D. K. Maheshwari

Bacillus strains isolated from rhizosphere showed plant growth promoting and antagonistic activity against phytopathogens

Seven bacterial isolates screened from rhizosphere of common bean growing at Uttarakhand Himalaya showed potential plant growth promoting (PGP) and antagonistic activities. Based on 16S rRNA gene sequence the isolate BPR7 was identified as Bacillus sp. BPR7. The strain BPR7 produced IAA, siderophore, phytase, organic acid, ACC deaminase, cyanogens, lytic enzymes, oxalate oxidase, and solubilized various sources of organic and inorganic phosphates as well as potassium and zinc. Strain BPR7 strongly inhibited the growth of several phytopathogens such as Macrophomina phaseolina, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Rhizoctonia solani and Colletotricum sp. in vitro. Cell-free culture filtrate of strain BPR7 also caused colony growth inhibition of all test pathogens. PGP and antifungal activities of Bacillus sp. BPR7 suggest that it may be exploited as a potential bioinoculant agent for P. vulgaris.

Plant growth and health promoting bacteria

Dardanelli MS, Carletti SM, Paulucci NS, Medeot DB, Rodriguez Caceres EA, Vita FA, Bueno M, Fumero MV, Garcia MB: Benefits of Plant Growth Promoting Rhizobacteria (PGPR) and Rhizobia in Agriculture.- Marcia do Vale Barreto Figueiredo, Lucy Seldin, Fabio Fernando de Araujo, Rosa de Lima Eamos Mariano: PGPR: Fundamentals and Applications.- Haluk Caglar Kaymak: Potential of PGPR in Agricultural Innovations.- G Seneviratne, MLMAW Weerasekara, KACN Seneviratne, JS Zavahir, ML Kecskes, IR Kennedy: Importance of biofilm formation in plant growth promoting rhizobacterial action.- Naveen K. Arora, Ekta Khare, Dinesh K. Maheshwari: PGPR: Constraints in Bioformulation, Commercialization and Future Strategies.- C.S. Quan, X. Wang, S.D. Fan: Antifungal Compounds of Plant Growth Promoting Rhizobacteria and its Action Mode.- Mohd. Sayeed Akhtar, Zaki A. Siddiqui: Role of Plant Growth Promoting Rhizobacteria in Biocontrol of Plant Diseases and Sustainable Agriculture.- Correa Olga Susana, Soria Marcelo Abel: Potential of Bacilli for Biocontrol and their Exploitation in Sustainable Agriculture.- Nico Labuschagne, T Pretorius, Idris A H: Plant Growth Promoting Rhizobacteria as Biocontrol Agents against Soilborne Plant Diseases.- Piyush Pandey, Abhinav Aeron, Dinesh Kumar Maheshwari: Sustainable Approaches for Biological Control of Fusarium Wilt in Pigeon Pea (Cajanus cajan L. Millspaugh).- Suikinai Nobre Santos, Vanessa Nessner Kavamura, Joao Luiz da Silva, Itamar Soares de Melo, Fernando Dini Andreote: Plant Growth Promoter Rhizobacteria in Plants Inhabiting Harsh Tropical Environments and its Role in Agricultural Improvements.- Pankaj Kumar Mishra, Piyush Joshi, Shekhar Chandra Bisht, Jaideep Kumar Bisht, Govindan Selvakumar: Cold tolerant Agriculturally Important Microorganisms.- Stephen P. Cummings, Caroline Orr: The Role of Plant Growth Promoting Rhizobacteria in Sustainable and Low Input Graminaceous Crop Production.- Janpem Prakamhang, Nantakorn Boonkerd, Neung Teaumroong: Rice Endophytic Diazotrophic Bacteria.- Venkadasamy Govindasamy, Murugesan Senthilkumar, Vellaichamy Magheshwaran, Upendra Kumar, Pranita Bose, Vikas Sharma and Kannepalli Annapurna: Bacillus and Paenibacillus spp.: Potential PGPR for Sustainable Agriculture.- Meenu Saraf, Chaitanya Kumar Jha, Dhara Patel: The Role of ACC Deaminase Producing PGPR in Sustainable Agriculture.- Vincent Gray: The Role on the C: N: P Stoichiometry in the Carbon Balance Dynamics of the Legume-AMF-Rhizobium Tripartite Symbiotic Association.- Marieta Hristozkova, Maria Geneva, Ira Stancheva: Regulation of Nitrogen Assimilation in Foliar Fed Legume Plants at Insufficient Molybdenum Supply.

Rhizosphere competent Mesorhizobiumloti MP6 induces root hair curling, inhibits Sclerotinia sclerotiorum and enhances growth of Indian mustard (Brassica campestris)

The bacterial strain Mesorhizobium loti MP6, isolated from root nodules of Mimosa pudica induced growth and yield of Brassica campestris. The isolate MP6 secreted hydroxamate type siderophore in Chrom-Azurol Siderophore (CAS) agar medium. Production of hydrocyanic acid (HCN), indole acetic acid (IAA) and phosphate solubilizing ability was also recorded under normal growth conditions. Root hair curling was observed through simple glass-slide technique. In vitro study showed a significant increase in population of M. loti MP6 in rhizosphere due to root exudates of B. campestris. In dual culture technique the strain showed a strong antagonistic effect against Sclerotinia sclerotiorum, a white rot pathogen of Brassica campestris. The growth of S. sclerotiorum was inhibited by 75% after prolonged incubation. Efficient root colonization of mustard seedlings was confirmed by using a streptomycin-resistant marker M. loti MP6strep+. The M. loti MP6 coated seeds proved enhanced seed germination, early vegetative growth and grain yield as compared to control. Also, a drastic decline (99%) in the incidence of white rot was observed due to application of M. loti MP6.

