ASSESSMENT OF IN VITRO ANTIOXIDANT POTENTIAL AND QUANTIFICATION OF TOTAL PHENOLS AND FLAVONOIDS OF AQUEOUS EXTRACT OF PHYLLANTHUS AMARUS

Objective: The modern research is directed towards finding naturally occurring antioxidants of plant origin. To search for new sources of safe and inexpensive antioxidants, present study was undertaken to quantify total phenols and flavonoids and, evaluation and correlation of antioxidant potential of aqueous extract of Phyllanthus amarus Schum & Thonn, (PAAEt) belongs to Euphorbiace family under in vitro condition.Methods: Determination of total phenolic and flavonoid contents was performed by UV-visible spectrophotometer. The antioxidant potential of P. amarus was tested with different antioxidant test systems; inhibition of lipid peroxidation (LPO), scavenging of 1,1-Diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, superoxide and nitric oxide radicals with reducing power. Results: The plant extract has appreciable amounts of total phenolic compounds (120±2.0 mg GA eq. g-1) and flavonoids (3.02±0.13 mg Q eq. g-1) of the extract. PAAEt exhibited effective and strong antioxidant activity in dose-dependent manners in inhibiting LPO (IC50 623.4 μg/ml) and scavenging of free radicals such as DPPH (IC50 200.2 μg/ml), hydroxyl (IC50 280.6 μg/ml), superoxide (IC50 201.5 μg/ml), nitric oxide (IC50 408.5 μg/ml) with reducing power (IC50 500.0 μg/ml). PAAEt showed effective and strong positive correlation with reducing power (r2= 0.972) and LPO inhibition (r2= 0.964) and free-radicals (P<0.05).Conclusion: Presence of high amount of phenolic and flavonoid compounds and appreciable amounts of IC50 for various free radicals and inhibition of LPO and reducing power with significant strong positive correlation for scavenging of free radicals, LPO inhibition and reducing power indicated that PAAEt has strong antioxidant potential.Â

Evaluation of Plant Growth-Promoting Actinomycetes on Vigna

The legume genus Vigna are grown in warm temperate and tropical regions globally but are particularly crucial to human nutrition in large parts of tropical Africa and Asia. It can also serve as forage crops. Among the Vigna species, the Asian Vigna has received little research initiatives than African Vigna such as cowpea and mung bean. From the last decade, the research initiatives are getting increased for both the Vigna species in the context of genetic resource analysis and genome mapping. The production status has remained stagnant in many countries due to long list of pest and pathogen attacks and abiotic stresses. Use of plant growth-promoting microbes for improving the productivity of Vigna species is still in its infancy, and there were very few field evaluation studies conducted. This chapter brings an overview of several reports which documented the various facets of plant growth-promoting microbes, particularly of actinomycetes, in increasing growth performance and productivity of Vigna

Plant growth-promoting traits of Streptomyces with biocontrol potential isolated from herbal vermicompost

Three strains of Streptomyces (CAI-21, CAI-26 and MMA-32) were earlier reported by us as having potential for biocontrol of charcoal rot of sorghum, caused by Macrophomina phaseolina (Tassi) Goid., and plant growth promotion (PGP) of the plant. In the present investigation, the three Streptomyces were characterised for their physiological traits (tolerance of salinity, temperature, pH and resistance to antibiotics) and further evaluated in the field for their PGP of rice, grown by a system of rice intensification methods. All three Streptomyces were able to grow in NaCl concentrations of up to 12% (except MMA-32), at pH values between 5 and 13 and temperatures between 20 and 40°C. They were highly resistant to ampicillin and trimethoprim (>800 ppm), sensitive to chloramphenicol, kanamycin and nalidixic acid (50–100 ppm) and highly sensitive to streptomycin and tetracycline (5–25 ppm). When evaluated for their PGP activity on seedlings of rice, % germination and shoot and root lengths were significantly enhanced over the control. In the field, the Streptomyces strains significantly enhanced the panicle length, filled grain numbers and weight, panicle weight, 1000 seed weight, tiller numbers, total dry matter, root length (39–65%), root volume (13–30%), root dry weight (16–24%), grain yield (9–11%) and stover yield (11–22%) over the control. In the rhizosphere soil (0–15 cm from root) at harvest, the population of actinomycetes was significantly enhanced as was microbial biomass carbon (27–83%) and nitrogen (24–43%), dehydrogenase activity (34–152%), available P (13–34%) and N (30–53%) and % organic carbon (26–28%). This study further confirms that the selected Streptomyces have PGP properties

