Fitness of Dicarboximide-Resistant and Sensitive Monilinia fructicola Isolated from Peach in Korea

Dicarboximide-resistant isolates of Monilinia fructicola grew readily on media amended with dicarbosimide fungicides, and showed cross-resistance to pentachlo-ronitrobenzene (PCNB). The fitness of resistant isolates was inferior to that of sensitive isolates. Mycelial growth on fungicide-free medium was not significantly different between the dicarboximide-resistant and sensitive isolates. The originally high $\textrm{EC}_{50}$ values of the resistant isolate decreased after storage for 16 weeks at $4^{\circ}$. After inoculation with the mixture of spore suspensions of resistant and sensitive isolates, the re-isolation rate of the resistant spores was significantly reduced regardless of the mixing ratio. From the results, it could be concluded that the competitive ability of the resistant isolates is inferior to the sensitive ones.