Research Article |
Corresponding author: Jingwu Zheng ( jwzheng@zju.edu.cn ) Academic editor: Sergei Subbotin
© 2020 Xuqing Li, Munawar Maria, Ruihang Cai, Eda Marie Barsalote, Vlada Peneva, Jingwu Zheng.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Li X, Maria M, Cai R, Barsalote EM, Peneva V, Zheng J (2020) Distribution of trichodorid species in mainland China with description of Trichodorus hangzhouensis sp. nov. (Nematoda, Triplonchida). ZooKeys 945: 163-189. https://doi.org/10.3897/zookeys.945.50424
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Seven trichodorid species including a new one (Trichodorus hangzhouensis sp. nov., T. nanjingensis, T. pakistanensis, T. cedarus, Paratrichodorus porosus, Nanidorus renifer and N. minor) were recovered from the rhizosphere of different hosts in 13 provinces of China. Each of the recovered species was characterized based on morphology and molecular data using rRNA gene sequences. Trichodorus hangzhouensis sp. nov. is characterized by its males having medium-sized onchiostyle (46–49 µm) and three ventromedian cervical papillae (CP) anterior to the secretory-excretory (S-E) pore, CP1 located opposite the anterior part of isthmus, S-E pore opposite the isthmus or anterior end of pharyngeal bulb, spicules slightly ventrally curved, relatively small, 33.2 (32.0–34.5) µm long, wider slightly marked capitulum, lamina partially striated without bristles at striation; and females having rounded triangular sclerotized vaginal pieces with tips directed towards vulva, 1.5–2.0 µm sized, at about 1 µm apart, vulva pore-like in ventral view. Phylogenetic analysis based on D2-D3 28S rRNA gene sequences differentiated the new species among Trichodorus species from Europe, Asia and USA which formed a large clade. A review of the distribution of Trichodorus, Nanidorus and Paratrichodorus species revealed that T. cedarus, T. nanjingensis, T. pakistanensis and P. porosus are the most widespread species recorded from different provinces of China. This is the first extensive study of trichodorid species occurring in China.
18S rRNA gene, D2-D3 28S rRNA gene, ITS2 region, host association, morphology, new species, phylogeny, taxonomy, Trichodoridae
Stubby root nematodes of the family Trichodoridae Thorne, 1935 are polyphagous root ectoparasites and have a global distribution (
Previously, morphological identification alone rendered difficulties due to the mixed species complexes, phenotypic variation (such as shape of some sclerotized structures, e.g., stylet, male spicules, vagina with its sclerotized pieces), overlapping diagnostic characters and uniformity in general appearance; however, DNA-based strategies have made it possible to overcome the limitations of the morphological approach only and provided useful insights into trichodorid taxonomy (
The agricultural land of China represents 10% of the total arable land in the world. About 75% of the lands are cultivated areas used for food production such as rice, wheat, potatoes, tea, soybean, various fruits, tea and sugarcane (
Considering the potential importance of trichodorids in China, an extensive survey of various biotopes was carried out during the recent years. The objectives of the present study are to: i) characterize morphologically and molecularly recovered trichodorid species including one new Trichodorus species; ii) evaluate the phylogenetic relationships of the new species with other members of the genera based on their 18S rRNA, D2-D3 expansion domain of 28S rRNA and ITS2 of rRNA gene sequences and iii) summarize the geographic distribution of Trichodorus, Nanidorus and Paratrichodorus species in China, in addition, providing a comprehensive list of the past records and present findings of trichodorid nematodes.
