ABSTRACT
Sustainable increase in agricultural productivity to feed the growing population demands eco-friendly remedies including the use of biocontrol agents to control diseases in food crops. Trichoderma spp. is one such agent which provides multiple plant health benefits, like disease control, plant growth promotion, development of resistance and stress tolerance. However, inappropriate concentration and less effective formulations with a poor shelf life of Trichoderma spp. have hampered its customized applications at large scale. Here, we studied the influence of various parameters on growth and mass production of customized applications of Trichoderma spp., including carrier materials, its shelf life and evaluation of antifungal activity of T. viridae. We observed optimum growth of T. viridae at 40°C, pH 6.0, maximum sporulation at 45°C and pH 6.0, with cellulose and carboxymethyl cellulose as a best utilizable carbon source. Neem cake came out as an excellent carrier as it gave a prolonged shelf life of 200 days during storage at 28°C with 35.78×106 cfu g-1 of T. viridae. Antifungal assay against plant pathogenic fungi revealed complete inhibition of growth and sporulation of fungal pathogens.
ABSTRACT
Contamination of food by aflatoxin of Aspergillus flavus is a major global problem affecting trade, quality, utility of food and human health. While all the members of A. flavus does not produce aflatoxin, sensitive, cost effective and reproducible methods for large scale screening and differentiation of toxigenic A. flavus from atoxigenic ones are scarce. Here, we made one such attempt using coconut milk agar (CMA), yeast extract sucrose agar (YESA), ammonium hydroxide vapour tests, enzyme linked immuno sorbent assay (ELISA) and polymerase chain reaction (PCR) for large scale screening of toxigenic strains of A. flavus. Fifty nine isolates of A. flavus obtained from major chilli growing regions of India were categorized into toxigenic and atoxigenic strains by using cultural, analytical and molecular methods. Forty two (71.18 %) isolates showed positive response in coconut milk agar (CMA), 17 (28.81%) isolates did not match while 23 (38.98 %) isolates showed red colour and 36 (61.01%) isolates did not produce red colour upon exposure to ammonia vapour in YESA. Out of 59 isolates, isolates CAF43 came out as highly toxigenic, as it produced 3128.20 μg kg-1 aflatoxin B1 followed by CAF 42 which produced 3035.10 μg kg-1. Among 59 isolates, eight A. flavus isolates were amplified with two regulatory (aflR and aflJ) and two structural (norA and ver1) genes at a region of 900, 450, 400 and 450 bp, respectively.
ABSTRACT
Chitinases, through decomposition of chitin, have wide applications, and hence are in demand. Researchers over the period, are looking for potential microbial sources and for optimal production of chitnases. Here, we report isolation of three chitinolytic bacterial species belonging to three genera from different agricultural soil sample collected from Shahada, Maharashtra, India, on minimal agar plates containing colloidal chitin as source of chitin. Stenotrophomonas was found to be the most dominant species, followed by Pseudomonas and Alcaligenes. Stenotrophomonas maltophilia identified using 16s rRNA sequencing, Biolog and GC-FAME analysis showed optimum (1.5 U/mL) chitinase activity on chitin agar plates and in submerged culture broth with pH 6-7, incubation of 2 days at 37°C. Presence of CaCl2 stimulated the enzyme production but EDTA was suppressive. The enzyme upon purification by using sephadex G-100 gel filtration showed improved chitinolytic activity, enzyme kinetics and 2.4 fold increase in purification yield. The molecular weight of purified chitinase as determined by SDS-PAGE was 50-55 kDa.
ABSTRACT
Rice sheath blight arising due to lack of systemic resistance against causative agent Rhizoctonia solani has been a major economic threat to rice growers across the globe. This warrants induced systemic resistance (ISR) in plant to make them disease resistant. Application of antibiotic producing Pseudomonads that also secrete defense inducing enzymes is known to impart resistance to plants. Here, we report induction of the induced systemic resistance (ISR) by six strains of rhizosphere fluorescent Pseudomonas possessing 2,4-diacetyl phloroglucinol (2,4-DAPG) antibiotic genes against rice sheath blight pathogen Rhizoctonia solani. In the preliminary screening, isolate EP5 (endophytic Pseudomonas fluorescens) showed 76.5% inhibition against R. solani. EP5 treated rice grains showed the highest germination of 96.6%, mean root length of 15.3 cm, shoot length of 12.6 cm and vigour index of 2104.9. Paddy grains treated with EP5 (through seed treatment followed by root dipping) upon challenge inoculation with R. solani (Rs1) gave higher activity of peroxidase (PO) 2.50 change in absorbance at 470 nm/min/mg protein), polyphenol oxidases (PPO), 2.25 change absorbance at 420 nm/ min/mg protein, phenyl alanine ammonia lyase (PAL) and 28.5 nmol transcinnamic acid/hr/mg protein. 2,4-DAPG positive fluorescent Pseudomonas strains produced PO, PPO, PAL and 28.5 nmol transcinnamic that resulted in ISR against rice sheath blight pathogen R. Solani.
ABSTRACT
Heavy metal contamination, particularly of cultivable lands, is a matter of concern. Bioremediation helps in reversing such contamination to certain extent. Here, we report isolation, polyphasic identification and the role of siderophore producing rhizobacteria Alcaligenes feacalis RZS2 and Pseudomonas aeruginosa RZS3 in bioremediation of heavy metal contaminated soil and plant growth promotion activity in such contaminated soil. Siderophore produced by A. feacalis RZS2 and P. aeruginosa RZS3 strains chelated various heavy metal ions like MnCl2.4H2O, NiCl2.6H2O, ZnCl2, CuCl2 and CoCl2 other than FeCl3.6H2O at batch scale. Their bioremediation potential was superior over the chemical ion chelators like EDTA and citric acid. These isolates also promoted growth of wheat and peanut seeds sown in heavy metal contaminated soil. Effective root colonizing ability of these isolates was observed in wheat and peanut plants.