First Report of Plant-Parasitic Nematode Meloidoderita salina in the Netherlands

After the description of the root-parasitic nematode Meloidoderita salina from a tidal salt marsh in France (1), an additional sampling was carried out to search for the presence of this unusual nematode in a tidal salt marsh area close to Sint-Annaland, Zeeland Province, the Netherlands. In August and October 2012, a total of 25 soil and root samples were collected from the halophytic plants Atriplex portulacoides L. (so far the only known host for this nematode species), A. littoralis L., A. prostrata Boucher ex DC., Limonium vulgare Mill., Salicornia europaea L., Aster tripolium L., and Plantago maritima L. All these halophytes grow in a cohesive muddy soil type within the salt marsh, except A. littoralis and A. prostrata, which grow in the litter tidal zones on the edges of this area. Nematodes from roots and soil were extracted by centrifugal flotation (2) and Oostenbrink's cotton-wool filter methods (4), respectively. Additionally, roots were used for direct observation of females and young cystoids with a dissecting microscope. Finally, all stages were compared morphologically with available type material (1). Root and soil samples demonstrated that only nematodes isolated from A. portulacoides, A. littoralis, and A. prostrata contained all life stages of the genus Meloidoderita, while on the roots of L. vulgare, S. europaea, A. tripolium, and P. maritima, no Meloidoderita was observed. The soil samples included males, cystoids, and second-stage juveniles (J2) in low densities (<20 nematodes/100 ml), while swollen females and young cystoids were observed on root samples. All stages (n = 10 per life stage) fit morphologically with the recently described M. salina. Females were swollen with an oval to pear shaped body with a small posterior protuberance, irregular and twisted neck, oval and backwardly sloping stylet knobs, a prominent secretory-excretory (S-E) pore with cuticular lobes, and a swollen uterus with a thick hyaline wall. Males were without stylet, strongly sclerotized S-E duct, and tail tapering to rounded terminus ending in one or two ventrally terminal mucron. J2s had a well-developed stylet and rounded knobs set off from shaft and conical tail slightly curved ventrally and tapering to a finely pointed terminus with a finger-like projection. Cystoids showing the unique sub-cuticular hexagonal beaded pattern (1). J2s were also used for molecular analysis. DNA was extracted by incubating individual J2s in a lysis buffer as described in (3). Two primer combinations were used to amplify the small subunit ribosomal DNA (SSU rDNA) from a 100-times-diluted crude lysate (two overlapping fragments, [3]). The resulting (nearly) full-length SSU-rDNA sequences (GenBank KF751617 and KF751618) showed >99% identity with M. salina sequences from nematodes collected in the aforementioned tidal salt marsh in France (FJ969126 and FJ969127). To our knowledge, this is the first report of M. salina in the Netherlands. Moreover, this is the first record of M. salina parasitizing A. littoralis and A. prostrata. Although these Atriplex species are used for human consumption, the effect of M. salina on the host is unknown so far. References: (1) S. Ashrafi et al. Zookeys 249:1, 2012. (2) W. A. Coolen. Pages 317-329 in: Root-knot nematodes (Meloidogyne species). Systematics, biology and control. Academic Press, New York, 1979. (3) Holterman et al. Mol. Biol. Evol. 23:1792, 2006. (4) M. Oostenbrink. Pages 85-102 in: Nematology. University of North Carolina Press, Chapel Hill, 1960.