Two-thousand and fifty-two soil samples have been collected from 13 provinces of China. Nematodes were extracted from soil samples using a modified Baermann funnel method and modified Cobb’ sieving and flotation-centrifugation method (
DNA was extracted from single specimens of all seven recovered species as described by
The partial sequences of 18S, D2–D3 fragment of 28S and ITS2 of rRNA gene of Trichodorus hangzhouensis sp. nov. were compared with those of other species of fam. Trichodoridae available in GenBank using the BLAST homology search program. The sequence data sets used in this study were selected based on previously published studies (
Model parameters were unlinked and the overall rate was allowed to vary across partitions. The number of generations for the total analysis was set to 10 million, with the chain sampled every 1000 generations and the burn-in value was 25%. The Markov chain Monte Carlo method within a Bayesian framework was used to estimate the posterior probabilities of the phylogenetic trees using the 50% majority rule (
(Figs
Light photomicrographs of Trichodorus hangzhouensis sp. nov., paratypes A female entire body, arrow points vulva B male entire body C, D anterior region of female E pharyngeal region of male, arrows pointing position of cervical papillae (CP) and excretory pore (exp) F, G vulval region H, I female tail, arrows pointing position of anus (a) J–L male tail, arrows pointing position of male tail supplements (SP). Scale bars: 100 μm (A, B) 20 μm (C–L).
Female. Body straight or slightly curved upon heat relaxation. Anterior region similar to that of male except for secondary male characteristics. S-E pore located opposite isthmus or anterior part of pharyngeal bulb. Reproductive system didelphic amphidelphic with reflexed ovaries. Two finely granular oviduct cells at the tip of reflexed ovary, sperm round in shape distributed in the distal part of the uteri. Vagina well developed, pars proximalis vaginae barrel shaped in lateral optical view extending less than half corresponding body diameter. Sclerotized vaginal pieces (= pars refringes vaginae) rounded triangular with tips directed towards vulva, pieces 1.5–2.0 µm sized, at about 1.0 µm distance from each other, vulva pore-like in ventral view. Copulatory plug observed in uterus of two specimens. One pair of sublateral body pores almost opposite the vulva. Tail terminus conoid to rounded, anus subterminal, caudal pores subventral, immediately posterior to anus.
Measurements of Trichodorus hangzhouensis sp. nov. males and females. All measurements are in µm and in the form: mean ± SD (range).
Characters | Holotype | Paratypes | |
---|---|---|---|
Male | Males | Females | |
n | 8 | 11 | |
L | 708 | 689.9 ± 30.4 (628–727) | 686.2 ± 29.8(646–744) |
Body diameter | 33 | 33.8 ± 2.2 (29–36) | 40.4 ± 3.3 (36.0–47.0) |
Pharynx | 145 | 140.8 ± 8.3 (125–146) | 143.3 ± 15.0 (117–171) |
Onchiostyle | 48 | 48.1 ± 1.2 (46–49) | 49.3 ± 1.8 (48–52) |
Onchium | 27 | 26.9 ± 2.3 (24–28) | 29.4 ± 1.9 (27–31) |
Onchiophore | 22 | 21.6 ± 0.7 (21–23) | 22.1 ± 0.9 (2–23) |
Pharyngostom | 53 | 50.5 ± 2.8 (47–54) | 54.6 ± 2.1 (52–56) |
Ant. end to S-E pore | 99 | 100.0 ± 4.0 (96.5–108) | 96.8 ± 8.2 (87–114) |
Ant. genital branch | – | – | 174.2 ± 6.8 (163–185) |
Post. genital branch | – | – | 170.1 ± 15.5 (137–193) |
a | 21.3 | 20.5 ± 1.1 (19.0–21.6) | 17.1 ± 1.5 (14.5–19.4) |
b | 4.9 | 4.9 ± 0.4 (4.3–5.6) | 4.8 ± 0.6 (3.8–6.0) |
V/T | 64.5 | 65.8 ± 1.4 (63.9–68.4) | 57.1 ± 2.0 (53.0–60.0) |
Length of vagina | – | – | 15.6 ± 1.4 (14–19) |
CP1-CP2 | 12 | 10.9 ± 1.9 (8–12.5) | – |
CP2-CP3 | 9 | 7.9 ± 1.7 (5–9) | – |
CP3 to S-E pore | 8 | 6.0 ± 1.5 (4–8) | – |
Spicules | 34.5 | 33.2 ± 1.0 (32–34.5) | – |
Gubernaculum | 15 | 14.7 ± 1.5 (11.5–17) | – |
Cloaca to SP1 | 23 | 25.7 ± 3.0 (22.5–32) | – |
SP1-SP2 | 24 | 31.3 ± 4.4 (24–37) | – |
SP2-SP3 | 37.0 | 38.0 ± 4.0 (33–45) | – |
The new species was detected in association with three plants, i.e., Eriobotrya japonica (Thunb.) Lindl., Morus alba L. and Toona sinensis (A. Jussieu) M. Roemer from the botanical garden of Huajiachi Campus, Zhejiang University, Hangzhou, Zhejiang Province, P. R. China. The specimens from E. japonica were regarded as a type population. The geographical position of the sampling site is: 120°19'06"E, 30°25'67"N.
