Verticillium Wilt Of Eggplant Research Articles

Comparative Proteomic Analysis of Roots from a Wild Eggplant Species Solanum sisymbriifolium in Defense Response to Verticillium dahliae Inoculation.

Eggplant verticillium wilt, caused by Verticillium spp., is a severe eggplant vascular disease. Solanum sisymbriifolium, a wild species of eggplant that is resistant to verticillium wilt, will be beneficial for genetically modifying eggplants. To better reveal the response of wild eggplant to verticillium wilt, proteomic analysis by iTRAQ technique was performed on roots of S. sisymbriifolium after exposure to Verticillium dahliae, and some selected proteins were also validated using parallel reaction monitoring (PRM). After inoculation with V. dahliae, the phenylalanine ammonia lyase (PAL) and superoxide dismutase (SOD) enzymes and the malondialdehyde (MDA) and soluble protein (SP) of S. sisymbriifolium roots all exhibited an increase in activity or content compared with that of the mock-inoculated plants, especially at 12 and 24 h post-inoculation (hpi). A total of 4890 proteins (47.04% of the proteins were from S. tuberosum and 25.56% were from S. lycopersicum according to the species annotation) were identified through iTRAQ and LC-MS/MS analysis. A total of 369 differentially expressed proteins (DEPs) (195 downregulated and 174 upregulated) were obtained by comparison of the control and treatment groups at 12 hpi, and 550 DEPs (466 downregulated and 84 upregulated) were obtained by comparison of the groups at 24 hpi. The most significant Gene Ontology (GO) enrichment terms at 12 hpi were regulation of translational initiation, oxidation-reduction, and single-organism metabolic process in the biological process group; cytoplasm and eukaryotic preinitiation complex in the cellular component group; and catalytic activity, oxidoreductase activity, and protein binding in the molecular function group. Small molecule metabolic, organophosphate metabolic, and coenzyme metabolic processes in the biological process group; the cytoplasm in the cellular component group; and catalytic activity and GTPase binding in the molecular function group were significant at 24 hpi. Then, KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis was performed, and 82 and 99 pathways (15 and 17, p-value < 0.05) were found to be enriched at 12 and 24 hpi, respectively. Selenocompound metabolism, ubiquinone, and other terpenoid-quinone biosyntheses, fatty acid biosynthesis, lysine biosynthesis, and the citrate cycle were the top five significant pathways at 12 hpi. Glycolysis/gluconeogenesis, biosynthesis of secondary metabolites, linoleic acid metabolism, pyruvate metabolism, and cyanoamino acid metabolism were the top five at 24 hpi. Some V. dahliae-resistance-related proteins, including phenylpropanoid-pathway-related proteins, stress and defense response proteins, plant-pathogen interaction pathway and pathogenesis-related proteins, cell wall organization and reinforcement-related proteins, phytohormones-signal-pathways-related proteins, and other defense-related proteins were identified. In conclusion, this is the first proteomic analysis of S. sisymbriifolium under V. dahliae stress.

Temporal Assessment of Biofumigation Using Mustard and Oilseed Rape Tissues on Verticillium dahliae, Soil Microbiome and Yield of Eggplant

Verticillium dahliae is a soil-borne pathogen that is difficult to eliminate, causes a severe reduction in the yield and quality of eggplant, and could be controlled through environmentally friendly biofumigation. However, the mechanisms of its effects on the dynamic changes of soil microbes is not clear. In this study, we examined the efficacy of two Brassica vegetables, mustard (Brassica napiformis, BFN) and oilseed rape (Brassica napus, BFC), as biofumigants to control Verticillium dahliae and observed their effects on the soil microbial community compared with chemical fumigants (CF) and a control (CN) in a greenhouse where eggplant was continuously cultivated for 12 years. Illumina MiSeq sequencing was used to analyse the soil microbiome. Real-time PCR was used to assay in order to estimate the soil abundance of Verticillium dahlia, and the glucosinolate concentration in biofumigants was determined using HPLC. Results showed that the BFN treatment had a significant biocidal effect on V. dahliae in the soil, decreasing its abundance by 64.74% compared to the control (CN). No significant difference was observed between BFC and CN treatments. Yield in the BFN treatment improved due to a lower disease incidence rate and disease index. Biofumigation had significant effects on the community structure and abundance of bacteria and fungi. The bacterial diversity of the BFN treatment was significantly lower than those of the other treatments, and beneficial bacterial community relative abundance, such as Flavobacteria, Pseudomonas and Bacillus, increased after the soil was biofumigated for 15 days. However, the temporal difference in bacterial and fungi structure among the different treatments was reduced with the development of the eggplant growth stage. The Mortierella, Altemaria and Chaetomium genera were significantly abundant across all treatments. Soil enzyme activities were also improved. In summary, biofumigation using mustard was efficient in controlling eggplant Verticillium wilt due to changes in the soil bacterial composition at the early eggplant growth stage; the initial conditions in the soil bacterial community are a key determinant of what is going to happen after Brassica biofumigation, which could be considered a practical addition to integrated pest management for the reduction of soil-borne pathogens.

