Rhodosporidium paludigenum induces resistance and defense-related responses against Penicillium digitatum in citrus fruit

• R. paludigenum induces resistance against Penicillium digitatum in citrus.
• Efficacy of induced resistance is dependent on the time of the yeast application.
• The inhibition rate is influenced by the concentration of yeast used.
• R. paludigenum stimulates the activities of GLU, PAL, POD and PPO in citrus.

Induced disease resistance against plant pathogens is a promising non-fungicidal decay control strategy. In this study, a potential biocontrol yeast, Rhodosporidium paludigenum, was investigated for its induction of disease resistance against Penicillium digitatum in citrus fruit. The results showed that R. paludigenum is the most effective yeast among three selected yeasts in stimulating the resistance of citrus fruit to green mold. When R. paludigenum was applied 48–72 h before inoculation with P. digitatum, disease incidence and disease severity in citrus fruit significantly decreased. Application of R. paludigenum at concentrations of 1 × 108 and 1 × 109 cells mL−1 respectively resulted in 49.6% and 52.5% reductions in the percentage of infections. Induction of resistance to P. digitatum by R. paludigenum treatment significantly enhanced the activities of defense-related enzymes, including β-1,3-glucanase, phenylalanine ammonia-lyase, peroxidase, and polyphenoloxidase, which may be an important mechanism by which the biocontrol yeast reduces the fungal disease of citrus fruit caused by P. digitatum.