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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 glyphosatetolerant 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.

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The host status of South African adapted, genetically modified (GM) glyphosate-tolerant soybean genotypes to root-knot (field and glasshouse) and lesion (field) nematodes were assessed. Analyses of root and soil samples of 29 genotypes (collected from seven production areas during the 2014/15 season) enabled the identification of nine plant-parasitic nematode genera and 10 species. Predominant endoparasitic genera in root samples were Meloidogyne (Meloidogyne incognita and M. javanica) and Pratylenchus (Pratylenchus brachyurus, P. zeae and P. teres). Rotylenchulus parvus was the predominant semi-endoparasite in soil, followed by Scutellonema brachyurus and Helicotylenchus sp. Only ‘PAN 1583 R’ and ‘PAN 1521 R’ maintained less than 10% of the Meloidogyne spp. densities present in roots of the most susceptible genotype, while all genotypes were susceptible to the Pratylenchus spp. The host status of 36 soybean genotypes to M. incognita infection, evaluated in two follow-up glasshouse experiments terminated 56 days after inoculation of ca. 1000 M. incognita eggs and second-stage juveniles (J2) per seedling, varied substantially for final population density (Pf), reproduction factor (Rf) and relative percentage susceptibility (%S). Only ‘PRF-GCI7’ and the resistant reference ‘LS 5995’ had Rfs < 1 for both experiments, despite higher minimum and maximum temperatures recorded for the second experiment. Continuous evaluation of soybean genotypes for their host status to predominant nematode pests and their use to reduce densities of such species in producer’s fields are crucial to enable sustainable crop production, and contribute towards food provision and security.