Effect of rhamnolipids on Rhodotorula glutinis biocontrol of Alternaria alternata infection in cherry tomato fruit

• R. glutinis integrated with rhamnolipids had a better inhibitory effect.
• Rhamnolipids promoted the population growth of R. glutinis in cherry tomatoes.
• Fruit resistance was induced when treated with both R. glutinis and rhamnolipids.

This study was conducted to evaluate the efficacy of the biocontrol yeast, Rhodotorula glutinis with a surfactant produced by Pseudomonas aeruginosa, rhamnolipids, on the inhibition of Alternaria alternata on cherry tomato fruit. A combination of R. glutinis with rhamnolipids at 500 μg/mL was more effective in suppressing A. alternata infection than application of R. glutinis or rhamnolipids alone. Moreover, integration of R. glutinis with rhamnolipids significantly stimulated peroxidase, polyphenoloxidase and phenylalanine ammonialyase activities of cherry tomato fruit, which were stronger than the single treatments. Rhamnolipids with reduced concentrations did not affect the growth of R. glutinis in vitro, but were utilized as carbon sources by yeasts under conditions of limited carbon sources. Moreover, rhamnolipids themselves reduced decay incidence of A. alternata on cherry tomato fruit and promoted the population growth of R. glutinis in vivo. This combined treatment could induce natural resistance as well as accelerate colonization of yeasts on the fruit surface, providing an effective and safe strategy to control postharvest diseases.