First report of Xiphinema hunaniense Wang & Wu, 1992 (Nematoda : Longidoridae) in Vietnam

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Commons CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/

JOURNAL OF NEMATOLOGY

e2020-78 | Vol. 52 Article | DOI: 10.21307/jofnem-2020-078

First report of Xiphinema hunaniense Wang & Wu, 1992 (Nematoda: Longidoridae) in Vietnam

Huu Tien Nguyen^1,2,3,*, Thi Duyen Nguyen^1,², Thi Mai Linh Le^1,² and Quang Phap Trinh^1,^2,*

1Institute of Ecology and Biological Resources, Vietnam Academy of Sciences and Technology, 18 Hoang Quoc Viet, Cau Giay, 100000, Hanoi, Vietnam.

2Graduate University of Science and Technology, Vietnam Academy of Sciences and Technology, 18 Hoang Quoc Viet, Cau Giay, 100000, Hanoi, Vietnam.

3Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium.

*E-mails: tien.quelampb@gmail.

com, tqphap@gmail.com This paper was edited by Zafar Ahmad Handoo.

Received for publication May 26, 2020.

Abstract

For the first time, a survey of plant-parasitic nematodes in the Central Highlands of Vietnam discovered a population of Xiphinema hunaniense Wang & Wu, 1992. The Vietnamese population of X. hunaniense is characterized by having an offset lip region, lack of anterior genital branch, vagina directed backward, and a digitate tail. Morphological features and morphometrics of this population are in agreement with the type population of X. hunaniense except for some variations. In addition, molecular characterization of this population and phylogenetic tree of 28S rDNA sequences of the genus are also provided.

Keywords

28S rDNA, Dagger nematode, Molecular identification, Plant-parasitic nematodes, Taxonomy, Xiphinema hunaniense.

The genus Xiphinema Cobb, 1913, commonly known as dagger nematodes, are migratory ectoparasitic nematodes that damage numerous wild and cultivated plants through direct feeding on the root and transmission of plant viruses (Taylor and Brown, 1997;

Perry and Moens, 2013). This genus is distributed worldwide and is divided in two groups, Xiphinema americanum group and non-Xiphinema americanum group, with more than 260 valid species (Gutiérrez- Gutiérrez et al., 2012). The conserved morphology and overlapping morphometrics of some species groups in the genus Xiphinema make quarantine regulations and protection methods more difficult. Therefore, accurate identification of Xiphinema species using integrate approach is strongly recommended to create a basis for plant pest management.

In Vietnam, eight species of the genus Xiphinema have been reported, however, molecular identification are not available for most of them (Nguyen and

Nguyen, 2000), and thus, a higher diversity of Xiphinema spp. is expected in the country with the use of molecular tools. Herein, a population of Xiphinema hunaniense Wang & Wu, 1992 in Vietnam is characterized by the combination of morphological characters and molecular data.

Material and methods

Soil and root samples were collected from the upper 30 cm layer of forest soil in the Central Highlands of Vietnam. Nematodes were extracted and permanent slides were made following Nguyen et al. (2019a).

Pictures and measurements were recorded using Carl Zeiss Axio Lab. A1 light microscope equipped with a Zeiss Axiocam ERc5s digital camera. For molecular characterization, the 5′-end region of 28S rDNA was amplified using DP391/501 primers (5′-AGCGGAGGA A A AGA A ACTA A-3′/5′-TCGG

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Xiphinema hunaniense Wang & Wu, 1992 in Vietnam: Nguyen et al.

AAGGAACCAGCTACTA-3′) following Nguyen et al.

(2019b). Forward and reverse sequences were assem- bled and analyzed using Geneious R11 (Nguyen et al., 2019b, 2019c). The best fit model was chosen using Mega 7 following Nguyen et al. (2019b).