Holotype male, 8 male and 11 female paratypes (slide nos. ZJU-29-01-ZJU-29-19) deposited in the Nematode Collection of Zhejiang University, Hangzhou, China, and 2 male and 13 female paratypes deposited in Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Bulgaria (slide nos. PNT 102-104).
The new species was molecularly characterized and newly obtained sequences were deposited in the GenBank with the accession numbers HM106498, MF979178 for 18S, MF979185–MF979186, HM106497 for 28S and MF979181, HM106496, MF979182 for ITS2 of rRNA gene. The available sequences of trichodorid taxa (accession numbers of 18S, D2–D3 region of 28S and ITS2 rRNA gene sequences in Suppl. material
The 18S rRNA gene tree (Fig.
In the 28S phylogenetic tree (Fig.
In ITS2 tree (Fig.
The other known Trichodorus, Nanidorus and Paratrichodorus species sequenced during this study clustered with their respective species available through GenBank database, thus supporting their identity.
The new species is characterized by the male having a relatively short onchiostyle (46–49 µm) and 3 ventromedian cervical papillae anterior to the S-E pore, CP1 located opposite isthmus, distance of CPl-CP2, CP2-CP3 and CP3-S-E becoming gradually shorter, S-E pore located opposite isthmus or anterior end of pharyngeal bulb, pharynx offset, spicules relatively short, slightly curved, 33.2 (32.0–34.5) µm long, with wider slightly marked capitulum, lamina partially striated and tapering gradually to the distal end, bristles at striation absent, three ventromedian precloacal supplements; female with barrel shaped vagina, vaginal scletorized pieces medium-sized (1.5–2.0 µm), rounded triangular with tips directed towards vulva, slightly separated from each other (c. 1.0 µm) , vulva pore-like in ventral view.
The species-specific codes sensu
T. cedarus – by having a different position of SP1 (at the level of spicules capitulum vs posterior), shorter spicules length (32.0–34.5 vs 36–53 µm), shape of vulva (pore-like vs slit-like) and shape of vagina (barrel vs pear);
T. guangzhouensis – by having a longer onchiostyle in females (48–52 vs 36.4–41.6 μm), striations on spicule (present vs absent), different spicule shape (without constriction vs with constriction) and shape of vulva in ventral view (pore-like vs a longitudinal slit);
T. reduncus – by having a longer onchiostyle in males (46–49 vs 36–40 µm) and female (48–52 vs 37–40 µm), striations on spicules (present vs absent), different proximal part of gubernaculum (not hooked vs hooked) position of vaginal pieces (close vs widely separated) and shape of vulva (pore-like vs a small transverse slit);
T. tricaulatus – by having different position of SP1 (at the level of spicule capitulum vs outside it), spicule bristles (absent vs present), longer onchiostyle in both males (49.3 (46–49) vs 42.6 (39–51) µm) and females (49.3 (48–52) vs 42.2 (39–44) µm), type of pharyngo-intestinal junction (pharyngeal bulb offset vs pharynx overlapping intestine ventrally) and shorter spicules (33.2 (32.0–34.5) vs 39 (36–53) µm);
T. yokooi – by having striation on spicule (vs absent), shorter onchiostyle both in males (46–49 vs 57–82 µm) and females (48–52 vs 62–77 µm) and spicule (32.0–34.5 vs 38–46 µm).
