Nematology

Yoshitomi, Kyoka; Kanzaki, Natsumi; Shinya, Ryoji

doi: 10.1163/15685411-bja10481pmid: N/A

SummaryTree sap flow is a chemically complex environment characterised by fermentation-derived stressors such as ethanol, low pH, high osmotic pressure and hypoxia. Bursaphelenchus tadamiensis is frequently isolated from tree sap flow, suggesting adaptation to such conditions, although its stress tolerance has not been systematically examined. In this study, we evaluated the tolerance of B. tadamiensis to four stress conditions expected to occur in sap flow environments: high ethanol concentration, low pH, high osmotic pressure and hypoxia. Survival and reproductive capacity were assessed and compared with those of B. okinawaensis and Caenorhabditis elegans. Environmental measurements of ethanol concentration, pH and sugar content in natural sap flows were also conducted. Bursaphelenchus tadamiensis showed high survival under all stress conditions tested. Notably, B. tadamiensis survived at ethanol concentrations up to 15.1% and reproduced at 12.3%, which are substantially higher than ethanol concentrations measured in natural tree sap, whereas B. okinawaensis and C. elegans showed lower tolerance. The observed ethanol tolerance appears to be species-specific and is likely related to physiological rather than structural factors. This tolerance may facilitate persistence and reproduction of B. tadamiensis in the chemically fluctuating sap flow environment.

Asgari, Mohsen; Banihashemian, Seyedeh Najmeh; Álvarez-Ortega, Sergio; Eskandari, Ali

doi: 10.1163/15685411-bja10482pmid: N/A

SummaryA survey of nematodes in forested areas of northern Iran (Guilan Province) resulted in the description of a new species, Amphidelus andrassyi sp. nov. (Alaimida: Alaimidae), based on an integrative taxonomic approach combining detailed morphological, morphometric and molecular analyses. In addition, molecular data were obtained for an Iranian population of the known species Paramphidelus dolichurus. The new species belongs to the relatively long-bodied group of the genus Amphidelus, with adult females exceeding 3 mm in body length. Morphologically, it is most similar to A. acutus and A. longus and the distinguishing differences among these species are discussed in detail. Molecular analyses based on three 18S rRNA gene sequences provide reliable data for the genus Amphidelus and contribute to clarifying its phylogenetic placement within Alaimidae. Because complete sequences from other Amphidelus species are unavailable, molecular comparisons with congeners are limited. The molecular data obtained from Paramphidelus dolichurus are consistent with previous taxonomic hypotheses regarding its generic placement. Both species were recovered from decaying wood, highlighting the diversity of saproxylic nematodes in forest ecosystems of northern Iran. Beyond the description of a new species, the study also presents an updated taxonomic synthesis of Amphidelus, including an updated identification key to all valid species and a tabular morphometric compendium to facilitate species recognition and comparative studies. Overall, this study provides reliable molecular evidence contributing to a better understanding of phylogenetic relationships within the family Alaimidae.

Sakata, Itaru; Kushida, Atsuhiko

doi: 10.1163/15685411-bja10483pmid: N/A

SummaryRoot-knot (Meloidogyne spp.) and root-lesion nematodes (Pratylenchus spp.) are important pests of various crops. In Japanese agricultural fields, the predominant nematode species include M. hapla, members of the M. incognita group (MIG: M. arenaria, M. incognita and M. javanica), as well as P. coffeae, P. crenatus and P. penetrans. Although real-time PCR methods have been reported for the diagnosis of these nematodes, most existing methods target only one species in a single reaction. Therefore, to facilitate a more efficient nematode diagnosis, we developed three real-time PCR methods for the simultaneous identification of three nematode species belonging to Meloidogyne and Pratylenchus. The target species of each method were M. hapla, P. crenatus and P. penetrans; MIG, P. coffeae and P. penetrans; and M. hapla, MIG and P. penetrans. To minimise the likelihood of mispriming and nonspecific amplification, we designed a common primer set for Meloidogyne and Pratylenchus and specific probes for each target. In real-time PCRs, each fluorescent signal was obtained only from the DNA of the corresponding target nematodes. In addition, when the DNA of multiple targets coexisted in a sample, each target was typically detected. However, when a sample used for DNA extraction comprised a few MIG individuals and at least five times as many M. hapla individuals, the real-time PCR method targeting M. hapla, MIG and P. penetrans may fail to detect MIG. A significant negative correlation was observed between the cycle threshold (Ct) values and the number of individuals (R2 ⩾ 0.9324). Real-time PCR methods using the common primer set are likely to be effective tools for the diagnosis of Meloidogyne and Pratylenchus species.

