| Losses of fresh vegetables and fruits after postharvest are very serious in the world, almost 10-30% of those got rot postharvest every year. It is particularly high in undeveloped countries (almost 40-50%) for being short of refrigerate equipment.In general, fungicides still provide a primary means of control. However, due to the development of fungicides-resistant isolate of pathogen, the possible deregistration of some of more effective postharvest fungicides, concern for public safety, and the residue of fungicide and so on, the fungicides is forbidden to use. The microbial antagonist for biocontrol of postharvest disease of fruits and vegetables has been made actively in the world as an alternative method to fungicidal treatment in recent years. Furthermore, the biocontrol had achieved a success. Several isolates of bacteria and yeasts had been shown to be effective against postharvest pathogens on a range of crops. Some had been patented and commercialized as biocontrol agents.In the present study, we evaluated the biocontrol activity of Rhodotorula glutinis against the major postharvest pathogen (Penicillium digitatuni) on citrus fruits and studied the biocontrol measures. In the study, we discussed the effect of some factors on the inhibiting activity of R.glutinis. The factors are as below: the characteristic and different treatments of R.glutinis; the condition of culture; different interval between antagonist and pathogen inoculated; combination of R.glutinis with assistant substance such as chemical compound, fungicides; the store temperature of citrus fruits; heat treatment before store; adding nutrients (carbohydrate and nitrogen); combination with other strains. In the same time, we determined the most effective treatment of R. glutinis, discussed the mechanism of the biocontrol of R.glutinis and explored the effect in vitro. The main results were as following:1. One strain (R. glutinis 3) was selected for its good biocontrol activity from the strains preserved in laboratory. In PDB, the cell suspension could inhibit the germination of pathogen spores and the length of the germ tube, and the biocontrol activity was inverse proportion with cell concentration. However, the culture filtrate and culture broth hadn't the same activity. The large of cell concentration of R.glutinis, the stronger of inhibition on the pathogen spores. The culture of R.glutinis had stronger inhibition activity on the germination of pathogen and not on the length of germ tube. The filtrate had no effect on the pathogen spores. We study the effect of the culture on citrus, the filtrate, the cells suspension, and theautoclaved culture. The cells suspension of R.glutinis had the best biocontrol activity; the effect of the culture broth containing the same concentration of yeast cells had the lower activity. However, culture filtrate and autoclaved culture weren't had inhibition activity. The higher concentration of cell suspension was, the better biocontrol effect achieved.Nutrients (carbohydrate and nitrogen) added to the cell suspension had different influence on the activity of R.glutinis. Moderate dose of organic carbohydrate and nitrogen could promote the inhibition activity of it, maybe it exhibit its action by promoting the growth of R.glutinis. The inorganic nitrogen added to cell suspension would decrease the biocontrol activity of the antagonist by promoting the growth of pathogen.The interval between R.glutinis and pathogen inoculation influence the activity of R.glutinis greatly. The earlier of antagonist inoculation, the better of biocontrol achieved. When R.glutinis was inoculated 4h or 36h before pathogen, the best biocontrol activity of it was obtained. So we forecast that the better inhibition activity of R.glutinis if we used it preharvest or immediately after harvest.The culture filtrate of Bacillus subtilis could enhance the biocontrol when combined with R.glutinis. It was considered B.subtilis exhibit its activity by producing the antibiotic (iturin). The best activity could be achi...
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