A new species of entomopathogenic nematode, Steinernema khoisanae n. sp. is
described from South Africa. The new species is characterised by
morphometrics of the infective juvenile with body length 1076 μm, narrow
body diameter of 33 μm, excretory pore 94 μm from anterior end, tail 85 μm
long, a = 33, D% = 68, H% = 57, and E% = 111. The lateral field pattern of
the new species is 2, 7, 8, 6, 4 and 2. The male of the first generation can
be recognised by the spicule and the gubernaculum shape, excretory pore
located posteriorly near the end of the pharynx, D% = 88, and SW% = 199. The
first generation female can be recognised by the non-protruding vulva and
tail bearing a prominent mucron. Steinernema khoisanae n. sp. is
characterised genetically by sequences of the internal transcribed spacers
and D2/D3 regions of 28S ribosomal DNA, by composition of their sequences
and by numerous unique, derived, nucleotide character states. Phylogenetic
trees show that S. khoisanae n. sp. and other members of the S.
glaseri-group form a monophyletic assemblage.
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.
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.
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 Deroceraspanormitanum. 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.
During a survey for entomopathogenic nematodes in the Western Cape Province
of South Africa, a new species in the genus Heterorhabditis was collected
from a peach orchard. The nematode was trapped by the insect-baiting
technique using last instar larvae of Galleria mellonella. The infective
juvenile of the new species differs from the morphologically closest
species, H. marelatus, in shorter body length 600 (550-676) vs 685 (588-700)
μm and the shorter tail of 93 (86-108) vs 107 (99-117) μm. It differs from
all other species in the vulva pattern of hermaphroditic female. The genital
papillae of the male H. safricana n. sp. are typical for species in the
megidis-group (three papillae in terminal group). The average length of the
gubernaculum is longer than that of all other species (24 vs 19-23 μm) and
the gubernaculum length as a percentage of spicule length (53.9) is less
than that of H. mexicana (56), similar to that of H. floridensis (53.8), but
larger than that of all others (51 or less). For molecular characterisation,
the species closest to H. safricana n. sp. is H. marelatus. The length of
the ITS rDNA sequence of the new species is characterised by 995 base pairs,
identical to that of H. marelatus, but differs from this species by 25
aligned positions, seven of which are unambiguous autapomorphies.
Phylogenetic trees show further evidence of a separate species status for H.
safricana n. sp.
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.
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.
Entomopathogenic nematodes (EPN) are successful biological control agents of a variety of soilborne insect pests. They have the potential to be mass-produced, using in vitro liquid culture technology, and can be formulated and sold as a biopesticide. To commercialise an EPN-based biopesticide successfully, the method of liquid mass production requires in-depth optimisation to reduce the cost of production and to increase yields, to make it affordable to the farming community. This study attempted to optimise the liquid culture protocol for the South African isolates, Steinernema jeffreyense and S. yirgalemense, by investigating the impact of cheaper medium ingredients on the recovery and yield of the liquid culture process. Studies were conducted by investigating alternative protein, lipid and nitrogen/yeast sources, compared to the more expensive laboratory-grade ingredients currently used. The results showed that egg yolk has no impact on the yield in the case of S. jeffreyense. However, for S. yirgalemense, egg yolk was shown to be a superior protein source to soy and insect-based protein in terms of nematode yield. Moreover, neither canola oil nor olive oil showed a significant difference in the yield of S. yirgalemense, with yeast extract being found to be the optimal nitrogen/yeast source. When comparing the yields with those in other liquid culture research on S. yirgalemense, yields have been successfully increased by 300%, with the cost of the nematode nutrient medium having decreased by 77%. Thus, it is imperative that, prior to a scale up to large bioreactors, the nutrient medium should be optimised to reduce the cost of production.
The occurrence and diversity of entomopathogenic nematodes (EPN) and their symbiotic bacteria was evaluated in commercial forestry plantations (Eucalyptus spp., Pinus spp. and Acacia mearnsii) and indigenous forests in South Africa. EPN were most prevalent in A. mearnsii plantations, accounting for 60.7% of the isolates, while indigenous forests, plantations of Pinus spp. and Eucalyptus spp. accounted for 35.7, 3.6 and 0% of the isolates, respectively. DNA sequences of the internal transcribed spacer (ITS) and D2-D3 28S rDNA regions were used to identify the nematode species. Four Steinernema spp. were identified, including S. citrae, S. sacchari, two undescribed species, as well as Heterorhabditis bacteriophora and H. baujardi. Heterorhabditis baujardi is reported from South Africa for the first time. Analysis of 16S rRNA of the bacteria confirmed the presence of at least three Xenorhabdus species from Steinernema isolates and two subspecies of Photorhabdus luminescens from Heterorhabditis species.