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During a survey on soil nematode diversity, the soil samples were collected from Field-1 (3-months-not-used land), Field-2 (5-years-not-disturbed land), Field-3 (the rhizosphere of tomatoes), and Field-4 (natural land, not disturbed for 50 years), in Dalmada, Limpopo Province, South Africa. A total of 25 nematode genera were found to be associated with the surveyed plant species. The result showed Acrobeloides, Aphelenchus, Aporcella, Ditylenchus, Mesorhabditis, Pratylenchus, and Rotylenchus with a 100% frequency of occurrence. Meloidogyne was detected only in association with Field-3, with a low frequency of occurrence (25%). The study of the relationship between nematodes with physicochemical properties in the soil using Pearson correlation revealed that phosphate of the soil had a positive correlation (r = 0.977) with Bitylenchus and Pseudacrobeles species. In contrast, pH strongly correlated with Nanidorus (r = 0.928), Trypilina (r = 0.925), Xiphinema (r = 0.925), and Zeldia (r = 0.860). The principal component analysis placed Field-4 and Field-3 in two groups, indicating the biodiversity dynamics among the two locations. Soil texture showed that clay was correlated with Rotylenchulus. In contrast, soil texture had no effect on Meloidogyne. The Shannon index was the lowest (1.7) for Field-1 in Dalmada compared to the other Fields, indicating lower nematode diversity. The structure index showed that Field-2 was disturbed with a low C:N ratio. In contrast, Field-3 and Field-4 had suppressive soil but matured and fertile. The network analysis showed that Panagrolaimus was only found in Field-4 and was the most engaging genus describing soil quality in the soil system in Dalmada. In conclusion, Field-2 showed a high diversity of free-living nematodes than the disturbed land of tomatoes. Additionally, plant-parasitic nematodes numbered more in the rhizosphere of tomatoes. The results suggest that the soil nematodes, especially free-living bacterivores, may mediate the effects of ecosystem disturbance on soil health.

The soil microbiome is crucial for the environment and significantly impacts the ecosystem. Understanding the microbiome and its interaction with soil microorganisms is essential for improving ecological and environmental strategies. In this study, Xiphinema elongatum nematodes were collected from water berry in Sovenga Hills, Limpopo Province, South Africa, and were analyzed their associated bacterial communities using metabarcoding analysis. The findings revealed that X. elongatum forms associations with a wide range of bacterial species. Among the most abundant species identified, we found Sphingomonas sp., a bacterial species commonly found in various habitats and primarily beneficial to plants, and Candidatus Xiphinematobacter , a bacterial species commonly found in nematode species of Xiphinema as an endosymbiont. The analysis using principal component analysis (PCA) revealed that the abundance of X. elongatum in the soil is inversely correlated with clay content ( r = -0.52) and soil pH levels ( r = -0.98), and directly correlated with soil sand content ( r  = 0.88). This study provides valuable insights into the bacterial species associated with plant-parasitic nematodes in trees in South Africa. It underscores the presence of various potentially detrimental and beneficial nematode-associated bacteria. The results could potentially influence the overall quality of the soil, leading to implications for the productivity and yield of fruit crops. Additionally, the results help us understand the interaction between bacteria and X. elongatum .

Soil nematodes are sensitive indicators of soil ecosystem functioning, yet their seasonal dynamics across tree hosts and edaphic gradients are poorly documented in southern Africa. We sampled rhizosphere soils of pomegranate (Punica granatum), lemon (Citrus sp.), and fig (Ficus carica) across four seasons in Sovenga Hills, Limpopo Province. We explicitly state that the rhizospheres of pomegranate, lemon, and fig were selected because they represent widely cultivated fruit trees in smallholder systems across Limpopo Province, where soil management practices and climate variability may influence nematode community dynamics. The hypothesis is that nematode assemblages exhibit seasonal shifts in diversity, trophic composition, and ecological indices across these hosts. The nematode genera were identified morphologically using standard diagnostic keys. A total of 29 genera were recorded. Bacterivores and herbivores dominated the assemblage, while fungivores, predators and omnivores were less abundant. Notably, Ditylenchus (fungivores) exhibited the highest Prominence Value (PV = 7926.1) and occurred in 83% of samples (Frequency of Occurrence (FO%) = 83), followed by a plant-parasitic nematode, namely Rotylenchulus (PV = 3279.8; FO% = 83%). Shannon diversity ranged from 2.09–2.34, and Maturity Index (MI) varied from 2.41–2.78 across seasons. Food-web indicators showed an enrichment index (EI) of 17–38 and structure index (SI) of 49–71, suggesting a moderately structured but dynamic soil food web. Spring communities exhibited the highest abundance (mean 471.7 individuals), biomass (0.49 µg), and composite/metabolic footprints, while autumn showed higher maturity and structural indices; summer recorded the lowest abundance and biomass. Principal component analysis (PCA) showed a total of 40.78% variation among the samples collected from different seasons and separated winter communities from autumn/spring ones (which partially overlapped). Soil pH, nitrate, phosphate, texture (sand/clay/silt), and electrical conductivity strongly associated with the observed seasonal patterns. The observed seasonal trends suggest that PV and FO% may serve as informative indicators for tracking shifts in nematode assemblages, but these patterns were not statistically significant (p > 0.05) and should therefore be considered preliminary rather than conclusive. These results highlight pronounced seasonal shifts in nematode assemblages and confirm PV and FO% as useful metrics for monitoring soil ecosystem dynamics.

