Biochemical and molecular characterization of Photorhabdus akhurstii associated with Heterorhabditis indica from Meerut, India

A population of Heterorhabditis (DH3) was isolated from agricultural fields from Meerut district, India by insect baiting technique. The isolate was identified as Heterorhabditis indica based on morpho-taxometrical and molecular analyses. The present populations were identical to the original description; however, the size of the 3 stages was longer than the topotype populations. Analysis of ITS-rDNA sequences showed 1 nucleotide base pair difference in aligned data with type description, however, no nucleotide base pair difference was seen in the D2D3 domain. The associated bacterial symbiont of the DH3 strain was identified as Photorhabdus akhurstii based on phenotypic, biochemical and 16S rDNA data. Most of the biochemical tests were negative and only three tests were found positive viz., Urease, Nitrogen reduction and Oxidase. Further, we evaluated its pathogenicity against Galleria mellonella and Helicoverpa armigera. The LD50 value of strain DH3 against G. mellonella larvae at 48 hours was 8 IJs/larva for 50% larval mortality whereas in Helicoverpa armigera it needed 13 IJs/larva, to kill 50% of the larvae.