The near-full-length 18S ribosomal DNA (rDNA) gene and internal transcribed spacer 1 region were amplified and sequenced from 52 nematode populations belonging to 28 representative species in 13 families recovered from turfgrasses in North Carolina (38 populations) and South Carolina (14 populations). This study also included 13 nematode populations from eight other plant hosts from North Carolina for comparison. Nematodes were molecularly characterized and the phylogenetic relationships were explored based on 18S rDNA sequences. Phylogenetic analysis using Bayesian inference was performed using five groups of the plant-parasitic nematode populations Tylenchids, Criconematids, Longidorids, Xiphinematids, and Trichodorids. The 65 nematode populations were clustered correspondingly within appropriate positions of 13 families, including Belonolaimidae, Caloosiidae, Criconematidae, Dolichodoridae, Hemicycliophoridae, Hoplolaimidae, Heteroderidae, Longidoridae, Meloidogynidae, Paratylenchidae, Pratylenchidae, Telotylenchidae, and Trichodoridae. This study confirms previous morphological-based identification of the plant-parasitic nematode species found in turfgrasses and provides a framework for future studies of plant-parasitic nematodes associated with turfgrasses based upon DNA sequences and phylogenetic relationships.
Root-knot nematodes (Meloidogyne spp.) are the most common and destructive plant-parasitic nematode group worldwide and adversely influence both crop quality and yield. In this study, a total of 51 root-knot nematode populations from turfgrasses were tested, of which 44 were from North Carolina, 6 from South Carolina and 1 from Virginia. Molecular characterisation was performed on these samples by DNA sequencing on the ribosomal DNA 18S, ITS and 28S D2/D3. Species-specific primers were developed to identify turfgrass root-knot nematode through simplex or duplex PCR. Four species were identified, including M. marylandi Jepson & Golden in Jepson, 1987, M. graminis (Sledge & Golden, 1964) Whitehead, 1968, M. incognita (Kofoid & White, 1919) Chitwood, 1949 and M. naasi Franklin, 1965 through a combined analysis of DNA sequencing and PCR by species-specific primers. M. marylandi has been reported from North Carolina and South Carolina for the first time. Molecular diagnosis using PCR by species-specific primers provides a rapid and cheap species identification approach for turfgrass root-knot nematodes.
The purposes of this paper are to clarify the taxonomic status of the fig-pollinating wasp associateSchistonchussensu lato(Nematoda: Aphelenchoididae) and to suggest directions for future research on the systematics, life history and ecology of the group. Molecular phylogenetic analyses suggest thatSchistonchus s.l.is polyphyletic, and the composition of the three major clades is outlined, together with information on nematode morphology, plant host species, associated pollinating wasp species, and distribution. Biological information and collection data is presented forSchistonchus s.l.fromFicussycones (Moracea) in Africa, Australia, Asia and Central America, and its putative phylogeny is discussed based on molecular and morphological evidence. Both wasps and figs are millions of years old and have worldwide distribution in tropical areas,i.e., opportunities forSchistonchus s.l.-like nematodes to have evolved could have occurred more than once. In addition, figs and their pollinating wasps have variable life histories, which could have provided opportunities forSchistonchus s.l.to also develop different life histories. However, these histories occur inside fig sycones and in association with wasps, which has apparently led to evolutionary convergence and extreme morphological conservatism. Diagnostic characters and their states, derived from examination of described species and morphospecies ofSchistonchus s.l.and informed by molecular phylogenetic inferences, are discussed and illustrated.Schistonchus sensu strictois redefined, andFicophagusn. gen. andMartinineman. gen. are proposed.Schistonchus s.s.is morphologically characterised by having the excretory pore opening in the region of, or posterior to, the metacorpus;Ficophagusn. gen. by having the excretory pore opening very near the cephalic region; andMartinineman. gen. by having it opening at the anterior end of the metacorpus. Several species ofSchistonchus s.s.have a labial disc, but there is no evidence of this in eitherFicophagusn. gen. orMartinineman. gen.