Ivanova, E.S.; Skiba, E.M.; Spiridonov, S.E.

doi: 10.1163/15685411-bja10484pmid: N/A

SummaryNematodes were isolated from the moss samples collected at Novolazarevskaya Antarctic research station in the sub-Antarctic ecological zone. Morphological and molecular-phylogenetic analyses of the nematodes showed that they belong to the Iotonchiidae family of the order Tylenchida. Iotonchiids are entomoparasitic nematodes with complex life style which includes fungi, insects (gnats) and free-living stage. Material collected contained only one life stage identified as infective pre-adult females. First SEM data were obtained for the representative of the genus Iotonchium.

Huang, Ling; Mo, Yixue; Li, Bingxue; Wu, Haiyan

doi: 10.1163/15685411-bja10485pmid: N/A

SummaryThe corn cyst nematode (Heterodera zeae) is an emerging pathogen of maize in China, posing a serious threat to maize production. This study investigated the effects of common fertilisers (urea, phosphate, potash), herbicides (glyphosate, atrazine, nicosulfuron, acetochlor) and metal ions (Fe3+, Cu2+, Zn2+, K+, Ca2+, Mg2+) on the hatching and mortality of H. zeae. For fertilisers, urea exhibited nematicidal activity, causing second-stage juvenile (J2) mortality of 35.8%, after 72 h at 2000 μg ml−1. Urea and phosphate fertiliser at 2000 μg ml−1 significantly suppressed the cumulative hatch from white females, whereas potassium fertiliser at the same concentration stimulated hatch, increasing the cumulative hatch by 9.27% compared to the control. Regarding herbicides, glyphosate demonstrated the highest toxicity toward J2, achieving 97.5% mortality within 72 h at 800 μg ml−1, and strongly inhibited hatch from white females, reducing the cumulative hatch by 56.8% after 21 days. Atrazine also exhibited nematicidal activity, causing 29.4% J2 mortality at 2000 μg ml−1 after 72 h. Additionally, atrazine and nicosulfuron at 2000 μg ml−1 significantly suppressed the cumulative hatch from white females. For metal ions, white females of H. zeae were treated with different metal ions at concentrations of 5 mM and 15 mM. Fe3+, Cu2+ and Zn2+ significantly inhibited hatch, with all treatments showing markedly lower cumulative hatch compared to the control after 21 days. By contrast, Ca2+ and Mg2+ had no significant effect on hatch, whereas K+ stimulated hatch. Treatment with 3-15 mM K+ increased the cumulative hatch by 9.89% to 15.41%. No significant influence on hatch was observed across different concentrations of Mg2+. These findings reveal the multifunctional roles of common fertilisers, herbicides and the metal ions they contain in integrated management of plant-parasitic nematodes and suggest their potential integration into sustainable control strategies.

