Resistance of phylloplane-inhabiting yeast to fungicides

Yeasts colonize the surface of plants and act as natural biological control agents, reducing the incidence and severity of diseases. However, fungicide applications can lead to the reduction and/or inhibition of these species in the phylloplane. The objective was to evaluate the sensitivity of yeast strains from the phylloplane against fungicidal products used in agriculture for the control of plant diseases. Thus, strains of different species of yeast from the leaf surface of plants were evaluated in vitro for sensitivity to fungicides, measuring the inhibition zone radius for each yeast strain exposed to fungicidal products. The yeast Zygoascus hellenicus, Rhodotorula aurantiaca, Pichia spp., and Sporobolomyces roseus were insensitive to most of the fungicidal. Regarding the products, those composed of a mixture strobilurins and carboxamides and the multisites were shown to be less toxic to yeast, whereas the compounds chemicals containing the active ingredient of the triazole group were shown to be more toxic. The products acting on only one mechanism of action, the inhibition of respiration, proved to be more selective to yeast. The yeast has natural resistance to most of the fungicidal products; however, some species show significant sensitivity to compounds containing the active principle of the triazole group.