Corresponding author: Jingwu Zheng (
Academic editor: Sergei Subbotin
Seven trichodorid species including a new one (
Li X, Maria M, Cai R, Barsalote EM, Peneva V, Zheng J (2020) Distribution of trichodorid species in mainland China with description of
Stubby root nematodes of the family
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
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
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
Line drawings of
Line drawings of
Light photomicrographs of
Measurements of
Characters | Holotype | Paratypes | |
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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 |
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 |
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.,
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
The new species is characterized by the male having a relatively short onchiostyle (46–49 µm) and 3 ventromedian cervical papillae anterior to the
The species-specific codes sensu
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 (
Distribution map of trichodorid species in China (stars indicate the occurrence of trichodorid taxa).
Photomicrographs of females of
Photomicrographs of
The occurrence of
Provinces (bold) /Localities | Species | Host | References |
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Nanjing |
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Suzhou |
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Linbao |
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Ganyu |
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Wuxi |
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Nanjing |
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Lianyungang |
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Nantong |
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Hangzhou |
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Hangzhou |
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Changxing |
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Huzhou |
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Fuyang |
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Ningbo |
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Ningbo |
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Ningbo |
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Ningbo |
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Ningbo |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Hangzhou |
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Fuyang |
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Linan |
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Taizhou |
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Yuyao |
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Yuyao |
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Lishui |
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Jinhua |
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Fenghua |
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Fenghua |
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Anding |
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Danzhou |
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Unknown |
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Danzhou |
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Danzhou |
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Danzhou |
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Beipei |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Hekou |
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Kunming |
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Chengong |
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Dabanqiao |
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Dabanqiao |
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Luliang |
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Luliang |
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Majie |
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Majie |
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Majie |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Kunming |
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Xundian |
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Shenzhen |
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Unknown |
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Unknown |
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Unknown |
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Guangzhou |
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Gaozhou |
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Guangzhou |
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Nankou farm |
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Nankou farm |
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Unknown |
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Nankou farm |
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Nankou farm |
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Unknown |
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Shisanling |
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Shisanling |
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Shisanling |
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Fenghuangling |
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Zhiwuyuan |
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This study |
Zhiwuyuan |
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Zhiwuyuan |
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Unknown |
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Xiangshan |
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Zhuolu |
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Xingtang |
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Linyi |
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Zhangzhou |
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Fuzhou |
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Putian |
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Fuzhou |
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Xiamen |
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Nan′an |
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Fuzhou |
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Fuzhou |
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Fuzhou |
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Fuzhou |
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Fuzhou |
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Fuzhou |
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Xiamen |
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Xiamen |
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Xiamen |
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Xiamen |
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Zhangzhou |
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This study |
Zhangzhou |
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Zhangzhou |
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Zhangzhou |
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Zhangzhou |
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Zhangzhou |
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Huangshan |
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Shexian |
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Changsha |
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Changsha |
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This study |
Measurements of females of
Species |
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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 |
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
Species |
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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 |
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 |
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,
Phylogenetic relationships of
The D2-D3 region of the 28S rDNA gene has been shown to be of importance in trichodorid molecular taxonomy (
Phylogenetic relationships of
In addition, the trichodorid species molecularly characterized during this study (
All present, and most previous, phylogenetic reconstructions inferred from three different gene sequences (18S, D2D3 28S and ITS2) showed that
Phylogenetic relationships of
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
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
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
species data