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Fusarium oxysporum f. sp. dianthi virus 1 Accumulation Is Correlated with Changes in Virulence and Other Phenotypic Traits of Its Fungal Host

Lemus-Minor, Carlos Germán, Cañizares, M. Carmen, García-Pedrajas, María Dolores, Pérez-Artés, Encarnación
Phytopathology 2018 v.108 no.8 pp. 957-963
Chrysoviridae, DNA, Dianthus caryophyllus, Fusarium oxysporum, Fusarium wilt, agar gel electrophoresis, biological control agents, conidiation, cultivars, double-stranded RNA, fungi, liquids, mycoviruses, phenotype, vegetative growth, virulence
Fusarium oxysporum f. sp. dianthi virus 1 (FodV1) was detected in isolate 116 (116V⁺) of Fusarium oxysporum f. sp. dianthi, reaching such a high accumulation level that it was clearly visible after agarose gel electrophoresis of total DNA extracts. FodV1 consists of four double-stranded RNA segments that correspond to a new mycovirus in the Chrysoviridae family. We obtained an isolate of F. oxysporum f. sp. dianthi 116 (116V⁻) with only a residual level of FodV1 RNA accumulation by single-conidia selection. Compared with 116V⁻, isolate 116V⁺ showed significant phenotypic alterations in vegetative growth and virulence. Thus, the presence of a high titer of mycovirus FodV1 was associated with a modified morphology and a reduced growth of the colonies on solid medium, and with a diminished conidiation in liquid medium. Inoculation of four susceptible carnation cultivars with either 116V⁻ or 116V⁺ showed that the presence of a high titer of FodV1 was also correlated with a significantly reduced virulence of its fungal host. All of the results suggest that FodV1 could be associated with hypovirulence, identifying it as a potential biocontrol agent for Fusarium wilt of carnation. This is the first report of a mycovirus potentially associated with the induction of hypovirulence in the species F. oxysporum.