Inhibiting Penicillium expansum infection on pear fruit by Cryptococcus laurentii and cytokinin

The effectiveness of the cytokinin N6-benzyladenine (6-BA), alone or in combination with the biocontrol yeast Cryptococcus laurentii, in controlling blue mold on pear fruit was assessed. The application of 6-BA (500–2000 μg mL−1) or C. laurentii was effective in reducing Penicillium expansum infection in pear fruit wounds, but its efficacy declined rapidly as the incubation time increased. Integrated application of C. laurentii and 6-BA at 500–2000 μg mL−1, especially at the optimal concentration (1000 μg mL−1), resulted in a more effective and stable inhibition of the mold rots than that of the 6-BA or C. laurentii alone. Treatments of pears with 6-BA at 1000 μg mL−1, alone or with C. laurentii also led to an increase in catalase activity and an inhibition of the activities of both peroxidase and lipoxygenase as well as ethylene production. In addition, 6-BA from 20 to 2000 μg mL−1 did not influence the population growth of C. laurentii in pear fruit wounds. These data suggested that a combination of 6-BA and C. laurentii could integrate the dual biological activities from 6-BA and C. laurentii and might be developed into a novel protection strategy for reduction of the blue mold rot of pear fruit.