The root lesion nematode, Pratylenchus spp., has a wide host range affecting many economically important crops (Castillo and Vovlas 2007). Cassava (Manihot esculenta Crantz) is an important food crop in several countries, commonly used for the material of bioethanol, animal feed, and starch extraction (Howeler 2014). Soil samples were collected from a mono-cropping cassava farm located in the Houbi district, Tainan city, in Southern Taiwan in October 2021 in a routine soil survey, and there is no obvious above ground symptoms. The cassava is a local cultivar, the sampled tuber did not have lesions, but small brown lesions were present on the roots. Nematodes were extracted using the modified Baermann funnel method (Tsay et al. 2004) for 24 h. Root lesion nematodes were the dominant genera in this sample, containing over 20 individuals per 100 cm3 of soil. Females of the root lesion nematodes were picked, and surface-sterilized with 2000 ppm malachite green for 30 sec and streptomycin for 30 mins. After sterilization, a single female was transferred onto the carrot discs to establish a pure line (Coyne et al. 2014). After 2 months, nematodes were extracted from that pure culture for morphometric, molecular identification, and pathogenicity tests. The female has a moderately slender body, a low and flat lip region, a sclerotized head frame, and a short ventral overlap of the esophagus, monovarial, prodelphic, and post-uterine sac. The tail is conical and the tip is rounded or flattened. The body measures of 20 females were: body length 564.43 μm (511 to 619 μm), stylet length 18.64 μm (18.1 to 19.5 μm), tail length 32.43 μm (27.1 to 38.5 μm), post uterine sac length 12.79 μm (9.41 to 16.9 μm), and V value 85.16% (84.1 to 86.6%). Values of a, b, c, and c’ ratios were 22.32 (18.9 to 26.1), 6.11 (5.36 to 6.73), 17.55 (13.8 to 20.5), and 1.18 (0.92 to 1.5), respectively. All morphometric data were similar to the previous description of P. brachyurus (Castillo and Volvlas 2007). DNA was extracted from three nematodes of the pure cultures using Viagen DirectPCR lysis buffer, and used for PCR amplification of the 18S rRNA fragment and the D2-D3 expansion segment of 28S rRNA using primer sets D2A/D3B and 988F/2646R, respectively (Holterman et al. 2006; Subbotin et al. 2006). The sequence of 18S ribosomal RNA (OP020594) shared 99% similarity with the P. brachyurus sequence deposited in the GenBank database (KY424148), and the sequence of 28S rRNA (OP020593) also shared 99% similarity with several P. brachyurus sequences (e.g. KF712473, MG745329). Bayesian consensus trees, constructed from both 18S and 28S sequences revealed that the nematodes collected in this study are clustered together with P. brachyurus sequences from other countries(Subbotin, et al. 2008). Therefore, the nematodes collected from cassava were identified as P. brachyurus based on morphology, molecular data, and phylogenetic relationship. To determine the pathogenicity, three eight-week-old cassava plants (cv. TMS 60444) were planted in 12-cm-diameter pots filled with 600 cm3 of sterile peat moss: sand (1:1, W: W) and inoculated with 50 nematodes containing different stages. Two plants treated with water were used as the mock control. Seventy-five days after inoculation, nematodes in the soil were recovered using the modified Baermann funnel method for 24 h, and the nematodes inside the root were stained with acid fuchsin. The average reproduction factor (final population/initial population) was 3.93, thus confirming cassava as a host of P. brachyurus. P. brachyurus was previously reported on peanuts and bananas in Taiwan, and wasn’t a dominant species in the field. Finding this nematode on this cassava farm suggests this nematode might have a wider distribution than expected.
