IN VITRO ANALYSIS OF LARVICIDAL ACTIVITY OF ENDOPHYTIC STREPTOMYCES SP. BLS-5 (ON090335) AGAINST CULEX QUINQUEFASCIATUS.

This investigation was performed to assess the mosquito larvicidal activity of an endophytic actinobacteria BLS-5 isolated from the stem of a weed Blumea lacera against Cx. quinquefasciatus, a mosquito vector transmitting lymphatic filariasis. The morphological and molecular characterization designated the strain as Streptomyces sp. BLS-5 with 99.86% sequence similarity to Streptomyces pilosus AB184161 and upon submission of the gene sequence in NCBI, an accession number ON090335 was allotted. Ethyl acetate extract among the other solvent extracts viz. petroleum ether, benzene, chloroform, acetone and methanol exhibited 100% larvicidal activity at 500 ppm at 48 h and was thus carried forward for dose-response bioassay at different concentrations ranging from 40 – 650 ppm against third instar larvae. The larval deaths were detected after 24, 48 and 72 h of treatment and the lethal concentrations with 95% confidence limits were found out using probit analysis. Calculated LC₅₀ and LC₉₀ values were 219.80 and 387.11 ppm (24 h), 148.19 and 290.55 ppm (48 h) and 77.02 and 159.58 ppm (72 h), respectively. These results indicate that the purified larvicidal metabolites of the ethyl acetate extract, which is in process, might have significant larvicidal activity and thus also proves the potentiality of endophytic Streptomyces sp. BLS-5 (ON090335) as environment-friendly larvicides. [ABSTRACT FROM AUTHOR]