First Report of the Root-Knot Nematode Meloidogyne artiellia in Belgium

In 2011, second-stage juveniles (J2) of an unknown root-knot nematode (Meloidogyne spp.) were detected during a routine survey for root-knot nematodes on arable land in Harveng, Belgium, after a crop of wheat. Most of the loamy soil samples (36 out of 42) contained J2 of the common root-knot nematode M. naasi Franklin, 1965 (1), while 15 of these also contained the unknown species, albeit in lower densities (22 J2/100 ml vs. 157 J2/100 ml soil). After detailed morphological observation of the unknown J2, they were until further notice identified as Meloidogyne artiellia Franklin, 1961 (2), the British root-knot nematode. To confirm the identification, a pure culture of M. artiellia was established by adding nematode suspensions to pots planted with kale (Brassica oleracea var. laciniata), a non-host for M. naasi (3). After 2 months, Meloidogyne spp. females, males, and J2 were isolated from galled kale roots. Morphological characteristics (n = 25) from the perineal pattern (rounded with fine striae, lateral area with coarse ridges, angular dorsal arch) and stylet knobs (small, ovoid, and backwardly sloping) for the females, the head shape (set off with distinct head cap) and stylet knobs (small, ovoid and backwardly sloping) for the males, the hemizonid position (anterior, adjacent to S to E pore), tail shape (conical), and short tail length (18 to 27 μm) for the J2, fit with previous observed populations of M. artiellia (3). Young egg-laying females were used for isozyme electrophoresis, and showed typical malate dehydrogenase (N1b) and esterase (M2-VF1) patterns (3). Additionally, DNA was extracted from single juveniles by incubating them in a lysis buffer (200 mM NaCl, 200 mM Tris-HCl (pH 8), 1% β-mercaptoethanol and 800 μg/ml Proteinase K) during 1.5 h at 65°C and 5 min at 99°C in a thermocycler. One microliter of crude DNA extract was used for PCR. ITS-rDNA sequencing (GenBank Accession Numbers JX393299 and JX393300) confirmed the identity, showing a 98 to 100% homology with other M. artiellia sequences (AY150368 and AF248478). To our knowledge, this is the first report of the root-knot nematode, M. artiellia, in Belgium. This nematode has been reported from the Mediterranean area, where it causes damage on chickpea and wheat (4), as well as from the U.K. Its finding in Harveng, close to the French border, suggests a more extensive geographical distribution. References: (1) M. T. Franklin. Nematologica 11:79, 1965. (2) M. T. Franklin et al. Suppl.:85, 1961. (3) G. Karssen. Pages 93-97 in: The Plant-Parasitic Nematode Genus Meloidogyne Göldi, 1892 (Tylenchida) in Europe, Brill Leiden, The Netherlands, 2002. (4) M. Di Vito and N. Greco. Revue Nématol. 11:223, 1988.

Small subunit rDNA-based phylogeny of the Tylenchida sheds light on relationships among some high-impact plant-parasitic nematodes and the evolution of plant feeding

Cyst (Heteroderidae), root knot (Meloidogyne spp.), and lesion (Pratylenchus spp.) nematodes all belong to a single nematode order, Tylenchida. However, the relationships between and within these economically highly relevant groups, and their relatedness to other parasitic Tylenchida is unclear. We constructed a phylogeny of 116 Tylenchida taxa based on full length small subunit ribosomal DNA (small subunit [SSU] rDNA) sequences. Ancestral state reconstruction points at a gradual development of simple to more complex forms of plant parasitism. Good resolution was observed in distal clades that include cyst, root knot, and lesion nematodes, and monophyly of most families was confirmed. Our data suggest that root knot nematodes have evolved from an ancestral member of the genus Pratylenchus, but it remains unclear which species is closest to this branching point. Contrary to the notoriously polyphagous distal representatives, basal members of the genus Meloidogyne (and probably, their common ancestor) have narrow host ranges. Our analysis also shows that mitotic parthenogeny has arisen at least two times independently among root knot nematodes. In many cases resolution till species was observed, suggesting that SSU rDNA sequences have a potential for DNA barcode-based species identification with, due to the overall conserved nature of this gene, limited intra-species variation.

