Plant growth promoting rhizobacteria as a biological tool for augmenting productivity and controlling disease in agriculturally important crop- A review

The ecological role of plant growth promoting bacteria associated with plant root environment is currently gaining increased attention. The tremendous use of chemical fertilizers and pesticides which are environmentally harmful can be replaced with these microbes generally called as Plant Growth Promoting Rhizobacteria (PGPR). These microbes can be developed as biofertilizers because they are eco-friendly, cost effective and are natural living organisms. The advantages of these microorganism rely on their production of novel bioactive metabolites that inhibit various pathogens in soil as well as their vast mechanisms in improving growth, productivity and yield in agriculturally important crops. Apart from this, their role in nutrient acquisition, soil fertility improvement and stress tolerance are also inevitable. This review represents the present scenario of beneficial bacteria as plant growth agents and disease control tools. They have been extensively studied for plant disease suppression, plant growth modulation, and interaction with plants. Here, some mechanisms employed by plant growth promoting bacteria from different environments are discussed

A COMPARATIVE STUDY ON THE IN-VITRO ANTIMICROBIAL ACTIVITY OF THE ROOTS OF FOUR THOTTEA SPECIES

Objective: The main objective of the present study was to investigate the antimicrobial activity of the methanol extract of the roots of four Thottea species. Methods: The root extracts of four Thottea species were subjected to antimicrobial assay by Minimum Inhibitory Concentration (MIC) and Agar Disc diffusion Assay against various medically important pathogens. Results: It is evident from the study that. Significant antibacterial activity was recorded by Thottea sivarajanii and highest activity was recorded against Pseudomonas aeruginosa and Staphylococcus epidermis (64 µg/ml). Out of the four extracts tested for antifungal activity, Thottea barberi and Thottea ponmudiana recorded significant antifungal activity and the highest activity was recorded by T. barberi against Trichophyton rubrum (16µg/ml). Conclusion: Results offer a scientific basis for the traditional use of Thottea species in the treatment of microbial infections, showing that the plant extract has an enormous potential as a prospective alternative drug against microbial pathogens. The present study lays the basis for future studies, to validate the possible use of Thottea species as a candidate in the treatment of microbial infections

Induction of systemic resistance against fusarial wilt in pigeon pea through interaction of plant growth promoting rhizobacteria and rhizobia

A Bacillus cereus strain BS 03 and a Pseudomonas aeruginosa strain RRLJ 04 were studied for their effect on induction of systemic resistance against Fusarium udum wilt in pigeon pea, both individually and in combination with a rhizobial strain RH 2. Split root experiments confirmed that plants with combination treatment of PGPR and Rhizobium can survive longer than individual treatments and control. An increased level of defense-related enzymes, viz., L-phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO), were also recorded in co-inoculated plants. Production of �-1,3- glucanase and polymethyl galacturonase by the pathogen in culture medium was also sharply reduced in presence of both the PGPR strains. An increased level of phenol content with a decreased level of nitrogen content was recorded in the leaves of bacterized plants grown in pathogen infested soil. Presence of BS 03 in the culture medium stimulated the production of chlamydospore-like structures in the funga

Potential for Improving pea production by co-inoculation with flourscent Pseudomonous and Rhizobium

Seed bacterization with five plant growth promoting fluorescent Pseudomonas strains isolated from Indian and Swedish soils and three Rhizobium leguminosarum biovar viceae strains isolated from Swedish soils were shown to promote plant growth in Pisum sativum L. cv. Capella. Co-inoculation of the fluorescent pseudomonads and Rhizobium improved plant growth in terms of shoot height, root length and dry weight. Both the fluorescent pseudomonads and Rhizobium were shown to exhibit a wide range of antifungal activity against pathogens specific to pea. Seed bacterization with plant growth promoting strains alone and together with a rhizobial isolate, R 361-27 reduced the number of infected peas grown in Fusarium oxysporum infested soils. We found that the introduced organisms were able to colonize the roots, which was confirmed using immunofluorescence staining and drug resistant mutant strains. In a synthetic culture medium, all the plant growth promoting fluorescent pseudomonads strains produced siderophores, which shown to express antifungal and antibacterial activity. Our results suggest the potential use of these bacteria to induce plant growth and disease suppression in sustainable agriculture production systems

