Soil-borne Plant Pathogens Research Articles

Transcriptional Regulator PhlH Modulates 2,4-Diacetylphloroglucinol Biosynthesis in Response to the Biosynthetic Intermediate and End Product.

Certain strains of biocontrol bacterium Pseudomonas fluorescens produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) to antagonize soilborne phytopathogens in the rhizosphere. The gene cluster responsible for the biosynthesis of 2,4-DAPG is named phlACBDEFGH and it is still unclear how the pathway-specific regulator phlH within this gene cluster regulates the metabolism of 2,4-DAPG. Here, we found that PhlH in Pseudomonas fluorescens strain 2P24 represses the expression of the phlG gene encoding the 2,4-DAPG hydrolase by binding to a sequence motif overlapping with the -35 site recognized by σ70 factors. Through biochemical screening of PhlH ligands we identified the end product 2,4-DAPG and its biosynthetic intermediate monoacetylphloroglucinol (MAPG), which can act as signaling molecules to modulate the binding of PhlH to the target sequence and activate the expression of phlG Comparison of 2,4-DAPG production between the ΔphlH, ΔphlG, and ΔphlHG mutants confirmed that phlH and phlG impose negative feedback regulation over 2,4-DAPG biosynthesis. It was further demonstrated that the 2,4-DAPG degradation catalyzed by PhlG plays an insignificant role in 2,4-DAPG tolerance but contributes to bacterial growth advantages under carbon/nitrogen starvation conditions. Taken together, our data suggest that by monitoring and down-tuning in situ levels of 2,4-DAPG, the phlHG genes could dynamically modulate the metabolic loads attributed to 2,4-DAPG production and potentially contribute to rhizosphere adaptation.IMPORTANCE 2,4-DAPG, which is synthesized by biocontrol pseudomonad bacteria, is a broad-spectrum antibiotic against bacteria, fungi, oomycetes, and nematodes and plays an important role in suppressing soilborne plant pathogens. Although most of the genes in the 2,4-DAPG biosynthetic gene cluster (phl) have been characterized, it is still not clear how the pathway-specific regulator phlH is involved in 2,4-DAPG metabolism. This work revealed the role of PhlH in modulating 2,4-DAPG levels by controlling the expression of 2,4-DAPG hydrolase PhlG in response to 2,4-DAPG and MAPG. Since 2,4-DAPG biosynthesis imposes a metabolic burden on biocontrol pseudomonads, it is expected that the fine regulation of phlG by PhlH offers a way to dynamically modulate the metabolic loads attributed to 2,4-DAPG production.

Degradation of the fungal cell wall by clostridial strains isolated from soil subjected to biological soil disinfestation and biocontrol of Fusarium wilt disease of spinach.

Biological soil disinfestation (BSD) involves elimination of soil-borne plant pathogens in an environmentally friendly manner. Two anaerobic bacterial strains (H110 and TB8) isolated from BSD-treated soil samples were analyzed for their roles in elimination of pathogenic fungi. The two strains were identified as Clostridium beijerinckii based on 16S rRNA gene sequences and phenotypic properties. The strains fermented various carbohydrates and produced acetate, butyrate, and n-butanol as major products as well as abundant gases (H2 and CO2). For evaluation of the antifungal potential of these strains, cells of a pathogen (spinach wilt disease, Fusarium oxysporum f. sp. spinaciae) were co-inoculated into anaerobic media with each anaerobic strain. After incubation for ~3weeks at 30°C, 10-30% of the cells of the pathogen survived when incubated without the anaerobic isolates, whereas the pathogen was eliminated when co-incubated with each anaerobe because of the growth of the anaerobic bacterium. It was found by microscopic examination that mycelial cells of the fungal pathogen were severely degraded during the first 3-7days of the co-incubation. The two strains utilized major cell wall polysaccharides of ascomycetous fungi-chitosan and ß-1,3-glucan (curdlan and laminarin)-as fermentative substrates added to the medium. Furthermore, both isolates degraded a cell wall preparation isolated from the mycelium of the Fusarium pathogen of spinach wilt disease. We concluded that the two anaerobic strains kill the pathogen of spinach wilt disease by degrading major fungal cell wall components as antifungal activities.