Chitinase-mediated destructive antagonistic potential of Pseudomonas aeruginosa GRC1 against Sclerotinia sclerotiorum causing stem rot of peanut

Pseudomonas aeruginosa GRC1 exhibited strong antagonistic activity against Sclerotinia sclerotiorum, in vitro and in vivo. Scanning electron microscopic (SEM) studies showed morphological abnormalities such as perforation, lysis and fragmentation of hyphae of S. sclerotiorum caused by P. aeruginosa GRC1. This strain produced extracellular chitinase enzyme, the role of which was clearly demonstrated through Tn5 mutagenesis. Bacterization of peanut seeds with GRC1 resulted in increased seed germination and reduced stem-rot of peanut in S. sclerotiorum-infested soil by 97%. Other vegetative and yield plant parameters such as nodules per plant, pods and grain yield per plant were enhanced with a statistical significance in comparison to control. Neomycin resistant (GRC1neo+) bacterium was a good root colonizer and frequently isolated from rhizosphere of peanut plants. These findings showed P. aeruginosa GRC1 as a potential biocontrol agent against S. sclerotiorum.

Rhizosphere Competent Pseudomonas aeruginosa GRC1 Produces Characteristic Siderophore and Enhances Growth of Indian Mustard (Brassica campestris)

Pseudomonas aeruginosa GRC1, an isolate of potato rhizosphere, was known to have several plant growth–promoting activities, including production of phytohormone and antibiotic substance. The isolate was found to have prolific production ability of hydroxamate siderophore in iron-deficient conditions. The siderophore of GRC1 was purified and characterized. The purified siderophore appeared to be of pyoverdin type with typical amino acid composition. In field trials, P. aeruginosa GRC1 enhanced the growth of Brassica campestris var Pusa Gold (Indian mustard). Significant increase in root and shoot weight, length, grain yield per plant, and total grain yield was recorded. Root colonization was studied with Tn5-induced streptomycin-resistant transconjugants of spontaneous rifampicin-resistant GRC1 (designated GRC1rif+strep+) after different durations. The strain was significantly rhizopheric competent and stabilized in the rhizosphere, without disturbing the normal indigenous bacterial population.

Paper mill sludge as a potential source for cellulase production by Trichoderma reesei QM 9123 and Aspergillus niger using mixed cultivation

Abstract Paper mill waste was tested as a possible substrate for cellulase production using mixed cultures of Trichoderma reesei QM 9123 and Aspergillus niger , a sludge isolate. The efficacy of the strains both by staggered and simultaneous cultivation were compared. Optimal cellulase production (0.8 mg/ml) along with the best utilization of substrate was observed with mixed cultivation of two strains simultaneously.

Plant Growth Promoting Rhizobacteria: Constraints in Bioformulation, Commercialization, and Future Strategies

Bioformulations for plant growth promotion continue to inspire research and development in many fields. Increase in soil fertility, plant growth promotion, and suppression of phytopathogens are the targets of the bioformulation industry that leads to the development of ecofriendly environment. The synthetic chemicals used in the agriculture to increase yields, kill pathogens, pests, and weeds, have a big harmful impact on the ecosystem. But still the chemicals rule the agroindustry. The aim of the review is to assess the constraints associated with the effective development of bioinoculant industry particularly in developing countries. Another objective of the review is to evaluate what should be explored in the future to uplift the stature of the bioinoculants. Bioformulations offer an environmentally sustainable approach to increase crop production and health, contributing substantially in making the twenty-first century the age of biotechnology.

Emerging Role of Plant Growth Promoting Rhizobacteria in Agrobiology

Plant growth promoting rhizobacteria (PGPR) colonize rhizosphere and reside in harmony with plants. These introduced or naturally occurring bacteria are known to enhance plant growth and yield components. Therefore, their potential has been exploited extensively to reduce the indiscriminate use of synthetic chemicals such as inorganic fertilizers, fungicides, and pesticides and prevent the accumulation of toxic, health hazardous chemicals in soil and water resources. Biological control of plant diseases and plant growth promotion approach becomes a prime focus of recent biotechnological trends in agro-ecosystem. Considerable research has been performed globally to exploit the functioning of beneficial bacterial communities in agro-industries. Further, advanced and better understanding of rhizobacteria will facilitate maintenance of natural soil structure, pure water resources, and increased productivity of agro- and forest-based industries to achieve their commercial success in sustainable ecosystems.

Effect of Chemical Fertilizer-adaptive Variants, Pseudomonas aeruginosa GRC2 and Azotobacter chroococcum AC1, on Macrophomina phaseolina Causing Charcoal Rot of Brassica juncea

Pseudomonas aeruginosa GRC2, siderophore-producing strain, inhibited growth of Macrophomina phaseolina in vitro and reduced charcoal rot in seeds of Brassica juncea in field when coated with adaptive strains. P. aeruginosa GRC2 and Azotobacter chroococcum AC1 produced indole-3-acetic acid and solubilized insoluble phosphate. A. chroococcum AC1 fixed nitrogen asymbiotically. Urea and diammonium phosphate-adaptive variant strains of P. aeruginosa and A. chroococcum strongly inhibited M. phaseolina in comparison to parental strains. Bacterization of seeds induced seed germination, seedling growth, and enhanced yield of B. juncea by 10.87% as compared to full doses of urea and diammonium phosphate. Both adaptive strains of chemical fertilizers aggressively colonized roots, showing effectiveness to growth and developments of B. juncea.

Bacteria in Agrobiology: Crop Productivity

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