanting revealed significant interactions that gave better control of wilt than either applied alone. The combination of antagonistic Streptomyces spp. was more effective with pendimethalin than with metribuzin and in nonsterilized soil than in sterilized soil. The combination of pendimethalin with S. corchorusii, S. mutabilis, or S. corchorusii plus S. mutabilis was more effective than the single treatment with microbial antagonists or the herbicide against F. oxysporum, P. solanacearum, and Pseudomonas plus Fusarium, respectively. In both soils, the combination of microbial antagonists with pendimethalin was most effective at 2.0 × 10−3 M, disease incidence being reduced to zero and the percent colonization of either pathogen being the lowest. The results also revealed that these combinations minimized the negative effects of the pathogens on tomato growth. This work demonstrates that two compatible control agents, biological and chemical, can be combined to give additional control of a plant pathogen. Keywords: Streptomyces spp., herbicides, Pseudomonas solanacearum, Fusarium oxysporum f.sp. lycopersici (Sacc.), wilt, Lycopersicon esculentum Mill.

Fungicidal activity of Ranunculus asiaticus and other weeds against Fusarium oxysporum f.sp. lycopersici

SummaryThe effects of aqueous extracts of some common weed species against Fusarium oxysporum Schlecht f.sp. lycopersici (the causal agent of tomato wilt disease) were investigated under laboratory conditions. Anagallis foemina L., Cerastium dicotomum L., Falcaria vulgaris L., Ranunculus asiaticus L., Scorpiurus mur‐icatus L. and Solanum nigrum L. extracts were the most toxic to the fungus. Further studies on buttercup (Ranunculus asiaticus L.) showed that fresh shoot extract of this species prevented growth of F. oxysporum when incorporated into agar medium. Extracts of different parts of the plant inhibited fungus growth and sporulation, but the fungitoxicity decreased with incubation period with only slight changes in the toxicity of fresh shoot extract. The shoot and fresh parts extracts were more toxic than root and dried tissue extracts. Addition of 0.5 ml fresh shoot or 1 ml fresh root extract to the growing medium significantly reduced fungal colony growth, and the effect was extract concentration dependent. Fresh shoot extract of R. asiaticus added to a liquid medium significantly reduced mycelial dry weight compared with the control, and incorporation of 0.1 g dried shoot or 0.2 g dried roots in the media strongly inhibited fungus growth. Results of a pot experiment showed no harmful effects of R. asiaticus extracts on tomato growth.