Vadlamudi Srinivas

Plant growth-promoting activities of Streptomyces spp. in sorghum and rice

Five strains of Streptomyces (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were earlier reported by us as biological control agents against Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceri (FOC). In the present study, the Streptomyces were characterized for enzymatic activities, physiological traits and further evaluated in greenhouse and field for their plant growth promotion (PGP) of sorghum and rice. All the Streptomyces produced lipase, β-1-3-glucanase and chitinase (except CAI-121 and CAI-127), grew in NaCl concentrations of up to 6%, at pH values between 5 and 13 and temperatures between 20 and 40°C and were highly sensitive to Thiram, Benlate, Captan, Benomyl and Radonil at field application level. When the Streptomyces were evaluated in the greenhouse on sorghum all the isolates significantly enhanced all the agronomic traits over the control. In the field, on rice, the Streptomyces significantly enhanced stover yield (up to 25%; except CAI-24), grain yield (up to 10%), total dry matter (up to 18%; except CAI-24) and root length, volume and dry weight (up to 15%, 36% and 55%, respectively, except CAI-24) over the control. In the rhizosphere soil, the Streptomyces significantly enhanced microbial biomass carbon (except CAI-24), nitrogen, dehydrogenase (except CAI-24), total N, available P and organic carbon (up to 41%, 52%, 75%, 122%, 53% and 13%, respectively) over the control. This study demonstrates that the selected Streptomyces which were antagonistic to FOC also have PGP properties.

Biological activity of entomopathogenic actinomycetes against lepidopteran insects (Noctuidae: Lepidoptera)

Vijayabharathi, R., Kumari, B. R., Sathya, A., Srinivas, V., Abhishek, R., Sharma, H. C. and Gopalakrishnan, S. 2014. Biological activity of entomopathogenic actinomycetes against lepidopteran insects (Noctuidae: Lepidoptera). Can. J. Plant Sci. 94: 759-769. The aim of the present study was to identify an efficient broad-spectrum bio-pesticide for the control of lepidopteran insects from microbes in various ecological niches. A total of 111 microbes isolated from various herbal vermi-composts and organically cultivated fields were evaluated for their intracellular metabolites (ICM), extracellular metabolites (ECM) and whole culture (WC) against early instars of lepidopteran insects. Fifteen actinomycete isolates which showed insecticidal activity against 2nd instar Helicoverpa armigera were selected and further screened against Spodoptera litura and Chilo partellus. A significant broad spectrum insecticidal activity was found in the order ECM>ICM>WC against all the insects under laboratory conditions. All these actinomycete isolates also registered significant activity under greenhouse conditions on 2nd instar H. armigera. The actinomycete isolates were identified by 16S rDNA sequencing and matched with Streptomyces species using BLAST search. Among all the 15 isolates, SAI-25 (S. griseoplanus), CAI-155 (S. bacillaris) and BCA-698 (S. albolongus) showed consistent entomopathogenic activity against all the three insects suggesting their potential as broad-spectrum biocontrol agents against other lepidopterans.

Biological control of Botrytis cinerea and plant growth promotion potential by Penicillium citrinum in chickpea(Cicer arietinum L.)

A total of 48 fungi were characterised for their antagonistic potential against Botrytis cinerea causing Botrytis Gray Mold (BGM) disease in chickpea by dual culture and metabolite production assays. The culture filtrate of the most promising isolate, VFI-51, was purified by various chromatographic techniques and identified as ‘citrinin’ by nuclear magnetic resonance and mass spectrometry studies. The efficacy of citrinin was demonstrated to control BGM in chickpea under greenhouse conditions. The sequences of 18S rDNA gene of the VFI-51 matched with Penicillium citrinum in BLAST analysis. The VFI-51 produced siderophore, hydrocyanic acid, indole-3-acetic acid, lipase, protease and β-1,3-glucanase; grew well in NaCl (up to 15%), at pH between 7 and 11 and temperatures between 20°C and 40°C; and was compatible with fungicides bavistin and thiram. Under greenhouse and field conditions, VFI-51 significantly enhanced the nodule number, nodule weight, root and shoot weight and stover and grain yield over the un-inoculated control. In the rhizosphere, VFI-51 also significantly enhanced total N, available P and OC over the un-inoculated control. Scanning electron microscopy analysis revealed that VFI-51 colonised on the roots of chickpea. This study concluded that VFI-51 has the potential for biocontrol of BGM and plant growth promotion in chickpea.