First Report of Root-Knot Nematode Meloidogyne enterolobii on Tomato and Cucumber in Switzerland

Severe stunting and extensive root galling were observed on tomato rootstock (Solanum lycopersicum L. cv. Maxifort) resistant to Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949, M. javanica (Treub, 1885), and M. arenaria (Neal, 1889) Chitwood, 1949 and cucumber (Cucumis sativus L. cv. Loustik) from two commercial greenhouses in the cantons Aargau and Lucerne in northern Switzerland. Examination of the roots of infected plants revealed the presence of root-knot nematodes in large numbers. Juveniles, males, and females were isolated, and the species was determined on the basis of morphological characteristics, including the female perineal pattern. Identification was confirmed by female esterase (Est) and malate dehydrogenase (MdH) electrophoresis (20 each for Est and MdH). All methods of identification were consistent with M. enterolobii Yang & Eisenback, 1983 (4). For further confirmation, type material of M. enterolobii (from the original host Enterolobium contortisiliquum (Vell.) Morong) from China (4) was used. Furthermore, comparison of the sequence data from 12 individuals of each of the two Swiss populations and the type material of a 310-bp fragment of cytochrome oxidase I (COI), a 723-bp fragment covering the internal transcribed spacer (ITS) region 1, 5.8s, ITS2, and part of the 26s, the mtDNA 63-bp repeat region, and a 780-bp fragment of the intergenic spacer region (1-3) showed 100% homology and confirmed the identification as M. enterolobii. The species M. enterolobii is of great importance because it is able to reproduce on resistant tobacco, pepper, watermelon, and tomato (4). To our knowledge, this is the first report of M. enterolobii in Switzerland. References: (1) M. A. M. Adam et al. Plant Pathol. 56:190, 2007. (2) V. C. Blok et al. Nematology 4:773, 2002. (3) T. C. Vrain et al. Fundam. Appl. Nematol. 15:565, 1992. (4) B. Yang and J. D. Eisenback. J. Nematol. 15:381, 1983.

First Report of the Root-Knot Nematode Meloidogyne minor on Turfgrass in Belgium

The root-knot nematode, Meloidogyne minor, was described during 2004 after it was found on potato roots in a field in the Netherlands and in golf courses in England, Wales, and Ireland (2). Since it is associated with yellow patch disease in turf grass and causes deformation of potato tubers (2), it is important to know whether this organism is already widespread in these and neighboring countries. In addition, it has a relatively wide host range (2,4). A small survey conducted in Belgium was comprised of 10 golf courses geographically spread over the country. In each location, 3 to 9 samples were taken (one per green) consisting of 30 to 40 cores (1.5 × 20 cm deep). Nematodes were extracted from a 200-g subsample (containing roots) from each sample using zonal centrifugation (1). All Meloidogyne spp. were mounted on semipermanent slides and identified morphologically. M. minor was discovered in 3 of 6 samples taken in April 2006 from a golf course in Hasselt (northeastern Belgium). Between 41 and 50 M. minor per 100 g of soil were found together with M. naasi (7 to 20 individuals per 100 g of soil). Occurrence of M. minor together with other Meloidogyne species has been reported in natural and cultivated sites (2,4). Moreover, spores of Pasteuria spp. were clearly visible on 42% of the observed second-stage juveniles of M. minor, but not on those of M. naasi. The infected juveniles had between 2 and 15 spores attached to their cuticles. Additional juveniles were extracted from the soil samples and used for molecular identification by real-time PCR (2), which confirmed the presence of M. minor. There were no symptoms on the grass, consisting of a mixture of Agrostis stolonifera (10%), Festuca rubra (30%), and Poa annua (60%). Grass was sown in Rhine sand and heath land compost used for the construction of the greens in Hasselt. It could be that these soil amendments were infested with M. minor or that M. minor was introduced by other means, e.g., shoes, maintenance machinery, or golf equipment. On the other hand, the detection of M. minor in this small survey indicates that the species may be prevalent in golf courses in the region. The nematode has been found in several golf courses and sport fields in the United Kingdom and the Netherlands, including a golf course at Breda (close to the Belgian border) (3). The survey will be expanded to include grasslands and dune areas, the presumed natural habitat of M. minor. References: (1) G. A. Hendrickx. Nematologica 41:308, 1995. (2) G. Karssen et al. Nematology 6:59, 2004. (3) W. Lammers et al. Meloidogyne minor. Pest Risk Assessment. Online publication, www.minlnv.nl/pd - Schadelijke organismen, 2006. (4) S. J. Turner and C. C. Fleming. Comm. Appl. Biol. Sci. Ghent University 70:885, 2005.