Integrated crop practices management stimulates soil microbiome for Verticillium wilt suppression

Understanding the components that shape the rhizosphere community is vital for sustainable disease management. This study evaluated an integrated Verticillium wilt management in eggplant and its influence on the soil microbiome. Six treatments; Self-rooted (control; CLA) and sole grafted (CLB) eggplants, Brassica + Self-rooted plant (BrA), and Brassica + Grafted plants (BrB), with Biochar (10 t/ha) + Brassica + Self-rooted plant (BBrA) and Biochar (10 t/ha) + Brassica + Grafted Plant (BBrB) were used. Soil microbiome was characterized using high-throughput sequencing. The grafted treatments significantly reduced the Verticillium abundance, disease index and improved the yield of eggplant compared with CLA (18.13 t/ha), with BBrB (41.54 t/ha) as the best treatment. Results showed that treatments CLB, BrB, and BBrB stimulated more beneficial microbes, especially Arthrobacter, Bacillus, and Sphingomonas for bacteria; and Mortierella, Tausonia, and Chaetomium for fungi. Treatment BBrB was biomarked by phylum Chloroflexi (o_SBR1031), Acidobacteria, Planctomycetes, and Patescibacteria, but only Chloroflexi (o_SBR1031) was found in BrB, and none of them in CLB and treatment BBrB also contained more biomarkers than other treatments. Similarly, the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis revealed that treatment BBrB contained more genes (17.5%) regulating disease resistance followed by BrB (17.3%) and CLB (16.6%) treatments. In conclusion, grafting with Brassica (biofumigation) under a biochar regime could reduce eggplant Verticillium wilt. This study expands knowledge on how soil microbiota can be enhanced using integrated disease management practices to exploit sustainable food production.

Effects of Trichoderma and PGPR applications on growth and Verticillium wilt of eggplant

In this study, effects of single and combined applications of biocontrol agents; Trichoderma spp. (T. atroviride, T. virens) and plant growth promoting rhizobacteria (Pseudomonas koreensis, Bacillus subtilis) on growth, wilt disease severity caused by Verticillium dahliae and plant defence-related enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonium lyase and β-1,3 glucanase) of eggplant, were investigated. It was determined that single and combined applications of biological control agents reduced the severity of wilt disease caused by the pathogen, and T. atroviride isolate and its combinations with bacteria were the most effective applications. Biological control agents not only increased plant growth parameters in the experimental groups they were applied, but also the activities of defence-related peroxidase, polyphenol oxidase, phenylalanine ammonium lyase and β-1,3 glucanase enzymes in the plant samples taken from these groups. Inoculations with biocontrol agents especially increased stem diameter, length, fresh and dry weights and root lengths of the eggplants, compared to the pathogen inoculated ones. Although the enzyme activities of the plants changed depending on the period after the inoculations, mostly found to be higher on the plants inoculated with the pathogen and/or biocontrol agents, compared to the non-inoculated control plants.

