桑树(MorusalbaL.)是越南非常重要的作物,通过蚕桑在国家经济中发挥关键作用,食物供应,制药,和饮料工业(Nguyen等人,,2018;Rohela等人。,2020)。最近,林东的许多桑树种植区,越南报告了与线虫感染有关的严重症状,包括变黄的叶子,发育迟缓,和严重的根部擦伤,导致桑树生产力显著下降。从2022年4月至12月,收集了来自林东桑树种植区的20个土壤和根系样品(大德:11°28\'48.11\“N;107°28\'23.74\”E海拔:133m;林哈11°48\'25.13\“N;108°14\'7.13\'E海拔:848m),以发现越南冬青桑树的存在。在本研究中,在分析的线虫种群中随机选择一个线虫种群进行表征。雌性是从重度干燥的根中提取的(图。S1)来自林东的一棵桑树,越南,使用针头和镊子(Subbotin等人。,2021)。成年女性(n=10)的会阴图案呈椭圆形,有清晰可见的相粒,还有一个突出的高的方形背弓。条纹光滑粗糙,而外阴区域仍然没有条纹。侧线看起来模糊,尾尖很容易观察到。形态测量如下:体长=585±78(464-724)µm,阀体宽度=367±75(271-529)µm,颈部长度=221.5±30.7(167-269.6)µm,探针长度=13.1±1.2(11.4-15.1)µm,外阴狭缝长度16.3±2.3(10.4-18)µm,外阴-肛门距离=16.8±3.0(11.4-18)µm,肛门-尾部尖端距离=10.3±2.1(6.9-14.2)µm,相间距离=15.9±3.7(10.3-23.4)µm。该线虫种群的形态与肠球菌的原始描述高度吻合(Yang&Eisenback,1983).还使用28SrRNA和18SrRNA的D2-D3鉴定了该群体(Powers等人。,2017;Subbotin等人。,2006)区域。来自该研究的28SrRNA序列的D2-D3(登录号:OR889633)与来自GenBank的肠杆菌序列(登录号:OR214950和ON496981)表现出99.5-99.8%的相似性。而18SrRNA序列(登录号:OR896547)显示与来自GenBank的肠杆菌序列(登录号:MZ955995、MZ531901和MW488150)的99.2-99.3%相似性。为了执行科赫的假设,在两个月大的桑树小植株(n=6)上接种了2000个来自收集的肠球菌卵质量(初始种群)的J2s,种植在温室内的2L盆上,未接种的小植株(n=6)作为阴性对照。接种后90天,线虫繁殖因子(RF=最终密度(线虫是从整个根系和相应的土壤样品中提取的(Subbotin等人。,2021))/初始人群)和根部损伤症状进行了评估。接种的小植株表现出一致的黄叶,发育迟缓,和根部擦伤症状(图。S1),反映现场的观察结果,平均RF为11.5。对照植物没有表现出症状。通过对28S和18SrRNA区域的D2-D3的分子分析,从根中提取的根结线虫被鉴定为肠分枝杆菌(GenBank登录号:OR889634(28S的D2-D3)和OR896548(18S)),从而证实桑树作为肠球菌的宿主。目前,据报道,这种线虫与两种不同的寄主植物有关,包括番石榴(Trinh等人,2022年)和柚子(Le等人。,2023年)。我们的发现标志着越南首例有记载的根结线虫寄生桑树的病例。虽然对桑树生产力的影响对于蚕桑食品供应仍然非常重要,制药,和饮料行业;肠杆菌的侵略性,正如在现场观察到并通过温室测试证实的那样,引起人们对桑树生产中潜在经济损失的担忧。因此,需要进一步的调查,以评估桑园中肠杆菌感染的程度,并制定有效的控制措施,以保障越南桑树种植的可持续性。
Mulberry (Morus alba L.) is highly important crop in Vietnam, playing a key role in the country\'s economy through sericulture, food supply, pharmaceuticals, and beverage industries (Nguyen et al., 2018; Rohela et al., 2020). Recently, many mulberry-growing areas in Lam Dong, Vietnam have reported severe symptoms associated with nematode infection, including yellowing leaves, stunted growth, and severe root galling, leading to a significant decline in mulberry productivity. From April to December 2022, twenty soil and root samples from mulberry-growing areas in Lam Dong (Da Teh: 11°28\'48.11\"N; 107°28\'23.74\"E elevation: 133m; Lam Ha 11°48\'25.13\"N; 108°14\'7.13\"E elevation: 848m) were collected to uncover the presence of Meloidogyne enterolobii parasitizing mulberry in Vietnam. One nematode population was randomly selected for characterizing in this study among analyzed nematode populations. Females were extracted from heavily galled roots (Fig. S1) from a single mulberry tree in Lam Dong, Vietnam, using a needle and forceps (Subbotin et al., 2021). The perineal patterns of adult females (n = 10) have an oval shape, with clearly visible phasmids, along with a prominently high and squared dorsal arch. The striae are smooth and coarse, while the perivulval region remains devoid of striae. The lateral lines appear indistinct, and the tail tip is