Postharvest biological control of gray mold decay of strawberry with Rhodotorula glutinis

Abstract

Rhodotorula glutinis was evaluated for its activity in reducing postharvest gray mold decay of strawberry caused by Botrytis cinerea in vitro and in vivo. In the test on PDA plates, R. glutinis significantly inhibit the growth of B. cinerea. Spore germination of pathogens in PDB was greatly controlled in the presence of living cell suspensions. Rapid colonization of the yeast in wounds was observed during the first 3 days at 20 °C, and then the populations stabilized for the remaining storage period. On strawberry wounds kept at 4 °C, the increase in population density of R. glutinis was lower than those kept at 20 °C, but continued over 8 days after application of the antagonist until it reached a high level. Number of inoculated strawberry fruit treated with 1 × 108 CFU/ml washed cell suspension of R. glutinis was 10% after 2 days at 20 °C, compared to 100%, respectively, in the control. Washed cell suspensions of yeast controlled gray mold better than yeast in culture broth. Treatment of wounds with autoclaved cell cultures or cell-free culture filtrate did not prevent decay. The concentrations of antagonist had significant effects on biocontrol effectiveness: the higher the concentrations of the antagonist, the lower the disease incidence regardless of whether the fruit was stored at 20 °C for 2 days or 4 °C for 7 days. At concentrations of R. glutinis 1 × 109 CFU/ml, the incidence of gray mold was reduced by 94.7 or 95%, respectively, compared with control, after storage at 20 °C for 2 days or 4 °C for 7 days, respectively. R. glutinis significantly reduced the natural development of decay of fruit following storage at 20 °C for 3 days or 4 °C for 5 days followed by 20 °C for 3 days.