ANTIFUNGAL POTENTIAL OF A BRASSICACEOUS WEED Sisymbrium irio AGAINST Macrophomina phaseolina

ABSTRACT Macrophomina phaseolina, a soil-borne plant pathogen, has the ability to cause diseases in about 500 plant species. Unfortunately, so far no registered fungicide is available against this fungal pathogen. In the present study, different extracts of Sisymbrium irio, a weed of family Brassicaceae, were tested for evaluation of their antifungal activity against M. phaseolina. In screening bioassays, antifungal activity of methanolic extracts of 1% to 6% concentrations of different parts (leaf, stem, root and fruit) of the weed was assessed against the fungal pathogen. Methanolic leaf and root extracts significantly reduced fungal biomass up to 59% and 69% over control, respectively. Methanolic leaf and root extracts were further partitioned using four organic solvents namely n-hexane, chloroform, ethyl acetate and n-butanol in order of increasing polarity. Antifungal activity of different concentrations of these fractions (3.125, 6.25, …, 200 mg mL-1) was assessed against the pathogen. Chloroform and n-hexane fractions of methanolic leaf extract showed highly pronounced activity resulting in 35-75% and 15-87% reduction in fungal biomass over corresponding control treatments, respectively. Likewise, the highest concentration (200 mg mL-1) of chloroform, ethyl acetate and n-butanol fractions of methanolic root extract reduced fungal biomass by 75%, 70% and 87%, respectively. The present study concludes that chloroform and n-butanol fractions of methanolic leaf and root extracts of S. irio, respectively, contain potent antifungal constituents for management of M. phaseolina.

The Role of Soil Solarization in India: How an Unnoticed Practice Could Support Pest Control.

Plant protection represents one of the strategies to fill the yield gap and to achieve food security, a key topic for India development. Analysis of climate risks for crops indicates that South Asia is one of the regions most exposed to the adverse impact on many plants that are relevant to inhabitants exposed to food safety risks. Furthermore, accumulation of pesticide residues in the aquatic and other ecosystems is becoming a significant threat in India. These perspectives require to develop programs of crop protection that can be feasible according to Indian rural development and pollution policy. Here we review the research works done on soil solarization in India. Soil solarization (also called plasticulture) is an eco-friendly soil disinfestations method for managing soil-borne plant pathogens. This is the process of trapping solar energy by moist soil covered with transparent polyethylene films and chemistry, biology and physical properties of soil are involved in pest control. So far, this technique is applied in more than 50 countries, mostly in hot and humid regions. India has 29 states and these states fall under five climatic zones, from humid to arid ones. We report pest management application in different climatic zones and their effects on production, weeds, nematodes, and pathogenic microorganisms. The analysis of soil temperatures and crop protection results indicate as environmental requirement for soil solarization fits in most of Indian rural areas. Soil solarization is compatible with future Indian scenarios and may support Indian national food security programs.

GC-MS ANALYSIS AND ANTIFUNGAL ACTIVITY OF METHANOLIC ROOT EXTRACT OF Chenopodium album AGAINST Sclerotium rolfsii

ABSTRACT Sclerotium rolfsii is a soil-borne fungal plant pathogen that causes diseases in more than 500 plant species. Chemical fungicides used to control this disease cause environmental pollution, therefore, plant derived compounds can be used as alternative to synthetic fungicides to reduce environmental pollution. Chenopodium album is a weed of family Chenopodiaceae that is used as food and also has medicinal importance. In the present study, antifungal activity of methanolic root extract of C. album was evaluated against S. rolfsii using six concentrations viz. 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 g 100 mL-1 amended in malt extract as growth medium. All the root extract concentrations significantly reduced fungal biomass by 15-58% over control. Gas chromatography-mass spectrometry (GC-MS) analysis of the methanolic root extract of C. album was performed. Six compounds were identified in methanolic root extract through GC-MS analysis. The most abundant compound was 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester (58.56%) followed by 9-octadecenoic acid (Z)-, methyl ester (12.75%) and 9-octadecenoic acid (Z)-, methyl ester (10.27%), which might be responsible for antifungal activity of methanolic root extract of C. album.

Rhizoctonia solani: taxonomy, population biology and management of rhizoctonia seedling disease of soybean

Rhizoctonia solani, the most important species within the genus Rhizoctonia, is a soilborne plant pathogen with considerable diversity in cultural morphology, host range and aggressiveness. Despite its history as a destructive pathogen of economically important crops worldwide, our understanding of its taxonomic relationship with other Rhizoctonia‐like fungi, incompatibility systems, and population biology is rather limited. Among the host of diseases it has been associated with, seedling diseases inflicted on soybean are of significant importance, especially in the soybean growing regions of North America. Due to the dearth of resistant soybean genotypes, as well as the paucity of information on the mechanisms of host–pathogen interactions and other molecular aspects of pathogenicity, effective management options have mostly relied upon a combination of cultural and chemical control options. The first section of this review summarizes what is currently known about the taxonomy and systematics, population biology and molecular genetics of R. solani. The second section provides an overview of the pathology and management of rhizoctonia root and hypocotyl rot of soybean, a seedling disease of importance in North America.