Evaluation of Streptomyces spp. for their plant-growth-promotion traits in rice

Five strains of Streptomyces (CAI-17, CAI-68, CAI-78, KAI-26, and KAI-27) were previously reported to have potential for charcoal rot control and plant growth promotion (PGP) in sorghum. In this study, those 5 Streptomyces strains were characterized for their enzymatic activities and evaluated for their PGP capabilities on rice. All the Streptomyces strains were able to produce lipase and β-1,3-glucanase; grew in NaCl (up to 8%), at pH 5–13, and at temperatures 20–40 °C; and were resistant to ampicillin, sensitive to nalidixic acid, and highly sensitive to chloramphenicol, kanamycin, streptomycin, and tetracycline. They were highly tolerant to the fungicide bavistin but were highly sensitive to benlate, benomyl, and radonil. When evaluated on rice in the field, Streptomyces significantly enhanced tiller and panicle numbers, stover and grain yields, dry matter, root length, volume and dry weight, compared with the control. In the rhizosphere at harvest, microbial biomass carbon and nitrogen, dehydrogenase activity, total nitrogen, available phosphorus, and % organic carbon were also found significantly higher in Streptomyces-treated plots than in the control plots. This study further confirms that the selected Streptomyces have PGP activities

Assessment of a diketopiperazine, cyclo(Trp-Phe) from Streptomyces griseoplanus SAI-25 against cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Microorganisms produce a range of metabolites with varying pest control properties. With this concept, we earlier identified 15 Streptomyces spp. strains with insecticidal activity against Helicoverpa armigera (Hübner), Spodoptera litura (Fabricius), and Chilo partellus (Swinhoe). In recent studies, we evaluated an insecticidal compound purified from the extracellular extract of S. griseoplanus SAI-25 by bioactivity-guided fractionation against H. armigera. Spectral studies by infrared (IR), nuclear magnetic resonance (NMR), and electron spray ionization mass spectroscopy (ESI-MS) confirmed that the purified compound was cyclo(Trp-Phe) of the diketopiperazines class. Cyclo(Trp-Phe) exhibited antifeedant (70 %), larvicidal (67 %), and pupicidal (59 %) action against H. armigera in a dose-dependent manner. The lethal dose for 50 % of the group (LD50) and LD90 values for larvicidal effect were 619 and 2750 ppm, respectively. In addition, the purified compound prolonged larval (10.3–11.1 days) and pupal (10.9–11.8 days) periods compared with the untreated control (larval duration 9.8 days, pupal duration 10.6 days). This is the first report on the presence and biological activity of cyclo(Trp-Phe) isolated from the genus Streptomyces

Biological options for crop health (Nutrition, pest and disease) management-sanguine to sustainable agriculture

Interest in biological control of plant insect pests and pathogens has been stimulated in recent years by trends in agriculture towards greater sustainability and public concern about the use of hazardous pesticides. Microorganisms have the capability to synthesize many different biologically active secondary metabolites such as antibiotics, herbicides, pesticides, antiparasitic and enzymes like cellulase, chitinase and xylanase. Microbial collection at ICRISAT, Patancheru, India has over 2000 accessions of bacteria and actinomycetes isolated from various sources and/or niches of composts, rhizosphere and rhizoplane soil samples of sorghum and rice. These accessions possess at least one of six agriculturally beneficial traits studied viz. phosphate solublization, siderophore production, cellulose degradation, nitrogen fixation, antagonism to disease causing fungi and fluorescent Pseudomonas. In addition to that ICRISAT has also identified 28 entomopathogenic bacteria and actinomycetes capable of managing the mos

Plant growth-promoting traits of biocontrol potential bacteria isolated from rice rhizosphere

