Characterisation of Steinernema abbasi (Rhabditida: Steinernematidae) isolated from Indian agricultural soils and their efficacy against insect pests

Abstract

ABSTRACT Ten Steinernema abbasi isolates were obtained during a soil survey in Western Uttar Pradesh, India. The nematode isolates were characterised using morpho-taxometrical and molecular approaches, and their biopesticide properties against two lepidopteran pests (i.e. Helicoverpa armigera and Spodoptera litura) were assessed. In addition, their Xenorhabdus bacterial symbionts were isolated, and physiologically and molecularly characterised. Lastly, the geographical dissemination of Steinernema abbasi was studied using meta-analyses of their ITS rDNA NCBI GenBank records. The morphology of the nematode isolates of this study was comparable with the S. abbasi specimens used in the original description with the only discrepancy that well-developed mucrons were observed in the second generation males and females of this study. The analyses of ITS rDNA from NCBI records show that S. abbasi is ubiquitous throughout the Indian subcontinent but rarely reported from South East Asia. There are no reports of this species outside of Asia. The bacterial symbionts of S. abbasi isolates show the phenotypic and molecular similitude with Xenorhabdus indica. Bioassays showed that the nematode isolates were highly virulent against cotton bollworm (Helicoverpa armigera) and tobacco cutworm (Spodoptera litura) larvae. This species being native to Indian Subcontinent could be explored further as a biocontrol agent.