Reactive oxygen species (ROS) mediated enhanced anti-candidal activity of ZnS-ZnO nanocomposites with low inhibitory concentrations

Enhanced antifungal activity against the yeast species Candida albicans, Candida tropicalis and Saccharomyces cerevisiae was displayed by ZnS-ZnO nanocomposites prepared by a simple precipitation technique. The antifungal activity was significantly more in the presence of indoor light than under dark conditions and was a clear confirmation of the inhibitory role of reactive oxygen species (ROS) generated in situ by the photocatalytic nanocomposites. The generation of ROS was further evidenced by flow cytometry results and membrane permeabilisation studies. Time kill assay and growth curve analysis indicated diminished antifungal activity under dark conditions due primarily to Zn2+ efflux in solution. © 2015 The Royal Society of Chemistry

Fluorescent Pseudomonas influence palisade mesophyll development and spatial root development in Phaseolus vulgaris

Three strains of plant growth promoting fluorescent Pseudomonads (HPR6, RRLJ008 and RRLJ134) were studied for their effect on growth and yield of French bean (Phaseolus vulgaris L.) under field conditions. The effect of these strains on nature of root development and leaf palisade tube length were also examined. The strains induced positive response on growth and physiological parameters resulting in higher yield in P. vulgaris. Strain HPR6 produced the most promising results in thickening of leaf palisade layer, spreading of lateral roots and production of root hairs. The increase in specific leaf weight (SLW), net assimilation rate (NAR) and relative growth rate (RGR) by these strains were 68%, 152% and 167%, respectively. The growth and yield parameters were also significantly improved compared to the uninoculated control. Antibiotic resistant mutant strains demonstrated that these bacteria effectively colonized the rhizosphere of French bean. The results suggest that the strains could be developed for field application on a large scale

Investigation of scaling effect on power factor of permanent magnet Vernier machines for wind power application

This study investigates the scaling effect on power factor of surface mounted permanent magnet Vernier (SPM-V) machines with power ratings ranging from 3 kW, 500 kW, 3 MW to 10 MW. For each power rating, different slot/pole number combinations have been considered to study the influence of key parameters including inter-pole magnet leakage and stator slot leakage on power factor. A detailed analytical modelling, incorporating these key parameters, is presented and validated with two-dimensional finite-element analysis for different power ratings and slot/pole number combinations. The study has revealed that with scaling (increasing power level), significant increase in electrical loading combined with the increased leakage fluxes, i.e. (i) magnet leakage flux due to large coil pitch to rotor pole pitch ratio, (ii) magnet inter-pole leakage flux and (iii) stator slot leakage flux, reduces the ratio of armature flux linkage to permanent magnet flux linkage and thereby has a detrimental effect on the power factor. Therefore, unlike conventional SPM machines, the power factor of SPM-V machines is found to be significantly reduced at high power ratings

Observations of trace gases and aerosols over the Indian Ocean during the monsoon transition period

Characteristics of trace gases (O3, CO, CO2, CH4 and N2O) and aerosols (particle size of 2.5 micron) were studied over the Arabian Sea, equatorial Indian Ocean and southwest part of the Bay of Bengal during the monsoon transition period (October-November, 2004). Flow of pollutants is expected from south and southeast Asia during the monsoonal transition period due to the patterns of wind flow which are different from the monsoon period. This is the first detailed report on aerosols and trace gases during the sampled period as the earlier Bay of Bengal Experiment (BOBMEX), Arabian Sea Monsoon Experiment (ARMEX) and Indian Ocean Experiments (INDOEX) were during monsoon seasons. The significant observations during the transition period include: (i) low ozone concentration of the order of 5 ppbv around the equator, (ii) high concentrations of CO2, CH4 and N2O and (iii) variations in PM2.5 of 5-20μg/m3