Results and discussion Measurements

Eight females: L = 2,095 ± 130 (1,947-2,189) µm, V% = 24.7 ± 0.4 (24.2-25), Odontostyle = 126 ± 5 (120-130) µm, Odontophore = 71 ± 1 (70-71) µm, Stylet = 196 ± 6 (190-201) µm, Tail length = 45 ± 1 (44-46) µm, Lip width = 13.6 ± 0.1 (13.5-13.7) µm, Lip height = 5.4 ± 0.2 (5.2-5.6) µm, Pharynx = 359 ± 3 (356-361) µm, Anterior end to guiding ring = 121 ± 7 (114-127) µm, Width at pharyngo-intestinal junction = 44 ± 1 (43-44) µm, Width at mid-body = 46 ± 1 (45-47) µm, Width at anus = 29 ± 2

(27-31) µm, a = 46 ± 2 (43-48), b = 5.8 ± 0.4 (5.4-6.1), c = 46 ± 4 (42-49), c′ = 1.6 ± 0.1 (1.5-1.7).

Remarks

The females of the Vietnamese population of X. hunaniense is characterized by an offset lip region from body contour, lack of anterior genital branch, vagina directed slightly backward, and a digitate tail (Fig. 1).

Morphology and morphometrics of this population are highly similar to the type population of X. hunaniense except for smaller a value (43-48 vs 51-57), c value (42- 49 vs 53-63), longer stylet (190-201 µm vs 180-187 µm), wider width at pharyngo-intestinal junction (43-44 µm vs 21-23 µm). However, these morphometric variations have been reported from other populations of X. hunaniense (Luc, 1981; Wu et al., 2007; Long et al., 2014). Two 28S rDNA sequences (1 bp difference) of the Vietnamese population of X. hunaniense were

Figure 1: Xiphinema hunaniense from Vietnam. A: entire body; B: Pharyngeal region; C: Vulva region; D: Tail region.

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Figure 2: BI phylogenetic tree generated from 28S rDNA sequences (GTR + G + I model, 1 × 10⁶ generations, 20% Burn-in). Bayesian posterior probabilities (in percentage) are given next to each node. Sequences of X. hunaniense from Vietnam are in bold font.

Xiphinema italiae KX062677 Xiphinema italiae KX062675 Xiphinema italiae FJ713153

Xiphinema italiae KX2442912 Xiphinema meridianum KX062679 Xiphinema pyrenaicum GU725073

Xiphinema adenohystherum KX244897 Xiphinema adenohystherum KX244898 Xiphinema adenohystherum GU725075 Xiphinema hispidium KX244906 Xiphinema histriae MK801305 Xiphinema histriae MK801303 Xiphinema sphaerocephalum KX244917

Xiphinema herakliense KM586352 Xiphinema barense K199692 Xiphinema barense K199691

Xiphinema nuragicum GU725067 Xiphinema nuragicum GU725069 Xiphinema nuragicum GU725070 KX062673 Xiphinema conurum

Xiphinema oleae KU171038 Xiphinema oleae KU171037 Xiphinema sp. KX062686

Xiphinema sp. KX062687 Xiphinema turcicum KX244919 Xiphinema turcicum KX244918

Xiphinema lupini HM921352 Xiphinema lupini KC567183 Xiphinema lapidosum MK801307 Xiphinema elongatum KF430802 Xiphinema elongatum KF430803 Xiphinema elongatum E140790

Xiphinema elongatum KF430801 Xiphinema insigne MF510430

Xiphinema insigne MT193456 Xiphinema insigne AY601619 Xiphinema insigne MT193455

Xiphinema radicicola AY601622 Xiphinema hangzhouense MF538772

Xiphinema setariae MF510429 Xiphinema chambersi KU680967 Xiphinema chambersi KT698208 Xiphinema chambersi KT698207 Xiphinema chambersi KU680965 Xiphinema chambersi AY601617 Xiphinema naturale DQ299515 Xiphinema hunaniense MT513135 Xiphinema hunaniense MT513136 Xiphinema hunaniense E188840 Xiphinema hunaniense KF290564 Xiphinema hunaniense MH156804 Xiphinema hunaniense KP793049

Xiphinema hunaniense EF026090 Xiphinema hunaniense E188841

Xiphinema hunaniense MF510432 Xiphinema hunaniense E188839 Xiphinema hunaniense KP793048

