Inhibitory effect of natamycin against carrot white mold caused by Sclerotinia sclerotiorum

This study was conducted to evaluate inhibitory effect of natamycin against three isolates of Sclerotinia sclerotiorum, the causal agent of carrot white mold in postharvest phase. The results showed that natamycin was able to markedly decrease radial growth and sclerogenesis of three isolates of the pathogen. In addition, natamycin significantly reduced myceliogenic and carpogenic germinations of sclerotia in three isolates. There was a clear positive correlation between natamycin concentration and efficacy against mycelial growth, sclerogenesis, and sclerotia germinations. Application of natamycin on carrot roots 2.5 h before inoculation with the pathogen markedly reduced white mold incidence. The treatment with natamycin enhanced relative conductivity of S. sclerotiorum mycelia over time compared with control. The concentration 2 mg L-1 increased the cell membrane permeability of mycelia more than the concentration 1 mg L-1 over 160 min. Moreover, an increase of carbohydrate leakage was observed in the pathogen mycelia incubated with natamycin. The content of methane dicarboxylic aldehyde (MDA) markedly increased at 5 h and the highest MDA content was observed after 20 h. Due to exposure to natamycin, a decrease percentage of catalase activity was observed in pathogen mycelia.