Find in Library

Entomopathogenic nematodes (EPNs) are insect parasitic nematodes of the genera <i>Het-erorhabditis</i> and <i>Steinernema</i>. These nematodes are symbiotically associated with the bacteria, <i>Photorhabdus</i> and <i>Xenorhabdus,</i> respectively. National parks in Thailand are a potentially rich resource for recovering native EPNs and their symbiotic bacteria. The objectives of this study are to isolate and identify EPNs and their bacterial flora from soil samples in four national parks in Thailand and to evaluate their efficacy for controlling mosquito larvae. Using a baiting method with a <i>Galleria mellonella</i> moth larvae and a White trap technique, 80 out of 840 soil samples (9.5%) from 168 field sites were positive for EPNs. Sequencing of an internal transcribed spacer resulted in the molecular identification of <i>Heterorhabditis</i> nematode isolates as <i>H. indica</i>, <i>H. baujardi</i> and <i>Heterorhabditis</i> SGmg3, while using 28S rDNA sequencing, <i>Steinernema</i> nematode species were identified as <i>S. guang-dongense</i>, <i>S. surkhetense</i>, <i>S. minutum</i>, <i>S. longicaudum</i> and one closely related to <i>S. yirgalemense</i>. For the symbiotic bacterial isolates, based on <i>recA</i> sequencing, the <i>Photorhabdus</i> spp. were identified as <i>P. luminescens</i> subsp. <i>akhurstii</i>, <i>P. luminescens</i> subsp. <i>hainanensis</i> and <i>P. luminescens</i> subsp. <i>australis</i>. <i>Xenorhabdus</i> isolates were identified as <i>X. stockiae</i>, <i>X. indica</i>, <i>X. griffiniae</i>, <i>X. japonica</i> and <i>X. hominickii</i>. Results of bioassays demonstrate that <i>Photorhabdus</i> isolates were effective on both <i>Aedes aegypti</i> and <i>Culex quinquefasciatus</i>. Therefore, we conclude that soil from Thailand’s national parks contain a high diversity of entomopathogenic nematodes and their symbiotic bacteria. <i>Photorhabdus</i> bacteria are larvicidal against culicine mosquitoes and may serve as effective biocontrol agents.