The species name is derived from the name of the city where the new species was recovered.
The geographical distribution of trichodorids recovered in 13 different provinces of China including Beijing, Shandong, Shanxi, Henan, Jiangsu, Anhui, Hunan, Chongqing, Zhejiang, Fujian, Yunnan, Hainan and Guangdong (based on 2054 examined soil samples) is mapped in Fig.
Two of the recorded species are known to transmit tobra viruses (N. minor and P. pachydermus) (
Provinces (bold) /Localities | Species | Host | References |
---|---|---|---|
Jiangsu | |||
Nanjing | T. nanjingensis | Prunus persica |
|
Suzhou | T. nanjingensis | Prunus salicina |
|
Linbao | T. nanjingensis | Malus domestica |
|
Ganyu | T. cedarus | Malus pumila |
|
Wuxi | T. cedarus | Prunus persica |
|
Nanjing | T. paracedarus | Lycopersicon esculentum |
|
Lianyungang | T. paracedarus | Prunus yedoensis |
|
Nantong | P. porosus | Marus alba |
|
Zhejiang | |||
Hangzhou | T. nanjingensis | Bambusa glaucescens |
|
Hangzhou | T. pakistanensis | Metasequoia glyptostroboides |
|
Changxing | T. cedarus | Pyrus pyrifolia |
|
Huzhou | P. porosus | Bambusa vulgates |
|
Fuyang | P. porosus | Camellia japonica |
|
Ningbo | T. cedarus | Hedera helix | This study |
Ningbo | P. porosus | Ilex chinensis | This study |
Ningbo | N. renifer | Myrica rubra | This study |
Ningbo | N. renifer | Myrica rubra | This study |
Ningbo | N. renifer | Myrica rubra | This study |
Hangzhou | T. nanjingensis | Morus alba | This study |
Hangzhou | T. hangzhouensis sp. nov. | Albizia julibrissin | This study |
Hangzhou | T. cedarus | Magnolia denudata | This study |
Hangzhou | T. cedarus | Osmanthus fragrana | This study |
Hangzhou | P. porosus | Eriobotrya japonica | This study |
Hangzhou | T. hangzhouensis sp. nov. + P. porosus | Firmiana simplex | This study |
Hangzhou | T. hangzhouensis sp. nov. | Toona sinensis | This study |
Hangzhou | T. hangzhouensis sp. nov. | Eriobotrya japonica | This study |
Hangzhou | T. nanjingensis | Pyrus sp. | This study |
Hangzhou | T. nanjingensis | Cinnamomum camphora | This study |
Hangzhou | T. cedarus | Cryptomeria fortune | This study |
Hangzhou | T. nanjingensis+P. porosus | Albizia julibrissin | This study |
Hangzhou | T. nanjingensis | Rosa rugosa | This study |
Hangzhou | T. pakistanensis | Magnolia grandiflora | This study |
Hangzhou | T. cedarus | Pseudotsuga sinensis | This study |
Hangzhou | N. renifer | Azalea sp. | This study |
Hangzhou | P. porosus | Gmelina hainanensis | This study |
Fuyang | P. porosus | Camellia japonica | This study |
Linan | P. porosus | Prunus pseudocerasus | This study |
Taizhou | P. porosus | Quercus acutissima | This study |
Yuyao | N. renifer | Myrica rubra | This study |
Yuyao | N. renifer | Myrica rubra | This study |
Lishui | P. porosus | Citrus reticulata | This study |
Jinhua | N. renifer | Rosa chinensis | This study |
Fenghua | P. porosus+ N. renifer | Acer truncatum | This study |
