PRELIMINARY SURVEY OF ENTOMOPATHOGENIC NEMATODES IN UPPER NORTHERN THAILAND.
Apichat VittaChamaiporn FukruksaThatcha YimthinKitsakorn DeelueChutima SaraiRaxsina PolseelaAunchalee ThanwisaiPublished in: The Southeast Asian journal of tropical medicine and public health (2018)
Entomopathogenic nematodes (EPNs) of the genera Steinernema and
Heterorhabditis are used as biocontrol agents for insect pests. Survey of indigenous
EPNs provides not only the diversity aspects but also the contribution in pest
management in local areas. The objective of this study was to survey EPNs in
upper northern Thailand. Nine hundred seventy soil samples were obtained from
194 sites in upper northern region of Thailand; of these 60 (6.2%) had EPNs in 2
genera: Steinernema (32 isolates) and Heterorhabditis (28 isolates). Most EPNs were
isolated from loam with a soil temperature of 24-38°C, a pH of 1.5-7.0 and a soil
moisture content of 0.5-6.8%. Molecular identification based on sequencing of a
partial region of an internal transcribed spacer was performed for Heterorhabditis
and the 28S rDNA for Steinernema. A BLASTN search of known sequence EPNs
revealed 24 isolates of S. websteri and one isolate of S. scarabaei were identified;
closely related to S. websteri (accession no. JF503100) and S. scarabaei (accession
no. AY172023). The Heterorhabditis species identified were: H. indica (11 isolates),
H. gerrardi (2 isolates) and Heterorhabditis sp (8 isolates). Phylogenetic analysis
revealed 11 isolates of Heterorhabditis were related to H. indica; 2 isolates were related
to Heterorhabditis gerrardi and 8 isolates were closely related to Heterorhabditis
sp SGmg3. The study results show the genetic diversity of EPNs and describe a
new observation of S. scarabaei and H. gerrardi in Thailand. This finding is new
and provides important information for further study on using native EPNs in
biological control.