First Report of the Dagger Nematode Xiphinema diversicaudatum in Citrus Orchards in Morocco

Xiphinema species are migratory ectoparasitic nematodes that feed on an extensive range of hosts, and several species are vectors of nepoviruses. In May 2012, during a survey of the citrus-growing areas in the Gharb region of Morocco, several Xiphinema nematodes were detected in three locations: Kénitra (INRA, plot P1), Sidi Kacem, and Sidi Slimane. Samples were taken 30 cm deep at 50 cm distance from the tree trunks, in 40-year-old orange groves planted with the variety Maroc Late, grafted on rootstocks of Sour Orange and Citrange Carrizo. The trees showed yellowing of leaves, reduced tree vigor, and swellings at the tips of the roots. There were no weeds or grasses in the sampled area. Nematodes were extracted from soil using an automated centrifuge for extracting free-living nematode stages (2) and identified morphologically and by sequencing. All specimens were identified as Xiphinema diversicaudatum based on key morphological features from females and males. The average measurements of six females were: body length 4.1 mm, body width 60.4 μm, odontostylet 133.5 μm, odontophore 64.0 μm, spear 197.5 μm, tail length 45 μm, body width at anus 31 μm, and vulval position 48%. The females had two genital branches of similar length and structure, which contained a pseudo-Z differentiation. The average measurements of four males were: body length 4.3 mm, body width 51 μm, odontostylet 139 μm, odontophore 70 μm, spear 209 μm, tail length 45 μm, body width at anus 35 μm. To confirm the morphological identification, molecular observations were made. DNA was extracted from one nematode of each location. The D3 expansion region of the 26S rRNA gene was amplified using the primers D3A (5′-GACCCGTCTTGAAACACGGA-3′) and D3B (5′-TCGGAAGGAACCAGCTACTA-3′) (1). The PCR products were purified and sequenced (Macrogen, Inc., Seoul, Korea). All sequences obtained (GenBank Accession Nos. KF057879, KF057880, and KF057881) were compared with sequences available from the GenBank database including several species of Xiphinema. This comparison revealed a sequence similarity of 99 to 100% with X. diversicaudatum. Morphological and molecular identification demonstrated that the isolates of dagger nematodes from three citrus growing areas in Gharb belonged to X. diversicaudatum. An average of six X. diversicaudatum per 100 cm3 soil were found. This is the first report of this species in Morocco. X. diversicaudatum can transmit Arabis mosaic and Strawberry latent ringspot viruses (3). Arabis mosaic virus is of great economic importance in viticulture as it is associated with grapevine fanleaf degeneration disease, together with Grapevine fan leaf virus transmitted by X. index (4). As vineyards are planted amid citrus orchards in the Gharb region, particular attention should be given to this nematode, especially to the risk of its spread by soil. Our finding of X. diversicaudatum in a citrus orchard does not necessarily imply that X. diversicaudatum causes damage in citrus. However, its presence indicates that this nematode species can survive in this environment from where it could spread to other, more susceptible, crops. References: (1) L. Al-Banna et al. Mol. Phylogenet. Evol. 7:94, 1997. (2) G. Hendrickx. Nematologica 41:30, 1998. (3) J. Hübschen et al. Eur. J. Plant Pathol. 110:779, 2004. (4) A. Marmonier et al. J. Plant Pathol. 92:275, 2010.

Morphological and molecular characterisation of the Saratov population of the European dagger nematode, Xiphinema diversicaudatum (Nematoda: Dorylaimida), with notes on phylogeography of the species

Plesiotype specimens of the European dagger nematode, Xiphinema diversicaudatum, were collected in Saratov, Russia, and morphologically, morphometrically and molecularly characterised. PCR with specific primer was developed for rapid diagnostics of this species. Phylogenetic relationships of X. diversicaudatum with other Xiphinema species, as inferred from the analyses of the D2-D3 expansion segments of 28S rRNA, ITS rRNA and coxI mtDNA gene sequences, are also provided. The study revealed that the clade X. diversicaudatum, together with X. bakeri (North America) and X. chengi (Asia), is related to Xiphinema species from the Mediterranean region and likely originated from a common ancestor inhabiting this area. The phylogenetic reconstructions with coxI mtDNA were used to describe the pattern of present genetic diversity of X. diversicaudatum and infer its biogeographical history in Europe. Haplotype diversity of X. diversicaudatum populations from Central Europe was significantly higher than those from south-eastern Europe, central, south-eastern and southern European Russia. It has been hypothesised that, during the Last Glacial Maximum, X. diversicaudatum populations probably persisted in refuge areas in the Carpathian mountains or the Alps, the species subsequently expanding from these areas and colonising other regions in Europe.

