Heat shock improves stress tolerance and biocontrol performance of Rhodotorula mucilaginosa

Biological control of postharvest diseases, utilizing wild species and strains of antagonistic yeasts, is an eco-friendly management approach that has received considerable attention over the past three decades. A few yeast-based biocontrol products are either in advanced stages of development or commercially available. Ecological fitness, stress tolerance and biocontrol performance are essential attributes for yeasts used as biocontrol agents. In the present study, a mild heat shock (HS, 40 °C for 30 min) pretreatment of the biocontrol yeast, Rhodotorula mucilaginosa, increased its tolerance to subsequent high temperature (48 °C), oxidative stress (70 mM H2O2), salt stress (3 M NaCl), and low pH (pH 4). Activation of the yeast antioxidant system by HS resulted in a lower accumulation of reactive oxygen species and less oxidative damage to proteins and lipids relative to control yeast cells when both were subjected to various abiotic stresses. Additionally, HS-treated yeast exhibited increased efficacy in controlling infection of apple fruit by Penicillium expansum, and a higher growth rate in apple wounds. These results suggest that stress adaptation is a viable approach for improving the efficacy of yeast biocontrol agents under the variable environmental conditions that exist in the postharvest environment of packing houses and storage facilities.