Insecticidal activity of endophytic actinomycetes isolated from Azadirachta indica against Myzus persicae

In the present study, 85 strains of actinomycetes were isolated from the neem tree ( Azadirachta indica ) and screened for their insecticidal activity against the green peach aphid, Myzus persicae . The results showed that crude extracts from 24 strains exerted a contact effect against M. persicae with different insecticidal efficacies. Crude extracts from 8 actinomycetes strains exhibited the highest insecticidal activity (above 60%). Out of these 8 strains, 3 isolates that produced the maximum mortalities were screened a second time. The crude extract from strain G30 was the most virulent against the green peach aphid, with LC 50 and LC 95 values of 1.680 mg/mL and 4.370 mg/mL, respectively, after 48 h of treatment. The following morphological, culture, physiological and biochemical characteristics of strain G30 were recorded: (i) ovate-orbicular and smooth surface spores with short and curve filaments; (ii) an aerial off-white mycelium with a mustered yellow base; (iii) inability to produce soluble pigments; (iv) the ability to hydrolyze starch but not cellulose; (v) the ability to utilize glycerin and several sugars as a carbon source but not L-rhamnose and sorbitol. Molecular identification of G30 revealed a 99.6% genetic similarity of the 16S rDNA sequence with Streptomyces albidoflavus . We conclude that the isolate G30 was S. albidoflavus and that the insecticidal activity of its crude extract was sufficiently high to become a candidate for bioinsecticide development. https://doi.org/10.2298/ABS170729052C Received: July 29, 2017; Revised: December 4, 2017; Accepted: December 5, 2017; Published online: December 12, 2017 How to cite this article: Chen Y, Shafi J, Li M, Fu D, Ji M. Insecticidal activity of endophytic actinomycetes isolated from Azadirachta indica against Myzus persicae . Arch Biol Sci. 2018;70(2):349-57.