Microbes as interesting source of novel insecticides: A review

Microbes are ubiquitous, survive in all sorts of environments and have a profound influence on the earth. In the present day plant protection scenario, development of resistance to chemical pesticides is the major hurdle in insect pest management. In recent years, several microbes with potential insecticidal properties have come to light. Viruses, bacteria, fungi and protozoa that are known to produce an array of metabolites or toxins, form the basis for microbial insecticides. Since these versatile organisms are amenable for genetic engineering, strains with good insecticidal properties can be identified, evaluated and utilized for pest control. This paper reviews the insecticidal properties of microbes and their potential utility in pest management. Keywords: Microbes, insecticides, metabolites, pest management. African Journal of Biotechnology , Vol 13(26) 2582-2592

Efficacy of Major Plant Extracts/Molecules on Field Insect Pests

Insect pests are considered the major hurdle in enhancing the production and productivity of any farming system. The use of conventional synthetic pesticides has led to the emergence of pesticide-resistant insects, environmental pollution, and negative effects on natural enemies, which have caused an ecological imbalance of the predator-prey ratio and human health hazards; therefore, eco-friendly alternative strategies are required. The plant kingdom, a rich repertoire of secondary metabolites, can be tapped as an alternative for insect pest management strategies. A number of plants have been documented to have insecticidal properties against various orders of insects in vitro by acting as antifeedants, repellents, sterilant and oviposition deterrents, etc. However, only a few plant compounds are applicable at the field level or presently commercialised. Here, we have provided an overview of the broad-spectrum insecticidal activity of plant compounds from neem, Annona, Pongamia, and Jatropha. Additionally, the impact of medicinal plants, herbs, spices, and essential oils has been reviewed briefly.

Formulations of Plant Growth-Promoting Microbes for Field Applications

Development of a plant growth-promoting (PGP) microbe needs several steps starting with isolation of a pure culture, screening of its PGP or antagonistic traits by means of different efficacy bioassays performed in vitro, in vivo or in trials under greenhouse and/or field conditions. In order to maximize the potential of an efficient PGP microbe, it is essential to optimize mass multiplication protocols that promote product quality and quantity and a product formulation that enhances bioactivity, preserves shelf life and aids product delivery. Selection of formulation is very crucial as it can determine the success or failure of a PGP microbe. A good carrier material should be able to deliver the right number of viable cells in good physiological conditions, easy to use and economically affordable by the farmers. Several carrier materials have been used in formulation that include peat, talc, charcoal, cellulose powder, farm yard manure, vermicompost and compost, lignite, bagasse and press mud. Each formulation has its advantages and disadvantages but the peat based carrier material is widely used in different part of the world. This chapter gives a comprehensive analysis of different formulations and the quality of inoculants available in the market, with a case study conducted in five-states of India.

Ensuring biological safety of drinking water at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh, India

Potability of drinking water from various sources at the campus of International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh, India had been assessed for 17 years (1994 to 2010). All four sources of drinking water at ICRISAT, including Manjeera water (Municipal corporation supplied drinking water), borewell 1, borewell 2 and ICRISAT water (mixture of both Manjeera as well as borewells after treatment), were tested for their potability once in two months by most probable number (MPN) method. The results indicated that water from borewells were not safe to drink without treatment as Escherichia coli was found in 10 and 12 years out of 17 tested years for bore wells 1 and 2, respectively. Manjeera water samples were also found unsafe in two out of the 17 years, whereas ICRISAT water was found safe to drink throughout the study period. This study indicated that even deep borewells (of about 135 ft) can get contaminated, and its water is not safe to drink without treatment, and an additional treatment of municipal water supply is required in order to have safe drinking water. Keywords: Potability, drinking water, Escherichia coli , borewell water, municipal water