Seven isolates of bacteria (SRI-156, SRI-158, SRI-178, SRI-211, SRI-229, SRI-305 and SRI-360) were earlier reported by us as having potential for biocontrol of charcoal rot of sorghum and plant growth promotion (PGP) of the plant. In the present study, the seven isolates were characterized for their physiological traits (tolerance to salinity, pH, temperature and resistance to antibiotics and fungicides) and further evaluated in the field for their PGP of rice. All the seven isolates were able to grow at pH values between 5 and 13, in NaCl concentrations of up to 8% (except SRI-156 and SRI-360), temperatures between 20 and 40?C and were resistant to ampicillin (>100 ppm; except SRI-158 and SRI-178) but sensitive (<10 ppm) to chloramphenicol, kanamycin, nalidixic acid, streptomycin (except SRI-156 and SRI-211) and tetracycline. They were tolerant to fungicides benlate and captan, except SRI-158 and SRI-178, bavistin and sensitive to thiram (except SRI-156 and SRI-211) at field application level. In the field, four of the seven isolates (SRI-158, SRI-211, SRI-229 and SRI-360) significantly enhanced the tiller numbers, stover and grain yields, total dry matter, root length, volume and dry weight over the un-inoculated control. In the rhizosphere soil at harvest, all the isolates significantly enhanced microbial biomass carbon (except SRI-156), microbial biomass nitrogen and dehydrogenase activity (up to 33%, 36% and 39%, respectively) and total N, available P and% organic carbon (up to 10%, 38% and 10%, respectively) compared to the control. This investigation further confirms that the SRI isolates have PGP properties

Assessment of different methods of rice (Oryza sativa. L) cultivation affecting growth parameters, soil chemical, biological, and microbiological properties, water saving, and grain yield in rice–rice system

Field experiments were conducted at DRR farm located at ICRISAT, Patancheru, in sandy clay loam soils during four seasons, Kharif 2008, Rabi 2008–2009, Kharif 2009 and Rabi 2009–2010, to investigate growth parameters, water-saving potential, root characteristics, chemical, biological, and microbial properties of rhizosphere soil, and grain yield of rice (Oryza sativa L.) by comparing the plants grown with system of rice intensification (SRI) methods, with organic or organic + inorganic fertilization, against current recommended best management practices (BMP). All the growth parameters including plant height, effective tillers (10–45 %), panicle length, dry matter, root dry weight (24–57 %), and root volume (10–66 %) were found to be significantly higher with in SRI-organic + inorganic over BMP. With SRI-organic fertilization, growth parameters showed inconsistent results; however, root dry weight (3–77 %) and root volume (31–162 %) were found significantly superior compared to BMP. Grain yield was found significantly higher in SRI-organic + inorganic (12–23 and 4–35 % in the Kharif and Rabi seasons, respectively), while with SRI-organic management, yield was found higher (4–34 %) only in the Rabi seasons compared to BMP. An average of 31 and 37 % of irrigation water were saved during Kharif and Rabi seasons, respectively, with both SRI methods of rice cultivation compared to BMP. Further, total nitrogen, organic carbon%, soil dehydrogenase, microbial biomass carbon, total bacteria, fungi, and actinomycetes were found higher in the two SRI plots in comparison to BMP. It is concluded that SRI practices create favorable conditions for beneficial soil microbes to prosper, save irrigation water, and increase grain yield

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

Management of Soil-Borne Diseases of Grain Legumes Through Broad-Spectrum Actinomycetes Having Plant Growth-Promoting and Biocontrol Traits

Chickpea (Cicer arietinum L.) and pigeonpea (Cajanus cajan L.) are the two important grain legumes grown extensively in the semiarid tropics (SAT) of the world, where soils are poor in nutrients and receive inadequate/erratic rainfall. SAT regions are commonly found in Africa, Australia, and South Asia. Chickpea and pigeonpea suffer from about 38 pathogens that cause soil-borne diseases including wilt, collar rot, dry root rot, damping off, stem canker, and Ascochyta/Phytophthora blight, and of which three of them, wilt, collar rot, and dry root rot, are important in SAT regions. Management of these soil-borne diseases are hard, as no one control measure is completely effective. Advanced/delayed sowing date, solarization of soil, and use of fungicides are some of the control measures usually employed for these diseases but with little success. The use of disease-resistant cultivar is the best efficient and economical control measure, but it is not available for most of the soil-borne diseases. Biocontrol of soil-borne plant pathogens has been managed using antagonistic actinobacteria, bacteria, and fungi. Actinobacterial strains of Streptomyces, Amycolatopsis, Micromonospora, Frankia, and Nocardia were reported to exert effective control on soil-borne pathogens and help the host plants to mobilize and acquire macro- and micronutrients. Such novel actinomycetes with wide range of plant growth-promoting (PGP) and antagonistic traits need to be exploited for sustainable agriculture. This chapter gives a comprehensive analysis of important soil-borne diseases of chickpea and pigeonpea and how broad-spectrum actinomycetes, particularly Streptomyces spp., could be exploited for managing them