Three species of entomopathogenic nematodes of the family Steinernematidae (Nematoda: Rhabditida) new to continental Portugal

Abstract

A survey was conducted to determine the species of entomopathogenic nematodes occurring in continental Portugal. Nematodes were recovered from soil samples collected from Alentejo (South) and central Portugal from 2006 to 2009. Nematode isolates were identified based on morphology and sequence analysis. Phylogenetic analysis was based on sequences of partial 28S (D2D3 domain), internal transcribed spacer (ITS) and cytochrome C oxidase subunit I gene (COI). Nematode isolates 59F, 15G, 20F and 2B were characterized in detail. In the collected samples, nematodes from the genera Steinernema and Heterorhabditis were identified, namely Heterorhabditis bacteriophora (1.9%), Steinernema feltiae (11.5%), S. kraussei (0.32%), S. intermedium (0.32%) and Steinernema sp. (0.63%) glaseri-group. Isolate 2B shows morphological characteristics identical to S. intermedium, which is a member of the affine/intermedium-group and is characterized by the presence of strongly curved and robust spicules with a distinct rostrum in the male, and dorsal tail depression in third-stage infective junveniles (IJ). However, the phylogenies based on the three molecular markers revealed that isolate 2B is more closely related to S. affine than to S. intermedium. Based on morphological observations, isolate 20F was identified as S. kraussei, which is a member of the kraussei/feltiae-group, characterized by IJs with a straight body of medium length (mean = 700-950 μm), lateral field mostly with eight ridges, rather broad, flatly rounded and continuous cephalic region, excretory pore at mid-pharynx level; males with mucronate tail, yellowish spicules ca. 50 μm long and wide manubria; females with short conoid tail with pointed non-mucronate tip. Based on morphology and sequence analysis, isolates 59F and 15G were considered conspecific and identified as a species belonging to the glaseri-group. More detailed studies are necessary to decide whether these isolates represent a new species.