Weeds have been reported to host a high number of plant-parasitic nematodes. The aim of this study was to analyze plant nematode feedback in two major weeds, Amaranthus palmeri and Parthenium hysterophorus. This study was conducted in two phases. In the first phase, we conducted a field survey to determine the rhizosphere nematode community associated with the two plants in the summer of 2020 and 2021. We then conducted a 6-week greenhouse study to determine the impact of soil nematodes on the growth of both A. palmeri and P. hysterophorus . During the 6-week period, we treated both weed species with the nematode communities extracted from their respective rhizospheres in the field.
Results/Conclusions
Our results show that both weeds harbored a high number of herbivore nematodes, followed by fungivore and bacterivore nematodes. Results of the greenhouse study showed that, while these two plant species harbored a high number of herbivore nematodes in their rhizosphere, the nematode treatment did not have any impact on the growth of P. hysterophorus and had a positive impact on the growth of A. palmeri . Our results indicate that A. palmeri harbors a high number of Helicotylenchus spp. in its rhizosphere and can potentially benefit from their presence in small numbers. In addition, the decline in the numbers of herbivore nematodes and the increase of bacterivore nematodes at the end of six weeks, in our pot experiment, indicate that the two weeds do not serve as direct hosts to the herbivore nematodes. Given the extent of direct damage caused by A. palmeri in global crop production, the plant nematode feedback in A. palmeri warrants further detailed studies.
