scholarly journals Isolation and Screening of Quorum Quenching Rhizobacterial Isolates from the Experimental Farms of Gandhi krishi vigyana Kendra, Bengaluru, Karnataka, India

2021 ◽  
pp. 1-11
Author(s):  
J. Saranya Packialakshmi ◽  
K. Tamilvendan ◽  
N. Earanna ◽  
B. C. Mallesha
Keyword(s):  
Soft Rot ◽  
Quorum Quenching ◽  
Root Surface ◽  
Soft Agar ◽  
Systemic Resistance ◽  
Field Bean ◽  
Vegetable Crops ◽  
Lablab Purpureus ◽  
Cell Wall Degrading Enzymes ◽  
Almost All

A group of synergistic bacteria that nestles on the root surface and provide a benefitting response to the plants are the rhizobacteria. The rhizobacteria benefit the plants by promoting growth and acts as biocontrol agents. Antibiosis, competition, synthesis of cell wall degrading enzymes, and eliciting induced systemic resistance are the mechanisms of biocontrol exhibited by rhizobacteria. Quorum quenching (QQ) is a new mechanism of biocontrol of pathogens whose virulence is induced by population density dependant chemical signaling. Efficient quorum quenching rhizobacteria isolated from the crop rhizospheres can be used as potential inoculums to control phytopathogens. Soft rot is one pernicious plant and storage disease affecting almost all vegetable crops. Hence, the present study was conducted to isolate rhizobacteria from the rhizospheres of six crops Rice (Oryza sativa), Maize (Zea mays), Finger millet (Eleusine coracana), Dolichos Bean (Lablab purpureus), Amaranthus (Amaranthus viridis), Field bean (Vicia faba) from the environs of GKVK. A total number of 96 rhizobacterial cultures were isolated from experimental fields of GKVK. The isolated cultures were screened for their quorum quenching ability by soft agar overlay assay and twenty-four out of ninety-six cultures were affirmative quorum quenchers. Proportionately, 25% of the total rhizobacterial isolates were quorum quenchers. The isolates were characterized morphologically and biochemically and a discussion of the obtained results are deliberately discussed.

scholarly journals Evaluation of Lablab Purpureus (L.) Sweet Germplasm Using Yield and Quality Traits

2021 ◽  
Author(s):  
VISHNU V S ◽  
P.M. RADHAMANY
Keyword(s):  
Tamil Nadu ◽  
Crop Improvement ◽  
Vegetable Crops ◽  
Micronutrient Deficiencies ◽  
Lablab Purpureus ◽  
Nutritional Factors ◽  
Yield And Quality ◽  
Multiple Characteristics ◽  
Almost All ◽  
Selection Of

Abstract The crops that are not commercially grown or widely traded are known as underutilized or unusable crops. Most of the legumes have come under these categories. Giving importance to such neglected and underutilized crops is an effective way to maintain a diverse and healthy diet and to combat micronutrient deficiencies. Lablab purpureus (L.) Sweet is one of the most important underutilized legume vegetable crops, which exhibits broad genetic variability in multiple characteristics such as the habit, pigmentation of the stem, and color of the pod. In the past, researchers paid very little attention to the systematic crop improvement of L.purpureus. In the present study, fifty accessions of L. purpureus were collected from different places of Kerala and Tamil Nadu and analyzed for yield, yield contributing characters, and biochemical factors. Nutritional and anti-nutritional factors were analyzed using the standard protocol. The accessions exhibited significant variations for all the characters tested. The nutritional content of all the accessions were found to be high, whereas anti-nutritional factors were very low. The differences in phenotypic and genotypic coefficient of variation was compared for different traits, and it was found to be very narrow for almost all the characters studied. The fifty genotypes involved in the study varied in the number of pod/ inflorescence, length and width of the pod, number of flower/ inflorescence, and length of the peduncle. So these observations can be used as a baseline data for the selection of parental lines for future improvement of Lablab purpureus.

