Tag: purification

The tobacco caterpillar, Spodoptera litura (Fab.) was considered the major pest of many crops such as tobacco, cotton, tomato, castor, cowpea, sesbania, etc. A total of 15 indigenous Streptomyces spp. strains were isolated from soil samples of the Western Ghats, Tamil Nadu, India. Isolation of Streptomyces strains was carried out by serial dilution method and plating technique. Purification of strain was done by streaking method on International Streptomyces Project 2 (ISP 2), ISP 4, and starch casein nitrate agar (SCNA) medium. The main challenges in the study was the isolation and purification of Streptomyces strains were difficult with the contamination of cultures. They were overcome by the addition of antibiotics such as Cyclohexamide and Streptomycin sulphate into the media. The morphological and biochemical characterization was performed for identifying the efficient strain. Diet impregnation bioassay was also carried out against the 2nd instar larvae of S. litura. Based on the results of morphological, biochemical, and diet impregnation bioassay, Strain 1 (ST1) was considered as the efficient strain. The ST 1 was molecularly identified by 16S rDNA sequencing and compared with Streptomyces species using NCBI BLAST program. Among the 15 isolated Streptomyces strains, ST 1 (Streptomyces katrae) showed a higher percentage of mortality (73.33 %) of S. litura. ST 1 showed the most efficient entomopathogenic activity against S. litura among the 15 isolates of Streptomyces. The metabolites present in the fermentation broth showed strong larvicidal, pupicidal and toxic effects against the notorious pest S. litura. These findings denote that the fermentation broth of S. katrae strain has the ability to control the S. litura pest populations at a considerable level.