easily observable. Morphometric measurements were as follows: body length = 585 ± 78 (464-724) µm, body width = 367 ± 75 (271-529) µm, neck length = 221.5 ± 30.7 (167-269.6) µm, stylet length = 13.1 ± 1.2 (11.4-15.1) µm, vulva-slit length 16.3±2.3 (10.4-18) µm, vulva-anus distance = 16.8±3.0 (11.4-18) µm, anus-tail tip distance = 10.3±2.1 (6.9-14.2) µm, interphasmidial distance = 15.9 ± 3.7 (10.3-23.4) µm. The morphology of this nematode population is highly in agreement with the original description of M. enterolobii (Yang & Eisenback, 1983). This population was also identified using the D2-D3 of 28S rRNA and
18S rRNA (Powers et al., 2017; Subbotin et al., 2006) regions. The D2-D3 of 28S rRNA sequences from this study (accession numbers: OR889633) exhibited 99.5-99.8% similarity to the sequences of M. enterolobii from GenBank (accession numbers: OR214950 and ON496981). While the
18S rRNA sequences (accession numbers: OR896547) showed 99.2-99.3% similarity to the sequences of M. enterolobii from GenBank (accession numbers: MZ955995, MZ531901, and MW488150). To carry out Koch\'s postulates, 2000 J2s from collected M. enterolobii egg masses (initial population) were inoculated on two-month-old plantlets of mulberry (n = 6), planted on 2L pots within a screenhouse, non-inoculated plantlets (n=6) served as negative controls. After 90 days post-inoculation, nematode reproduction factors (RF = final density (nematodes were extracted from the whole root system and corresponding soil samples (Subbotin et al., 2021)) / initial population) and root damage symptoms were evaluated. The inoculated plantlets exhibited consistent yellowing leaves, stunting, and root galling symptoms (Fig. S1), mirroring observations from the field, with an average RF of 11.5. Control plants displayed no symptoms. Root-knot nematodes extracted from the roots were identified as M. enterolobii through molecular analyses of D2-D3 of 28S and
18S rRNA regions (GenBank accession numbers: OR889634 (D2-D3 of 28S) and OR896548 (
18S)), thereby confirming that mulberry acts as a host for M. enterolobii. Currently, this nematode has been reported to be associated with two different host plants, including guava (Trinh et al., 2022) and pomelo (Le et al., 2023). Our discovery marks the first documented case of Meloidogyne enterolobii parasitizing mulberry in Vietnam. While the impact on mulberry productivity remains to be really important for sericulture food supply, pharmaceuticals, and beverage industries; the aggressive nature of M. enterolobii, as observed in the field and confirmed by the screenhouse tests, raises concerns about potential economic losses in mulberry production. Therefore, further investigations are needed to assess the extent of M. enterolobii infestation in mulberry orchards and to develop effective control measures to safeguard the sustainability of mulberry cultivation in Vietnam.