Diseases of the kumara crop

2009 ◽  
Vol 62 ◽  
pp. 402-402
Author(s):  
S.L. Lewthwaite ◽  
P.J. Wright
Keyword(s):  
Fungal Pathogens ◽  
Ipomoea Batatas ◽  
Mechanical Damage ◽  
Soft Rot ◽  
Economic Loss ◽  
Root Surface ◽  
Black Rot ◽  
Rhizopus Stolonifer ◽  
Ceratocystis Fimbriata ◽  
Pink Rot

The predominant diseases of the commercial kumara (Ipomoea batatas) or sweetpotato crop are caused by fungal pathogens The field disease pink rot results from infection by the fungus Sclerotinia sclerotiorum Lesions form on vines but may spread down stems to the roots The widespread nature of this disease in sweetpotato appears peculiar to New Zealand Scurf is a disease caused by Monilochaetes infuscans which occurs in the field but may proliferate amongst stored roots The disease causes a superficial discolouration of the root surface which is mainly cosmetic but can also increase root water loss in storage Infection by Ceratocystis fimbriata produces a disease known as black rot The disease can be transmitted amongst plants at propagation but is particularly rampant amongst roots in storage This disease is readily transmitted and can cause severe economic loss Fusarium oxysporum causes surface rots in stored roots characterised by light to dark brown lesions that tend to be firm dry and superficial The lesions may be circular and centred on wounds caused by insects or mechanical damage at harvest Soft rot caused by Rhizopus stolonifer generally occurs in roots after they are washed and prepared for the market Fungal infection occurs through wounds or bruised tissue producing distinctive tufts of white fungal strands and black spores

scholarly journals Developing a method for real-time visualization of cellulase activity

2020 ◽  
Author(s):  
Pallavi Kumari ◽  
Tali Sayas ◽  
Patricia Bucki ◽  
Sigal Brown Miyara ◽  
Maya Kleiman
Keyword(s):  
Real Time ◽  
Plant Cell Wall ◽  
Plant Root ◽  
Cellulase Activity ◽  
Root Surface ◽  
Surface Microstructure ◽  
Root Extract ◽  
Cell Wall Degrading Enzymes ◽  
Real Time Visualization ◽  
Replication Technique

AbstractStudying the interactions between microorganisms and plant roots is crucial for understanding a variety of phenomena concerning crop yield and health. The role of root surface properties in these interactions, is rarely addressed. To this end, we previously built a synthetic system, from the inert polymer polydimethyl siloxane (PDMS), mimicking the root surface microstructure, using a replication technique. This replica enables the study of isolated effects of surface structure on microorganism-plant interactions. Since the root surface is composed mostly of cellulose, using cellulose-like materials as our replica, instead of PDMS, is the next logical step. This will enable following the hydrolysis of such surfaces as a result of microorganisms secreting Plant Cell Wall Degrading Enzymes (PCWDE), and in particular, cellulase. Visualization of such hydrolysis in a synthetic system can assist in studying the localization and activity of microorganisms and how they correlate with surface microtopography, separately from chemical plant signals.In this work, we modified the known carboxymethyl cellulase (CMC) hydrolysis visualization method to enable real-time tracking of cellulase activity of microorganisms on the surface. Surface was formed from pure CMC, rather than CMC incorporated in agar as is often done, and by that, eliminating diffusion issues. Acridine orange dye, which is compatible, at low concentrations, with microorganisms, as opposed to other routinely used dyes, was incorporated into the film. The dye disassociated from the film when hydrolysis occurred, forming a halo surrounding the point of hydrolysis. This enabled real-time visualization since the common need for post hydrolysis dyeing was negated. Using Root Knot Nematode (RKN) as a model organism that penetrates the plant root, we showed it was possible to follow microorganism cellulase secretion on the surface in the form of CMC film hydrolysis. Furthermore, the addition of natural additives, in the form of root extract was also shown to be an option and resulted in an increased RKN response. We tested our newly developed method by changing temperature and pH conditions and by characterization of the hydrolyzed surface using both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).This method will be implemented in the future on a root surface microstructure replica. We believe the combination of this new method with our previously developed root surface microstructure replication technique can open a new avenue of research in the field of plant root-microorganism interactions.

scholarly journals Do plants use root-derived proteases to promote the uptake of soil organic nitrogen?

2020 ◽  
Vol 456 (1-2) ◽  
pp. 355-367
Author(s):  
Lucy M. Greenfield ◽  
Paul W. Hill ◽  
Eric Paterson ◽  
Elizabeth M. Baggs ◽  
Davey L. Jones
Keyword(s):  
Protease Activity ◽  
Organic Nitrogen ◽  
N Uptake ◽  
Root Surface ◽  
Organic N ◽  
Soil Organic Nitrogen ◽  
Poor Access ◽  
N Deficiency ◽  
Almost All ◽  
Soil Protein

Abstract Aims The capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? Methods Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. Results We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity. Conclusions Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.

scholarly journals Endophytic Actinomycetes: A Novel Source of Potential Acyl Homoserine Lactone Degrading Enzymes

