Nematodes and the effect of seasonality in grassland habitats of South Africa.

Nematodes in South Africa have mainly been studied for their diversity and agricultural importance. However, the ecological status of nematodes and the effect of seasonal variation in local grasslands remain unknown. For this reason, a nematode study was conducted in the Telperion Nature Reserve and represented the first ecological study in a natural grassland area in South Africa. In total, 104 soil samples were collected during four consecutive seasons from 2015 until 2016 in three habitats, viz. (i) open grassland, (ii) shrubland with rocky outcrops, and (iii) riparian zone. From these the nematode community structure and soil ecosystem status were studied. In total, 93 genera from 50 families were recorded with herbivores and bacterivores being the most abundant trophic groups in all three habitats. Linear mixed models revealed that season had an overwhelmingly dominant impact on the condition, food web status, and functioning of the soil ecosystems with pairwise comparisons indicating that significantly higher values were recorded during winter. Interestingly, this seasonal shift can largely be attributed to fluctuations in the populations of only a few nematode groups (namely Aporcelaimellus, Dorylaimidae, Iotonchus, and Mononchus) with high colonizer-persister values. Although the reason for the higher abundance of specific nematode groups recorded during the winter is not explicitly clear, it is possibly linked to reduced competition from other soil fauna. This study clearly shows that further investigations are required to better understand the dynamics of grassland ecosystems.

Terrestrial Non-Parasitic Nematode Assemblages associated With Glyphosate-tolerant and Conventional Soybean-Based Cropping Systems.

Information about the effects of glyphosate on nematodes is limited and contradictory, while none existing for South African agricultural fields. The abundance and identity of non-parasitic nematodes in the rhizospheres of commercial glyphosate-tolerant and conventional (non-glyphosate-tolerant), soybean cultivars from cultivated fields, and adjacent natural vegetation (reference system) were obtained for two growing seasons. The impact of glyphosate was also investigated on non-parasitic nematodes in a 2-year soybean-maize cropping system. Thirty-two non-parasitic nematode genera were identified from soils of the three field ecosystems, with most of the genera occurring in natural vegetation (28), and less in conventional (23) and glyphosate-tolerant soybean (21). Bacterivores had the greatest diversity in soils of all three ecosystems during both seasons, while fungivores tended to be more abundant in glyphosate-tolerant soybean fields especially during the second season. Soils from the three ecosystems were disturbed and degraded with low abundance and diversity of omnivores and predators. Of the 14 genera identified from the soybean-maize cropping experiment, bacterivores dominated in terms of diversity in non-treated, and fungivores in glyphosate-treated plots. Soils from glyphosate-treated plots were degraded, less enriched and fungal-mediated, while those from non-treated plots were disturbed, enriched, and bacterial-mediated.

First report and molecular characterization of the dagger nematode, Xiphinema oxycaudatum (Nematoda, Dorylaimidae) from South Africa.

Plant-parasitic nematodes of the genus Xiphinema Cobb, 1913 comprise a complex group of nematode species, some of which are important vectors of plant viruses. During a field survey to determine the soil health of an abandoned honeybush (Cyclopia genistoides) monoculture, a high density of the dagger nematode, Xiphinema oxycaudatum Lamberti & Bleve-Zacheo, 1979 (Nematoda, Dorylaimidae), was observed in soil around the roots of honeybush plants in an abandoned farmland at Bereaville, an old mission station in the Western Cape province of South Africa. Soil samples were taken from the rhizosphere of plants and nematodes were extracted from the soil using a modified extraction tray method. Specimen of the dagger nematodes were processed for scanning electron microscopy, morphological and molecular analysis. Molecular profiling of the nematode species was done in order to give an accurate diagnosis and to effectively discriminate the nematode from other species within the Xiphinema americanum group. Phylogenetic analysis based on the D2D3 expansion segment of the 28S gene supported a close relationship of species within the americanum group, however, the protein-coding cytochrome oxidase (coxI) of the mitochondrial gene provided a useful tool for distinguishing the nematode from other species within the group. This study represents the first report of X. oxycaudatum from South Africa.

Description of two new species, Aphanolaimus strilliae n. sp. (Nematoda:br />Aphanolaimidae) and Makatinus africanus n. sp. (Nematoda: Aporcelaimidae), and SEM observations on three known species from freshwater sources in the Telperion Nature Reserve (Mpumalanga, South Africa).

