The Study Of Inducing Biocontrol Efficacy Of Rhodotorula Glutinis With Chitin Or Chitosan And The Possible Mechanisms Involved

Postharvest fungal diseases result in substantial economic losses to fruits world-widely, which is controlled mainly by treatment with synthetic fungicides. However, there is increasing concern about the potential harmful effects on the environment and human health that synthetic fungicides may have. Biological control with antagonistic yeasts has emerged as a promising way to reduce synthetic fungicide usage. Strains of Rhodotorula glutinis are well known as postharvest biological control yeasts, which have been shown with high antagonistic activity in various fruits. However, at present, the effectiveness and stability of yeast antagonists have not been reached an adequate control level compared with the synthetic fungicides. So, antagonistic activity should be further enhanced, which has received the extensive concern of scholars at home and abroad. Therefore, the objective of this research was to stimulate yeast physiology through induction culture of chitin and chitosan for improving the efficacy of R. glutinis in controlling postharvest diseases of fruits and explore the possible mechanisms involved.The main research findings were summarized as follows:1. Application of chitin or chitosan could significantly enhance antagonistic activity of R. glutinis to Penicillium expansum, Botrytis cinerea (Pers.:Fr.) or Rhizopus stolonifer in fruits after cultivation of the yeast in a liquid media amended with chitin or chitosan at 0.5% or chitin at 1% insteading of glucose as the main carbon source. Moreover, R. glutinis after induced incubation remarkably reduced the natural development of decay of strawberry, peach or pear and did not impair postharvest quality parameters of these fruits including mass loss, firmness, total soluble solids, ascorbic acid or titratable acidity and browning under normal shelf-life condition.2. The mode of augmented antagonistic activity of R. glutinis might be related to stimulation of the chitinase secretion, enhancement of the population growth of R. glutinis in fruit wounds, and its ability to induce more defense enzymes such as polyphenoloxidase(PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), β-l,3-glucanase and inhibit lipid peroxidation after cultivation by chitin or chitosan, as to enhance competitiveness of yeast antagonist for nutrients and space with pathogens , delay the senescence and induce the resistance in fruits.3. The proteomic analysis and comparison of R. glutinis in response to chitin or chitosan was analyzed based on two-dimensional gel electrophoresis. Results showed that the expression of many proteins which is related to basic metabolism was induced or repressed.