A new species of entomopathogenic nematode, Steinernema sacchari n. sp., was isolated by trapping with the sugar cane borer, Eldana saccharina, from soil of a sugar cane field in the KwaZulu-Natal ...province of South Africa. The new species is morphologically characterised by the length of the infective juvenile (IJ) of 680 (630-722) μm, tail length of 64 (51-74) μm, ratio a = 19 (14-23), H% = 49 (43-57) and E% = 82 (70-109). The pattern of the lateral field of the IJ of the new species is 2, 5, 2 ridges (3, 6, 3 lines or incisures). The male of the first generation can be recognised by the long spicule of 83 (73-89) μm, gubernaculum of 61 (50-68) μm, D% = 67 (54-88) and GS% = 73 (66-81). The first generation male lacks a mucron, while the second generation male always has one. The first generation female can be recognised by the vulval lips not being raised, the possession of long double-flapped epiptygmata and the lack of a postanal swelling. Analysis of the ITS and D2D3 regions showed S. sacchari n. sp. to differ from all other Steinernema species and to belong to a new monophyletic group, the 'Cameroonian' clade, consisting of S. cameroonense, S. nyetense and S. sacchari n. sp. This group is closely related to the feltiae-kraussei-oregonense Clade III.
Steinernema nguyeni n. sp. was recovered by baiting from beneath an Olea africana tree in South Africa. The combination of morphological and molecular features suggests that S. nguyeni n. sp. is a ...member of the feltiae-kraussei-oregonense group, clustering with members of this group in Clade III. The new species is morphologically characterised by the infective juvenile body length of 737 (673-796) μm and the number of ridges in the infective juvenile lateral field is 2, 8, 2. The male of the first generation can be recognised by the spicule length of 66 (58-75) μm and a gubernaculum length of 43 (30-55) μm. The first generation female can be recognised by the vulval lips only slightly protruding and the presence of low, double-flapped epiptygmata. Analysis of the ITS and D2-D3 regions of the ribosomal DNA confirms that S. nguyeni n. sp. differs from all other known Steinernema species.
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.
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.
Abstract
During a survey for entomopathogenic nematodes in citrus orchards throughout
South Africa, a new species of Steinernema was isolated
from a citrus orchard on Rietkloof farm, near the town of ...Piketberg in the
Western Cape Province, South Africa. The nematode was isolated from soil
using the Galleria-baiting technique. Steinernema
citrae n. sp. is characterised by the following morphological
characters: third-stage infective juvenile with a body length of 754
(623-849) μm, distance from head to excretory pore of 56
(49-64) μm, tail length of 71 (63-81) μm,
and ratio E value of 110 (85-132). The lateral pattern for the new species
is 2, 7, 8, 6, 4, 2 and is not typical for the genus. Steinernema
citrae n. sp. is closely related the
feltiae-group. The body length of the IJ is close to that
of S. texanum and S. weiseri, though it
differs in body diam., the length of the pharynx and E%. The male of
S. citrae n. sp. differs from S.
feltiae in the length and shape of the spicule and body diam.
Steinernema citrae n. sp. differs from all species in
the feltiae-group in the morphology of the vulva, as it has
a single flapped, low, epiptygma. It also differs from the most closely
related species, S. feltiae, as there is no interbreeding
between the two species. In addition, the new nematode differs from other
species of the feltiae-group by characteristics of the ITS
and D2D3 regions of its rDNA.
In January 2017 Heterodera schachtii Schmidt, 1871 was collected from a potato field, formerly planted to cabbage, in the Tarlton area of South Africa. As H. schachtii from South Africa has never ...been studied molecularly, this short communication is the first of its kind for this country. Two PCR amplification primers that amplify the ITS region, including the 5.8S ribosomal gene, as well as short parts of the 18S and 28S ribosomal genes, were used for the molecular study. According to the MP consensus tree the South African population is closely related to an H. schachtii population from the Netherlands. The GenBank accession number of the ITS-rDNA sequence of the specimen is MF 754150. As voucher specimens, the terminal patterns of two cysts and four infective juveniles with accession numbers 50551 and 50552 have been deposited in the National Collection of Nematodes (NCN) at the Nematology Unit, ARC-PHP, Pretoria, South Africa. The present study includes interesting scanning electron micrographs (SEM) of the external morphology of the cyst cone, as well as the presence of the second stage juveniles in the gelatinous egg sac of the cysts. This is novel information since, according to literature, to date only eggs have been found in the egg sac of this species.
