Molecular Characterization and First Report of Entomopathogenic Nematodes from Carob Forests in Tumbes, Peru

Abstract

Given their ability to attack and eliminate insects that impact various ecosystems, entomopathogenic nematodes (EPNs) are considered effective biological pest control agents. However, there are few studies focused on their identification or their association with forest species such as the carob tree. The objective of the present study was to isolate and molecularly identify entomopathogenic nematodes from carob tree (Neltuma spp.) forests in Tumbes, Peru. One-kilogram soil samples were collected from ten localities located across four districts in the Tumbes region. In each soil sample, Galleria mellonella Linnaeus 1758 (Lepidoptera: Pyralidae) larvae were exposed as bait for the detection and isolation of EPNs. Exposure times were controlled at 12, 24, 48, 72, and 84-96 hours. The isolated nematodes were morphologically characterized, and their genomic DNA was extracted. The 18S ribosomal DNA (rDNA) gene was amplified via polymerase chain reaction (PCR). Six of the ten evaluated soils showed G. mellonella infection, with a positive correlation between exposure time and infection rate. However, due to marked infectivity divergences (where samples 02 and 06 exhibited the highest percentages), three representative strains were selectively isolated from soil samples 02, 05, and 06. Subsequent morphological characterization and molecular identification determined their taxonomic identity as Heterorhabditis bacteriophora and Heterorhabditis indica. This finding represents the first report of EPNs associated with carob tree plantations in northern Peru and highlights their pathogenic potential against insect larvae. It is recommended that the nematodes identified at the species level be considered in integrated pest management (IPM) programs.