Preeti Saini

Plant Growth-Promoting Microbes (PGPM) as Potential Microbial Bio-Agents for Eco-Friendly Agriculture

The use of chemical fertilizers generates environmental and public health problems. The exploitation of beneficial microbes as a biofertilizer has become of foremost importance in agriculture sector for their impending role in sustainable crop production. Eco-friendly approaches inspire a wide range of application of plant growth-promoting rhizobacteria (PGPRs), endo- and ectomycorrhizal fungi, cyanobacteria and many other useful microorganisms for improved nutrient uptake, plant growth and plant tolerance to abiotic and biotic stress. PGPR use different mechanisms like biofertilization including biological fixation of atmospheric nitrogen, phosphate solubilization, siderophore production and exopolysaccharides production; phytostimulation including production of indole acetic acid, gibberellins, cytokinins and ethylene; and biocontrol including stimulation of systemic resistance, competition for iron, nutrient and space, production of antibiotics, lytic enzymes, hydrogen cyanide and volatile compounds. In scrutiny of the recent advances in PGPR biotechnology, this chapter describes the rhizospheric PGPRs and the different mechanisms used by PGPR to promote the plant’s growth and health.

Assessment of bioactivity of endophytic actinomycetes from some medicinal plants

Out of 70 isolates of actinomycetes obtained from medicinal plants, 21 displayed antagonistic activity against Alternaria alternata, Fusarium oxysporum and Rhizoctonia solani. All the isolates were screened for hydrolytic enzymes production. Among these, 47 isolates produced amylase, 25 protease and 16 were having ability to produce chitinase. The extracellular chitinase activity of two selected isolates AR3 and O9 was evaluated (0.083 and 0.080 U/ml) with 0.6% colloidal chitin, which was found better as compared to 1% colloidal chitin. Scanning electron microscopy revealed rupture of F. oxysporum mycelial cell wall at the area of interaction with O9. The endophytic actinomycete isolate O9 was identified as Streptomyces rochei strain KMB-1 by 16S rDNA sequencing. This isolate was found to be promising in terms of seed germination and Fusarium wilt control in muskmelon under green house conditions.