Identification of miRNA targets in eggplant in response to Verticillium dahliae by degradome sequencing

Verticillium wilt is a vascular disease caused by Verticillium dahliae, which has a serious impact on the yield and quality of eggplant. MiRNAs regulates plant growth, development, environmental adaptation and other life activities by controlling the expression of target genes. Although miRNAs have been systematically studied by high-throughput sequencing in eggplant (Solanum melongena L.), their target genes are not identified systematically, which would provide the basis for exploring the mechanism of miRNA mediated gene regulation in response to Verticillium wilt of eggplant. In this study, degradome sequencing was performed using two libraries separately prepared from mock-inoculated and V. dahliae-inoculated seedlings of eggplants. A total of 122 target genes for 49 miRNAs families were identified. Of them, 62 target genes were significantly induced by V. dahliae, including 34 targets were found only in the inoculated seedlings library and 28 targets were shown to be differentially expressed between both two libraries. Further analysis showed that a conserved miRNA could target various genes ranging from one up to 15 or a target gene could be cleaved by 1–5 different miRNAs. QRT-PCR analysis on five miRNAs and their target genes confirmed the reliability of the degradome sequencing data. GO analysis revealed that target genes owned diverse biological functions and transcription regulation was the largest functional category. Analysis on KEGG showed that target genes were mainly involved in plant-pathogen interaction pathway and plant hormone signal transduction pathway to resist disease. This result will provide basic information for further studying the regulatory mechanism of eggplant miRNAs in response to Verticillium wilt infection.

Eggplant by grafting enhanced with biochar recruits specific microbes for disease suppression of Verticillium wilt

The suppressiveness of soils to inhibit pathogens mostly require rich microbiome harbouring plant growth-promoting microbes in the soil, especially rhizosphere. The present study evaluates the suppressiveness of the rhizosphere of a grafted eggplant under biochar amendment and its effects on the microbial communities involved. This study used four treatments consisting of grafted (CB) and self-rooted (CA) eggplants, with 10 t/ha biochar addition each (as BB and BA). Results revealed that BB significantly suppressed the incidence of Verticillium wilt by more than 70% and improved the yield of eggplant compared with the control. Treatment of CB and BB showed significant effects on the community structure and abundance of bacteria and fungi. The bacteria diversity and richness of CB and BB were higher than those of the BA and CA, respectively. For bacteria, the analysis showed the genus Bacillus to be abundant in the rhizosphere of both CB and BB, while genera Humicola, Chaetomium, Mortierella, and Tausonia were the dominant fungi, suggesting they may play an active part in disease suppression. Based on Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis, the results showed that CB and BB harbored more genes responsible for disease resistance than CA and BA. In summary, grafting with the addition of biochar was effective in suppressing Verticillium wilt of eggplant and can be given as a recommendation to eggplant growers to alleviate Verticillium wilt.

Screening of phenotypic conversion mutant strains of Ralstonia solanacearum for effective biological control of Verticillium wilt in eggplant

Ralstonia solanacearum causes bacterial wilt and undergoes spontaneous phenotypic conversion (PC) from its wild-type form to non-pathogenic form. We previously reported that the pre-inoculation of PC mutants in Solanum plants suppressed bacterial wilt. In the present study, we clarified the inoculation method of PC mutants and PC mutant strains for effective control the eggplant Verticillium wilt caused by Verticillium dahliae, a soil-borne fungal plant pathogen. We first investigated three different methods for pre-inoculating PC mutants in the five-leaf-stage seedlings of eggplant: Method A involved soaking plant roots in the PC mutant suspension immediately before challenge-inoculation with V. dahliae; Method B involved irrigation with the PC mutant suspension in pots at 7 days before challenge-inoculation with the pathogen; and Method C involved soaking plant roots in the PC mutant suspension at 3 weeks before challenge-inoculation with the pathogen. The highest biological control was achieved with Method A. To quickly and easily select effective PC mutants for biological control of Verticillium wilt in a growth chamber, a simplified evaluation method based on Method A was applied using the young (two-leaf-stage) seedlings of eggplant. Furthermore, we investigated the biological control efficacies of 27 PC mutants against Verticillium wilt in eggplants using the simplified evaluation method in vivo, and growth inhibition of V. dahliae by PC mutants in vitro. However, no relationship existed between the biological control and growth inhibition of V. dahliae, suggesting that it is unlikely to be involved as the main factor affecting the biological control by PC mutants. Three PC mutants, 8345PC, 8109PC, and 8107PC, which showed high biological control efficacies in the simplified evaluation method (64.6%, 66.0%, and 68.9%, respectively), were evaluated for their biological control using five-leaf-stage eggplant seedlings in greenhouse test. Among these three mutants, the 8107PC strain showed the highest biological control of 43.3% and was selected as the most effective PC mutant for suppressing Verticillium wilt in eggplant. Thus, the use of PC mutants is expected to be effective in the control of Verticillium wilt in eggplant.

