Extracellular biosynthesis of silver nanoparticles using Streptomyces griseoplanus SAI-25 and its antifungal activity against Macrophomina phaseolina , the charcoal rot pathogen of sorghum

Streptomyces griseoplanus SAI-25 isolated from rice rhizospheric soils with previously demonstrated insecticidal activity is currently characterized for silver nanoparticle synthesis using its extracellular extract. The synthesized particles showed the characteristic absorption spectra of silver nanoparticles at 413–417 nm. Spectral analysis by FTIR confirmed the presence of alcohols, amines, phenols and protein in the cell-free extracellular extract of SAI-25. These functional groups could have served dual roles in silver nanoparticle synthesis like reducing and stabilizing agents. Microscopic and spectroscopic analysis such as SEM, TEM, EDAX and XRD has provided the size, shape and composition of the synthesized nanoparticles. DLS and Zeta potential further confirms the size and characteristic negative charges of AgNPs respectively. The observed antifungal activity against charcoal rot pathogen Macrophomina phaseolina shows a base for the development of Streptomyces mediated nanoparticles in controlling this polyphagus pathogen and key role of biopesticides in improving agricultural economy

Secondary Metabolites of Entomopathogenic Microbes to Control Lepidopteran Pests

Global crop losses due to Helicoverpa amzigerahave been estimated to be over US $ 2 billion annually whereas 80% of this loss occurs in India causing wide spread misery to the farmers who face the risk of frequent crop failures. Secondary metabolites from microbes, particularly bacteria and actinomycetes, are known to kill various insects including H. armigera. Spinosad extracted from soil actinomycetes Sachharopolyspora spinosacaused significant effect on H. amzigera ...

Formulation and Commercialization of Rhizobia: Asian Scenario

The symbiotic agreement of rhizobia with leguminous plants is making a valuable contribution to agriculture primarily as nitrogen fixers and secondarily as plant growth promoters by their key role as phosphate solubilizers, growth hormone producers, abiotic and biotic stress relievers, and host-plant resistance enhancer. In the so far identified 14 genera and 105 species of rhizobia, a huge number of research reports were reported in various aspects. Genetically modified rhizobia with desirable traits have also been surfed to a large extent. Besides their potentiality, the commercial success of rhizobia as a bio-inoculant is poor, because most of the inoculants produced worldwide are of poor or suboptimal quality. Though voluminous data and better understanding are available on various formulation technologies, longevity and efficacy of the final product are loosed at the farmer’s end. This book chapter is focused to address various types of formulations applicable to rhizobia, quality control for longevity, gaps in knowledge on bringing the native potential of rhizobia during formulation, and critical control points to be considered during its development. The chapter also shares ICRISAT’s experience in its rhizobial collection, formulation developments, and efficacy testing

Soil Microbes: The Invisible Managers of Soil Fertility

Soil health is represented by its continuous capacity to function as a vital living system. Since soil health is the major driving factor for sustainable agriculture, it has to be preserved. Microorganisms are an essential and integral part of living soil influencing various biogeochemical cycles on major nutrients such as carbon, nitrogen, sulphur, phosphorous and other minerals and play superior role in maintaining soil health than other biological component of soil. They also have the capacity to suppress soil borne pathogens and indirectly help in agricultural productivity. Besides contribution of specific microbes to soil health by participating on nutrient cycles, certain other microbes directly/indirectly promote plant growth through the production of phytohormones, enzymes and by suppressing phytopathogens and insects. The vast functional and genetic diversity of microbial groups including bacteria, fungi and actinomycetes supports in all the above ways for soil health. This book chapter gives an outline of such microbes and their contribution in promoting soil health and its role as soil health indicators

Exploration of Plant Growth-Promoting Actinomycetes for Biofortification of Mineral Nutrients

Mineral malnutrition, especially Fe and Zn, affects more than two million people around the world and increases vulnerability to illness and infections. These malnourished people live in developing countries and rely upon staple foods routinely with inability to either afford for dietary diversification or pharmaceutical supplementation or industrial fortification of minerals. Biofortification is a strategy that can tackle hidden hunger merely through staple foods that people eat every day. This strategy can be achieved through agronomic practices and conventional breeding and genetic engineering approaches, and each has their own pros and cons. The sustainability of such grain fortification with higher seed mineral concentration is soil health dependent, especially on the availability of mineral in the rhizosphere. Microorganisms, the invisible engineers in improving the soil health by solubilizing trace elements and by driving various biogeochemical cycles of soil, have the ability to serve as a key solution for this complex issue. In specific, plant growth-promoting (PGP) microbes reside in root-soil interface and employ the use of siderophores, organic acids, and exopolysaccharides for increasing the mineral availability and subsequent mobilization to the plants. Increasing the seed mineral density with the use of such PGP microbes, especially actinomycetes, is in its infancy. Hence, this chapter is aimed to bring a view on the role of microbes, especially actinomycetes, with metal-mobilizing and PGP traits for biofortification as this strategy may act as a complementary sustainable tool for the existing biofortification strategies

Plant Growth Promoting Actinobacteria : A New Avenue for Enhancing the Productivity and Soil Fertility of Grain Legumes

