SUMMARY
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 LC50 and LC95 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/ABS170729052CReceived: July 29, 2017; Revised: December 4, 2017; Accepted: December 5, 2017; Published online: December 12, 2017How 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.