Acrostichus dauer larvae (JIII) were recovered during dissections of the palmetto weevil, Rhynchophorus cruentatus, from southern Florida, and the palm weevil, R. palmarum, from Colombia, Costa Rica and Trinidad. Based upon morphological and molecular studies, the four isolates are conspecific and are described herein as A. rhynchophori n. sp. Acrostichus rhynchophori n. sp. is characterised by narrow, flap-like dorsal tooth, female gonads not reflexed to the level of the vulva, male spicule and gubernaculum morphology, i.e., spicule with small and indistinct manubrium embedded in lamina/calomus complex, strong expansion just posterior to manubrium and smoothly curved and smoothly tapered lamina/calomus complex, and gubernaculum with claw-like anterior end in lateral view and three distal branches in ventral view. The new species is distinguished from A. superbus by morphology of the spicule and gubernaculum. Type specimens of four other Acrostichus species, originally described from bark beetles from North America, i.e., A. concolor, A. gubernatus, A. ponderosus and A. taedus, were re-examined and photo-documented.
A nematode recovered from syconia of Ficus hirta from Guangzhou, P. R. China, during a survey of nematode biodiversity from 2007 to 2009, is described herein as Schistonchus hirtus n. sp. and is differentiated by a combination of morphological characters, including excretory pore (EP) located near the metacorpus, a short post-uterine sac (PUS) (0.5 vulval body diam. (VBD) long), rose thorn-shaped spicules, amoeboid sperm, absence of gubernaculum, three pairs of subventral papillae on the male tail, host-Ficus and host-wasp species and DNA sequence data. Morphologically, S. hirtus n. sp. is close to S. centerae, S. altermacrophylla, S. aureus, S. laevigatus and S. virens based upon the length of the PUS (about 0.5 VBD long). However, the relative position of the EP in S. hirtus n. sp. is very different from these species (near metacorpus vs near head). With regard to the EP character, S. hirtus n. sp. is very similar to S. macrophylla, S. guangzhouensis and S. caprifici where the EP is at metacorpus level. However, S. hirtus n. sp. differs from S. macrophylla and S. guangzhouensis by possessing a shorter PUS and smaller spicules, and differs from S. caprifici by a shorter female stylet and smaller spicules. Schistonchus hirtus n. sp. was easily differentiated from other sequenced species by the proportion of parsimony informative changes in the partial small subunit rRNA gene (SSU) and D2/D3 expansion segments of the large subunit rRNA gene (LSU). Phylogenetic analysis with SSU sequences suggests that S. hirtus n. sp. is in a highly supported monophyletic clade with Aphelenchoides and Laimaphelenchus and is polyphyletic to other sequenced Schistonchus species. With LSU sequence data, it forms a clade with S. caprifici and they appear polyphyletic relative to S. guangzhouensis, S. centerae, S. aureus, S. laevigatus and S. virens.