Xiphinema brasiliense AY601616 Xiphinema brasiliense KP793050 Xiphinema macrodora KU171044 Xiphinema macrodora KU171043 Xiphinema macrodora KU171042 Xiphinema macrodora KU171041 Xiphinema macrodora KU171040 Xiphinema cadavalense KX244900 Xiphinema baetica KC567168 Xiphinema andalusiense KX244887 Xiphinema andalusiense KX244885 Xiphinema andalusiense KX244886 Xiphinema coxi KC567179 Xiphinema coxi KC567174 Xiphinema coxi KC567177

Xiphinema belmontense KC567172 Xiphinema bakeri KF292278 Xiphinema bakeri KF292277 Xiphinema diversicaudatum JQ780360

Xiphinema diversicaudatum JQ780366 Xiphinema pseudocoxi KX244915 Xiphinema globosum GU549474

Xiphinema turdetanense KC567186 Xiphinema castilloi KF446655 Xiphinema sp. LT883657 Xiphinema montenegrinum MT271611 Xiphinema pyrenaicum AY601626 Xiphinema cretense KJ802879 Xiphinema cretense KJ802878 Xiphinema basiri AY601629 Xiphinema basiri AY601630 Xiphinema macroacanthum HF546081 Xiphinema index HM921406 Xiphinema index HM921363 Xiphinema index HM921364 Xiphinema index AY584243 Xiphinema tica KY623485 Xiphinema tica KY623488 Xiphinema tica KY623492 Xiphinema tica KY623486 Xiphinema tica KY623489

Xiphinema americanum KU680975 Xiphinema americanum KU680974 Xiphinema rivesi KU680968 Xiphinema brevicollum H84473

Xiphinema brevicollum KR095280 Longidorus macrosoma AY580055

Longidorus dunensis AY593057

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Xiphinema hunaniense Wang & Wu, 1992 in Vietnam: Nguyen et al.

obtained, 942 to 944 bp long. These sequences are 98.9 to 99.5% similar (3-8 bp difference) to 28S rDNA sequences of X. hunaniense from other populations.

The Bayesian inference phylogenetic tree showed that 28S rDNA sequences of the Vietnamese population of X. hunaniense were placed together with sequences of X. hunaniense from other populations (100% PP) and this group has a sister relationship (73% PP) to the sequences of X. brasiliense (Fig. 2).

When it comes to morphology, X. hunaniense is closest to X. radicicola, and therefore, it has been synonymized with X. radicicola by Loof et al. (1996).

However, based on the observation of different populations of X. hunaniense and X. radicicola, Robbins and Wang (1998) re-established X. hunaniense as a valid species that was agreed by Zheng and Brown (1999). 28S rDNA sequences of X. hunaniense has a sister relationship to X. brasiliense, but X. hunaniense can be differentiated from X. brasiliense by the moderately offset terminal peg vs distinct peg-shaped tail and X. brasiliense usually has more posterior vulva position. Besides, the 28S rDNA sequences of X. hunaniense from Vietnam were only 87 to 88%

similar (84-85 bp difference) to X. brasiliense.

Due to the conserved morphology in some Xiphinema species groups, i.e. X. hunaniense – X. radicicola – X. brasiliense (Zheng and Brown, 1999) or X. americanum group (Gutiérrez-Gutiérrez et al., 2012), the combination of morphological characters and molecular data is needed to identify Xiphinema species.

This is the first report of X. hunaniense in Vietnam with the support of molecular data of 28S rDNA sequences, adding to the total number of nine Xiphinema species in Vietnam, including X. americanum, X. brasiliense, X. brevicolle, X. diffusum, X. elongatum, X. insigne, X. longicaudatum, X. radicicola, and X. hunaniense.

Acknowledgments

This research was supported by a fund from the Institute of Ecology and Biological Resources (code:

IEBR ThST.8-20). Huu Tien Nguyen thanks to a special research fund from Ghent University (BOF-DOS 01W02619) for his study in Belgium. The authors would like to thank Dr. Bui Van Thanh for his help in sampling.

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