White mold disease or cottony rot affects over 450 species of plants including many important cash crops. It is caused by Sclerotinia sclerotiorum, a fungus that is commonly found in the soil on farms. It is capable of infecting plants at any stage of growth including harvested produce and seeds in storage. Historically, fungal infections of cash crops have caused drastic losses in crop yields in U.S.A. until the discovery of fungicides in the 1900s. Currently, farmers rely on fungicides to prevent outbreak of diseases like white mold on their farms. However, the increasing use of fungicides have generated concerns over their long term effect on human health. Moreover, some fungicides such as chlorothalonil is harmful to aquatic life whilst others such as triazole can only be used at specific growth stages of plants. Farmers engaged in organic agriculture use copper and sulfur as a natural fungicide, however, overexposure to these chemicals could have some negative impact on human health. In view of these challenges, researchers at SDSU have been working on an environmentally friendly approach to control the spread of fungus on farms.
This technology describes the use of a unique mycovirus of S. sclerotiorum to block growth and infectivity of the fungus on seeds and plants. It constitutes a proprietary infectious clone of ssHADV-1 (Sclerotinia sclerotiorum hypovirulence associated DNA virus) capable of replication in the fungal host. Researchers have shown that infection of fungi by the mycovirus suppresses the fungi’s ability to form infectious lesions on plants thereby inhibiting fungal growth. This is an environmentally friendly approach in which ssHADV-1 could be used as a biopesticide spray or seed coating to suppress white mold disease caused by S. sclerotiorum on a large scale.
ssHADV-1 is a naturally occurring mycovirus and strains have been isolated from dragonfly and damselfly in USA. Infection by ssHADV-1 is highly specific to S. sclerotiorum and has no negative impact on plant, animal and human health. The use of ssHADV-1 mediated fungal control as a biopesticide spray or seed coating will help farmers to cut cost of fungicides and minimize the negative side effects associated with the use of synthetic chemicals.