The Root-Knot Nematode Meloidogyne fallax on Strawberry in the Netherlands

The root-knot nematode Meloidogyne fallax Karssen is closely related to M. chitwoodi Golden, O'Bannon, Santo & Finley. Both species have a wide host range and have been designated as quarantine nematodes by several countries. Strawberry (Fragaria ananassa L.) is considered a poor host for M. chitwoodi (2,3), but the host status for M. fallax in unknown. During 2003, a host suitability study was performed with four common strawberry cultivars (Ciflorette, Elsanta, Kimberly, and Mara des bois) on a field naturally infested with M. fallax near Wintelre, the Netherlands. The identity of the nematode was confirmed, prior to and after the test, by using morphological characteristics, isozymes, and polymerase chain reaction (PCR). The field was not infested with M. hapla Chitwood. The host test included 15 replicates per cultivar and started in April with a mean initial M. fallax density of approximately 4,500 second-stage juveniles per 100 ml of soil. The plants used in the field trial were multiplied by cuttings and grown on artificial substrate free from any Meloidogyne species. Upon plant harvesting in October, the number of root galls were counted and cvs. Mara des bois and Ciflorette did not show any typical root-knot symptoms, while cvs. Elsanta and Kimberly expressed only a few small galls. Additionally, high numbers of nematodes were found in the roots using the centrifugal floating method (1). The mean numbers of isolated nematodes for all cultivars (females, 116; males, 80; second-stage juveniles, 6,636; third- and fourth-stage juveniles, 49; and eggs, 920 per 10 g of roots) suggests that the tested strawberry cultivars are good hosts for M. fallax despite the lack of clear root galling or visible plant grow reduction as has been observed in the past for M. javanica on strawberry (4). To our knowledge, this is the first report of strawberry as a host for M. fallax, and it suggests that M. fallax could be spread by strawberry transplant grown in M. fallax infested soil. The Dutch Plant Protection Service is currently discussing appropriate action, such as an additional root-knot nematode test in addition to visual root inspection, before strawberry plants are shipped and cultivated. References: (1) W. A. Coolen and J. D'Herde. A method for the quantitative extraction of nematodes from plant tissue. Ghent State Agriculture Research Centre, 1972. (2) A. M. Golden et al. J. Nematol. 12:319, 1980. (3) J. H. O'Bannon et al. Plant Dis. 66:1045, 1982. (4) D. P. Taylor and C. Netscher. Cah. O.R.S.T.O.M, Ser. Biol. 10:247, 1975.

First Report of the Root-Knot Nematode Meloidogyne ethiopica on Tomato in Slovenia

The root-knot nematode Meloidogyne ethiopica Whitehead originally described from Tanzania is also distributed in South Africa, Zimbabwe, and Ethiopia (3). Although this species is a relatively unknown root-knot nematode, M. ethiopica parasitizes several economical important crops, such as tomato, cowpea, bean, cabbage, pepper, pumpkin, tobacco, lettuce, and soybean (4). This species can be morphologically confused with M. incognita (Kofoid & White), and therefore, is probably easily overlooked (1). Recently, characteristic esterase isozyme patterns were described for this species, which provide a more reliable identification (2). In October 2003, Lycopersicum esculentum cv. Belle plants with large root-galls were observed in a greenhouse at Dornberk, Slovenia, which were identified as an unknown root-knot nematode within the M. incognita group. Subsequent sampling revealed infestation of all tomato plants within this greenhouse with obvious aboveground symptoms of stunting and wilting. Additional morphological and isozyme studies identified this root-knot nematode as M. ethiopica. The identification was based on female, male, and second-stage juvenile morphology and malate dehydrogenase and esterase isozyme phenotypes from young egg-laying females isolated from 20 tomato plants and compared with a culture of M. ethiopica from Africa. To our knowledge, this is not only the first report of M. ethiopica in Slovenia, but also the first report of this species in Europe. References: (1) A. M. Golden. Fundam. Appl. Nematol. 15:189, 1992. (2) W. Mandefro and K. Dagne. Afr. J. Plant Prot. 10:39, 2000. (3) A. G. Whitehead. Trans. Zool. Soc. Lond. 31:263, 1968. (4) A. G. Whitehead. Nematologica 15:315, 1969.

