Molecular Identification of Entomopathogenic Nematode Isolates from the Philippines and their Biological Control Potential Against Lepidopteran Pests of Corn

Collection site (sample code)	Associated crop	Soil type/pH/% OM	Detected EPN species	% Nucleotide identity/GenBank Acc. No. of significant hit	Assigned GenBank acc. nos. (for this paper)
Atisan, San Pablo, Laguna (ASPL3)	Bignay (Antidesma bunius)	Loam/6.1/4.40	Steinernema minutum	98/GU647156.1 (Maneesakorn et al., 2010)	KY807711
Curba, Calauan, Laguna (CCL4)	Cassava (Manihot esculenta)	Clay Loam/6.4/2.37	S. minutum	98/GU647156.1 (Maneesakorn et al., 2010)	KY807712
Mataas na Bayan, Lemery, Batangas (MBLB)	Sugarcane (Saccharum officinarum)	Sandy Loam/4.4/0.99	Steinernema abbasi (=thermophilum)	99/AY248749.1 (Nguyen and Byron, 2003)	KY807713
Puting Bato, Calaca, Batangas (PBCB)	Mango (Mangifera indica)	Sandy Loam/6.6/4.55	Heterorhabditis indica	100/GQ377411.1 (Khatri-Chhetri et al., 2010)	KY807714
Poblacion, Impasug-ong, Bukidnon (PIB2)	Sugarcane (S. officinarum)	Clay/5.2/3.79	S. minutum	98/GU647156.1 (Maneesakorn et al., 2010)	KY807715
Paraiso, Koronadal City, S. Cotabato (PKSC1)	Sugarcane (S. officinarum)	Sandy Loam/5.0/1.04	Steinernema tami	98/AY171280.1 (Spiridonov et al., 2004)	KY807716
San Rafael, Santo Tomas, Batangas (SRSTB3)	Corn (Zea mays)	Silty Clay Loam/5.0/2.43	S. minutum	98/GU647156.1 (Maneesakorn et al., 2010)	KY807717

[i] OM, organic matter.

The Philippine map showing the sampling sites for entomopathogenic nematodes. The occurrence and distribution of *Heterorhabditis indica* (Δ), *Steinernema abbasi* (■), *Steinernema minutum* (●), and *Steinernema tami* (▢). Collection sites where no entomopathogenic nematodes (x) was isolated were also indicated. The figure was created using “maps” (Minka and Deckmyn, 2017) and “GIS tools” (Brunsdon and Chen, 2014) libraries in R software.

Mean percentage mortality of *Helicoverpa armigera, Ostrinia furnacalis,* and *Spodoptera litura* 48 hr post infection exposed to 200 IJ per larva of the Philippine entomopathogenic nematode isolates namely, *Heterorhabditis indica* PBCB (Hi PBCB), *Steinernema abbasi* MBLB (Sa MBLB), *Steinernema minutum* (Sm ASPL3, Sm CCL4, Sm PIB2 and Sm SRTSB3), and *Steinernema tami* PKSC1 (St PKSC1). Different letters for mean percentage mortality show significant difference between the EPN isolates within the insect species after two-way ANOVA followed by Tukey’s multiple comparison test (alpha = 0.05).

Table 2

Mean percentage penetration rate of Heterorhabditis indica PBCB and Steinernema abbasi MBLB in Helicoverpa armigera, Ostrinia furnacalis, and Spodoptera litura larvae at 48 hr post inoculation.

	Mean penetration rate (%) ± SE
EPN isolate	H. armigera	O. furnacalis	S. litura
Hi PBCB	14.35 ± 0.49^a	14.25 ± 0.35^a	18.18 ± 1.35^a
Sa MBLB	28.15 ± 2.51^b	14.54 ± 0.41^a	23.15 ± 0.29^b
Control	0.00^c	0.00^b	0.00^c

[i] Different letters (a,b,c) for mean penetration rate show significant difference between the EPN isolate within the insect species after two-way ANOVA and Tukey’s multiple comparison test (alpha = 0.05).

[ii] SE, standard error.

Table 3

Median lethal concentration (LC₅₀) estimates of the Philippine Heterorhabditis indica PBCB (Hi PBCB) and Steinernema abbasi MBLB (Sa MBLB) isolates to lepidopterous pests of corn, Helicoverpa armigera, Ostrinia furnacalis, Spodoptera litura.

			95% Fiducial limit
EPN isolate	Insect species	LC₅₀ (IJs/larva)	Lower	Upper	Slope ± SE		χ ²	df
Hi PBCB	H. armigera	19.98^b	16.63	24.32	1.58	±0.16	1.87	3
	O. furnacalis	10.52^a	8.82	12.74	1.65	±0.16	1.65	3
	S. litura	8.89^a	6.98	10.98	2.857	±0.24	3.46	3
Sa MBLB	H. armigera	22.57^b	18.80	27.61	1.60	±0.16	0.98	3
	O. furnacalis	10.98^a	8.25	15.21	1.88	±0. 17	3.60	3
	S. litura	17.08^ab	12.27	24.07	2.03	±0.17	3.77	3

[i] SE, standard error; χ ², Pearson χ ²; df, degrees of freedom.

Table 4

Median lethal time (LT₅₀) estimates of Philippine Heterorhabditis indica PBCB (HiPBCB) and Steinernema abbasi MBLB (SaMBLB) isolates on lepidopterous pests of corn Helicoverpa armigera, Ostrinia furnacalis, Spodoptera litura. Lethal times were estimated using 200 IJ/larvae within 48 hr post infection.

			95% Fiducial limit
EPN isolate	Insect species	LT₅₀ (h)	Lower	Upper	Slope ± SE		χ ²	df
Hi PBCB	H. armigera	30.962^c	29.835	32.015	6.947	±0.954	0.224	5
	O. furnacalis	21.901^a	21.273	22.440	12.797	±1.059	3.684	5
	S. litura	24.309^b	23.567	24.994	8.763	±0.826	0.802	5
Sa MBLB	H. armigera	32.264^c	29.929	35.835	3.892	±0.514	1.423	4
	O. furnacalis	24.177^a	23.322	24.960	10.282	±0.882	0.253	3
	S. litura	26.586^b	25.847	27.312	12.036	±0.938	2.119	3

[i] SE, standard error; χ ², Pearson χ ²; df, degrees of freedom.

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DOI: https://doi.org/10.21307/jofnem-2018-024 | Journal eISSN: 2640-396X | Journal ISSN: 0022-300X

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Language: English

Page range: 99 - 110

Published on: Jun 3, 2018

Published by: Society of Nematologists, Inc.

In partnership with: Paradigm Publishing Services

Publication frequency: 1 issue per year

Keywords:

Biological control,

Entomopathogenic nematode,

Helicoverpa armigera,

Heterorhabditis indica,

Internal transcribed spacer,

Ostrinia furnacalis,

Ribosomal DNA region,

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© 2018 Barbara L. Caoili, Romnick A. Latina, Regina Faye C. Sandoval, Joey I. Orajay, published by Society of Nematologists, Inc.
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 50 (2018): Issue 2 (January 2018)

Molecular Identification of Entomopathogenic Nematode Isolates from the Philippines and their Biological Control Potential Against Lepidopteran Pests of Corn

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