Thesis (PhD)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: A molecular, morphological and biological characterisation of the genus Globodera (Nematoda: Heteroderidae) in South Africa is ...presented. The aims of the study were to determine the spread of the genus in South Africa; to study the systematics and describe the characteristics of the group and to gain a more complete understanding of the biology of the group as agricultural pests. Surveys were conducted in the Cape Floristic Region and in all the potato-producing areas of South Africa. The surveys unearthed new species of cyst nematodes and determined the spread of Globodera rostochiensis in the country. Phylogenetic analysis of sequences from ITS-rDNA was used to infer phylogenetic relationships among cyst nematodes from South Africa. The analyses established the distinct phylogenetic positions of cyst nematode populations from South Africa relative to an array of other cyst nematode species and indicated the existence of four new species of cyst nematodes. Analysis of random amplified polymorphic DNA (RAPD) banding patterns revealed intraspecific genetic variation amongst populations of Globodera rostochiensis. In order to provide molecular protocols for the accurate identification of South African cyst nematodes, species-specific primers and restriction enzymes were tested for their ability to discriminate between local Globodera spp. A combination of the molecular, morphological and morphometric characteristics of these populations were used to describe three new species of cyst nematodes. Experiments to determine the effect of storage temperature on the viability and hatching of South African populations of G. rostochiensis, showed differences in the responses of different populations to different storage temperatures. Experiments to determine the effect of field conditions on the viability and hatching of South African populations of G. rostochiensis, indicated that a decline in viable eggs in cysts from different populations occur, but suggests that the cysts will be able to survive for much longer in these soils than was expected. Spontaneous hatch was the main contributor to the decline of viability of cysts in the soil. Recording of soil temperatures in different locations indicated that the average temperature at 20 cm depth was approximately 20°C, the optimum temperature for the reproduction of G. rostochiensis, as confirmed by in vitro reproduction tests, which also showed that multiplication and survival is influenced negatively when the temperatures rise above 25°C. Reproduction on differential potato clones confirmed the pathotype of all the South African populations of G. rostochiensis as Ro1. After assessing the reproduction of G. rostochiensis on indigenous solanaceous plants, it was concluded that none of these plants induce substantial hatch in G. rostochiensis, nor do they support multiplication of the nematode. The results of this project have an impact on inquiries at all taxonomic levels, while also having an essential practical application in nematology. Knowledge of the distribution, pathogenicity, survival potential and reproduction capacity of Globodera species in South African soils are valuable for the design of effective management strategies as well as regulatory measures.
AFRIKAANSE OPSOMMING: ‘n Molekulêre, morfologiese en biologiese karakterisering van die genus Globodera (Nematoda: Heteroderidae) in Suid-Afrika word aangebied. Die doelwitte van die studieprojek was om die verspreiding van die genus in Suid-Afrika vas te stel, om die sistematiek van die groep te bestudeer en om ‘n meer volledige begrip van die biologie van die groep te bekom. Opnames is in die Kaapse Floristiese streek en in al die aartappelproduserende gebiede in die land gedoen. Tydens die opnames is nuwe sist nematode spesies gevind en die verspreiding van Globodera rostochiensis in Suid-Afrika is vasgestel. Filogenetiese analises van die basispaar opeenvolgings van ITS-rDNS is gebruik om die filogenetiese verwantskappe tussen die sist nematodes van Suid-Afrika vas te stel. Die spesifieke filogenetiese posisies van die nematodes, relatief tot ander spesies het gedui op die teenwoordigheid van 4 nuwe spesies. ‘n Analise van “random amplified polymorphic DNA” (RAPD) bandpatrone het intraspesifieke variasie tussen populasies van G. rostochiensis uitgewys. Diagnostiese tegnieke, aan die hand van spesies-spesifieke inleiers en restriksie-ensieme, is geevalueer vir hul vermoë om Globodera spesies van mekaar te onderskei. ‘n Kombinasie van molekulére, morfologiese en morfometriese karaktertrekke is gebruik vir die beskrywing van drie nuwe Globodera spesies. Eksperimente om die effek van verskillende temperature op die lewenskragtigheid en uitbroei van Suid-Afrikaanse populasies van G. rostochiensis vas te stel, het verskille in die reaksies van die poulasies uitgewys. Eksperimente om die effek van veldtoestande op die lewenskragtigheid en uitbroei van Suid-Afrikaanse populasies van G. rostochiensis vas te stel, het gewys dat alhoewel ‘n afname in die lewenskragtigheid van eiers plaasvind, sal die siste nog steeds langer in die grond oorleef as wat verwag is. Spontane uitbroei van eiers was die grootste oorsaak van die afname in lewenskragtigheid van siste in die grond. Die monitoring van grondtemperature in verskillende lokaliteite, het gewys dat die gemiddelde temperatuur, 20 cm onder die grond, nagenoeg 20°C was. Die optimum temperatuur vir die aanteling van G. rostochiensis, soos gewys deur in vitro toetse is ook 20°C, maar ‘n skerp daling vind plaas by temperature hoer as 25°C. Aanteling op verskillende aartappel cultivars, het gewys dat die patotipe van plaaslike populasies van G. rostochiensis, Ro1 is. Toetse op inheemse Solanum plante het gewys dat die plante nie goeie gashere vir G. rostochiensis is nie. Die bevindings van hierdie studieprojek het ‘n impak op die taksonomie van die groep en kennis van die verspreiding, patogenisiteit en oorlewing van die nematodes onder Suid-Afrikaanse toestande is van waarde vir die daarstelling van effektiewe beheerstrategiee en wetstoepaslike regulasies.