Morphological characterisation and diagnostics of Xiphinema non-americanum group species (Nematoda: Longidoridae) from Romania using mutiplex PCR

Additional data on the occurrence and distribution of Xiphinema non-americanum group species in Romania are provided. Xiphinema diversicaudatum, X. index, X. vuittenezi and X. italiae were recovered from vineyards and cherry fruit trees; adults and juvenile stages were described and analysed and the morphology/variability discussed. Multiplex PCR diagnostic test using species-specific primers designed by Wang et al. (2003) yielded amplification products with expected lengths for all screened populations of these four species. Two ribosomal markers (D2-D3 28 LSU rDNA and ITS) were sequenced and ITS RFLP patterns were obtained from two X. vuittenezi populations, which have shown some morphological differences. Comparatively low level of interpopulation genetic dissimilarity (<1 %) was revealed for both markers (for D2D3 — 0.5 %; for ITS — 0.7 %). Both populations of X. vuittenezi studied produced identical ITS-RFLP specific pattern that clearly identify this species.

Arabis mosaic virus. [Distribution map].

A new ditribution map is provided for Arabis mosaic virus (ArMV; Comoviridae: Nepovirus). It has a wide host range. Information is given on the geographical distribution in Europe (Austria, Belarus, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Moldova, Netherlands, Norway, Poland, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, UK, England, Wales, Northern Ireland, Scotland and Ukraine), Asia (China, India, Himachal Pradesh, Iran, Israel, Japan, Honshu, Kazakhstan, Lebanon, Syria and Turkey), Africa (South Africa), North America (Canada, British Columbia, Nova Scotia, Ontario, Quebec, Mexico, USA, Connecticut, Florida, Michigan, Minnesota, Missouri, Nebraska and South Carolina), South America (Chile) and Oceania (Australia, Tasmania, Victoria and New Zealand). The main vector of ArMV is the nematode Xiphinema diversicaudatum. Other dorylaimid nematodes may also be vectors. ArMV is also seed-transmitted.

Detection of Cherry leaf roll virus and Strawberry latent ring spot virus by one-step RT-PCR

A one-step reverse transcription-polymerase chain reaction (RT-PCR) protocol was developed and used for the detection of <i>Cherry leaf roll virus</i> (CLRV) and <i>Strawberry latent ring spot virus</i> (SLRSV). The protocol was used to test infected screen house plants and also plants from orchards and vineyards where the vector (<i>Xiphinema diversicaudatum</i>) of SLRSV was detected from the soil. The one-step RT-PCR protocol is rapid and sensitive and has the potential to be used for the diagnosis of CLRV and SLRSV in routine diagnostic laboratories.

A single bivulval female of Xiphinema diversicaudatum and two bivulval females of Xiphinema vuittenezi (Nematoda: Longidoridae)

A population of Xiphinema vuittenezi from an apple orchard and a population of X. diversicaudatum from a peach orchard yielded bivulval females. Morphometrics of these females are presented.

Xiphinema diversicaudatum. [Distribution map].

A new distribution map is provided for Xiphinema diversicaudatum (Micoletzky) Thorne Nematoda: Dorylaimida: Longidoridae Hosts: Mainly fruit crops, including strawberry (Fragaria X ananassa[Fragaria ananassa]) stone fruits (Prunus spp.), Rubus spp., grapevine (Vitis vinifera); also roses (Rosa spp.). Information is given on the geographical distribution in EUROPE, Belgium, Bulgaria, Croatia, Czech Republic, - Denmark, France, Germany, Ireland, Italy, Moldova, Netherlands, Norway, Poland, Portugal, Azores, Madeira, Mainland Portugal, Central Russia Russia, Southern Russia, Slovakia, Spain, Sweden, Switzerland, UK, Ukraine, AFRICA, South Africa, NORTH AMERICA, Canada, Ontario, USA, California, OCEANIA, Australia, Victoria, New Zealand.