Spray-Induced Gene Silencing Suppresses Gene Expression and Growth of the Fruit-Rot Pathogen Colletotrichum fioriniae

The fungal pathogen Colletotrichum fioriniae causes disease in plant species such as hops, blueberries, and apples. Management of the pathogen is highly reliant on conventional synthetic fungicides, with cultivars having uncharacterized or incomplete resistance. This is increasingly problematic with fungicide-resistant populations of C. fioriniae being identified. Spray-induced gene silencing (SIGS) is a developing method of disease control that has recently been investigated in various pathosystems, though it has been reported ineffective in some Colletotrichum species. This study investigated the potential of SIGS as a means of inhibiting the growth of C. fioriniae. The capacity of C. fioriniae to uptake exogenous double-stranded RNA (dsRNA) in-vitro was demonstrated visually by co-incubation with fluorescent dsRNA. Incubation of a green-fluorescent protein (eGFP) expressing transformant of C. fioriniae in potato-dextrose broth with 0.5 and 1 ng/µL of an anti-egfp dsRNA resulted in reduced expression of egfp as evaluated by qPCR with the ∆∆Ct method. Treating cultures of C. fioriniae on potato-dextrose agar (PDA) with 0, 50, and 150 ng/µL of an anti-tef1 dsRNA resulted in a dose-dependent reduction in colony diameter. Our results lay the groundwork for future studies to evaluate the potential of SIGS as a biopesticide tool for controlling fruit-rots caused by C. fioriniae.