Detection of Verticillium species in Swedish soils using real-time PCR

Verticillium species are soilborne plant pathogens, responsible for big yield losses worldwide. Here, we report improved procedures to generate DNA from Verticillium species imbedded in farm soils. Using new genomic sequence information, primers for V. dahliae, V. albo-atrum, V. tricorpus, and V. longisporum were designed. In a survey of 429 samples from intensively farmed soil of two Swedish regions, only V. dahliae and V. longisporum were identified. A bias towards V. longisporum (40%) was seen in the south, whereas V. dahliae was more frequent in the western region (19%). Analyses of soil and leaf samples from 20 sugar beet fields, where foliar wilting had been observed, revealed V. dahliae DNA in all leaf and soil samples and V. longisporum in 18 soil samples, illustrating host choice and longevity of the V. longisporum microsclerotia. This study demonstrates the applicability of new molecular diagnostic tools that are important for growers of variable crops.

Plant Phenotypic and Transcriptional Changes Induced by Volatiles from the Fungal Root Pathogen Rhizoctonia solani.

Beneficial soil microorganisms can affect plant growth and resistance by the production of volatile organic compounds (VOCs). Yet, little is known on how VOCs from soil-borne plant pathogens affect plant growth and resistance. Here we show that VOCs released from mycelium and sclerotia of the fungal root pathogen Rhizoctonia solani enhance growth and accelerate development of Arabidopsis thaliana. Seedlings briefly exposed to the fungal VOCs showed similar phenotypes, suggesting that enhanced biomass and accelerated development are primed already at early developmental stages. Fungal VOCs did not affect plant resistance to infection by the VOC-producing pathogen itself but reduced aboveground resistance to the herbivore Mamestra brassicae. Transcriptomics of A. thaliana revealed that genes involved in auxin signaling were up-regulated, whereas ethylene and jasmonic acid signaling pathways were down-regulated by fungal VOCs. Mutants disrupted in these pathways showed similar VOC-mediated growth responses as the wild-type A. thaliana, suggesting that other yet unknown pathways play a more prominent role. We postulate that R. solani uses VOCs to predispose plants for infection from a distance by altering root architecture and enhancing root biomass. Alternatively, plants may use enhanced root growth upon fungal VOC perception to sacrifice part of the root biomass and accelerate development and reproduction to survive infection.

Bean root rot management: Recommendations based on an integrated approach for plant disease control

A systematic understanding of agro-ecosystems suppressing soil-borne plant pathogens is one of the most desired objectives in plant disease management. Large-scale detection of agro-ecological descriptors of variations among crop-disease pathosystems will certainly save time to screen a wider range of conditions and identify more effective factors, to further examine at smaller scales, and to develop an integrated crop-disease management program. Therefore, a fairly comprehensive array of agronomic and environmental traits was examined across commercial fields cultivated with the common bean, Phaseolus vulgaris L. Then, ten factors chosen according to practical relevance to root rot epidemics and bean production were studied in laboratory, greenhouse or experimental field. The advantages and findings of this case study as a useful framework in plant pathology were discussed in this short review.

Variability of Effective Micro-organisms (EM) in bokashi and soil and effects on soil-borne plant pathogens

The microbial inoculant ‘Effective Microorganisms’ (EM) has been used to promote soil fertility and plant growth in agriculture. We tested effects of commercial EM products on suppression of soil-borne diseases, microbial activity and bacterial composition in organically managed sandy soils. EM was supplied as microbial stock suspension and fermented organic matter (EM-bokashi). Bioassays for soil-borne disease incidence were conducted with a naturally infested soil and inoculated disease-free organically managed nonamended soils or the same soils amended with EM-bokashi or sterilized EM-bokashi. Soil respiration analysis and denaturing gradient gel electrophoresis (DGGE) were performed to determine microbial activity, and bacterial composition and diversity. Disease incidence of cucumber plants was not affected by EM-bokashi but reduced by sterilized bokashi compared to the control in naturally infested soil. Pythium ultimum damping-off of cucumber in inoculated soil was enhanced by EM-bokashi and sterilized bokashi compared to the control. In one of three soils, infection of carrot by Rhizoctonia solani was reduced by EM-bokashi compared with sterilized bokashi. Soil respiration increased one week after soil amendment with EM-bokashi and sterilized EM-bokashi compared to the control, but not seven weeks later. DGGE showed that two batches of EM products had different microbial communities and soil amendment with EM-bokashi or sterilized EM-bokashi did not change the bacterial community and diversity in two soils. The added microorganisms in EM were possibly outcompeted and did not affect the existing bacterial community. We conclude that EM did not consistently suppress soil-borne diseases or change microbial activity and bacterial composition and diversity.

