Family Longidoridae Research Articles

Cryptic speciation in the nematode family Longidoridae from South America: description of Xiphinema cryptocostaricense sp. nov. from Colombia and notes on X. seinhorsti

Abstract The genus Xiphinema Cobb, 1913 belongs to the family Longidoridae and consists of approximatelly 280 described species of plant-root ectoparasites. They occur on all continents except Antarctica and many species are important pests of crops, harming plants either by direct parasiting or by vectoring of nepoviruses. Due to their economic importance, several species were subjected to regulations aimed to limit their global spread. Moreover, the use of molecular techniques allowed to confirm the occurrence of cryptic species within the genus. In this paper we describe Xiphinema cryptocostaricense sp. nov., which constitutes the first instance of cryptic speciation within the family Longidoridae from South America. In terms of morphology this species is characterised by the body measuring 2.00–2.35 mm; lip region detached from the body outline only by a shallow constriction; odontostyle 129–135 µm long; V = 34.0–36.6; anterior branch of the genital tract largely reduced; tail short, almost hemispherical; lack of males and presence of four juvenile stages. This species is also characterised using molecular markers D2-D3 expansion domains of 28S rRNA, ITS1 rRNA and partial cytochrome oxidase c subunit 1 gene sequences. Based on morphology, this species is indistinguishable from X. costaricense Lamberti and Tarjan (Nematologia Mediterranea, 2, 1–11 1974). Additionally, a nomenclature remark is given- the name X. cryptocostaricense sp. nov. has been created by adding prefix ‘crypto’ to an already existing name of species. The advanatage of this approach is that it immediately points to which species it is cryptic to. Finally, new data regarding the second species, X. seinhorsti are given, including a first report of this species outside the place of its original description, data on molecular markers and morphology, including the first description of the J1 and J2 stages.

Use of Biochar to Control Root-Feeding Soil Nematodes on Muna Local Tomatoes Variety

Energy pathways in soil nematode communities consist of energy pathways for roots, bacteria, and fungi. The dominance of the root energy pathway indicated an increase in nematode attacks on the roots that can be regulated through changes in food availability and the environment. This study aimed to (i) determines the effect of the biochar rate on soil nematode energy pathways on local tomato plants and (2) determine the biochar rate that can suppress the dominance of root-feeding nematodes of local varieties of Muna tomato plants. The treatment tested was the biochar rate expressed as a percentage of the biochar weight the soil weight, namely 0%, 5%, 10%, and 15%. Each was repeated three times, randomly placed in the experimental plot following the randomized block design procedure. The results showed that the addition of biochar to 10% of the soil weight decreased the abundance of the total nematodes and family Longidoridae, on the other hand, increased Aphelenchoididae, Spearman rho correlation. The abundance of root eaters decreased; on the other hand, fungivores increased with the biochar rate. Spearman rho indicated that fungivores were negatively correlated with root-feeders and omnivores while positively correlated with predators. It was concluded that applying biochar up to a rate of 10% of the soil weight before planting could suppress the abundance of root-feeding nematodes in the vegetative growth phase of Muna local tomatoes variety.

New evidence of cryptic speciation in the family Longidoridae (Nematoda: Dorylaimida)

This research was supported by grant 201740E042 “Analisis de diversidad molecular, barcoding, y relaciones filogeneticas de nematodos fitoparasitos en cultivos mediterraneos” from the Spanish National Research Council (C.S.I.C.) and by the Humboldt Research Fellowship for Postdoctoral Researchers awarded for the second author. The first author acknowledges the China Scholarship Council (CSC) for financial support. The second author is a recipient of Humboldt Research Fellowship for Postdoctoral Researchers at Helmholtz Centre for Environmental Research‐UFZ, Leipzig, Germany. The fourth author acknowledges Spanish Ministry of Economy and Competitiveness for the “Ramon y Cajal” Fellowship RYC‐2017‐22228.

