Characterizing A Soybean Cyst Nematode Mycobiome From Waseca Long-term Soy-corn Rotation Experiment in Search of Fungal Biological Control Agents and Bio-nematicides

Abstract

The Soybean Cyst Nematode (SCN, Heterodera glycines) is the most economically consequential pathogen of the soybean plants worldwide. Integrated management of this pathogen currently relies on using genetic resistance and crop rotation with a non-host such as corn. Additional help from chemical and biological agents could lead to better management of this pathogen by supplementing the biological limitations of genetic resistance and economical limitations of using a non-host crop. Identifying natural antagonists of SCN is a good first step towards finding potential biocontrol agents. In this study, I have cultured and identified fungi from 6000 SCN cysts obtained from a long-term soy-corn rotation experiment with no nematicide applied, over a period of 3 years. ITS barcode sequences from all the isolates (about 5000 from 6000 cysts) obtained from these cysts, as well as their colony morphologies were used to identify the fungi against NCBI database. ITS sequences were then used to cluster them into 326 OTU groups based on at least 99% sequence similarity. OTU cluster representatives were evaluated in vitro for their ability to produce anti-nemic metabolites and to directly parasitize SCN eggs. Ten high anti-nemic metabolite producers (‘A’ through ‘J’) and ten high parasitic fungi (‘K’ through ‘T’) were then evaluated in vivo using a growth chamber-based cone-tainer assay. Top three performers in the cone-tainer assay, isolates ‘D’, ‘E’ and ‘T’ were subsequently evaluated in greenhouse potted plant assays. Isolates ‘E’ and ‘T’ were as good as commercially available biocontrol agent Melocon WG, even at 40-400 folds lower concentration.