Field application of plant resistance inducers (PRIs) to control important root rot diseases and improvement growth and yield of green bean (Phaseolus vulgaris L.)

The efficiency of plant resistance inducers (PRIs) i.e. chitosan (CH), salicylic acid (SA) and humic acid (HA) in controlling Fusarium solani and Rhizoctonia solani the causal agents of root rot diseases under in vitro and on growth and yield of green bean cv. Giza 3 were evaluated. In vitro treatments of CH 1.0 g/l, CH 1.0 g/l + HA 5.0% and CH 0.5 g/l + SA 2.5%, as sterilized PDA medium addition, caused the highest reduction in mycelia growth and spore germination of F. solani and R. solani on incubated plates compared to control plates (medium free of inducers). Under greenhouse conditions, combined treatments of PRIs were superior than single treatments, while, CH 1.0 g/l + SA 5% or HA 5.0% treatments were more effective than single treatments in controlling of Rhizoctonia root rot. These treatments caused disease reduction reached to 70.4 and 67.4% of pre-emergence stage after 10 days of seed sowing, and 62.8 and 60.4% of post-emergence stage after 40 days of seed sowing. Meanwhile, the highest values of survival plants 79.4 and 77.8% were recorded with the same treatments. Under field conditions, the obtained results indicated that soaking bean seeds in CH 1.0 g/l + SA 5% followed by foliar application with half of this concentrations CH 0.5 g/l + SA 2.5%, (for 3 times in 7 days interval starting from the second true leaf stage), resulted in the higher percentages of reduction of damping-off and root rot incidence 68.2, 63.8, 70.0% and 67.4, 63.3, 69.6% after 10, 40 and 60 days during both seasons, respectively, compared with other treatments. Furthermore, such treatment was superior than commercial fungicide seed treatment in controlling of green bean root rot, where, fungicide treatment reduced damping-off and root rot incidence after 10, 40 and 60 days up to 64.6, 60.4, 64.0% and 64.0, 59.6, 63.4% during both seasons. Combined treatments of PRIs and commercial fungicide treatment resulted in increasing of vegetative growth characters, yield and quality of green bean pods compared to other treatments during two successive seasons. It could be suggested that using plant resistance inducers in comparison with fungicides, might be considered as an eco-friendly, safe, cheap and easily applied method for controlling such soil-borne plant pathogens considering the avoidance of environmental pollution and the side effects of fungicides application.

Effect of boron on mycelial growth, sporangiogenesis and zoosporogenesis of Phytophthora nicotianae and the possible inhibitory mechanisms

Phytophthora nicotianae is one of the most important soil-borne plant pathogens. Sporangia and zoospores of P. nicotianae are responsible for primary infection and disease dissemination. The disease caused by P. nicotianae was difficult to control by fungicide. Boron, an essential plant micronutrient, was found to have a direct effect on other pathogens. In this paper, the effects of B on the growth, antioxidant system and gene differential expression of P. nicotianae were tested. The results showed that 0.1 mM B could dramatically decrease the sporangiogenesis and zoosporogenesis of P. nicotianae. Mycelial growth of P. nicotianae was significantly inhibited when the concentration of B reached 8 mM. A high-quality differential expression sequence csn4 was obtained by gene differential expression analysis. Under the treated of B, csn4 expression was inhibited, activity of superoxide dismutase (SOD) and catalase (CAT) significantly decreased and the malondialdehyde (MDA) content notably increased compared to control. It is suggested that B could serve as a potential fungicide for the control of plant disease caused by P. nicotianae.

