| Grape is a very important economic fruit in China,however,fruits are vulnerable to pathogen infection caused by decay during growth and storage,which causes huge economic losses.In traditional ways,the diseases of table grapes caused by mold are mainly controlled by the use of chemical fungicide.However,pesticide residues have great harm to human health and the ecological environment.In recent years,there have been many studies focused on alternative means to control postharvest decay in table grapes as well as other agricultural commodities.Biological control has been proposed as a potential alternative to chemical fungicide use,and has shown great potential for controlling postharvest decay of fruits and vegetables.Yeast has been shown to act as an important biocontrol agent against plant pathogens.At present,China has no successful case of yeast preparation research.The purpose of this study is to screen out the antagonistic yeast,and to study the yeast preparation in order to provide valuable information about Chinese commercial production and application of biocontrol agents.The main research findings were summarized as follows:(1)Four strains of yeast with high biocontrol efficacy on postharvest disease of table grapes were isolated from the vineyard,in vitro and in vivo screening experiments indicated that,Y16 has the best control effect on disease.Four strains of antagonistic bacteria were identified by morphological and molecular biology,the results identified Y13 as Rhodosporidium babjevae strain,Y14 as Cryptococcus laurentii strain,Y15 as Cryptococcus flavescens strain,Y16 as Sporidiobolus pararoseus strain.There was no report on the prevention of postharvest Aspergillus niger of table grapes by using the yeast Sporidiobolus pararoseus.(2)Acute oral toxicity test indicated that S.pararoseus Y16 is a safe yeast strain with no toxic effects.(3)Through the study of the effect of S.pararoseus Y16 on the biocontrol control the postharvest diseases of table grapes,S.pararoseus Y16 can significantly inhibited A.niger on table grapes at concentrations of 1 × 106 cells/mL,1 × 107cells/mL,1 × 108cells/mL and 1 × 109 cells/mL.And with the increase of yeast concentration,the antibacterial effect is enhanced.In the vineyard,the results of yeast spraying test showed that S.pararoseus Y16 could inhibit the pathogen by spraying and significantly reduce the decay rate of grape berry.The weight loss and natural decay rate of table grape treated by S.pararoseus Y16 was obviously lower than that of control group,and will not have an impact on the storage quality of table grapes.(4)The population dynamics results showed that S.pararoseus Y16 could rapidly survive and proliferate in table grape wounds or on table grape surfaces,and these results point to the main mode of action of S.pararoseus Y16 being competition for space and nutrient with pathogens.Moreover,its ability to enhance polyphenol oxidase(PPO),catalase(CAT),phenylalanine ammonia-lyase(PAL),chitinase(CHI)and ascorbate peroxidase(APX)activity of table grapes,to induce expression of defense enzymes in table grapes,thereby enhancing the disease resistance of the fruits.(5)Add appropriate protective agent to prepare S.pararoseus Y16 liquid and solid preparations.The results showed that the prepared S.pararoseus Y16 liquid preparation and lyophilized solid preparation could maintain high vigor and good biocontrol effect for a long time.The liquid preparations prepared with 10% acacia seyal,10% sucrose,2.5% trehalose,2% mannose,0.04% Vc and 0.5% chitosan were stored at 4oC for 30 days and the yeast survival rate was 71.74%;The solid preparation prepared with 10% skimmed milk powder + 10% treh alose + 1% Vc as a freeze-dried protective agent was stored at 4oC for 7 months and the yeast survival rate was still 60.87%. |
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