Myolaimus byersi n. sp., a phoretic associate of the crane fly, Limonia (Rhipidia) schwarzi (Diptera: Limoniidae), was recovered from moist and decaying tissue from the crown shaft of a living spindle palm, Hyophorbe verschaffeltii, in southern Florida and is described herein. Dauers were carried in the abdominal folds of male and female L. schwarzi. Examination of the highly mobile crane fly larvae and pupae confirmed that the dauers were externally associated with the cuticle. Dauers from crane flies were culturable to adults on 1/20 strength TSB agar. The association appears to be relatively host specific. SEM studies, early embryonic development, dauers, molecular data and TEM ultrastructural comparisons of the stoma, sensory structures and sperm are used to discuss the relative placement of Myolaimus within the Nematoda. The stoma resembles diplogastrids in being strongly anisomorphic with an enlarged dorsal sector of the stegostom, yet also resembles rhabditids in having three triangular flaps in the metastegostom and matches cephalobs and panagrolaims in having a pharyngeal collar with two sets of three interradial muscles followed by two sets of six adradial muscles. The ultrastructure of the cheilostom epidermis shows a high degree of conservation with several Rhabditida. The sperm of M. byersi n. sp. is nearly identical to that of Caenorhabditis elegans. In early cell division, M. byersi n. sp. is closest to Parascaris equorum followed by C. elegans. Myolaimus apparently represents a divergent lineage that has followed a non-coalescing trajectory for a long time, allowing it to retain some highly conserved characters while also developing some surprisingly unique features, such as a baggy cuticle and males that lack a gubernaculum or spicules. Giblin-Davis, 1997). Myolaimus is very interesting because it is the only known free-living nematode that has evolved a unique mating strategy involving the loss of its gubernaculum and spicules (Fürst von Lieven et al., 2005), the copulatory structures used by almost all other male nematodes to anchor and mate with females. In addition, members of the genus possess a uniquely baggy cuticle that drapes loosely around © Koninklijke Brill NV, Leiden, 2010 M. heterurus in
An emerging threat to agriculture, Meloidogyne enterolobii Yang & Eisenback, 1983 is a tropical species and considered to be the most damaging root-knot nematode (RKN) in the world because of its wide host range, aggressiveness, and ability to overcome resistance to RKN in many crops. It was first detected in the USA on ornamental plants in Florida in 2001, but has since been identified in North Carolina, South Carolina and Louisiana. Several thousand RKN populations were collected from North Carolina field crops, ornamental plants and turfgrasses for species identification in the Nematode Assay Laboratory in the North Carolina Department of Agriculture & Consumer Services (NCDA&CS). From 2006 to 2019, root systems showing galling symptoms were dissected under the microscope and females were obtained for DNA analysis. When only soil samples were submitted, the second-stage juveniles or males were used instead. Molecular characterization was performed by PCR using species-specific primers and DNA sequencing on the ribosomal DNA 18S-ITS1-5.8S and 28S D2/D3, and mitochondrial DNA CoxII-16S. One hundred and thirty-five representative RKN populations from North Carolina were characterized and identified as M. enterolobii. Six populations from China where the species was originally described were included in this study for identity confirmation and comparison. As of December 2019, M. enterolobii was confirmed from a limited number of fields in 11 North Carolina counties, including Columbus, Craven, Greene, Harnett, Johnston, Lenoir, Nash, Pitt, Sampson, Wayne and Wilson. Currently, M. enterolobii is the most important emerging RKN species in the USA and causes severe damage to agronomic and horticultural crops, especially sweetpotato in North Carolina.
Schistonchus microcarpus n. sp. was recovered from the syconia of Ficus microcarpa from Shenzhen and Guangzhou, Guangdong Province, China, during a survey of nematode biodiversity from 2007 to 2009. It is characterised by possessing the combined characters of a short post-uterine sac (PUS) (3-11 μm or <0.4 vulval body diam. (VBD) long), excretory pore located just posterior to the head but anterior to the conus level of the stylet, prominent amphids, three pairs of subventral papillae on the male tail (one pair adcloacal, one pair halfway between cloaca and tail terminus, and one pair near tail tip), unique recurved and sickleshaped spicules with finely rounded tip with cucullus, amoeboid sperm, and rounded male tail tip with or without mucron. Schistonchus microcarpus n. sp. is morphologically differentiated from all other described species in this genus by the possession of a spicule with a cucullus on the tip. Schistonchus microcarpus n. sp. was easily differentiated from other sequenced species by the partial small subunit rRNA gene (SSU) and D3 expansion segments of the large subunit rRNA gene (LSU). Phylogenetic analysis with partial SSU sequences suggests that S. microcarpus n. sp. is in a highly supported monophyletic clade with sequenced Schistonchus species except for S. hirtus. Based upon inferences using D3 LSU sequence data, it forms a clade with an undescribed species of Schistonchus ex F. benjamini from Australia and is part of a larger clade of Schistonchus that mostly share the character of an anteriorly placed excretory pore. Sequences of partial mtDNA COI (590 bp) from males of S. microcarpus n. sp. with and without a mucronate tail tip were identical, proving that these two morphotypes are conspecific.
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