Control of postharvest pear diseases using Rhodotorula glutinis and its effects on postharvest quality parameters

Rhodotorula glutinis was evaluated for its activity in reducing postharvest gray mold decay and blue mold decay of pear caused by Botrytis cinerea and Penicillium expansum respectively, and in reducing natural decay development of pear fruits, as well as its effects on postharvest quality of fruits. There was a significant negative correlation between concentrations of the yeast cells and infectivity of the pathogens. At concentrations of R. glutinis at 5x108 CFU/ml, the gray mold decay was completely inhibited after 7 days incubation at 20 degrees C, while the control fruit had 100% disease incidence and 2.15 cm lesion diameter respectively, at challenged with B. cinerea spores suspension of 1x105 spores/ml; No completely control was got to blue mold, when pear fruits stored at 20 degrees C for 7 d (challenged with P. expansum spores suspension of 5x104 spores/ml), but the decay was distinctly prevented with 20% and 0.60 cm of disease incidence and lesion diameter respectively, while the control fruits were 100% and 2.74 cm, respectively. Rapid colonization of the yeast in wounds was observed during the first 1 d at 20 degrees C, and then the populations stabilized for the remaining storage period. On pear wounds kept at 4 degrees C, rapid colonization of the yeast in wounds was observed during the first 3 d, and then the increase in population density of R. glutinis turned slow, which continued over 6 d after application of the antagonist until it reached a high level. Then, the populations stabilized for the remaining storage period. In the test on PDA plates, R. glutinis significantly inhibit the growth of B. cinerea and P. expansum. Spore germination of pathogens in PDB was greatly controlled in the present of living yeast cell suspensions. R. glutinis significantly reduced the natural development of decay of pear following storage at 20 degrees C for 7 days or at 4 degrees C for 30 days followed by 20 degrees C for 5 days, and did not impair quality parameters, including mass loss, firmness, TSS, ascorbic acid or titratable acidity. Thus, the application of R. glutinis can be an alternative to chemicals for control of postharvest diseases on pear fruits.