Fenghua | P. porosus+ N. renifer | Acer palmatum | This study |
Hainan | |||
Anding | P. pachydermus | Saccharum officinarum |
|
Danzhou | P. pachydermus | Saccharum officinarum |
|
Unknown | T. pakistanensis | Saccharum officinarum | This study |
Danzhou | N. minor | Solanum melongena | This study |
Danzhou | N. minor | Melia azedarach | This study |
Danzhou | N. minor | Lactuca sativa | This study |
Chongqing | |||
Beipei | T. pakistanensis | Trachycarpus fortunei | This study |
Yunnan | |||
Kunming | T. nanjingensis | Pyrus sp. |
|
Kunming | T. rinae | Pyrus sp. |
|
Kunming | T. cedarus | Pyrus sp. |
|
Kunming | P. porosus | Pyrus sp. |
|
Hekou | T. cedarus | Musa sp. |
|
Kunming | N. minor | Hydrangea macrophylla |
|
Chengong | N. minor | Prunus persica | This study |
Dabanqiao | N. minor | Pyrus sp. | This study |
Dabanqiao | N. minor | Pyrus sp. | This study |
Luliang | P. porosus | Pyrus sp. | This study |
Luliang | P. porosus | Pyrus sp. | This study |
Majie | P. porosus | Pyrus sp. | This study |
Majie | P. porosus | Pyrus sp. | This study |
Majie | P. porosus | Solanum tuberosum | This study |
Kunming | P. porosus | Sapindus delavayi | This study |
Kunming | P. porosus | Corylus chinensis | This study |
Kunming | P. porosus | Diospyros kaki | This study |
Kunming | P. porosus | Sophora japonica | This study |
Kunming | P. porosus | Quercus variabilis | This study |
Kunming | P. porosus | Abies holophylla | This study |
Kunming | T. pakistanensis | Acer truncatum | This study |
Kunming | N. minor | Juglansregia | This study |
Kunming | P. porosus | Prunus persica | This study |
Xundian | P. porosus | Pinus massoniana | This study |
Guangdong | |||
Shenzhen | P. porosus | Litchi chinensis |
|
Unknown | T. cedarus | Salix babylonica |
|
Unknown | P. porosus | Magnoliaceae glanca |
|
Unknown | N. renifer | Magnoliaceae glanca |
|
Guangzhou | T. guangzhouensis | Lactuca sativa |
|
Gaozhou | P. pachydermus | Musa paradisiaca |
|
Guangzhou | P. porosus | Osmanthus fragrana | This study |
Beijing | |||
Nankou farm | T. nanjingensis | Malus domestica |
|
Nankou farm | T. nanjingensis | Mains baccata |
|
Unknown | T. nanjingensis | Malus domestica |
|
Nankou farm | T. pakistanensis | Malus domestica |
|
Nankou farm | T. pakistanensis | Malus domestica |
|
Unknown | P. porosus | Vitis sp. |
|
Shisanling | T. nanjingensis | Prunus persica | This study |
Shisanling | T. nanjingensis | Juglans regia | This study |
Shisanling | T. nanjingensis | Malus pumila | This study |
Fenghuangling | T. nanjingensis | Pyrus sp. | This study |
Zhiwuyuan | T. nanjingensis | Malus micromalus | This study |
Zhiwuyuan | T. nanjingensis | Prunus persica | This study |
Zhiwuyuan | T. nanjingensis | Cotoneaster multiflorus | This study |
Unknown | T. nanjingensis | Prunus blireana | This study |
Xiangshan | T. nanjingensis | Prunus armeniaca | This study |
Hebei | |||
Zhuolu | P. porosus | Vitis vinifera |
