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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.

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.

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.

Abstract 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

Third-stage larvae (L3) of Steinernema feltiae exist as free-living infective juveniles (IJ), with suspended development activities. In contrast, parasitic stages (L1, L2, L4, adult) have mutualistic relations with Xenorhabdus species bacteria, along with unique morphological changes and development inside the cadaver of host insects and/or plant-parasitic nematodes. Commercial IJ strains are tolerant to cucurbitacin-containing phytonematicides, but we have scant information on how morphological adjustments in IJ are achieved. In this study, we investigated the nature of morphological adjustments in commercial S. feltiae IJ strains to Nemafric-BL phytonematicide, which contains cucurbitacin B as active ingredient. Post-72 h exposure to phytonematicide concentration, IJ specimens were fixed on mounting slides. Length (body, excretory pore to anterior end, pharynx, rectum, stoma, tail), diameter (head width, neck base, mid-body, anal body), cuticle thickness and De Man ratios were measured with a computer software programme attached to Omax light microscope. Morphometric data against increasing phytonematicide concentration exhibited either density-dependent quadratic, linear or neutral relations. Increase in body length at low phytonematicide concentration was accompanied by decrease in tail length and pharynx length during muscle contraction when IJ were still alive. After death at high phytonematicide concentration, the opposite morphometric effects ensued due to muscle relaxation. The observed changes in morphometric structures were explained on the basis of morphological adjustments that modulated volumes of pseudocoelom cavity in IJ. The modulation is intended to maintain hydrostatic pressure within permissible upper limits in order to avoid structural damage to internal organs embedded in the pseudocoelom fluids.

Shelf-life information provides end-users with the assurance that the product is still in compliance with label claims. Behavioral reaction orders of the Arrhenius model had been consistently used under fixed conditions to provide shelf-life in food products. Due to non-conformity of the cucurbitacin-containing phytonematicides to the Arrhenius behavioral reaction orders, an alternative quadratic model consistent with the behavioral reaction orders of cucurbitacins was developed under chilled (5°C at 95-98% RH) and fixed tropical (38°C at 90% RH) conditions, while room temperature constituted unfixed conditions. Sampling for cucurbitacins was done at time-frames compliant with geometric series, with cucurbitacin analysis regularly performed using high-performance liquid chromatography techniques. Under chilled conditions, neither the Arrhenius nor the quadratic model could predict the shelf-life for Nemarioc-AL phytonematicide, whereas Nemafric-BL phytonematicide had shelf-life of 35 weeks. In contrast, under tropical conditions, the positive quadratic models showed that Nemarioc-AL and Nemafric-BL phytonematicides had shelf-life of 35 and 825 weeks, respectively. In conclusion, the two phytonematicides could be stored under fixed tropical conditions to enhance the shelf-life of their active ingredients.

During a survey of soil nematodes in Iran, some known species belonging to the genus Ditylenchus were recovered from the rhizosphere of alfalfa: Ditylenchus acutus, Ditylenchus myceliophagus and Ditylenchus terricolus. Measurements and illustrations are provided for these species. A molecular study of the 28S rDNA region of the Ditylenchus species from Iran placed them in separate clades. Phylogenetic analysis indicates that Ditylenchus destructor is a monophyletic taxon. In addition, D. acutus places together with D. destructor, Ditylenchus arachis, Ditylenchus sarvarae, Ditylenchus persicus and Ditylenchus halictus in a clade. While D. myceliophagus and D. terricolus form a separate clade. Phylogenetic positions and morphometrics of D. acutus, D. myceliophagus and D. terricolus are given.

During a survey on the entomopathogenic nematodes from Kerman province of Iran, three new populations of Heterorhabditis bacteriophora were recovered from natural areas. Description, measurement and illustration are provided for these isolates. Molecular analysis on ITS sequence of new isolates of H. bacteriophora set these populations close to a population from South Africa (EU700310). H. bacteriophora and H. georgiana formed a monophyletic group. This is the first data of ITS rDNA of H. bacteriophora from south eastern Iran (Kerman province). Analysis of Iranian H. bacteriophora showed that Kerman isolates place close to Mashhad isolates.