Occurrence and molecular identification of nematodes associated with brinjal (Solanum melongena L.) var. Mattu Gulla

The nematodes which belong to the family Longidoridae are obligatory plant parasites and are considered as economically significant pests since they cause severe crop losses around the world. Conventional identification of nematodes using morphological features is a time-consuming and challenging task. To overcome the challenges in conventional identification methods, rapid and reliable identification methods need to be established which will not only enable proper identification but also provide effective management program for nematodes which devastate the root system. In the present study, we have observed the nematode infection in a unique brinjal variety (Solanum melongena L. var. Mattu Gulla) grown in Mattu Village, Udupi District of Karnataka, India and identified the nematodes on the basis of molecular characterization using D3 expansion region of 28S rRNA gene sequence. Cephalobus cubaensis was found from the roots of Mattu Gulla for the first time. Our study will facilitate further screening and characterization of the root-knot and root-lesion nematode infections in both nursery as well as post-transplantation seedlings of Mattu Gulla in the field conditions.

Morphological and chorological characterization of Longidorus intermedius Kozlowska & Seinhorst, 1979 firstly reported from Ukraine with the comments on Longidorus elongatus (de Man, 1876) Thorne & Swanger, 1936

The family Longidoridae Thorne, 1935 is a big taxon of Dorylaimina sub-family. Its species are ectoparasites of vascular plants inhabiting terrestrial biotopes. Longidoridae is one of the most homogeneous groups of Dorylaimina, which differs distinctly in morphology and biology from other dorylaimids, but its representatives structurally and ecologically are very similar to each other. Seventeen species of this family belonging to three genera were previously reported from the territory of Ukraine. This paper pre­sents first record of Longidorus intermedius Kozlowska & Seinhorst, 1979 and new records of closely related species Longidorus elongatus (de Man, 1876) Thorne & Swanger, 1936 from Ukraine. Data on morphology, morphometrics and main differen­ces between Ukrainian populations of these two species are provided. Ukrainian populations of L. intermedius are also compared in details with other previously reported populations of this species, and main differences are described. The presence of only three juvenile deve­lopmental stages in L. intermedius was confirmed. In model natural and anthropogenically altered localities on the territory of Opillia, the host preference of L. intermedius and L. elongatus was analyzed in detail. On this territory, L. intermedius is closely associated with Quercus robur L., so it can be used as an indicator for natural and semi-natural forests in which oak associations represent a primary vegetation type. On the contrary, L. elongatus populations were reported from the rhizosphere of a wide range of host plants. According to its chorological characters, L. intermedius can be also used in phylogeographical research in order to determine the formation ways of nemoral complexes of soil organisms after the Last Glacial Maximum.

Research Note. New data on plant parasitic nematode Longidorus distinctus Lamberti, Choleva & Agostinelli, 1983 (Nematoda: Longidoridae) from Poland

Summary During a survey on the occurrence of the plant parasitic nematodes of the family Longidoridae in Poland, 925 soil samples were taken. Longidorus distinctus was present in 10 (1.08 %) of these samples. In this Research Note we provide: 1) distribution map of these populations, 2) morphometric data, 3) sequence data for D2-D3 28S rDNA and (partial)18S-ITS1 -5.8S(partial) markers and 4) LdistFOR primer (5′-GGCTGTAAAGATATATGCGT-3’) effective in obtaining ITS1 sequence for the species. Morphometric similarities and dissimilarities with data on other published populations are discussed.

Mitochondrial genome diversity in dagger and needle nematodes (Nematoda: Longidoridae)