|
Xingtang | P. porosus | Vitis vinifera |
|
Shandong | |||
Linyi | P. porosus | Malus pumila |
|
Fujian | |||
Zhangzhou | T. pakistanensis | Litchi chinensis |
|
Fuzhou | T. pakistanensis | Dimocarpus longan |
|
Putian | T. pakistanensis | Dimocarpus longan |
|
Fuzhou | T. pakistanensis | Canarium album |
|
Xiamen | T. pakistanensis | Ficus carica |
|
Nan′an | N. minor | Myrica rubra |
|
Fuzhou | T. pakistanensis | Dimocarpus longan | This study |
Fuzhou | T. pakistanensis | Eriobotrya japonica | This study |
Fuzhou | T. pakistanensis | Citrus reticulata | This study |
Fuzhou | T. pakistanensis | Ilex chinensis | This study |
Fuzhou | P. porosus | Citrus reticulata | This study |
Fuzhou | T. pakistanensis | Dimocarpus longan | This study |
Xiamen | T. pakistanensis | Xylosma congestum | This study |
Xiamen | P. porosus+ N. minor | Dimocarpus longan | This study |
Xiamen | P. porosus | Dimocarpus longan | This study |
Xiamen | T. pakistanensis | Dimocarpus longan | This study |
Zhangzhou | P. porosus | Litchi chinensis | This study |
Zhangzhou | T. pakistanensis | Dimocarpus longan | This study |
Zhangzhou | T. pakistanensis | Dimocarpus longan | This study |
Zhangzhou | T. pakistanensis | Dimocarpus longan | This study |
Zhangzhou | T. pakistanensis | Litchi chinensis | This study |
Zhangzhou | T. pakistanensis | Dimocarpus longan | This study |
Anhui | |||
Huangshan | P. porosus | Boehmeria nivea |
|
Shexian | T. pakistanensis | Boehmeria nivea |
|
Hunan | |||
Changsha | P. porosus | Averrhoa carambola |
|
Changsha | P. porosus | Pinus massoniana | This study |
Measurements of females of Trichodorus, Paratrichodorus and Nanidorus species from China (all measurements in μm).
Species | T. nanjingensis | T. pakistanensis | T. cedarus | P. porosus | N. renifer | N. minor |
---|---|---|---|---|---|---|
Location | Beijing | Fuzhou Fujian Province | Hangzhou Zhejiang Province | Xiamen Fujian Province | Jinhua Zhejiang Province | Danzhou Hainan Province |
n | 10 | 11 | 13 | 25 | 19 | 6 |
L | 1099.1 ± 117.7 (836–1284) | 1051.7 ± 91.2 (883.5–1175) | 749.2 ± 56.5 (680–843) | 731.9 ± 113.4 (498.5–898) | 538.1 ± 36.8 (466.5–607.5) | 645.8 ± 16.9 (632–678) |
Body diam | 52.9 ± 7.7 (389–63) | 49.2 ± 5.9 (39–59) | 45.9 ± 4.3 (34–52) | 48.0 ± 6.6 (36–58) | 24.3 ± 2.9 (20.6–29.3) | 31.6 ± 3.6 (27–35) |
Pharynx | 170.6 ± 16.7 (155–214) | 159.9 ± 11.1 (139–172) | 176.7 ± 10.8 (161–197) | 143.9 ± 19.0 (103–173) | 111.4 ± 10.3 (91–133) | 129.7 ± 2.6 (126–133) |
Onchiostyle | 54.3 ± 4.5 (47–63) | 50.7 ± 2.1 (47–54) | 66.2 ± 2.3 (62–-70) | 53.5 ± 1.7 (49–57) | 36.3 ± 1.7 (33–41) | 35.3 ± 0.7 (34.5–36.5) |
Ant. end to S-E pore | 139.7 ± 7.9 (137–154) | 116.5 ± 11.6 (110–134) | 122.8 ± 8.0 (111–-135) | – | 105 | – |
Ant. genital branch | 217.2 ± 35.5 (172–274) | 185.8 ± 35.5 (141–265) | 186.1 ± 34.2 (141–266) | 122.6 ± 22.4 (91–153) | 114.2 ± 16.7 (69.5–136) | 120.2 ± 31.7 (90.5–154) |
