| This thesis contained two aspects; one was exploring the field application of biocontrol agents, antagonistic yeast Hanseniaspora uvarum with Pichia guilliermondii against gray mould of postharvest strawberry, and studying the effect of preharvest spraying single and composite antagonistic yeast on strawberries and the best time of preharvest spraying. Preharvest application of biocontrol agents could control the diseases during fruit grows in the field at source, and reduced pathogenic bacteria infection again. Research on the compatibility of H.uvarum with P.guilliermondii applications and improving the control effect of H. uvarum alone were conductive to the commercialization of biocontrol agents. Based on research of H.uvarum inhibiting Botrytis cinerea in our laboratory, which was mainly to explore the phenomenon of parasitism and yeast volatile metabolites on inhibiting pathogen in vivo from strawberries, the second research was aimed to explore the inhibitory mechanism of antagonistic yeast and how to improve biocontrol effect, therefore provided a theoretical basis for the preparation of the commercial application of biocontrol agents. Specific results were as follows:1. Through the preharvest spraying different concentration of antagonistic yeast screening test, antagonistic yeasts could significantly reduce decay index and improve commodity rate, better maintain postharvest storage quality of strawberry. The higher concentration of yeast was, the stronger inhibitory effect was. The effect of composite antagonistic yeast was better than yeast alone. Preharvest application of 1×10 CFU·mL-1 complex yeast was better than 1×108 CFU·mL-1 H. uvarum and P.guilliermondii alone. Thus,1×106 CFU·mL-1 composite yeast was the most optimal concentration.2. Through the preharvest spraying antagonistic yeast screening test at different time, it was confirmed that preharvest spraying time would affect the antagonistic yeast control effect on strawberry diseases. Under the same preharvest spraying time conditions, the control effect of composite antagonistic yeasts was superior to that of H. uvarum used alone. Three days before harvest strawberry, the decay index was significantly lower than that in the control group and seven days before harvest groups, and had better preserve appearance, slowing lower of hardness, TSS, pH value and vitamin C content, maintained the color and texture of strawberry; effectively enhancing SOD, POD, APX, CAT degrading enzyme activity of reactive oxygen species and PPO, PAL, β-1,3-glucanase resistance defensive activity, reducing the content of MDA. In addition, antagonistic yeast could affect the colonization of the fruit epidermis.3. Through SEM observation of strawberry fruit which was inoculated with the yeast H. uvarum and B.cinerea and stored at 25℃ for 5 days, the mold and hyphae are much less than those in control group. In the group treated with H. uvarum gathered and adsorbed on the mycelium, and mycelium shape had slightly changed, which was thicken and bending. After ultrasonic treatment, some yeast still did not leave the mycelium and embed in it, which destroyed the hyphae.4. The yeast H. uvarum volatile gas could significantly reduce the strawberry decay index, keep the fruit color and appearance quality and prolong storage life.5. GC-MS determination of yeast H. uvarum volatile components identified the yeast mainly produce alcohols, acids, esters, aldehydes, which contained 3-methy-l-butanol antibacterial ingredient and higher level. Other gas components still need futher analysis and research. |
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