First Report of the Root-Knot Nematode Meloidogyne marylandi on Turfgrasses in Israel

In a turfgrass nursery in Arava, Israel, a population of root-knot nematodes was isolated from poorly growing Zoysiagrass (Zoysia japonica Steud.) with symptoms of foliar chlorosis and roots with very small, smooth galls and protruding egg masses. The isolated population (genus Meloidogyne) included females and second-stage juveniles, whereas no males were observed. Measurements and morphological observations of 20 second-stage juveniles (body length = 423 ± 13 μm, dorsal gland orifice from stylet base = 2.6 ± 0.4 μm, tail length = 63 ± 3 μm, hyaline tail length = 12.4 ± 0.9 μm and hemizonid posterior to excretory pore) and 10 adult females (stylet length = 12.5 ± 0.7 μm, dorsal gland orifice from stylet base = 3.3 ± 0.5 μm, excretory pore to head end = 11.9 ± 1.3 μm and perineal patterns rounded to ovoid with coarse striae) conformed to the description of Meloidogyne marylandi Jepson and Golden (3). Additionally, the identification was confirmed when females and second-stage juveniles were compared with available paratype slides. The isozymes malate dehydrogenase (EC 1.1.1.37) and esterase (EC 3.1.1.1) of young, adult females were also different from those of other described root-knot nematode species, including M. graminis, a taxon closely related to M. marylandi (4). M. marylandi was discovered and described from Bermudagrass (Cynodon dactylon (L.) Pers) in Maryland in 1987. Outside the United States, it has only been isolated from Zoysia matrella in Japan (1,2,3). In host range tests with different turfgrasses, stolons with roots were inoculated after 1 week with 500 second-stage juveniles per plant and 6 weeks later, the produced egg-masses where counted. These tests showed that this root-knot nematode isolate reproduced on Z. japonica and Pennisetum clandestinum, while no egg masses were observed on the roots of Dactyloctenium australe, Paspalum vaginatum, and Stenotaphrum secundatum. Additionally, some cereals grown from seeds were tested. Wheat (Triticum aestivum), barley (Hordeum vulgare), and bristle oat (Avena strigosa) were infested with this nematode, while oat (A. sativa) was not. Although the origin of this root-knot nematode in Israel is unknown, it could have been distributed throughout the country with commercial turfgrass. To our knowledge, this is the first report of M. marylandi in Israel and outside the United States and Japan. References: (1) M. Araki. Jpn. J. Nematol. 22:49, 1992. (2) A. M. Golden. J. Nematol. 21:453, 1989. (3) S. B. Jepson and A. M. Golden. Pages 263-265 in: Identification of Root-Knot Nematodes (Meloidogyne species). CAB International, Wallingford, U.K., 1987. (4) G. Karssen. The plant-parasitic nematode genus, Meloidogyne Göldi, 1892 (Tylenchida) in Europe. Brill, Leiden, the Netherlands, 2002.

Occurrence of the Root-Knot Nematodes Meloidogyne incognita and M. hapla in Slovenia