Post. genital branch | 224.6 ± 30.9 (160–269) | 172.6 ± 39.8 (132–262) | 178.5 ± 26.5 (144–221) | 149.0 ± 32.0 (104–212) | 105.3 ± 14.3 (67–133) | 98.5 ± 25.4 (70–119) |
a | 21.1 ± 2.9 (15.6–25.7) | 21.6 ± 2.8 (18.2–26.6) | 16.5 ± 1.8 (14.1–20.3) | 15.2 ± 1.5 (12.4–19.2) | 22.4 ± 2.1 (17.7–25.5) | 20.7 ± 2.4 (17.9–23.6) |
b | 6.5 ± 0.9 (4.7–7.7) | 6.6 ± 0.8 (5.6–8.4) | 4.2 ± 0.3 (3.8–4.6) | 5.1 ± 0.6 (4.2–6.3) | 4.9 ± 0.5 (4.1–6.0) | 5.0 ± 0.1 (4.9–5.2) |
V | 56.1 ± 2.4 (50.3–57.9) | 56.6 ± 0.9 (55.1–57.8) | 57.7 ± 1.1 (55.8–59.7) | 54.8 ± 2.2 (50.9–57.7) | 56.4 ± 1.7 (53.7–59.1) | 56.3 ± 0.0 (52.5–58.8) |
Length of vagina | 18.8 ± 1.7 (16–21) | 17.1 ± 0.9 (15–18) | 18.5 ± 1.6 (17–22) | 8.6 ± 1.3 (6–10) | 6.1 ± 0.7 (5–7) | 11 |
Size of vaginal pieces | 2 | 2.3 ± 0.2 (2–3) | 2 | 1 | 1.5 ± 0.1 (1–2) | 2 |
Measurements of males of Trichodorus species from China (all measurements in μm).
Species | T. nanjingensis | T. pakistanensis | T. cedarus |
---|---|---|---|
Location | Beijing | Fuzhou Fujian Province | Hangzhou Zhejiang Province |
n | 16 | 9 | 14 |
L | 1011.7 ± 122.9 (731–1163) | 933.7 ± 91.4 (812–1074) | 765.3 ± 54.3 (650–862) |
Body diam | 48.7 ± 9.1 (35.5–60) | 43.7 ± 6.3 (34–53) | 42.8 ± 4.2 (36.9–49.1) |
Pharynx | 160.6 ± 14.6(132–190) | 159.9 ± 11.5 (147–177) | 174.5 ± 7.3 (160–187.5) |
Onchiostyle | 54.2 ± 3.4 (49–59) | 50.9 ± 2.5 (48–54) | 67.7 ± 1.5 (65–70) |
Ant. end to S-E pore | 127.6 ± 12.8 (113–142) | 124.8 ± 8.5 (113–135) | 127.0 ± 7.2 (117–142) |
CP1-CP2 | 12.3 ± 1.4(11–15) | 11.8 ± 2.9 (8–17) | 10.1 ± 1.7 (7–14) |
CP2-CP3 | 15.1 ± 0.7 (14–16) | 8.9 ± 1.5 (5–10) | |
CP3 to S-E pore (CP2 to S-E pore for T. nanjingensis) | 14.2 ± 3.4 (7–19) | 6.4 ± 1.0 (5–8) | 7.6 ± 3.8 (2.5–17) |
a | 21.1 ± 2.5 (17.0–25.3) | 21.7 ± 3.3 (17.0–26.8) | 18.0 ± 1.9 (15.1–22.2) |
b | 6.3 ± 1.0 (4.5–8.7) | 5.9 ± 0.5 (4.8–6.4) | 4.4 ± 0.3 (4.1–4.9) |
T | 61.0 ± 4.2 (56.7–68.0) | 61.7 ± 3.8 (57.1–69.5) | 64.6 ± 3.8 (57.4–69.6) |
Spicules | 48.3 ± 2.7 (43–53) | 54.4 ± 2.8 (48.5–57.2) | 44.6 ± 2.5 (40–48) |
Gubernaculum | 21.3 ± 1.7 (19–24) | 15.7 ± 1.6 (12–18) | 20.3 ± 1.3 (19–22) |
Cloaca to SP1 | 27.7 ± 3.4 (21.5–34) | 37.5 ± 3.6 (33–44) | 27.5 ± 2.0 (24–30.5) |
SP1-SP2 | 35.5 ± 4.2 (27–40) | 45.2 ± 5.8 (39.5–59) | 40.2 ± 5.2 (30.5–51) |
SP2-SP3 | 50.3 ± 10.6 (30.5–65) | 51.8 ± 8.3 (36–65) | 44.9 ± 4.0 (38–50) |
Among trichodorids, Trichodorus, Nanidorus and Paratrichodorus are cosmopolitan genera, species of those genera have been reported from all the continents except Antarctica (
Phylogenetic relationships of Trichodorus hangzhouensis sp. nov. and other trichodorid species based on partial 18S rRNA gene sequences. The Bayesian tree was inferred under the general time-reversible model of sequence evolution with correction for invariable sites and a gamma-shaped distribution (GTR+I+G). Tripyla sp. served as an outgroup species. Posterior probability values exceeding 70% are given on appropriate clades.
