Tankerville夫人,一种罕见的兰花物种(Phiiustankervilleae(BanksexL\'Hér.)Blume)在越南,不仅以其迷人的花朵增强了周围环境的美学价值,而且还具有很高的经济价值(Aver\'janov&Averyanova,2003).从11/2020到12/2021,调查了根系的坏死症状,并在越南海阳省的市场上拒绝了LadyTankerville,我们发现了螺旋线虫的大量侵染(24/24植物被感染),Helicotylenchussp.线虫种群是从根际土壤中提取的,根,使用改良的Baermann托盘技术(Whitehead&Hemming,1965),进行彻底的表征。平均线虫密度测量为525±85(350-670)线虫/250cm3土壤,202±56(198-264)线虫/15克根,和80±15(72-95)线虫/15g茎。将来自同一种群的200种线虫接种到另一种健康的兰花中进行保存和进一步的感染测试。根据Fotedar和Kaul(1985)的密钥和Sher(1966)的描述,该物种在形态上被鉴定为Helicotylenchusdihystera。雌性(n=12)的形态测量如下:体长=632-725(681±32)µm;a=24-34(28±3);b=5.1-7.2(6.0±0.6);b'=4.3-6.4(5.3±0.6);c=33-46(39±5);c'=1.1-1.4(1.2±0.1);V=62-78(65±39-9.2D21)=为了验证形态学观察,ITS的分子分析(Vrain等人,1992)和28SrRNA的D2-D3(Subbotin等人。,2006年)进行。这项研究的ITS和D2-D3序列(登录号:PP060444和PP033748)与GenBank中的H.dihystera序列(KM506885和MW023215)具有99.8%和100%的最高相似性,分别。感染试验在28±2℃的温室中进行。三个月大的Phiiustankervilleae(n=8)分别在装有无菌沙子的15x15厘米深的盆中生长,并接种了500只H.dihystera的妊娠雌性(Rashid&Azad,2013).两个未接种的植物作为对照。接种60天后,症状如太阳黑子和根部坏死,在市场上观察,出现在测试的植物中(图。S1).土壤中H.dihystera感染的存在和诊断,根,兰花的生长阶段和茎表明线虫是一种专性寄生虫。线虫穿透根部,导致特征性坏死病变最初是黄色的,然后变成红棕色到黑色,连同在变色的组织中的棕色根斑点。开花后的严重侵扰导致广泛的坏死,失真,和根的腐烂。本研究中H.dihystera的平均繁殖因子(最终种群/初始种群)为22.2。对照植物保持无症状。值得注意的是,100%的测试植物被感染,强调H.dihystera的严重影响。通过分子分析(登录号:PP060615(ITS)和PP033748(D2-D3)),成功地将线虫重新分离并鉴定为H.dihystera。重申自己的身份。除了越南的32个寄主植物(Nguyen等人。,2023),我们的研究揭示了一种寄生在Tankerville夫人兰花上的H.dihystera菌株,其繁殖因子和感染率相对较高。这标志着越南首次报道的H.dihystera寄生在Tankerville夫人兰花中,强调需要采取积极措施保护该工厂。
Lady Tankerville, a rare orchid species (Phaius tankervilleae (Banks ex L\'Hér.) Blume) in Vietnam, not only enhances the aesthetic value of the surroundings with its enchanting blooms but also holds high economic value (Aver\'janov & Averyanova, 2003). Investigating the necrosis symptom on the root system and declined Lady Tankerville in the market in Hai Duong province in Vietnam from 11/2020 to 12/2021, we discovered a substantial infestation (24/24 plants were infected) of a spiral nematode, Helicotylenchus sp. The nematode population was extracted from the rhizosphere soil, roots, and stems of a single orchid using the modified Baermann tray technique (Whitehead & Hemming, 1965), for thorough characterization. The average nematode density was measured at 525±85 (350-670) nematodes/250 cm3 of soil, 202±56 (198-264) nematodes/15 g of roots, and 80±15 (72-95) nematodes/15 g of stem. Two hundred nematodes from the same population were inoculated into another healthy orchid for preservation and further infection tests. This species was morphologically identified as Helicotylenchus dihystera according to the key of Fotedar and Kaul (1985) and the description of Sher (1966). Morphometric measurements of the females (n = 12) are as follows: body length = 632-725 (681 ± 32) µm; a = 24-34 (28 ± 3); b = 5.1-7.2 (6.0 ± 0.6); b\' = 4.3-6.4 (5.3 ± 0.6); c = 33-46 (39 ± 5); c\' = 1.1-1.4 (1.2 ± 0.1); V = 62-78 (65 ± 4)%; O = 30 -49 (39 ± 6); stylet length = 21-26 (24 ± 2) µm; DGO = 9.2-12.4 (10.8 ± 1.1) µm. To validate morphological observations, molecular analyses of the ITS (Vrain et al., 1992) and the D2-D3 of
28S rRNA (Subbotin et al., 2006) were conducted. The ITS and D2-D3 sequences from this study (accession number: PP060444 and PP033748) exhibited the highest similarity of 99.8% and 100% to the sequence of H. dihystera in GenBank (KM506885 and MW023215), respectively. The infection test took place in a greenhouse at 28 ± 2℃. Three-month-old Phaius tankervilleae (n=8) were individually grown in 15 x 15 cm deep pots filled with sterilized sand and inoculated with 500 gravid females of H. dihystera (Rashid & Azad, 2013). Two noninoculated plants served as controls. After 60 days of inoculation, symptoms such as sunspots and root necrosis, observed in the market, appeared in the tested plants (Fig. S1). The presence and diagnosis of H. dihystera infestation in soil, roots, and stems across growth stages of orchids indicates the nematode to be an obligate parasite. The nematodes penetrate the roots, causing characteristic necrotic lesions initially yellow, then turn reddish-brown to black, along with brown root flecks in discolored tissues. Heavy infestations post-flowering led to extensive necrosis, distortion, and decay of the roots. The average reproduction factor (final population/initial population) of H. dihystera in this study was 22.2. Control plants remained symptom-free. Notably, 100% of tested plants were infected, highlighting the severe impact of H. dihystera. The nematodes were successfully reisolated and identified as H. dihystera through molecular analyses (accession number: PP060615 (ITS) and PP033748 (D2-D3)), reaffirming its identity. In addition to 32 host plants in Vietnam (Nguyen et al., 2023), our study reveals a strain of H. dihystera parasitizing Lady Tankerville orchids with a relatively high reproduction factor and infection rate. This marks the first reported instance of H. dihystera parasitizing Lady Tankerville orchids in Vietnam, emphasizing the need for proactive measures to protect this plant.