The root-knot nematode Meloidogyne incognita (Kofoid & White) Chitwood is one of the most harmful species within the genus Meloidogyne. It has been detected regularly in greenhouses throughout Europe, while in the field it is restricted to the southern parts of Europe (4). M. incognita is able to parasitize more than 700 plant species and varieties, including the majority of our economically important crops (1). It has been recorded in most parts of the world, including former Yugoslavia; however, there is no data about its presence in Slovenia. In late summer of 2002, large galls were observed on roots of pepper, Capsicum annuum L., grown in a greenhouse located in Portorož near the Adriatic Coast of Slovenia. Different root-knot nematode stages, i.e., males, females, and second-stage juveniles, were isolated and morphologically identified as M. incognita (2). Additional isozyme gel electrophoresis confirmed this (3). To our knowledge, this is the first report of M. incognita from Slovenia. In addition, M. hapla Chitwood was found for the first time in a field in Slovenia. Previously, it had been detected on different host plants, all restricted to greenhouses. In October 2002, M. hapla was isolated and identified from relatively small galls of sweet pepper, C. annuum L., grown in a field near Ljubljana, located in central Slovenia. Additional resampling of the soil comfirmed the presence of M. hapla in this field. References: (1) J. D. Eisenback. Root-Knot Nematode Taxonomic Database. CD-ROM, CABI, Wallingford, UK, 1998. (2) J. D. Eisenback and H. Hirschmann Triantaphyllou. Root-knot nematodes: Meloidogyne species and races. Pages 191-274 in: Manual of Agricultural Nematology. W. R. Nickle, ed. Marcel Dekkers, Inc., New York, 1991. (3) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (4) G. Karssen. Revision of the European root-knot nematodes III on mono- and dicotyledons. Pages 119-121 in: The Plant-Parasitic Nematode Genus Meloidogyne Göldi, 1892 (Tylenchida) in Europe. Koninklijke Brill NV, Leiden, the Netherlands, 2002.

First Report of the Dagger Nematode Xiphinema rivesi, a Member of the X. americanum Group, from Slovenia

The dagger nematode, Xiphinema rivesi Dalmasso, is a virus-transmitting plant-parasitic nematode described from France (2) and also reported from Germany, Portugal, and Spain. While this species is only known from a few local sites within Europe, it is widespread in North America and also present in Peru and Pakistan (3). X. rivesi is able to transmit at least four North American nepoviruses, including Cherry rasp leaf virus, Tobacco ringspot virus, Tomato ringspot virus, and Peach rosette mosaic virus (1,4). In early spring 2002, nematodes of the X. americanum group were detected in soil samples taken near the roots of peach plants from an orchard in Bilje near Nova Gorica, Slovenia. Resampling in June and September at the same site and at an adjacent, approximately 30-year-old peach orchard confirmed the presence of the nematode in relatively high numbers (5 per 100 ml of soil). Adult females were isolated and sent for further identification to the Plant Protection Service in Wageningen, the Netherlands. The nematode was morphologically identified as X. rivesi and confirmed at the rDNA-level with internal transcribed spacer restriction fragment length polymorphism analysis. Because both sampling sites where the nematode was found are close to the Vipava River in an area of extensive stone and pome fruit production, it is likely that the nematode is also present in other orchards in this region. The origin of this quarantine nematode is unknown as there is no direct link with Slovenian orchards and import of plant material from abroad in the last decades. To our knowledge, this is the first report of X. rivesi in Slovenia and the fourth report of this species in Europe. References: (1) D. J. F. Brown et al. Phytopathology 84:646, 1994. (2) A. Dalmasso. Mem. Mus. Hist. Nat. Nouv. Série A., Zool. 61:33, 1969. (3) Data Sheets on Quarantine Pests: Xiphinema americanum sensu lato. Page 629 in: Quarantine Pest for Europe, CABI, Wallingford, UK, 1997. (4) L. W. Stobbs et al. Plant Dis. 80:105, 1996.

First Report of the Root-Knot Nematode Meloidogyne kralli in Switzerland

The root-knot nematode Meloidogyne kralli Jepson was originally described from Carex acuta L. near the Elva River in Estonia (3). This species, which was rarely detected in Russia, Poland, and the UK, was observed on Cyperaceae hosts in very wet, sandy, peat, and silt soils (1). Although marked as a rare and unusual root-knot nematode, a wider European distribution was hypothesized, particularly for natural habitats where Cyperaceae are common (4). In October 2001, we finished the first root-knot nematode survey in Switzerland, which included a protected peat-moss area named Hüttensee near Wädenswil at 660 m altitude. Small smooth galls were observed on the roots of different Carex species. These galls contained several hatched second-stage juveniles, partly swollen juveniles, and a few swollen adult females with small egg masses. No protruding egg masses were observed outside the galls and no males were observed inside. Second-stage juveniles together with males also were isolated from adhering soil. The identification of these nematodes as M. kralli was based on female and second-stage juvenile morphology, and female malate dehydrogenase and esterase isozyme phenotypes (2,4). M. kralli is the only root-knot nematode known to parasitize Cyperaceae hosts, although this nematode has other monocotyledonous hosts, such as Hordeum vulgare L. (1). To our knowledge this is the first published report of M. kralli from the Alps. References: (1) M. W. Brzeski. Nematodes of Tylenchina in Poland and Temperate Europe. Page 242 in: Muzeum i Instytut Zoologii PAN, Warszawa, Poland, 1998. (2) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (3) S. Jepson. Rev. Nematol. 6:239, 1983. (4) G. Karssen and T. van Hoenselaar. Nematologica 44:713, 1998.