Evaluation of the Biocontrol Potential of Purpureocillium lilacinum QLP12 against Verticillium dahliae in Eggplant.

A fungus with broad spectrum antifungal activity was isolated from the soil in Qinling Mountain, Shaanxi Province, in China. The fungus was identified as Purpureocillium lilacinum based on ITS rDNA gene analysis. The strain, coded as QLP12, showed high inhibition activity on fungal mycelium growth in vitro, especially to Mucor piriformis, Trichothecium roseum, Rhizoctonia solani, and Verticillium dahliae, and its potential for biocontrol efficacy of eggplant. Verticillium wilt disease caused by Verticillium dahliae among 10 fungal species tested was explored. In greenhouse experiments, QLP12 showed an excellent growth-promoting effect on eggplant seed germination (76.7%), bud growth (79.4%), chlorophyll content (47.83%), root activity (182.02%), and so on. QLP12 can colonize the eggplant interior and also develop in rhizosphere soil. In greenhouse, the incidence of Verticillium wilt decreased by 83.82% with pretreated QLP12 fermentation broth in the soil. In the field, QLP12 showed prominent biocontrol effects on Verticillium wilt by reducing the disease index over the whole growth period, a decline of 40.1%. This study showed that the strain QLP12 is not only an effective biocontrol agent for controlling Verticillium wilt of eggplant, but also a plant growth-promoting fungus that deserves to be further developed.

De Novo Sequencing and Analysis of the Transcriptome of the Wild Eggplant Species Solanum Aculeatissimum in Response to Verticillium dahliae

Eggplant verticillium wilt, caused by Verticillium dahliae, is one of the most severe diseases of eggplant worldwide. Transferring of resistance genes from wild relatives would be valuable for the continued improvements of eggplant. Solanum aculeatissimum, a wild relative of eggplant possessing resistance to verticillium wilt, is potentially useful for genetically enhancing eggplant. To better understand the defense response to V. dahliae, transcriptome analysis of roots from S. aculeatissimum in response to V. dahliae infection was performed. A total of 69,824 all-unigenes were obtained through Illumina/Solexa sequencing. Functional annotations by aligning all-unigenes with public protein databases including NCBI non-redundant protein (NR), Clusters of Orthologous Groups (COG), Swiss-Prot protein, and Kyoto Encyclopedia of Genes and Genomes (KEGG) were obtained. The gene expression profiles of S. aculeatissimum infected with V. dahliae were compared to those of non-infected plants, and 11,696 upregulated and 5949 downregulated genes were identified. Gene Ontology (GO) enrichment and metabolic pathway-enrichment analysis were performed. Some V. dahliae-resistant related genes, including putative resistance genes (R-genes), phenylpropanoid pathway-related genes, genes encoding pathogenesis-related proteins (PRs) and transcription factors were identified. Taken together, this is the first transcriptome sequencing of S. aculeatissimum under V. dahliae stress.

Crop rotation with broccoli suppresses Verticillium wilt of eggplant

In this study, we assessed whether crop rotation with broccoli suppressed eggplant Verticillium wilt. In 6 trials of crop rotation in 5 fields from 2009 to 2013, broccoli rotation was coupled with postharvest residue incorporation before planting eggplant. Meta-analysis of the disease incidence data from all the trials revealed that the combined relative disease risk was 0.53 (95 % confidence interval 0.34–0.83). Thus, the disease incidence of eggplant in crop rotation with broccoli decreased to 53 % of that of eggplant without broccoli rotation. Browning of vascular tissue from Verticillium dahliae infection was observed in broccoli, but was limited to the roots and did not reach the aerial plant portion where V. dahliae forms microsclerotia. Estimation of V. dahliae population in soil using quantitative nested real-time polymerase chain reaction indicated that V. dahliae DNA copy number in soil samples tended to decrease owing to broccoli cultivation. These results suggest that broccoli root could act as a “decoy” that traps V. dahliae in soil. Further studies are necessary to elucidate the mechanisms of disease suppression; this is the first report that broccoli cultivation and subsequent incorporation of residue into the soil suppresses Verticillium wilt of eggplant.