The D2-D3 region of the 28S rDNA gene has been shown to be of importance in trichodorid molecular taxonomy (
Phylogenetic relationships of Trichodorus hangzhouensis sp. nov. and other trichodorid species based on D2-D3 28S rRNA gene sequences. The Bayesian tree was inferred under the general time-reversible model of sequence evolution with correction for invariable sites and a gamma-shaped distribution (GTR+I+G). Tripylina tamaki served as an outgroup species. Posterior probability values exceeding 70% are given on appropriate clades.
In addition, the trichodorid species molecularly characterized during this study (T. nanjingensis, T. cedarus, T. pakistanensis, P. porosus, N. minor, N. renifer) clustered with the known species from different countries; these results further validated their identity. It is also noted that the position of T. hangzhouensis sp. nov. differs more or less in the phylogenetic trees based on the different gene sequences, and this could be also caused by the incomplete sequence data for a given species.
All present, and most previous, phylogenetic reconstructions inferred from three different gene sequences (18S, D2D3 28S and ITS2) showed that Nanidorus and Paratrichodorus species each formed highly supported clades. Trichodorus species studied molecularly so far take three different positions based on D2D3 28S r RNA gene sequences: i) the large part containing only Trichodorus species and forming Clade I sensu
Phylogenetic relationships of Trichodorus hangzhouensis sp. nov. and other trichodorid nematodes based on ITS2 sequences. The Bayesian tree was inferred under the general time-reversible model of sequence evolution with correction for invariable sites and a gamma-shaped distribution (GTR+I+G). Thoracostoma trachyga served as an outgroup species. Posterior probability values exceeding 70% are given on appropriate clades.
All the three aforementioned genera occur in China. From our observations, trichodorids seem not host specific and can be found in various types of ecosystems. The occurrence of Trichodorus, Nanidorus and Paratrichodorus recovered from soils in China is quite low (4.1%) compared to trichodorid occurrence in other countries such as Great Britain (22%), Italy (9.6%), Iran (7%), Belgium (19.6), Portugal (32.6%) and Slovak Republic (33%) (
In the past surveys concerning the stubby root nematodes, this group is reported being generally in somewhat low densities (
In conclusion, this study provides a morphological and molecular characterization of T. hangzhouensis sp. nov. and three known trichodorid species together with updated records of this group in China. Among 164 populations recovered in China, the highest number of records is for P. porosus (42.6%) followed by T. nanjingensis (39.6%). The systematics and diagnostics of trichodorid nematodes are important because of regulatory and management issues attributed to this group of nematodes being vectors of tobra viruses. Thus, updated descriptions based on sufficient examination material and accurately identified specimens, coupled with molecular analysis are necessary for better understanding of the current distribution and host association of this complex group of nematodes.
This research was supported by the National Natural Science Foundation of China (No: 31371921) and a Sino-Bulgaria government cooperation project (No. 14-7 and ДНТС Китай 01/03).
Table S1. Sequences of nematode species used for the phylogenetic analyses
Data type: species data