The gene task1 is involved in morphological development, mycoparasitism and antibiosis of Trichoderma asperellum

ABSTRACTCompetitive activity, mycoparasitism and antibiosis of Trichoderma asperellum are considered essential mechanisms in its suppressive activity against soil-borne plant pathogens. The role of the mitogen-activated protein kinase encoding gene task1 on morphological development, mycoparasitic interaction and the production of cell wall degrading enzymes and secondary metabolites were examined in T. asperellum. The Δtask1 mutant had altered growth morphology, lost its ability to parasitise plant pathogens and showed increased expression of several cell wall degrading enzymes during confrontation with Rhizoctonia solani. T. asperellum task1 expression was negatively correlated with cell wall degrading enzyme activities during inducing experiments using pathogen cell wall compounds. In antibiosis assays, task1 deletion caused increased output of 6-pentyl-α-pyrone and inhibition of pathogen growth.

Identification and characterization of the major antifungal substance against Fusarium Sporotrichioides from Chaetomium globosum.

Fusarium sporotrichioides, is a common soil-borne plant pathogen causing dry rot of potato in Northeast China. The objective of this study was to identify the main antifungal substances from Chaetomium globosum W7 against F. sporotrichioides. Strain W7 can significantly inhibit F. sporotrichioides without direct contact, suggesting that its antifungal substance was extracellular, and the solubility of this antifungal substance in ethyl acetate was superior to that in water. Acetone was selected as the optimum solvent for the extraction of the metabolites of C. globosum. Metabolites were then separated with thin-layer chromatography. Following antifungal tests on bands, a dark brown band with Rf value of 0.20 was determined as the antifungal substance, and identified as chaetoglobosin A. The antifungal activity test showed that the minimum inhibitory concentration of chaetoglobosin A to F. sporotrichioides was 9.45-10.50μg/mL, IC50 being 4.344μg/mL. Chaetoglobosin A also proved to have an excellent preventive effect on potato dry rot caused by F. sporotrichioides. To summarize, chaetoglobosin A was identified as the main active substance of C. globosum to inhibit F. sporotrichioides for the first time, and demonstrated a potential application value in agriculture.

Comparative Analysis of Ralstonia solanacearum Methylomes

Ralstonia solanacearum is an important soil-borne plant pathogen with broad geographical distribution and the ability to cause wilt disease in many agriculturally important crops. Genome sequencing of multiple R. solanacearum strains has identified both unique and shared genetic traits influencing their evolution and ability to colonize plant hosts. Previous research has shown that DNA methylation can drive speciation and modulate virulence in bacteria, but the impact of epigenetic modifications on the diversification and pathogenesis of R. solanacearum is unknown. Sequencing of R. solanacearum strains GMI1000 and UY031 using Single Molecule Real-Time technology allowed us to perform a comparative analysis of R. solanacearum methylomes. Our analysis identified a novel methylation motif associated with a DNA methylase that is conserved in all complete Ralstonia spp. genomes and across the Burkholderiaceae, as well as a methylation motif associated to a phage-borne methylase unique to R. solanacearum UY031. Comparative analysis of the conserved methylation motif revealed that it is most prevalent in gene promoter regions, where it displays a high degree of conservation detectable through phylogenetic footprinting. Analysis of hyper- and hypo-methylated loci identified several genes involved in global and virulence regulatory functions whose expression may be modulated by DNA methylation. Analysis of genome-wide modification patterns identified a significant correlation between DNA modification and transposase genes in R. solanacearum UY031, driven by the presence of a high copy number of ISrso3 insertion sequences in this genome and pointing to a novel mechanism for regulation of transposition. These results set a firm foundation for experimental investigations into the role of DNA methylation in R. solanacearum evolution and its adaptation to different plants.

An In vitro Study of Bio-Control and Plant Growth Promotion Potential of Salicaceae Endophytes.

