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

Abstract

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.

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

“…Substantial yield losses in maize (up to 60%) (Riekert and Henshaw, 1998) and soybean (up to 100%) ( Smit and De Beer, 1998 ; Fourie et al, 2013 ) due to infection by this genus demonstrate its adverse impact on crop production. Moreover, Helicotylenchus , Rotylenchulus , and Scutellonema are also abundant in local crop fields, indicating their potential impact on crop production ( Fourie et al, 2001 ; Bekker et al, 2016 ; Mbatyoti et al, 2018 ). Therefore, grasslands may act as reservoirs for herbivores that pose a threat to crop production should such areas be converted into agricultural fields.…”

“…Studying the nematode communities of grasslands is not only relevant from an ecological perspective, but also from a conservation perspective. Nematodes are valuable indicators of soil ecosystem disturbance affected by, for example, agricultural activities and climate change (Ferris and Bongers, 2009;Zhong et al, 2017;Zhang et al, 2020). Therefore, studying the nematode communities of natural, undisturbed grasslands will generate valuable baseline data for monitoring disturbance and implementing conservation policies.…”