Effect of pyrimethanil on Cryptococcus laurentii, Rhodosporidium paludigenum, and Rhodotorula glutinis biocontrol of Penicillium expansum infection in pear fruit

• Pyrimethanil (Pyr) at 400 μg/mL efficiently inhibited blue mold rot.
• Pyr at 40 μg/mL failed to reduce P. expansum infections in vivo
• C. laurentii was insensitive to pyr in vitro and in vivo.
• C. laurentii with pyr at 40 μg/mL significantly enhanced mold inhibition.

The effect of biocontrol yeasts and pyrimethanil at low concentration on inhibition of blue mold rot caused by Penicillium expansum in pear fruit was investigated. Pyrimethanil at low concentration (40 μg/mL) alone had little inhibitory activity against the P. expansum infection in pear fruit wounds although it was effective in inhibiting the survival of P. expansum on Asp-agar medium. Pyrimethanil at this low concentration significantly enhanced the efficacy of Cryptococcus laurentii at 1 × 107 CFU/mL in reducing blue mold rot in vivo compared with C. laurentii at 1 × 107 CFU/mL alone. However, there was no additive inhibitory activity when pyrimethanil was combined for application with biocontrol yeasts Rhodosporidium paludigenum or Rhodotorula glutinis. Combination of pyrimethanil and C. laurentii at low concentration also inhibited blue mold rot when P. expansum was inoculated into fruit wounds 12 h before treatment and fruit was stored at low temperature (4 °C). Pyrimethanil at 0.04 to 400 μg/mL did not influence the survival of C. laurentii in vitro, and it only slightly reduced the population growth of C. laurentii after 48 h of incubation in the pear fruit wounds. There was no significant difference in quality parameters including total soluble solids, titratable acidity and ascorbic acid of pear fruit wounds among all treatments after 5 days of treatment at 25 °C. Integration of C. laurentii and pyrimethanil at low concentration might be an effective and safe strategy to control P. expansum infection in pear fruit, especially in an integrated postharvest disease management strategy.