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Surang Chankhamhaengdecha ◽  
Suphatra Hongvijit ◽  
Akkaraphol Srichaisupakit ◽  
Pattra Charnchai ◽  
Watanalai Panbangred
Keyword(s):  
Pathogenic Bacteria ◽  
Sequence Similarity ◽  
Soft Rot ◽  
Quorum Quenching ◽  
Homoserine Lactone ◽  
Amide Bond ◽  
Side Chain ◽  
Signal Molecules ◽  
Endophytic Actinomycetes

Several Gram-negative pathogenic bacteria employN-acyl-L-homoserine lactone (HSL) quorum sensing (QS) system to control their virulence traits. Degradation of acyl-HSL signal molecules by quorum quenching enzyme (QQE) results in a loss of pathogenicity in QS-dependent organisms. The QQE activity of actinomycetes in rhizospheric soil and inside plant tissue was explored in order to obtain novel strains with high HSL-degrading activity. Among 344 rhizospheric and 132 endophytic isolates, 127 (36.9%) and 68 (51.5%) of them, respectively, possessed the QQE activity. The highest HSL-degrading activity was at151.30±3.1 nmole/h/mL from an endophytic actinomycetes isolate, LPC029. The isolate was identified asStreptomycesbased on16S  rRNAgene sequence similarity. The QQE from LPC029 revealed HSL-acylase activity that was able to cleave an amide bond of acyl-side chain in HSL substrate as determined by HPLC. LPC029 HSL-acylase showed broad substrate specificity from C6- to C12-HSL in which C10HSL is the most favorable substrate for this enzyme. In anin vitropathogenicity assay, the partially purified HSL-acylase efficiently suppressed soft rot of potato caused byPectobacterium carotovorumssp.carotovorumas demonstrated. To our knowledge, this is the first report of HSL-acylase activity derived from an endophyticStreptomyces.

scholarly journals The Significance of Bacillus spp. in Disease Suppression and Growth Promotion of Field and Vegetable Crops

2020 ◽  
Vol 8 (7) ◽  
pp. 1037 ◽  
Author(s):  
Dragana Miljaković ◽  
Jelena Marinković ◽  
Svetlana Balešević-Tubić
Keyword(s):  
Plant Growth ◽  
Plant Pathogens ◽  
Growth Promotion ◽  
Disease Suppression ◽  
Biocontrol Agents ◽  
Systemic Resistance ◽  
Steady Increase ◽  
Vegetable Crops ◽  
Wide Range ◽  
Bacillus Spp

Bacillus spp. produce a variety of compounds involved in the biocontrol of plant pathogens and promotion of plant growth, which makes them potential candidates for most agricultural and biotechnological applications. Bacilli exhibit antagonistic activity by excreting extracellular metabolites such as antibiotics, cell wall hydrolases, and siderophores. Additionally, Bacillus spp. improve plant response to pathogen attack by triggering induced systemic resistance (ISR). Besides being the most promising biocontrol agents, Bacillus spp. promote plant growth via nitrogen fixation, phosphate solubilization, and phytohormone production. Antagonistic and plant growth-promoting strains of Bacillus spp. might be useful in formulating new preparations. Numerous studies of a wide range of plant species revealed a steady increase in the number of Bacillus spp. identified as potential biocontrol agents and plant growth promoters. Among different mechanisms of action, it remains unclear which individual or combined traits could be used as predictors in the selection of the best strains for crop productivity improvement. Due to numerous factors that influence the successful application of Bacillus spp., it is necessary to understand how different strains function in biological control and plant growth promotion, and distinctly define the factors that contribute to their more efficient use in the field.

scholarly journals Modes of action of non-pathogenic strains of Fusarium oxysporum in controlling Fusarium wilts

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. 195-199 ◽  
Author(s):  
C. Alabouvette ◽  
Ch. Olivain
Keyword(s):  
Fusarium Oxysporum ◽  
Plant Defence ◽  
Root Surface ◽  
Systemic Resistance ◽  
Induce Systemic Resistance ◽  
Biocontrol Efficacy ◽  
Modes Of Action ◽  
Defence Reactions ◽  
Chlamydospore Germination ◽  
Fusarium Wilts

Many studies have demonstrated the capacity of non-pathogenic strains of F. oxysporum to control Fusarium diseases.<br />These non-pathogenic strains show several modes of action contributing to their biocontrol capacity. They are able to<br />compete for nutrients in the soil, affecting the rate of chlamydospore germination and the saprophytic growth of the<br />pathogen, diminishing the probability for the pathogen to reach the root surface. They are competing with the pathogen<br />at the root surface for colonization of infection sites, and inside the root where they induce plant defence reactions. By<br />triggering the defence reactions, they induce systemic resistance of the plant. Depending on the strain, and on the plant<br />species, these mechanisms are more or less important, leading to a more or less efficient biocontrol efficacy.

