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  • Author or Editor: Louwrens R. Tiedt x
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Abstract

Criconema zantene n. sp., found in the rhizosphere of a Podocarpus sp. tree, is described and illustrated. Females are characterised by having 46-56 body annuli covered with tile-like scales, stylet 101-122 μm long, one lip annulus with a greater diameter than first body annulus, distinct submedian lobes, tooth-like lobes on posterior body annuli with a double row of lobes on first annulus directly posterior to vulva, a sigmoid vagina and an overhanging anterior vulval lip. Second, third and fourth stage juveniles with varying numbers of longitudinal rows of filamented scales on cuticle. Criconema princeps (Andrássy, 1962) Raski & Luc, 1985, Mesocriconema dherdei (De Grisse, 1967) Loof & De Grisse, 1989 and Paratylenchus straeleni (De Coninck, 1931) Oostenbrink, 1960 are reported from South Africa for the first time. These species are briefly discussed, illustrated and morphometrics given. Additional data is given for C. pauciannulatum Van den Berg, 1992.

In: Nematology

Pin nematodes of the genus Paratylenchus are widely distributed across the world and associated with many plant species. Morphological identification of Paratylenchus species is a difficult task because it relies on many characters with a wide range of intraspecific variation. In this study we provide morphological and molecular characterisation of several pin nematodes: Paratylenchus aquaticus, P. dianthus, P. hamatus, P. nanus and P. straeleni, collected in different states of the USA and South Africa. Paratylenchus aquaticus is reported from South Africa and Hawaii and P. nanus is found from South Africa for the first time. Morphological descriptions, morphometrics, light and scanning electron microscopic photos and drawings are given for these species. Molecular characterisation of nematodes using the D2-D3 of 28S rRNA and ITS rRNA gene sequence revealed that samples morphologically identified as P. aquaticus, P. hamatus and P. nanus indeed represent species complexes containing several species. Sequences of the rRNA genes are also provided for several unidentified Paratylenchus. Phylogenetic relationships within the genus Paratylenchus are given as inferred from the analyses of the D2-D3 of 28S rRNA and ITS rRNA gene sequences. We present here the most complete phylogenetic analysis of the genus.

In: Nematology

Worldwide interest in Phasmarhabditis originates from the successful commercialisation of P. hermaphrodita as a biological control agent against molluscs in Europe. To date, P. hermaphrodita has not been isolated from South Africa and, therefore, the formulated product may not be sold locally. During a survey for mollusc-associated nematodes, P. papillosa was dissected from the slug, Deroceras reticulatum, collected from George, South Africa. The nematode was identified using a combination of morphological, morphometric, molecular and phylogenetic techniques. Virulence tests were conducted which demonstrated that P. papillosa caused significant mortality to the European invasive slug Deroceras panormitanum. Additional data are provided in the morphometrics of the infective juvenile and in the molecular identification, using the mitochondrial cytochrome c oxidase subunit I (cox1) gene. This is the first report of P. papillosa from the African continent and of its virulence against D. panormitanum.

In: Nematology

Summary

Two isolates of Steinernema bertusi n. sp. were separately recovered from Tito, Mpumalanga, and Port Edward, Kwa Zulu Natal, South Africa. In this paper, we describe the isolates as a new entomopathogenic nematode (EPN) species using molecular and morphological methodologies. The new species belongs to the cameroonense-clade, which consists of nematodes only isolated from the African continent. Steinernema bertusi n. sp. is characterised by having the longest infective juvenile (IJ) for this clade at 716 (628-814) μm. The IJ is further characterised by a body diam. of 32 (28-36) μm and the pattern for the arrangement of the lateral ridges from head to tail is 2, 4, 5, 4, 2. The first-generation male spicule and gubernaculum length is 82 (72-88) μm and 63 (54-72) μm, respectively. Only 25% of the second-generation males possess a mucron. The first-generation females of S. bertusi n. sp. have a slightly protruding vulva, with double-flapped epiptygmata and a mucron at the posterior end. The new EPN species is most closely related to S. sacchari and is the sixth species to be included in the cameroonense-clade.

In: Nematology

Summary

Calcaridorylaimus heynsi n. sp. is the second species of the genus to be described by both morphological and molecular techniques. Morphologically, it can be distinguished from all known species of Calcaridorylaimus by a combination of the following characters: presence of advulval ornamentations, short body (0.90-1.33 mm), slightly anteriorly positioned vulva (V = 47.6 (45.8-49.8)), short odontostyle in females and males (13.1 (11.5-14.5) μm and 13.5 (12.0-18.0) μm, respectively), number of supplements (2 + 9-11), short spicules when measured along the median line (40.4 (38-42) μm) and pore-like vulval opening. It is closest to C. sirgeli, especially in the presence of advulval ornamentations and the pore-like vulva. Phylogenetic analysis based on partial D2-D3 segment of 28S rDNA sequences showed that C. heynsi n. sp. is in a well-supported sister relation with Mesodorylaimus sp. in a clade with C. cignatus and Mesodorylaimus spp. In the Bayesian tree, using partial sequences 18S rDNA, M. japonicus was the closest taxon to the new species.