Cockscomb (Celosia argentea) is commonly found in subtropical and temperate zones of Africa, South America and South East Asia, and is a popular ornamental plant in the family Amaranthaceae. Cockscomb has been known to contain antiviral proteins, betalains, and anthocyanin, which can be applied in beneficial ways (2). In September 2020, a cockscomb plant (Celosia argentea var. cristata) showing typical galling root symptoms likely infected by root-knot nematodes (Meloidogyne sp.) was collected from a garden in Taichung, Taiwan, and a quick exam of several individuals using MK7F/R primers (7) indicating they were M. enterolobii. Nematode population was established from a single egg mass and was later used for species identification and pathogenicity tests. Five perineal patterns of mature females from the single female population show round to oval shapes with weak lateral lines. Dorsal arches are moderate to high, almost squared, with the smooth ventral striae. Second-stage juveniles are vermiform and have a slender tail, tapering to rounded tip with distinct hyaline region at the tail terminus. Morphological measurements of 28 J2s revealed body length = 457.2 ± 20.6 (416.1-506.9) μm, body width = 16.0 ± 2.0 (13.4-20.3) μm, stylet length = 14.7 ± 0.5 (13.9-15.9) μm, dorsal gland orifice to the stylet base = 4.0 ± 0.5 (2.0-4.8) μm, and tail length = 56.0 ± 3.8 (47.4-60.3) μm. Female perineal patterns and morphometric data are similar to the original description of Meloidogyne enterolobii (9). DNA purified from approximately 1500 juveniles using GeneMark Tissue & Cell Genomic DNA Purification Kit (GeneMark, Taiwan) was used to amplify 18S rDNA fragment, D2-D3 expansion segments of 28S rDNA, and a COII region on mtDNA with primer sets 1A/MelR, D2A/D3B, and C2F3/1108, respectively (4,5,6). The 18S rDNA sequence (OK076893) of this study shares 99.94% nucleotide identity with those of M. enterolobii isolated from the United States (KP901058) and China (MN832688). D2D3 sequence of haplotype 1 (OK076898) shows 100% identity to those of M. enterolobii from China (MT193450) and Taiwan (KP411230). Sequence of haplotype 2 (OK076899) shows 99.86% identity to those of M. enterolobii from the United States (MN809527) and China (MN269945). Sequence of the COII region (OK086042) show 99.86% identity to that of M. enterolobii from China (MN269945). Phylogenetic trees of the three gene sequences were plotted following Ye et al.(10), revealing that the newly described root-knot nematode on Cockscomb is grouped with other M. enterolobii isolates. DNA fragment amplified by primer sets Me-F/R(3) and MK7F/R specifically targeting of M. enterolobii yielded 236 bp and 520 bp, respectively. Pathogenicity tests were assayed, from July to September 2021, on three-week-old nematode-free cockscomb plant directly germinated from seeds of SkyStar® (ASUSA SPIKE SEEDS, Taipei, Taiwan) planted in a 10.5 cm diameter pot filled with 600 ml sterilized peat moss: sand (1:1, v/v) soil in a 28℃walk-in chamber. Nematode eggs were extracted using 0.05% NaoCl as described by Vrain(8), and cockscomb plants (n=3) were inoculated by adding 6000 eggs (10 eggs/ cm3). Cockscomb plants treated with water were used as mock controls. Rf value of the inoculated plants were determined by the method of Belair and Benoit (1) 45 days after inoculation, and the average was 4.13. No galls were observed on the roots of control plants. The results confirmed that cockscomb is the new host of M. enterolobii. To the best of our knowledge, this is the first report of M. enterolobii on Celosia argentea var. cristata in Taiwan.
Poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch.), originated in southern Mexico and northern Guatemala, is the most valuable potted flowering plant in the spurge family (Euphorbiaceae). The European Union and the United States are two biggest poinsettia markets (Taylor et al. 2011), with a wholesale value of $153 million in the United States in 2019. Root knot galls of poinsettia ‘Luv U Pink’ were collected from a production greenhouse located in Nantou County, Taiwan in March 2021. No aboveground symptoms were observed. A nematode population was established from a single female and used for identification and the Koch’s postulate. The perineal patterns of randomly picked 5 females are round or ovoid with moderate to high dorsal arches, but no distinct lateral lines, ventral striae are fine and smooth. The Morphometric characters of second-stage juvenile include: a vermiform body shape, tail narrow and tapering with rounded tail tips, and a distinct hyaline tail end. Measurements of 20 J2 are as follows: body length, 430 (398 - 473) μm; body width, 15.4 (13.4 - 17.8) μm; stylet length,13.4 (13.0 - 14.0) μm; dorsal esophageal gland orifice to basal knob, 3.4 (2.8 - 3.9) μm; tail length, 52.9 (47.6 - 62.2) μm. All morphometric data were consistent with the original description of Meloidogyne enterolobii (Yang and Eisenback 1983). Nematode DNA was extracted using GeneMark Tissue & Cell Genomic DNA Purification Kit (GeneMark, Taiwan) from approximately 1500 J2 and used for amplification of 18S rRNA gene, a D2-D3 region of 28S rRNA gene, and a mtDNA COII region with primer sets 1A/MelR, D2A/D3B, and C2F3/1108, respectively (Power and Harris 1993, Subbotin et al. 2006, Tigano et al. 2005). The sequence of 18S rRNA gene (accession no. MZ948800 haplotype 1 and MZ955998 haplotype 2), haplotype 1 shared 100% identity with that of M. enterolobii from the United States (KP901058) and China (MN832688); haplotype 2 shared 99.8% identity with that of KP901058 and MN832688. The sequence of the D2-D3 region (MZ955995) shared 99% identity with that M. enterolobii from the United States (KP901079). Sequence of the COII region (MZ964625) also shared 99% identity with that of M. enterolobii from the United States (AY446975) and China (MN840970). Phylogenetic trees of the three gene sequences plotted as described by Ye et al. (2021) revealed that the newly described nematode was grouped with M. enterolobii. Sequence analysis of two fragments: 236 bp and 520 bp amplified with gene specific primers Me-F/R and MK7F/R, respectively (Long et al. 2006, Tigano et al. 2010) also confirmed the identity of M. enterolobii. To measure the reproductive factor (Rf), the Poinsettia ‘Luv U Pink’ seedlings with eight true leaves were transplanted into three 12-cm diameter pots each containing 6000 eggs or water (mock control). Forty-five days after inoculation, the average Rf value of three inoculated plants was 6, and no galls were observed on mock control plant roots, confirming that poinsettia is the host of M. enterolobii. M. enterolobii has been reported in several Euphorbia species, including E. heterophylla, E. prostrata, E. punicea and E. tirucalli (Han et al. 2012, Rich et al. 2009). To the best of our knowledge, this is the first report of M. enterolobii infecting E. pulcherrima ‘Luv U Pink’.