Du, Yu; Zhou, Shao Fang; Lei, Qu Wen; Jian, Zhou; Li, Min; Yang, Yan; Fang, Kui

doi: 10.1163/15685411-bja10486pmid: N/A

SummaryMeloidogyne enterolobii is a highly pathogenic, polyphagous root-knot nematode with the ability to overcome common resistance genes and is recognised as a quarantine pest in many countries and regions. During plant quarantine inspections, root-knot nematodes were intercepted on Hosta plantaginea from The Netherlands and multiple ornamental plants including Anthurium sp., Alocasia sp., Caladium sp., Epipremnum sp., Euonymus sp., and Hoya carnosa from Thailand, and a weed (Bidens pilosa) and a crop (Ipomoea batatas ‘Purple’) from Vietnam imported into China. Three developmental stages including eggs, second-stage juveniles (J2), males and females were detected on The Netherlands population, while only J2 were recovered from samples originating in Thailand and Vietnam. Morphological and morphometric analyses were performed on females, males and second-stage juveniles from the H. plantaginea population, and on J2 from the H. carnosa and I. batatas ‘Purple’ populations. Molecular characterisation based on near-full-length 18S rDNA, the D2-D3 expansion domains of 28S rDNA, and ITS rDNA confirmed that all intercepted populations clustered in a well-supported clade with reference sequences of M. enterolobii from diverse geographical origins and hosts. The present study provides the first report of M. enterolobii on H. plantaginea worldwide, and documents association for this nematode species with multiple plant species from Thailand and Vietnam. These interceptions underscore the ongoing phytosanitary risk posed by M. enterolobii and highlight the need for continued surveillance of high-risk plant commodities in international trade.

Abolafia, Joaquín; Robles, María-Cristina; García-Ruiz, Miriam

doi: 10.1163/15685411-bja10487pmid: N/A

SummaryAprutides guidettii is redescribed from natural and agricultural areas of the southern Iberian Peninsula, including the first record of the male of the species. The Spanish material is characterised by females 403-527 μm long and males 366-504 μm long, lateral fields with three longitudinal incisures at mid-body, conoid-truncate lip region developing an offset oral disc, amphidial openings in the form of small lateral slits located at the base of the oral disc, stylet 12-14 μm long with slightly developed basal knobs, pharynx with a well-developed median bulb and pharyngeal glands overlapping the intestine, excretory pore located at the level of the posterior part of the metacorpus, post-vulval uterine sac 1.3-1.5 times the corresponding body width, female tail slightly recurved ventrally with a clavate terminus (32-53 μm, c = 9.4-13.7, c′ = 3.6-5.6), spicules 12-16 μm long, gubernaculum not discernible, male tail not or slightly clavate (29-40 μm, c = 12.0-13.8, c′ = 2.9-3.7), bursa absent, and genital papillae not clearly discernible. The topology of the Bayesian phylogenetic tree reconstructed using some currently available small subunit ribosomal DNA (SSU rDNA) sequences of the genus Aprutides and relevant genera is discussed.

Mulusew, Addisie B.; Meressa, Beira H.; Couvreur, Marjolein; Bayissa, Wakuma; Getachew, Sihen; Teklu, Misghina G.; Bert, Wim

doi: 10.1163/15685411-bja10490pmid: N/A

SummaryGinger is one of Ethiopia’s most widely cultivated crops, and is second-most-important spice, yet its productivity is constrained mainly by bacterial wilt and plant-parasitic nematodes (PPN). Despite their impact, the occurrence, distribution and population density of PPN associated with ginger in Ethiopia remains limited. To address this knowledge gap, a survey was conducted in 2022 across eight major ginger-producing districts in southern Ethiopia, collecting 330 soil and rhizome samples. Nematodes were extracted and identified using morphological and molecular methods. Six PPN genera were identified, including: Meloidogyne, Scutellonema, Helicotylenchus, Rotylenchulus, Crossonema and Mesocriconema. Meloidogyne was the most prevalent genus, occurring in 86% of the fields with densities ranging from 102 to 368 second-stage juveniles (J2) per 100 ml of soil and a frequency of occurrence (FO) of 20-92%. It was also the only genus recovered from ginger, with densities reaching up to 1158 J2 per 10 g rhizomes with roots and 100% FO. Other genera included Rotylenchulus, Scutellonema and Helicotylenchus with densities up to 72, 108 and 116 individuals (100 ml soil)−1, and 68, 60 and 84% FO, respectively, while Mesocriconema and Crossonema had the lowest FO. Molecular analysis, including D2D3 of 28S rDNA, NADH dehydrogenase subunit 5, cytochrome c oxidase subunit I and cytochrome c oxidase subunit II, further confirmed the presence of seven PPN species, with Meloidogyne javanica being the most prevalent root-knot nematode, followed by M. incognita. Importantly, Rotylenchulus borealis and Scutellonema paralabiatum are reported for the first time from ginger in Ethiopia. These findings provide a foundation for improved monitoring and management of PPN, supporting sustainable ginger production in the region.