Indian Journal of Experimental Biology Vol. 50, August 2012, pp. 559-568 A promising strain of Streptomyces sp. with agricultural traits for growth promotion and disease management Mansoor Alam 1 *, Seema Dharni 1 , Abdul-Khaliq 1 , Santosh Kumar Srivastava 2 , Abdul Samad 1 & Mahesh Kumar Gupta 3 Department of Plant Pathology, 1 Analytical Chemistry and 3 Biotechnology, CSIR-Central Institute of Medicinal & Aromatic Plants (CIMAP), Lucknow 226 015, India Received 6 January 2012; revised 1 June 2012 A bacterial strain, Streptomyces sp. CIMAP- A 1 was isolated from Geranium rhizosphere and identified by morphological, physiological, biochemical and molecular characters (16S rDNA gene sequence). Phylogenetically, it was found most closely related to S. vinacendrappus, strain NRRL-2363 with 99% sequence similarity. The strain had potential antagonistic activity (in vitro) against wide range of phytopathogenic fungi like Stemphylium sp., Botrytis cinerea, Sclerotinia sclerotiorum, Colletotrichum spp., Curvularia spp., Corynespora cassicola and Thielavia basicola. The extracellular secondary metabolites produced by the strain in the culture filtrates significantly inhibited the spore germination, growth of germ tube of the germinated spores and radial growth of Alternaria alternata, Colletotrichum acutatum, Curvularia andropogonis and Fusarium moniliforme. The extraction of culture filtrate with solvents and purification by following VLC and PTLC methods always yielded a 10 th fraction antifungal compound showing activity against wide range of phytopathogenic fungi. The strain was able to produce siderophores and indole-3-acetic acid. The strain was found to enhance the growth and biomass production of Geranium. It increased 11.3% fresh shoot biomass of Geranium and 21.7% essential oil yield. Keywords: Geranium, Phytopathogenic fungi, Streptomyces sp. CIMAP-A 1 , S. vinacendrappus Streptomyces is the largest prokaryotic genus containing 490 validly described species 1 . Streptomyces kills fungal pathogens due to production of secondary antifungal metabolites 2-4 . Recently, few agriculturally important antifungal metabolites, such as fungichromin, coronamycin, aerugine and neopeptins have been isolated and characterized 5-8 . Streptomyces is also used as potential antifungal biocontrol agent in the form of spores, mycelia or combination of two in growth chambers and greenhouses 9-13 . The two commercially available bio- control products, Streptomyces griseoviridis strain K61 (Mycostop) and Streptomyces lydicus (Actino-Iron and Actino Plus/M) are used to control plant diseases caused by Rhizoctonia, Pythium, Botrytis and Fusarium 14 . The strain Streptomyces sp. CIMAP-A 1 was isolated from the rhizospheric soil of healthy rose-scented Geranium (Pelargonium graveolens L) 15 . The investigations were carried out on the cultural, morphological, physiological, biochemical and molecular characteristics of the strain by following light as well as scanning electron microscopic observation 16,17 and 16S rDNA analysis 18 . The antagonistic activity of the strain and the antifungal compound produced by the organism were evaluated against wide range of plant pathogenic fungi by dual culture technique 19 and paper disk technique 20 , respectively. The characteristic features of Streptomyces sp. CIMAP-A 1 strain, isolation, purification and chemical characterization of the antifungal compound, its antagonistic activity against wide range of plant pathogenic fungi and biomass enhancing capacity for Geranium are reported in the present communication. Materials and Methods Isolation and identification of Streptomyces sp. CIMAP- A 1    The culture of Streptomyces CIMAP-A 1 strain 15 was revived on fresh PDA slants from the stock cultures maintained in the culture collections of the department. The culture was grown on Potato- Dextrose-Agar (200 g/L potato infusion, 20 g/L ___________ *Correspondent author Telephone: + 91 522 23 59 624 Fax: + 91 522 23 42 666 E-mail: email2alam@rediffmail.com 3 Present address: E309, East Wing, Second Floor, CSIR-Centre for Cellular and Molecular Biology (CCMB), Hyderabad 500 007, India