Phylogenetic relationships of entomopathogenic nematodes and their bacterial symbionts from coastal areas in Lebanon

Abstract

Entomopathogenic nematodes (EPNs) are parasites of soil-dwelling insects that occur in natural and agricultural soils around the world. The current study focuses on the unexplored coastal zone of Lebanon where soil samples were taken in different sites chosen randomly along the coast like beaches, agricultural and herbaceous fields. In total, 350 soil samples were collected, mainly from the southern part of the country. An integrated approach, combining both traditional (morphological) and molecular methods, was used to characterize entomopathogenic nematode species encountered. Two named-species are added to the EPNs catalog in Lebanon from 4 samples out of the total 350 samples isolated: Heterorhabditis indica, reported for the first time in the country (samples AYAB6 and BRA20) and Steinernema feltiae (samples ANFA5 and EDA1). Furthermore, one undescribed potential entomopathogenic nematode belonging to Oscheius genus was recovered. The symbiotic bacteria from S. Feltiae and H. Indica were also molecularly identified through the use of five gene fragments recA, gyrB, dnaN, gltX and infB. Phylogenetic relationships of entomopathogenic nematodes and their symbiotic bacteria were inferred by using maximum-likelihood analysis. Soil studies were subsequently carried out in order to assess a possible relationship between soil parameters and their effects on EPNs. Results indicate that sandy texture and moisture are key factors for the presence and survival of EPNs in the soil in Lebanon.