After hatch, second-stage juveniles (J2) of root-knot ( Meloidogyne species) nematodes could spend at least 12 weeks in soil solutions searching for penetration sites of suitable host plants. The external covering of nematodes, the cuticle, consists of various layers that contain glycoproteins, lipids, soluble proteins (collagens) and insoluble proteins (cuticulins). Generally, cucurbitacins are lipophilic, but there is scant information on how cuticular proteins relate to these complex terpenoids. A study was conducted to investigate the nature and extent of damage post-exposure of J2 to a wide range of Nemafric-BL phytonematicide concentrations. Post-72 h exposure to Nemafric-BL phytonematicide, nematode morphometrics versus phytonematicides exhibited either negative quadratic, positive quadratic, or negative linear relations, with the models explained by significant ( P  < 0.05) associations (R-squared). Similarly, total proteins versus phytonematicide exhibited significant negative quadratic relations. The principal component analysis indicated that concentration level of 2–4% of Nemafric-BL phytonematicide have the highest impact on the morphometric changes of J2. In conclusion, the nature and extent of damage suggested that Nemafric-BL phytonematicide was highly nematicidal as opposed to being nematostatic, thereby explaining its potent suppressive effects on nematode population densities.

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = −0.770) and Hemicycliophora sp. (r = −0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = −0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil.

This study investigates the impact of golden moles (Amblysomus sp.) on the abundance, diversity, and community structure of nematodes in kweek grass (Cynodon dactylon) within the Sovenga Hills of Limpopo Province, South Africa. Eight sites were sampled: four with active moles (sites: M1–M4), and four without (sites: T1–T4). Eighty soil samples were collected, and nematodes were extracted. A total of 23 nematode genera were identified, including 3 plant-parasitic and 20 free-living genera. The frequency of occurrence (FO) data showed that Aphelenchus sp. and Acrobeles sp. were the most prevalent nematodes, each occurring in 87.5% of the samples. In contrast, Eucephalobus sp., Tripylina sp., Discolaimus sp., and Tylenchus sp. had the lowest FO, appearing in only 12.5% of samples. The diversity indices (the Shannon index, the maturity index, and the plant-parasitic index) showed significant differences between the two environments. The Shannon index (H′) and maturity index were the most effective indicators of ecosystem disturbance. The lowest H′ was found at T4 (1.7 ± 0.2), compared with a higher value at M1 (2.4 ± 0.1). The principal component analysis (PCA) results revealed a positive correlation between Ditylenchus and the clay in the soil. In addition, Cervidellus was associated with soil pH. Network analysis revealed increased complexity in the nematode community structure at mole-affected sites. These findings suggest that mole activity alters soil properties and indirectly affects nematode diversity and trophic structure.

The Limpopo Province, situated in the northern part of South Africa, is mainly comprising rural areas that lack adequate facilities for drinking water. Boreholes are the main source of drinking water in rural and urbanized areas of Limpopo Province. Sixty-three water samples, from three locations in Limpopo Province, namely Mankweng, Dalmada, and Polokwane, plus two samples from a river in Magoebaskloof and still water as controls, were collected and subjected to analysis. The Sodium Absorption Ratio (SAR) analysis ranged from 1.4 to 35.6, revealing that 25% of the samples from Mankweng bear low quality with a high amount of sodium. Piper plot showed that two major water types exist in the samples, 33% and 67% of the water samples were of Na-Cl and Ca-Cl types, respectively. To identify the leading natural and anthropogenic processes causing variation in groundwater chemistry, principal component analysis (PCA) was used. The most detected heavy metal was V (vanadium) with 0.00 to 0.59 (mg/mL). The PCA results grouped all water samples from Dalmada together. However, the water samples from Mankweng were divided into three groups by PCA, with borehole samples showing a correlation with heavy metals. In conclusion, the study revealed that natural and anthropogenic activities cause groundwater variation in the Limpopo Province. All the boreholes sampled showed the presence of total coliform, but no E. coli was detected. In addition, regarding microbial contamination, water samples were suitable for drinking and irrigation purposes.