Aphanolaimus strilliae n. sp. and Makatinus africanus n. sp. are described from freshwater sources in the Telperion Nature Reserve, Mpumalanga, South Africa. Aphanolaimus strilliae n. sp. is characterised by a body length of 1240-1613 µm, more than 800 body annules, lateral field originating between the first and second lateral body pore at the 34th-46th annule, first lateral body pore located at the 25th-35th annule, vagina V-shaped and bent anteriorly, 142-195 µm long uterus and 165-207 µm long tail with spinneret offset. This species is ovoviviparous and no males were found. Makatinus africanus n. sp. is characterised by a large, thick body (3228-4128 µm long, a = 30-39 wide), slightly set off lip region with amalgamated lips; 31-34 µm long odontostyle; long tongue-shaped cardia, and stout, short tail (30-43 µm long) with a small peg / digitate extension and male absent. Populations of three known species, Chronogaster africana, Eutobrilus annetteae and Neotobrilus ampiei, from fresh water at the Telperion Nature Reserve are described and scanning electron microscope graphs of these species published for the first time.

Aphelenchoides spp. (Nematoda: Aphelenchida) and Panagrolaimus leperisini (Nematoda: Rhabditida) found associated with grass seeds in the Telperion Nature Reserve, South Africa.

As part of the South African Plant-Parasitic Nematode Survey (SAPPNS), an extensive nematode diversity survey was conducted in the Telperion Nature Reserve, Mpumalanga, South Africa. During this survey, samples of grass seeds were collected. Some of these seeds yielded specimens of the genera Aphelenchoides, Aphelenchus and Panagrolaimus. Identified species include Aphelenchoides africanus, A. besseyi, A. lichenicola, A. rutgersi, A. spicomucronatus and Panagrolaimus leperisini. Four of these species are new records for South Africa and the South African populations of these species are described in this paper.

Ditylenchus sarvarae sp. n. (Tylenchina: Anguinidae) from Iran.

During a survey of soil nematodes in Iran, a new species of Ditylenchus Filipjev, 1936 was discovered. Ditylenchus sarvarae sp. n. is characterised by its body length (1.0-1.4 mm), lateral field with seven incisures and without areolation, long postuterine sac (1.8-2.8 times the corresponding body diameter) and conical female tail with pointed tip (68-89 µm long, c = 13.7-18.2, c' = 4.2-5.1). Male specimens have conical tails (64-70 µm long, c = 14.5-16.7, c' = 4.0-4.5), spicules (22-26 µm long) and gubernaculum (8-10 µm long). Measurements and illustrations are provided for this new species. A molecular study of the 28S rDNA region of D. sarvarae sp. n. demonstrates that the Iranian species belongs to a separate group compared with the other molecularly characterized species of genus Ditylenchus.

A survey of the Cape Floristic Region of South Africa for the presence of cyst nematodes (Nematoda: Heteroderidae).

A survey was performed to detect the presence of cyst nematodes in the Cape Floristic Region of South Africa. Soil was collected in the rhizosphere of the dominant plant species within blocks of indigenous vegetation and cysts were extracted from them. A total of 81 blocks of indigenous vegetation were sampled as described. Cysts were detected in 7 of these samples, representing 6 different vegetation types. One set of primers was used to amplify the ITS regions from these cysts, including the 5.8S ribosomal gene, as well as short parts of the 18S and 28S ribosomal genes. ITS-rDNA sequences from the indigenous isolates were aligned with selected sequences of other species from the Heteroderidae. Phylogenetic analyses to resolve the relationships between indigenous isolates and selected representatives of the Heteroderidae were conducted using the Maximum Parsimony method. The consensus tree resulting from alignment of the circumfenestrate cysts revealed that isolates SK18, WK1 and WK26 are included in a clade of Globodera species that parasitise non-solanaceous plants, forming a monophyletic group with G. millefolii, G. artemisiae, and an unidentified Globodera sp. from Portugal. In a tree resulting from the alignment of the Heterodera spp., isolates OK14 and WK2 are included in the Afenestrata group, forming a monophyletic group with H. orientalis.This survey unearthed at least four potentially new species of cyst nematodes, which may prove invaluable for the study of the evolution and biogeography of the group.