Evaluation of Streptomyces spp. for the biological control of corky root of tomato and Verticillium wilt of eggplant

The effects of Streptomyces spp. isolates in the biological control of corky root of tomato and Verticillium wilt of eggplant was determined in in vitro, greenhouse and field trials. Twenty-six Streptomyces spp. isolates were obtained from the rhizospheres of different vegetable crops in southern Italy. In in vitro dual culture tests, mycelial radial growth of Pyrenochaeta lycopersici and Verticillium dahliae was reduced up to 18.6% and 30.1%, respectively. Radial growth of seven other fungal pathogens was variably reduced as well. The isolates StB-3, StB-6, StB-11 and StB-12 showed a good antagonistic effect against both P. lycopersici and V. dahliae, while the rest of isolates eventually showed antagonism against only one pathogen.In pot-experiments in the greenhouse three of the four above-mentioned Streptomyces spp. isolates significantly reduced corky root up to 64.9% (StB-11), and all four isolates reduced foliar symptoms of Verticillium wilt (AUDPC) up to 48.3%, but none of them reduced the severity of vascular browning. In naturally infested field trials, StB-11 significantly reduced corky root severity in tomato by 48.2%, StB-12 by 35% and StB-6 by 32.6%, but none of the isolates were effective in controlling Verticillium wilt of eggplant. The effectiveness of the streptomycete AtB-42, successfully used in previous researches, was here confirmed as it reduced corky root of tomato in the field by 33.6%. In conclusion, our research demonstrates that under field conditions corky root of tomato, but not Verticillium wilt of eggplant, can be effectively controlled by the Streptomyces spp. isolates used in this study.

Seedling vaccination by stem injecting a conidial suspension of F2, a non-pathogenic Fusarium oxysporum strain, suppresses Verticillium wilt of eggplant

Several bacterial and fungal strains have been evaluated as biocontrol agents (BCAs) against Verticillium dahliae. In these studies, the BCAs were applied as a root drenching inoculum; however, this application method may have an adverse effect on the native, beneficial for the plants, microbial community. In the present study, it was evaluated whether endophytic application by stem injecting a conidial suspension of the non pathogenic Fusarium oxysporum F2 strain, isolated from a V. dahliae suppressive compost amendment, could reduce significantly Verticillium wilt symptom development in eggplants. It was revealed that stem injection of F2 seven days before transplanting the seedlings to soil infested by V. dahliae microsclerotia resulted in reduced disease severity compared to the control treatment. To visualise F2 ramification into the plant vascular system eggplant stems were injected with an EGFP transformed F2 strain. It was shown that F2 colonises effectively the plant vascular tissues over a long period of time as it was assessed by F2 DNA levels. In parallel, qPCR analysis showed that the application of F2 reduced significantly the amount of V. dahliae DNA in the stem tissues compared to the control treatment.

Varietal Difference in Resistance to Verticillium Wilt of Eggplant in Rootstock

Varietal Difference in Resistance to Verticillium Wilt of Eggplant in Rootstock

Isolation and Characterization of EndophyticBacillius subtilisJaas ed1 Antagonist of Eggplant Verticillium Wilt

An endophytic bacterial strain, Jaas ed1, was isolated from the interior of eggplant (Solanum melongena L.) stems in Jiangsu Province, China. According to the morphological and physiological characteristics and phylogenetic analysis of the 16s rDNA sequence, it was identified as Bacillius subtilis. Strain Jaas ed1 and its cell-free filtrate had strong antifungal activity against Verticillium dahliae. The strain was an internal colonizer within the eggplant without any harmful side effects to the plant. In greenhouse experiments, the strain cell suspension effectively controlled Verticillium wilt of eggplant, and its control efficiency was far more significant than that of the cell-free filtrate after inoculation of V. dahliae.

Suppression of Verticillium Wilt of Eggplant by Earthworms.