Deciphering the tri-dimensional effect of endophytic Streptomyces sp. on chickpea for plant growth promotion, helper effect with Mesorhizobium ciceri and host-plant resistance induction against Botrytis cinerea

A total of 219 endophytic actinobacteria, isolated from roots, stems and leaves of chickpea, were characterized for antagonistic potential against Botrytis cinerea, causal organism of Botrytis grey mold (BGM) disease, in chickpea. Among them, three most potential endophytes, AUR2, AUR4 and ARR4 were further characterized for their plant growth-promoting (PGP) and nodulating potentials and host-plant resistance against B. cinerea, in chickpea. The sequences of 16 S rDNA gene of the three endophytes were matched with Streptomyces but different species. In planta, the isolate AUR4 alone was able to significantly enhance PGP traits including seed numbers (11.8 vs. 9.8/Plant), seed weight (8 vs. 6.8 g/Plant), pod numbers (13.6 vs. 11.5/Plant), pod weight (9.3 vs. 7.5 g/Plant) and biomass (10.9 vs. 8 g/Plant) over the un-inoculated control in chickpea genotype JG11. Interestingly, consortium of the selected endophytes, AUR2, AUR4 and ARR4 were found less effective than single inoculation. Co-inoculation of the selected endophytes with Mesorhizobium ciceri significantly enhanced nodulation and nitrogenase activity in five chickpea genotypes including ICCV2, ICCV10, ICC4958, Annigeri and JG11 over the un-inoculated control. The selected endophytes showed antagonistic potential in planta by significant reduction of disease incidence (28─52%) in both single inoculation and consortium treatments over the un-inoculated control across the genotypes ICC4954 (susceptible), ICCV05530 (moderately resistant) and JG11 (unknown resistance). Further, antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, phenylalanine ammonia-lyase and polyphenol oxidase and phenolics were found induced in the leaves of chickpea inoculated with selected endophytes over un-inoculated control. Principal component analysis revealed that, the antioxidant enzymes and phenolics were found in the magnitude of ICC4954 < JG11 < ICCV05530 which correlates with their resistance level. The selected endophytes enhanced the plant growth and also host plant resistance against BGM in chickpea.

Streptomyces sp. as plant growth-promoters and host-plant resistance inducers against Botrytis cinerea in chickpea

ABSTRACT Two hundred and fifty seven actinobacteria, isolated from five different rhizosphere soils of chickpea, were evaluated for their antagonistic potential against Botrytis cinerea, causal agent of Botrytis grey mold (BGM) disease in chickpea, by dual culture assay. Of them, three most promising isolates (ATIRS43, ATIRS65 and ARRS10) with highest inhibitory activity (67–77%) were identified as Streptomyces sp. These selected isolates induced growth of chickpea genotype JG11 as a consortium rather than an individual inoculum. Co-inoculation of the selected Streptomyces sp. with Mesorhizobium ciceri UPM-Ca7T enhanced nodulation and nitrogenase activity in five chickpea genotypes (ICCV2, ICCV10, ICC4958, Annigeri and JG11). The selected Streptomyces sp. significantly reduced the disease incidence caused by B. cinerea by 28–47% over the un-inoculated control across the chickpea genotypes ICC4954 (susceptible), ICCV05530 (moderately resistant) and JG11 (unknown resistance). The Streptomyces sp. were also able to induce host-plant resistance, irrespective of the genotype, through the induction of various antioxidant enzymes and phenolics. Phenolic profiling of B. cinerea-affected and Streptomyces treated plants of ICCV05530 further confirmed host-plant resistance traits. This study indicated that the selected Streptomyces sp. have the potential for biological control of BGM disease in chickpea.