Global yields of legumes have been relatively stagnant for the last five decades, despite the adoption of conventional and molecular breeding approaches. The use of plant growth-promoting (PGP) bacteria for improving agricultural production, soil and plant health has become one of the most attractive strategies for developing sustainable agriculture. Actinomycetes are bacteria that play an important role in PGP and plant protection, produce secondary metabolites of commercial interest, and their use is well documented in wheat, rice, beans, chickpeas and peas. In order to promote legumes, the general assembly of the UN recently declared 2016 the “International Year of Pulses.” In view of this development, this book illustrates how PGP actinomycetes can improve grain yield and soil fertility, improve control of insect pests and phytopathogens, and enhance host-plant resistance. It also addresses special topics of current interest, e.g. the role of PGP actinomycetes in the biofortification of legume seeds and bioremediation of heavy metals

A Renaissance in Plant Growth-Promoting and Biocontrol Agents by Endophytes

Endophytes are the microorganisms which colonize the internal tissue of host plants without causing any damage to the colonized plant. The beneficial role of endophytic organisms has dramatically documented worldwide in recent years. Endophytes promote plant growth and yield, remove contaminants from soil, and provide soil nutrients via phosphate solubilization/nitrogen fixation. The capacity of endophytes on abundant production of bioactive compounds against array of phytopathogens makes them a suitable platform for biocontrol explorations. Endophytes have unique interaction with their host plants and play an important role in induced systemic resistance or biological control of phytopathogens. This trait also benefits in promoting plant growth either directly or indirectly. Plant growth promotion and biocontrol are the two sturdy areas for sustainable agriculture where endophytes are the key players with their broad range of beneficial activities. The coexistence of endophytes and plants has been exploited recently in both of these arenas which are explored in this chapter

Plant growth promoting rhizobia: Challenges and opportunities

Modern agriculture faces challenges, such as loss of soil fertility, fluctuating climatic factors and increasing pathogen and pest attacks. Sustainability and environmental safety of agricultural production relies on eco-friendly approaches like biofertilizers, biopesticides and crop residue return. The multiplicity of beneficial effects of microbial inoculants, particularly plant growth promoters (PGP), emphasizes the need for further strengthening the research and their use in modern agriculture. PGP inhabit the rhizosphere for nutrients from plant root exudates. By reaction, they help in (1) increased plant growth through soil nutrient enrichment by nitrogen fixation, phosphate solubilization, siderophore production and phytohormones production (2) increased plant protection by influencing cellulase, protease, lipase and β-1,3 glucanase productions and enhance plant defense by triggering induced systemic resistance through lipopolysaccharides, flagella, homoserine lactones, acetoin and butanediol against pests and pathogens. In addition, the PGP microbes contain useful variation for tolerating abiotic stresses like extremes of temperature, pH, salinity and drought; heavy metal and pesticide pollution. Seeking such tolerant PGP microbes is expected to offer enhanced plant growth and yield even under a combination of stresses. This review summarizes the PGP related research and its benefits, and highlights the benefits of PGP rhizobia belonging to the family Rhizobiaceae, Phyllobacteriaceae and Bradyrhizobiaceae

Plant growth-promoting actinobacteria: a new strategy for enhancing sustainable production and protection of grain legumes

Grain legumes are a cost-effective alternative for the animal protein in improving the diets of the poor in South-East Asia and Africa. Legumes, through symbiotic nitrogen fixation, meet a major part of their own N demand and partially benefit the following crops of the system by enriching soil. In realization of this sustainability advantage and to promote pulse production, United Nations had declared 2016 as the “International Year of pulses”. Grain legumes are frequently subjected to both abiotic and biotic stresses resulting in severe yield losses. Global yields of legumes have been stagnant for the past five decades in spite of adopting various conventional and molecular breeding approaches. Furthermore, the increasing costs and negative effects of pesticides and fertilizers for crop production necessitate the use of biological options of crop production and protection. The use of plant growth-promoting (PGP) bacteria for improving soil and plant health has become one of the attractive strategies for developing sustainable agricultural systems due to their eco-friendliness, low production cost and minimizing consumption of non-renewable resources. This review emphasizes on how the PGP actinobacteria and their metabolites can be used effectively in enhancing the yield and controlling the pests and pathogens of grain legumes

Plant growth-promoting actinobacteria on chickpea seed mineral density: an upcoming complementary tool for sustainable biofortification strategy

The present study was evaluated to test the potential of plant growth-promoting actinobacteria in increasing seed mineral density of chickpea under field conditions. Among the 19 isolates of actinobacteria tested, significant (p < 0.05) increase of minerals over the uninoculated control treatments was noticed on all the isolates for Fe (10–38 %), 17 for Zn (13–30 %), 16 for Ca (14–26 %), 9 for Cu (11–54 %) and 10 for Mn (18–35 %) and Mg (14–21 %). The increase might be due to the production of siderophore-producing capacity of the tested actinobacteria, which was confirmed in our previous studies by q-RT PCR on siderophore genes expressing up to 1.4- to 25-fold increased relative transcription levels. The chickpea seeds were subjected to processing to increase the mineral availability during consumption. The processed seeds were found to meet the recommended daily intake of FDA by 24–28 % for Fe, 25–28 % for Zn, 28–35 % for Cu, 12–14 % for Ca, 160–167 % for Mn and 34–37 % for Mg. It is suggested that the microbial inoculum can serve as a complementary sustainable tool for the existing biofortification strategies and substantially reduce the chemical fertilizer inputs