Soil Nematode Trophic Group Composition and Influence on Growth of Amaranthus palmeri and Parthenium hysterophorus

Weeds have a significant impact on agricultural systems. They not only cause a loss in crop yield by competing with them for resources, but they can also serve hosts for several pests and parasties such as plant parasitic nematodes casusing additional crop loss. The aim of this study was to analyze plant-nematode feedback in two major weeds, Amaranthus palmeri S Watson and Parthenium hysterophorus L. First, a field survey was conducted to determine the rhizosphere nematode trophic groups associated with these two plants in the summer of 2020 and 2021. Then a 6-week greenhouse study was conducted where the two weed species were treated with nematode communities extracted from their respective rhizospheres. Results from this study show that both weeds harbored a high number of herbivore nematodes, followed by fungivore and bacterivore nematodes. Total number of these nematodes were highly influenced by total sol carbon, pH and salinity. Under greenhouse conditions, the nematode treatment did not have any impact on the growth of P. hysterophorus but A. palmeri plants treated with nematodes had significantly higher above ground biomass. In conclusion, plant-nematode relationships are complex. Given the extent of direct damage caused by these weeds and plant parasitic nematodes in global crop production, the weeds-nematode feedback warrants further detailed studies.