In: Nematology

During a survey in the Mpumalanga province of South Africa, a Steinernema species was isolated from a soil sample taken from a litchi orchard. Steinernema litchii n. sp. can be separated from other, closely related, species in the glaseri-group by morphological, morphometric and molecular analyses. The infective third-stage juvenile of the new species has a body length of 1054 (953-1146) μm, distance from head to excretory pore of 78 (64-86) μm, as well as eight ridges (i.e., nine lines) in the mid-body region. The c-ratio of 10 (9-13) is low and the tail is long at 95 (73-105) μm. First generation males have a spicule length of 86 (76-96) μm and a gubernaculum length of 65 (59-72) μm. The tail of the first generation male lacks a mucron; that of the second generation always bears one. The genital papillae total 23 and consist of 11 pairs and an unpaired precloacal papilla. The vulva of S. litchii n. sp. has a slightly asymmetrical protuberance and short, double-flapped epiptygmata. The female has a slightly protuberant postanal swelling. Phylogenetic analysis of the internal transcribed spacer (ITS) and of the 28S (D2-D3) regions of the ribosomal DNA (rDNA) confirmed the close relationship of S. litchii n. sp. to the Karii-clade. Both morphological and molecular evidence support the species status of S. litchii n. sp.

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In: Nematology

The genus Scutellonema contains more than 40 species of spiral nematodes with enlarged phasmids called scutella. In this study, we provide morphological and molecular characterisation of S. clavicaudatum sp. n., S. brachyurus, S. bradys, S. cavenessi, S. transvaalense, S. truncatum and Scutellonema sp. A. from North and Central America, and Africa. The new species, S. clavicaudatum sp. n., was found on sugarcane in South Africa and is characterised by a lack of lip annuli as in S. africanum, S. siamense and S. truncatum. The lip region, in both males and females, is conical and marked by six large rectangular blocks separated or fused with the submedian and lateral lip sectors, which surround a round and distinct labial disc. Females of this new species also have large vaginal glands, a functional spermatheca, the lateral field posterior to the scutellum ending in a bluntly pointed shape and a clavate tail. Morphological descriptions, measurements, light and scanning electron microscopic photos and drawings are also given for S. bradys, S. cavenessi, S. transvaalense and S. truncatum. The study of spiral nematode samples from Florida, USA, confirmed the presence of a morphologically and genetically atypical populations of S. bradys. The morphology of the S. bradys population from Bermuda grass in pasture land from central Florida fits that of type specimens of this species, but differs in having a truncate tail terminus rather than round and also a prominent spermatheca filled with flagellate spermatozoa. Other Florida Scutellonema samples analysed in this study belonged to S. cavenessi, a species native to West Africa. This is the first report of S. cavenessi in Florida, where it parasitises the ornamental plant Sansevieria trifasciata. Our study showed a high level of intraspecific variation for Scutellonema rRNA and mtDNA genes, which can reach 5.6% for the D2-D3 of 28S rRNA, 12.9% for the ITS rRNA genes and 14.4% for the COI gene. Phylogenetic relationships within Scutellonema are given as inferred from the analyses of the D2-D3 of 28S rRNA, ITS rRNA and the COI mtDNA gene sequences.

In: Nematology

A new cyst nematode, herein described as Globodera capensis n. sp., was found on several farms in the Swartland and Sandveld areas in South Africa. As the host plant of G. capensis n. sp. is currently unknown, the species is represented by cysts and second-stage juveniles (J2) only. The cysts have a spherical form, are yellow to dark brown in colour and have bullae (vulval bodies) and subcuticular punctations. Six to 20 cuticular ridges/lines are present between the anus and vulval basin, Granek’s ratio is 0.7-4.0, the vulval basin diam. is 16-28.5 μm and vulval basin to anus distance is 19-60 μm. The J2 is 430-528 μm long and the stylet is 23-28 μm long with anteriorly flattened to rounded stylet knobs. These stages are morphologically and morphometrically very near to, or indistinguishable from PCN, G. artemisiae, G. millefolii and G. tabacum tabacum. It can be distinguished by the molecular characteristics of the ITS-region of the ribosomal DNA. Pairwise distances between closely related Globodera species show that G. capensis n. sp. differs the least in number of base differences per sequence from G. millefolii (63-64 bp) and most from an undescribed Globodera from Chile (72-73 bp). Phylogenetic relationships of G. capensis n. sp. with selected species of Punctoderinae, inferred from ITS-rRNA sequences by using the Maximum Likelihood method, indicate that G. capensis n. sp. occupies a basal position within a lineage of Globodera species from Europe, Asia and New Zealand that parasitises non-solanaceous plants. For diagnostic purposes, digestion of the ITS1 with AluI will distinguish G. capensis n. sp. from G. mexicana, G. pallida, G. rostochiensis and G. tabacum, but not from G. artemisiae, G. millefolii and G. zelandica, whilst FauI will distinguish G. capensis n. sp. from all the other Globodera species tested.

In: Nematology

During recent collections in South Africa, two species of Criconemoides were found. Criconemoides brevistylus is described and illustrated from a golf course in KwaZulu-Natal Province. It is compared with several closely related species, and three previously described species (C. helicus, C. onostris and C. paronostris) are regarded as junior synonyms of C. brevistylus. Criconemoides obtusicaudatus is described and illustrated from a maize field in Limpopo Province. The male of the species is described for the first time. Molecular characterisation of C. brevistylus and C. obtusicaudatus using the D2-D3 expansions segments of 28S rRNA and ITS rRNA gene sequences are provided. Phylogenetic relationships of these species with other Criconemoides are discussed.

In: Nematology

Abstract

Two Hemicycliophora species, H. lutosa and H. typica, found in samples from fallow soil and sugarcane soil in South Africa, were studied morphologically and, for the first time, molecularly. Diagnostic PCR-IT-rRNA-RFLP profiles generated by five restriction enzymes are provided. Study of phylogenetic relationships using D2-D3 expansion segment of 28S rRNA gene sequences revealed that H. lutosa was related to H. poranga. Hemicycliophora lutosa and H. poranga are compared morphologically. SEM photographs are given for H. typica and for H. lutosa for the first time. The male of H. typica represents a first report for South Africa.

In: Nematology