The role of earthworms in plant disease has received little attention. To address whether earthworms would affect the severity of Verticillium wilt of eggplant (Solanum melongena) in the field, we grew eggplants in experimental field plots that were naturally infested with Verticillium dahliae in 2005, 2006, and 2007. Three earthworm treatments were compared: (i) no treatment (untreated control), (ii) earthworm populations reduced via chemical eradicants (carbaryl or hot mustard) (reduced treatment), and (iii) earthworm populations increased by addition of adult Canadian nightcrawlers (Lumbricus terrestris, 11 earthworms per m2) (augmented treatment). Compared to the untreated control, the estimates of the area under the disease progress curve (AUDPC) were reduced while estimates of the canopy growth curve (CGC) and the final plant weights were increased in plots augmented with earthworms in all 3 years. In 2 out of 3 years, eggplant yield (weight and number of fruit) was increased in plots augmented with earthworms. When a carbaryl drench was used to reduce earthworm numbers, the treatment resulted in plants with more disease than in the untreated controls in 2005. However, in 2005 and 2006, carbaryl-treated plants had larger CGC values and higher yield than in the untreated controls and were not significantly different from the augmented plots. When a hot mustard extraction procedure was used to reduce earthworm densities in 2007, plant growth, yield, and disease variables did not differ from the untreated control. Although the effects of reducing earthworms were variable and difficult to explain, our findings suggest that augmenting earthworm populations can suppress Verticillium wilt of eggplant, and strategies that increase earthworm numbers may contribute to disease suppression.

Influence of Earthworm Activity on Soil Microbes and Soilborne Diseases of Vegetables.

Earthworm densities have been regarded as reliable indicators of soil health, but their role in suppression of plant disease has not received much attention. Several greenhouse studies were done to determine if soils infested with soilborne pathogens and augmented with earthworms (Lumbricus terrestris) could reduce disease of susceptible cultivars of asparagus (Asparagus officinalis), eggplant (Solanum melongena), and tomato (Solanum lycopersicum). Soils planted with asparagus were infested with Fusarium oxysporum f. sp. asparagi and F. proliferatum, eggplant with Verticillium dahliae, and tomato with F. oxysporum f. sp. lycopersici Race 1. In each host-disease system, earthworm activity was associated with an increase in plant growth and a decrease in disease. In general, plant weights were increased 60 to 80% and estimates of disease (area under the disease progress curve, percent vascular discoloration, and percent root lesions) were reduced 50 to 70% when soils were augmented with earthworms. Soil dilutions on selective media revealed that densities of fluorescent pseudomonads and filamentous actinomycetes were consistently higher for rhizosphere soils augmented with earthworms. In the studies with Verticillium wilt of eggplant, compared to the controls, the densities of total bacteria and Mn-transforming microbes were reduced in the presence of earthworms while population densities of bacilli and Trichoderma spp. were not affected. Disease suppression may have been mediated through microbiological activity. These studies suggest that strategies to increase earthworm densities in soil should suppress soilborne diseases.

The Effect of Organic Amendments from Brassicaceae and Solanaceae Plants and Trichoderma harzianum on the Development of Verticillium dahliae Kleb.

The Effect of Organic Amendments from Brassicaceae and Solanaceae Plants and Trichoderma harzianum on the Development of Verticillium dahliae Kleb. The aim of this work was to evaluate the effectiveness of plant material from Brassicaceae and Solanaceae plants, containing biologically active compounds, and antagonistic microorganisms on survival of microsclerotia and development of Verticillium wilt of eggplant. Water extracts from tomato and rapeseed plants added to the agar media showed negative effect on the development of fungus Verticillium dahliae. The most toxic effect was observed for the fresh extract from tomato green parts. The pasteurization or sterilization of extracts in an autoclave decreased their detrimental effect. The addition of water extracts from rapeseed and tomato plants also hampered growth of mycelia and development of V. dahliae microsclerotia on Czapek-Dox medium with cellophane. The addition of rapeseed meal, water extracts from rapeseed meal or tomato plants, significantly decreased number of V. dahliae propagules in the soil. Also, the inoculation of soil with antagonistic fungus Trichoderma harzianum strain PBG decreased population of V. dahliae in soil samples. The plant material and T. harzianum strain PBG had positive effect on the growth and yield of eggplants in the soil infested with microsclerotia of V. dahliae. However, the most beneficial effect exerted fumigation of the infested soil with Nemazin 97 XX (97% dazomet), used in this experiment as a reference treatment.

