Naturally occurring mycovirus developed as a biopesticide to protect plants from Sclerotinia sclerotiorum in the greenhouse and in the field

Authors: Marzano, Shin-Yi; Pedersen, Connor; FENG, CHENCHEN - University Of Toledo; HARBACH, CHELSEA - Iowa State University; WU, CHIEN-FU - The Ohio State University; TSENG, YI-WEN - The Ohio State University; ADEGOKE, DAVID - University Of Toledo

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sclerotinia sclerotiorum is a fungal pathogen that causes economically important diseases (e.g., white mold) in several crop species, many of which have not been adequately controlled by conventional pesticides. Viral biopesticides were developed long ago for insecticides, but there has not been a viral biopesticide developed for fungal disease control. Based on prior lab-based results, we further develop formulations that show promise in the greenhouse and field application to control S. sclerotiorum. We found that soil inoculation upon seeding, fungal homogenate spray, and viral particle preparation provide crop protection under high disease pressure with the first two having potential to promote plant growth under low disease pressure. These viral biopesticides provide promising biocontrol alternatives for disease management of white mold.

Technical Abstract: A mycovirus-based biopesticide has not been available even though many studies showed promise in the lab. Based on our prior research on a mycovirus, soybean leaf associated Gemygorvirus 1 (SlaGemV1), that showed promise in the lab, we further tested three formulation types to evaluate the effects on Sclerotinia sclerotiorum dis-ease control. The study shows that incorporating hypovirulent S. sclerotiorum infected by SlaGemV1 directly into soil improved plant health and reduced disease symptoms from subsequent S. sclerotiorum infection in the greenhouse. We observed increased leaf area, plant height, and photosynthetic efficiency in the field under low/no disease pressure. Next, fungal homogenate containing SlaGemV1 showed protective effect against S. sclerotiorum infection, reducing sclerotia formation and lesion length 7 days post infection in the greenhouse (P<0.05). Fungal homogenates also result in smaller lesions in pinto beans, resulting in plants maintaining greater above-ground dry weights after infection. In the field, under low/no disease pressure, similar effects of growth promotion were observed. Finally, using viral particles preparation, we showed that both in the greenhouse and in the field, under medium/high disease pressure in 2023 and 2024, the protective effects of viral particles were significantly greater than water control (P=0.1). Therefore, we conclude that SlaGemV1 adds to the toolbox of integrated path-ogen control when sprayed during the R1/R2 critical time of the fungal pathogen’s life cycle.