scholarly journals Assessment of pesticides and ripening chemicals used in selected vegetables at different locations of Bangladesh

2019 ◽  
Vol 44 (2) ◽  
pp. 261-279
Author(s):  
MGF Chowdhury ◽  
MA Rahman ◽  
M Miaruddin ◽  
MHH Khan ◽  
MM Rahman
Keyword(s):  
Tomato Fruit ◽  
Protective Measure ◽  
Vegetable Crops ◽  
Gross Margin ◽  
Hand Pump ◽  
Color Development ◽  
Lambda Cyhalothrin ◽  
Synthetic Pesticides ◽  
Almost All ◽  
Early Market

A survey was conducted in seven districts namely Bogura, Rajshahi, Jashore, Narsingdi, Cumilla, Jamalpur and Gazipur to assess the present status of the usage of pesticides and ripening chemical in major vegetable crops such as tomato, brinjal, country bean and bitter gourd. A total of 280 respondents having 40 respondents from each district were selected randomly for the study. The maximum number of vegetable growers belonged to the age group of 21-40, which is about 50%. About 41% and 25% of farmers accomplished their primary and secondary education in the study areas. Tomato fruit had the highest yield (27.74 tha-1) whereas the highest gross margin was attained from country bean 4,06,832 Tk.ha-1. Almost all of the vegetable growers were used synthetic pesticides (chemical group of Cypermethrin, Emamectin Benzoate, Chlorpyriphos, Carbendazim, Lambda Cyhalothrin, Mencozeb etc.) for protecting their crops from pests and most of them used own hand pump sprayer. Farmers of the study areas applied synthetic pesticides frequently with much higher dosages (8-30 times) than the recommendation. Few farmers practice Integrated Pest Management (IPM) for their crops. Seventy five percent farmers had protective measure during insecticide-pesticide spray and about 40% growers felt uncomfortable after hand spray to the crops. Most of the tomato growers in the study areas (Rajshahi and Jashore) were applied Plant Growth Regulator (PGR)/ripening agents mainly Ethephon @ 2500-8000ppm before 1-3 days of harvest in immature green tomato (1-4 times) for uniform color development to get higher price in the early market. Few traders (10-15%) were applied Ethephon in premature vegetables after harvest. It is strongly recommended to use IPM technology for controlling insects and pest and to create awareness regarding pesticides use practice and safety precautions. Bangladesh J. Agril. Res. 44(2): 261-279, June 2019

scholarly journals Redox-Active Pyocyanin Secreted by Pseudomonas aeruginosa 7NSK2 Triggers Systemic Resistance to Magnaporthe grisea but Enhances Rhizoctonia solani Susceptibility in Rice

2006 ◽  
Vol 19 (12) ◽  
pp. 1406-1419 ◽  
Author(s):  
David De Vleesschauwer ◽  
Pierre Cornelis ◽  
Monica Höfte
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Rhizoctonia Solani ◽  
Magnaporthe Grisea ◽  
Root Surface ◽  
Sheath Blight ◽  
Blast Disease ◽  
Systemic Resistance ◽  
Sodium Ascorbate ◽  
In Planta ◽  
Pyocyanin Production

Pseudomonas aeruginosa 7NSK2 induces resistance in dicots through a synergistic interaction of the phenazine pyocyanin and the salicylic acid-derivative pyochelin. Root inoculation of the monocot model rice with 7NSK2 partially protected leaves against blast disease (Magnaporthe grisea) but failed to consistently reduce sheath blight (Rhizoctonia solani). Only mutations interfering with pyocyanin production led to a significant decrease in induced systemic resistance (ISR) to M. grisea, and in trans complementation for pyocyanin production restored the ability to elicit ISR. Intriguingly, pyocyanin-deficient mutants, unlike the wild type, triggered ISR against R. solani. Hence, bacterial pyocyanin plays a differential role in 7NSK2-mediated ISR in rice. Application of purified pyocyanin to hydroponically grown rice seedlings increased H2O2 levels locally on the root surface as well as a biphasic H2O2 generation pattern in distal leaves. Co-application of pyocyanin and the antioxidant sodium ascorbate alleviated the opposite effects of pyocyanin on rice blast and sheath blight development, suggesting that the differential effectiveness of pyocyanin with respect to 7NSK2-triggered ISR is mediated by transiently elevated H2O2 levels in planta. The cumulative results suggest that reactive oxygen species act as a double-edged sword in the interaction of rice with the hemibiotroph M. grisea and the necrotroph R. solani.

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