Microbial communities in the endosphere of Salicaceae plants, poplar (Populus trichocarpa) and willow (Salix sitchensis), have been demonstrated to be important for plant growth promotion, protection from biotic and abiotic stresses, and degradation of toxic compounds. Our study aimed to investigate bio-control activities of Salicaceae endophytes against various soil borne plant pathogens including Rhizoctonia solani AG-8, Fusarium culmorum, Gaeumannomyces graminis var. tritici, and Pythium ultimum. Additionally, different plant growth promoting traits such as biological nitrogen fixation (BNF), indole-3-acetic acid (IAA) biosynthesis, phosphate solubilization, and siderophore production were assessed in all bio-control positive strains. Burkholderia, Rahnella, Pseudomonas, and Curtobacterium were major endophyte genera that showed bio-control activities in the in-vitro assays. The bio-control activities of Burkholderia strains were stronger across all tested plant pathogens as compared to other stains. Genomes of sequenced Burkholderia strains WP40 and WP42 were surveyed to identify the putative genes involved in the bio-control activities. The ocf and hcnABC gene clusters responsible for biosynthesis of the anti-fungal metabolites, occidiofungin and hydrogen cyanide, are present in the genomes of WP40 and WP42. Nearly all endophyte strains showing the bio-control activities produced IAA, solubilized tricalcium phosphate, and synthesized siderophores in the culture medium. Moreover, some strains reduced acetylene into ethylene in the acetylene reduction assay, a common assay used for BNF. Salicaceae endophytes could be useful for bio-control of various plant pathogens, and plant growth promotion possibly through the mechanisms of BNF, IAA production, and nutrient acquisition.

Bioassays Guided Fractionation of Senna occidentalis for Identification of Natural Antifungal Constituents Against Macrophomina phaseolina

ABSTRACT Macrophomina phaseolina is one of the most destructive soil-borne fungal plant pathogens. In the present study, different aerial parts of Senna occidentalis were analyzed for their antifungal activity against M. phaseolina. In initial screening bioassays, 0.5-3.0% concentrations of methanolic extracts of fruit, leaf and stem were tested against M. phaseolina. The methanolic leaf extract showed the greatest activity causing up to 29% suppression in biomass production of M. phaseolina. Fractionation of leaf extract of S. occidentalis was carried out with four organic solvents. Bioassays with a range of concentrations (2.34-150 mg mL-1) of these sub-fractions revealed that the chloroform sub-fraction was the most effective, causing 93-98% reduction in the biomass of M. phaseolina, followed by 59-92% suppression in fungal biomass due to the n-hexane sub-fraction. The ethyl acetate and n-butanol sub-fractions were only effective at higher concentrations. GC-MS analysis of chloroform sub-fraction was performed to identify different compounds. Six compounds were identified in this fraction; 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester was the predominant compound (53.55%) followed by 9,10-dimethyltricyclo[4.2.1.1 (2,5)]decane-9,10-diol (22.68%), cyclohexanol, and 2-(2-hydroxy-2-propyl)-5-methyl (9.87%).

Morphological and molecular based identification of Antifungal bacillus licheniformis

At present, plant diseases caused by soil borne plant pathogens have major constraints on crop production. Which include genera Fusarium spp, Phytophtora spp, Sclerotinia and Altenaria. Due to this reason, chemical fungicides are routinely used to control plant disease, which is also true in Mongolian case. However, use of these chemicals has caused various problems including environmental pollution with consequence of toxicity to human health also resistance of some pathogens to these fungicides are present. Fortunately, an alternative method to reduce the effect of these plant pathogens is the use of antagonist microorganisms. Therefore, some species of the genus Bacillus are recognized as one of the most effective biological control agent.Our research was focused to isolate Bacillus licheniformis, with antifungal potential, from indigenous sources. In the current study, 28 bacterial cultures were isolated from soil and fermented mare’s milk also named as koumiss. Isolated bacterial cultures were identified according to simplified key for the tentative identification of typical strain of Bacillus species. As a result 8 strains were positive and further screened for antifungal activity against Fusarium spp and Alternaria solani. Out of these 8 strains 5 strains are selected based on their high effectiveness against fungal pathogens and for further confirmation Polymerase Chain reaction run for effective bacterial strains using specific primers B.Lich-f and B.Lich-r.

Evaluation of biocontrol potential of some fungal decomposers of Sesbania aculeata L. green manure against some soil-borne plant pathogens

Evaluation of biocontrol potential of some fungal decomposers of Sesbania aculeata L. green manure against some soil-borne plant pathogens

Pathogenicity Assay of Verticillium nonalfalfae on Hop Plants.

Verticillium nonalfalfae is a soil-borne plant pathogen that infects its hosts through roots. It spreads in the plant's xylem and causes wilt disease symptoms by secreting different virulence factors. Hop (Humulus lupulus) is a primary host of V. nonalfalfae, so it is used as a model plant for studying this phytopathogenic fungus. Artificial infections of hop plants and disease scoring are prerequisites for studying the pathogen's virulence/pathogenicity and its interaction with hop plants. In this protocol, we describe the root dipping inoculation method for conducting pathogenicity assay of V. nonalfalfae on hop plants.