Turfloop constitutes an area in Mankweng, situated in the Limpopo Province of South Africa, where several villages are home to smallholder farmers who specialize in vegetable farming. Among the most crucial crops cultivated in this region is tomato, a fruit that has gained significant commercial importance due to its high demand and versatility in various culinary applications. To determine the relationship of plant-parasitic nematodes and soil physicochemical properties, soil samples were collected from tomato fields. Overall, our results showed that seven nematode genera were in the tomato fields. There was a significant positive correlation between the number of Meloidogyne and potassium (r = 0.903) and a negative correlation with Na (r = −0.684). In contrast, there was no association between the number of Meloidogyne spp. and the pH and texture of the fields. The number of Criconema in the field was negatively correlated with pH (r = −0.732). Soil texture percentages, including clay (r = 0.744), sand (r = −0.744), and silt (r = 0.706), were only correlated with the number of Criconema. The number of dagger nematodes, Xiphinema, was only correlated negatively with NH4+ (r = −0.589) and positively with boron (B) (r = 0.779). None of the soil variables were correlated with the number of Pratylenchus. The principal component analysis (PCA) placed soil samples of tomatoes together, in which the number of Meloidogyne was not correlated to any soil sample site. In conclusion, plant-parasitic nematodes that were associated with tomatoes are of high economic importance as they can reduce the yield. Criconema was found to be sensitive to the soil’s physicochemical properties. In addition, Helicotylenchus was found in all soil samples. Our results suggest that the plant-parasitic nematodes in tomatoes have high diversity with the potential to reduce crop production.

Lance nematodes (Hoplolaimus spp.) feed on the roots of various plants, including key horticultural products. An investigation of the genetic diversity and structure of six Hoplolaimus species, utilizing the cytochrome c oxidase I (COI) of the mtDNA gene, was based on 174 sequences available on the NCBI. Based on the COI of mtDNA, the haplotype analysis revealed 44 haplotypes. Nucleotide diversity was low among all species of Hoplolaimus, except for H. magnistylus (π = 0.04915) and H. stephanus (π = 0.06746). In contrast, haplotype diversity (Hd) was high, especially for H. stephanus (Hd = 0.89) and H. pararobustus (Hd = 0.90). Phylogenetic analysis grouped the various populations into eight clades, and the result showed that H. magnistylus was placed in three different clades, which showed high variability in haplotype supported by the haplotype network. Neutrality tests and mismatch distribution based on the mtDNA supported the hypothesis of a constant population with no expansion in Hoplolaimus, except for H. concaudajuvencus (Tajima (D) = −0.84971) and H. columbus (Tajima (D) = −0.87674). In conclusion, genetic analysis showed a neutral evolution amongst the Hoplolaimus species. The result of the present study provides a better insight into the Hoplolaimus species toward species delimitation and managing this plant-parasitic nematode in various crops.

Mononchida members are predatory nematodes with the potential to reduce the number of plant-parasitic nematodes in the soil. During a survey on Mononchida in Iran, several populations of Mylonchulus were recovered from various localities. A population of M. hawaiiensis was studied using 18S rDNA. The phylogenetic analysis using Bayesian inference placed the sequenced M. hawiinesis (OP210758) together with other M. hawaiiensis from Japan (AB361438-AB361442) with a 1.00 posterior probability support. In addition, morphological differences between six Mylonchulus (Nematoda; order: Mononchida; Family: Mylonchulidae) populations were investigated in Iran using discriminant analyses (DA), PERMANOVA, and principal coordinate analysis (PCoA). The purpose was to evaluate the efficacy of PCoA and DA in separating the Mylonchulus species, namely M. sigmaturus, M. paitensis, M. lacustris, M. brachyuris, M. kermaninesis, and M. hawaiiensis. To achieve this, 16 morphometric measurements (body length, a, b, c, c′, V, G1, G2, buccal cavity length, buccal cavity width, dorsal tooth apex, dorsal tooth length, neck length, amphid from anterior end, rectum, and tail length) were made on 160 specimens. The analysis of variance showed that all features were significantly different among the species, except a, b, and the amphid position from the anterior end and tail length. The stepwise discriminant analysis revealed that body length, tail length, neck length, and c′ value were the four most discriminating variables useful to distinguish clearly the six species of Mylonchulus. The variables with strong discriminatory power correctly classified 98.87% of individuals from Iran’s sample of known Mylonchulus species. The results provide a morphometric basis for effectively distinguishing Mylonchulus species.