Characterization of chitinase secreted by Bacillus cereus strain CH2 and evaluation of its efficacy against Verticillium wilt of eggplant

A chitinase-secreting strain CH2 was one of 353 strains isolated from rhizosphere of eggplant. Based on 16S rDNA sequence alignment and several biochemical and physiological characteristics, the strain was identified to be of Bacillus cereus. On chitin-Ayers (CA) medium, the strain secreted chitinase. Evaluation of its activity, combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), showed it to be a 15.0-KD chitinase. On glass slides, germination of the fungal spores was effectively suppressed by the bacterial suspension, supernatant from the suspension, and 0.005% solution of chitinase extracted from the strain CH2. The optimum pH for chitinase was 7.1 and optimum temperature was 40°C. At that temperature, high-level chitinolytic activity was retained for 10 days. In greenhouse experiments, suspension of the cells of the CH2 strain reduced the severity of Verticillium wilt on eggplant by 69.69%, its supernatant by 54.04%, and the enzyme diluted to 0.01% strength by 53.13% in 14 days. Strain CH2 and its chitinase have good commercial potential in controlling Verticillium wilt.

Managing soilborne diseases of vegetable crops with a pre-plant soil or substrate amendment of a corn distillation product1

The efficacy of condensed distiller's solubles (CDS), a co-product of ethanol production from corn, rich in organic matter, and high in carbon to nitrogen ratio, was tested as a pre-plant amendment against Verticillium wilt of eggplant and potato scab in potato soils from commercial fields and against damping-off diseases of radish and cucumber seedlings in a peat-based mix and muck soil. Eggplants grown in a potato soil amended with CDS (1% mass/mass) showed less Verticillium wilt and increased fresh (37–54%) and dry (31–45%) plant biomass compared to the control in the greenhouse. In a potato soil with medium levels of disease, CDS (1 or 2%) increased the percentage of marketable tubers by 116% under greenhouse, 119% under micro-plot and 75% under field conditions. In the growth room, CDS (1, 2, and 4%) amendment to a peat-based mix infested with Rhizoctonia solani 1 week before planting seeds improved the percentage of healthy radish seedlings (22–72% healthy seedlings compared to 2% in the control). Levels of disease suppression increased with the incubation time prior to planting. Disease control effect of CDS was not consistent between different batches of peat-based mix. In a non-suppressive batch of peat-based mix, disease suppression by CDS was enhanced by a bio-control agent, Trichoderma hamatum 382. In muck soil from a commercial field naturally-infested with Pythium spp., CDS (0.25, 0.5, and 1%) provided protection of cucumber seedlings from damping-off immediately after incorporation, but the maximum protection was seen after 1 week with all three rates. The number of total bacteria was enhanced in the CDS-amended muck soil. In the micro-plots, CDS (0.5 and 1%) as an amendment to muck soil 2 weeks before planting improved the percentage of healthy cucumber seedlings and fresh plant weight compared to the control. CDS is not toxic to the pathogens and disease suppression is believed to be due to biological activity stimulated by CDS in the substrate.

Efficacy of acibenzolar-S-methyl and two strobilurins, azoxystrobin and trifloxystrobin, for the control of corky root of tomato and verticillium wilt of eggplant

The efficacy of two fungicides, azoxystrobin and trifloxystrobin, and a plant defense activator, acibenzolar-S-methyl, for the control of tomato corky root and eggplant verticillium wilt, was evaluated under greenhouse and field conditions by means of dips, soil drenches or foliar sprays. The strobilurins provided excellent control of the two diseases under greenhouse conditions. Azoxystrobin was more effective than trifloxystrobin and reduced the severity of tomato corky root and eggplant verticillium wilt by 98% and 95%, respectively. Acibenzolar-S-methyl caused plant stunting and severe leaf chlorosis in the greenhouse experiments. In the field, azoxystrobin provided the best control. Tomato corky root severity was reduced by 83% and eggplant verticillium wilt severity by 29%. At the dosage used, acibenzolar-S-methyl was effective only in controlling tomato corky root. No phytotoxic symptoms were observed by any material in the field.