Abstract
There is increasing concern regarding the use of fungicides to control plant diseases, whereby interest has increased in the biological control of phytopathogenic fungi by the application of hypovirulent mycoviruses as a possible alternative to fungicides. Transmission of hypovirulence-associated double-stranded RNA (dsRNA) viruses between mycelia, however, is prevented by the vegetative incompatibility barrier that often exists between different species or strains of filamentous fungi. We determined whether protoplast fusion could be used to transmit FgV1-DK21 virus, which is associated with hypovirulence on F. boothii (formerly F. graminearum strain DK21), to F. graminearum, F. asiaticum, F. oxysporum f. sp. lycopersici, and Cryphonectria parasitica. Relative to virus-free strains, the FgV1-DK21 recipient strains had reduced growth rates, altered pigmentation, and reduced virulence. These results indicate that protoplast fusion can be used to introduce FgV1-DK21 dsRNA into other Fusarium species and into C. parasitica and that FgV1-DK21 can be used as a hypovirulence factor and thus as a biological control agent.
Highlights
Fungicides successfully control many diseases caused by plant-pathogenic fungi, fungal pathogens remain a major source of plant disease
Only slight morphological alterations were evident in the virus-infected F. oxysporum f. sp. lycopersici strain when growing on potato dextrose agar (PDA) (Figure 3A)
FgV1DK21 double-stranded RNA (dsRNA) were detected in F. graminearum and F. asaticum strains, but not in F. oxysporum f. sp. lycopersici when extracted total RNAs were separated on agarose gel (Figure S2A)
Summary
Fungicides successfully control many diseases caused by plant-pathogenic fungi, fungal pathogens remain a major source of plant disease. Because of the development of fungicideresistant strains, and increasing public concern regarding environmental and food safety, there is renewed interest in biological control based on application of hypovirulent mycoviruses. The success of biological control with hypoviruses depends on their ability to reduce the virulence (to induce hypovirulence) of the target fungus. Hypoviruses can be transmitted from a hypovirulent strain to a virulent fungal strain by hyphal fusion (anastomosis) when the two strains are vegetatively compatible, but hypoviruses cannot be transmitted when applied by extracellular routes [2,3]. Because only closely related fungal strains are vegetatively compatible, vegetative incompatibility among many fungal species in agricultural ecosystems is a major barrier to the use of hypoviruses as biological control agents [4,5]
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