In vitro Screening of a Culturable Soybean Cyst Nematode Cyst Mycobiome for Potential Biological Control Agents and Biopesticides.

Fungal biological control of Soybean Cyst Nematodes (SCN) is an important component of integrated pest management for Soybean. However, very few fungal biological control agents are available in the market. In this study, we have screened fungi previously isolated from SCN cysts, over three years, from a long-term crop rotation field experiment for their ability to antagonize SCN using (i) parasitism, (ii) egg hatch-inhibition, and (iii) J2 mortality. We evaluated egg-parasitism using an in-vitro egg parasitism bioassay and scored parasitism using the Egg Parasitic Index (EPI) and fluorescent microscopy. The ability of these fungi to produce metabolites causing egg hatch-inhibition and J2 mortality was assessed in bioassays using filter-sterilized culture filtrates. We identified ten high-performing isolates each for egg-parasitism and toxicity towards SCN eggs and J2s and repeated the tests after storage for 1 year of cryopreservation at -80 degrees C to validate the durability of biocontrol potential of the chosen twenty isolates. Although the parasitic ability changed slightly for the majority of strains after cryopreservation, they still scored 5/10 on EPI scales. There were no differences in the ability of fungi to produce anti-nemic metabolites after cryopreservation.