Taxometrical and numerical characterization of an isolate of Steinernema abbasi (Elawad et al., 1997) with larger infective juveniles comprehensive from ITS1-5.8SITS2 region of rRNA

In present investigation Steinernema sp. isolate CS_1 was identified with the aid of numerical taxonomy as an additional tool. Presence of two horn-like structures on head region of 3rd stage infective juveniles (IJs) placed the nematode in bicornutum group and differentiated from other compared Steinernema spp. The morphological characters of 3rd stage infective juveniles and 1st generation males showed close resemblance with S. abbasi, S. thermophilum and S. pakistanense however, the body length was varied (583mm vs 541mm, 555 mm and 683 mm, respectively). The morphometrical characters and life history events placed the present specimen near to the S. abbasi. Results obtained through the phylogenetic utility of maximum parsimony, maximum likelihood and neighbour joining methods and comparative account on nucleotides analyses based on ITSs study confirmed the present specimens as isolates of S. abbasi. The nucleotide composition resemblance within 5.8S gene with other Steinernema species evident the less polymorphism and highly conserved nature of this region as compared to ITS1 and ITS2 and delimit the relationship of steinernematid nematodes.