First Report of the Root-Knot Nematode Meloidogyne ardenensis on Lady's Mantle in Norway

In August 2000, several small galls were observed on roots of lady's mantle (Alchemilla acutiloba Opiz) from an old grassland near Kristiansund in northern Norway. These plants, without clear above-ground symptoms, were infected with an unknown root-knot nematode. Soil and plant samples were collected in July 2001 at the previous year's location and sent for identification to the Plant Protection Service in Wageningen, the Netherlands. The smooth elongated galls included several males, swollen adult females with protruding small egg masses and hatching second-stage juveniles. Males and second-stage juveniles also were isolated from adhering soil. The root-knot nematode was identified as Meloidogyne ardenensis Santos (1). Identification was based on female, male, and second-stage juvenile morphology and female isozyme electrophoresis with malate dehydrogenase and esterase. M. ardenensis parasitizes several dicotyledonous hosts, primarily herbaceous and woody plants, and is distributed throughout Europe, with Scotland the most northern area (2). To our knowledge, this is not only the first published report of M. ardenensis in Scandinavia, but also the first report of this species on lady's mantle. References: (1) M. S. N. de A. Santos. Nematologica 13:593, 1968. (2) P. R. Thomas and D. J. F. Brown. Plant Pathol. 30:147, 1981.

Interspecific Hybridization of Meiotic Parthenogenetic Meloidogyne chitwoodi and M. fallax

ABSTRACT Hybridization between two meiotic parthenogenetic species of root-knot nematodes, Meloidogyne chitwoodi and M. fallax, was investigated in two different crossing experiments on tomato plants grown in sand. The first experiment was a controlled cross between the two species. The second experiment was a bulk mating in a 1:1 mixture of two isolates. The haploid chromosome number of the parental isolates was n = 18. Successful interspecific hybridization was obtained, and the resulting hybrids produced egg masses. In eggs, cell division was observed, but most of them were without clear differentiation and consequently were sterile. Hatched F(2) juveniles were small in number, not viable, and showed morphological distortions. In the progeny of the isolate mixture of the bulk mating experiment, parental-type females of the two isolates were present in equal numbers, and 10% of all females were nonviable hybrids. Similar ratios of parental-type and hybrid females were detected in roots of test plants grown in soil from a field sample that contained a mixture of M. chitwoodi and M. fallax populations. In the controlled cross experiment, isozyme electrophoresis of malate dehydrogenase was applied to distinguish the two species and their hybrids. In the bulk mating experiment, malate dehydrogenase, esterase, and glucose 6-phosphate dehydrogenase were used as markers, two by two simultaneously on the same individual females, providing conclusive evidence for the occurrence of hybrids. This is the first report on interspecific hybridization in Meloidogyne. The possible role of interspecific hybridization in species differentiation and interspecific exchange of genetic material within Meloidogyne is discussed.

Species identification of cyst and root-knot nematodes from potato by electrophoresis of individual females

To carry out rapid and reliable species identification of Globodera and Meloidogyne specimens, two electrophoretic methods were modified and adapted for an automated electrophoresis system (PhastSystem, Pharmacia). Proteins of individual Globodera cysts were identified using isoelectric focusing and a sensitive silver stain. Proteins of young single Meloidogyne females were separated using polyacrylamide gradient gels and stained for the isozymes esterase and malate dehydrogenase.