Dagger and needle nematodes included in the family Longidoridae (viz. Longidorus, Paralongidorus, and Xiphinema) are highly polyphagous plant-parasitic nematodes in wild and cultivated plants and some of them are plant-virus vectors (nepovirus). The mitochondrial (mt) genomes of the dagger and needle nematodes, Xiphinema rivesi, Xiphinema pachtaicum, Longidorus vineacola and Paralongidorus litoralis were sequenced in this study. The four circular mt genomes have an estimated size of 12.6, 12.5, 13.5 and 12.7 kb, respectively. Up to date, the mt genome of X. pachtaicum is the smallest genome found in Nematoda. The four mt genomes contain 12 protein-coding genes (viz. cox1-3, nad1-6, nad4L, atp6 and cob) and two ribosomal RNA genes (rrnL and rrnS), but the atp8 gene was not detected. These mt genomes showed a gene arrangement very different within the Longidoridae species sequenced, with the exception of very closely related species (X. americanum and X. rivesi). The sizes of non-coding regions in the Longidoridae nematodes were very small and were present in a few places in the mt genome. Phylogenetic analysis of all coding genes showed a closer relationship between Longidorus and Paralongidorus and different phylogenetic possibilities for the three Xiphinema species.

Role of Longidoridae and Trichodoridae phytonematodes in vectorial transfer of viral plant pathogens

Purpose. To review domestic and foreign scientific sources on the role of phytonematodes of Longidoridae and Trichodoridae families in transferring pathogens of viral plant diseases.Results. The nematodes carrying viruses are attributed to the order of Dorylaimida, suborder Dorylaimina, family Longidoridae, genus Longidorus, Longidoroides, Paralongidorus, and Paraxiphidorus (known since 1995), Xiphidorus, Xiphinema and to the order of Triplonchida, suborder Diphtherophorina, family Trichodoridae, genus Allotrichodorus, Monotrichodorus, Paratrichodorus, and Trichodorus. The viruses they carry are attributed to soil viruses. Nematode species of genus Longidorus, Paralongidorus and Xiphinema are the vectors of ‘spherical’ viruses (nepoviruses) while nematodes of genus Trichodorus and Paratrichodorus carry rodlike viruses (tobraviruses).Conclusions. Based on studies of recent years it was found that 19 nematode species of family Longidoridae are able to carry 15 species of nepoviruses (mosaic of rock-cress, bromus inermis and peach, curl leaf of cherry, ringspot of raspberry, carnations, tomatoes, tobacco and mulberry, latent ringspot of strawberries, black ringspot of tomatoes, flabellate grape leaves, yellow variegation and leaf vein variegation of potatoes, Italian latent virus of artichoke), and 14 species of nematodes of family Trichodoridae can carry 3 species of tobraviruses (tobacco rattle virus, pea early browning and ringspot of pepper).

Description of the first-stage juveniles of Xiphinema cretense and X. herakliense - Distribution of Xiphinema and Longidorus species in olive orchards and grapevines in Crete, Greece

Summary The occurrence of nematodes of the family Longidoridae was investigated in soil samples collected from cultivated and wild olives and grapevines in Crete. The first-stage juveniles of Xiphinema cretense and X. herakliense are described for the first time. The species X. israeliae, X. cretense, X. herakliense and Longidorus pseudoelongatus, previously recorded exclusively from olives in Crete, are herein reported in the rhizosphere of grapevines. Also L. iranicus is reported for the first time in cultivated olive, while X. italiae and L. closelongatus are reported for the first time in wild olive in Crete. Data on the occurrence of phytoparasitic nematode species in cultivated olives, wild olives and grapevines are updated with those previously published.

Revision of some species of the genus Paralongidorus sensu Siddiqi et al. (1993), with a discussion on the relationships within the family Longidoridae (Nematoda: Dorylaimida)

Abstract A study of type material of several longidorid species revealed misinterpretations of the amphid structure with respect to shape of the amphidial fovea and amphidial aperture. A standardised terminology of the amphid structure within the Longidoridae is proposed. Former and recent hypotheses on phylogenetic relationships within the family based, respectively, on morphological and on molecular data are discussed, as well as possible implications for the systematics of the family Longidoridae. As a result of this study the following new combinations are proposed: Longidorus boshi n. comb. (syn. Paralongidorus boshi); Longidorus monegrensis n. comb. (syn. P. monegrensis); Longidorus spiralis n. comb. (syn. P. spiralis) and Longidorus cedari n. comb. (syn. Longidoroides cedari). Additional information is provided for Longidoroides bikanerensis, Paralongidorus buchae and P. zenobiae.