Longan (Dimocarpus longan Lour.) is a subtropical fruit, widely grown in China, Taiwan, and Southeast Asia. Longan has a high commercial value, US$242,200 of dried longan fruits are exported to the United States from Taiwan every year (Wang et al. 2010). A soil sample from a longan orchard located in Changhua County, Taiwan (24.0162657, 120.529-1457) was collected in June 2019. Sheathoid nematodes were the dominant species in this sample and over 40 adult individuals per 100 g soil were found. In December 2019, sheathoid nematodes were collected again from the same tree and processed for identification by morphological and molecular characteristics. Nematodes were extracted using the modified Baermann funnel method (Wu et al. 2010) for 24 h. The morphometric data from fifteen females with variant tail types were taken. All individuals had a closely sheath, lip region set off with two annuli, stylet frequently slightly dorsally curved with rounded knobs, no vulval flaps, tail narrowing to a broadly rounded terminus, or tapering to a truncate end, anus situated 3-4 annuli posterior to the vulva. The body length = 552 μm (483 to 616 μm), body width at mid-body = 34.02 μm (27.75 to 40.03 μm), a = 15.93 (14.73 to 18.87), b = 4.65 (4.04 to 5.06), V% = 91.57 (86.74 to 92.56), stylet length = 66.66 μm (63.51 to 69.6 μm), tail length = 28.48 μm (23.56 to 37.45 μm), ring number 114 to 130, Rs = 14 to 19, Roes = 22 to 28, RV = 9 to 13, Ran = 5 to 9 and RVan = 3 to 4. Since the stylet length were less than 70μm, they are more fitted to be Hemicriconemoides litchi (Van den Berg et al. 2015). DNA samples extracted using VIAGEN® DirectPCR lysis buffer from single females (n = 10) were processed to amplify the 28S D2-D3 expansion segment and the ITS region using primers sets D2A and D3B, TW81 and AB28, respectively (Van den Berg et al. 2014). The D2-D3 region of the nematodes collected in this study (MT-539384) shared 99% similarity with several H. litchi sequences deposited in the GenBank database (e.g. KP192481, KF856540), and the ITS region (MT556011) also shared 99% similarity with several H. litchi sequences (e.g. KP192482, GQ354786). Therefore, based on morphological, molecular data and phylogenetic relationship analysis (Nguyen et al. 2020) the nematodes from the Longan orchard were determined to be H. litchi. To measure the reproductive factor (Rf), 60 sheathoid nematodes (57 females and three males) recovered from Baermann extraction were inoculated onto root systems of a longan tree in a 15-cm-d pot filled with sterilized soil. One hundred and sixty eight days after inoculation, three 100 cm3 subsamples of soil from the pot were processed as mentioned previously, and the average number was 48/100 cm3 of soil. The final population was approximately 768 nematodes per 1600 cm3 of soil with the Rf value of 12.8 confirming Longan as a host, although no symptoms were observed. The DNA from three individuals in the three subsamples with variant tail types were used to obtain D2-D3 and ITS region sequences, and confirmed the species as H. litchi. Hemicriconemoides spp. is associated with root malformation and nutrient deficiencies on agricultural fruit trees (Milne et al. 1971; McSorley et al. 1980); however, aboveground evidence of damage may not become immediately obvious and the importance of sheathoid nematodes is easily overlooked (Chen et al. 2011). This is the first report of H. litchi as a parasite of longan tree in Taiwan.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.