Isolation And Identification Of Biocontrol Yeast On Fruit Surface And Its Prevention And Treatment Of Kiwi Fruit Postharvest Diseases

Blue mold,gray mold and black spot are the main infectious diseases during kiwifruit storage,leading to significant losses.So far,chemical fungicides have been widely used in management of postharvest diseases of fruit and vegetable.However,there are many disadvantages of pesticide residues,such potential health issue,environmental pollution and pathogenic resistance,etc.An eoc-friendly method is urgently needed to serve as an alternative of the use of chemical fungicides.Among the alternatives,biological control utilizing biocontrol yeast is a potential method.Biocontrol yeasts and their subsidiary products are harmless to human health and have antagonistic effect on plant pathogen,which can effectively inhibit the microbial growth.It is an effective way to control postharvest diseases of fruits and vegetables.The purpose of this study is to isolate and screen antagonistic strains that can manage postharvest diseases of fruits,identify their biological characteristics,and determine the inhibitory effects of the selected strains Li 1(isolated from pulm surface),Pu 1(isolated from grape surface)and Shan 2(isolated from mangosteen surface)on blue mold,gray mold and black spot,as well as the colonization and growth in the wounds of fruits The possible mechanims involved have been preliminarily investigated.The main results are as follows:1.Isolation and screening of antagonistic yeasts: antagonistic yeasts were isolated from different fruit surfaces by aseptic water separation method,and then purified by dilution plate method.Results showed that 27 yeasts were screened out,which had obvious inhibitory effect on Penicillium expansum.2.Identification of antagonistic yeasts: Based on the morphological characteristics,identification of ITS sequence.Through homology comparison and phylogenetic analysis,antagonistic bacteria Li 1 was identified as Candida fructus,Pu 1 as Pichia terricola,and Shan 2 as Hanseniaspora opuntiae.The first is Candida radionensis,the second is Geotrichum,and the third is Hanseniaspora meyeri.3.Antagonistic test: the antagonistic yeasts,Li 1,Pu 1 and Shan 2 at 1x10~7CFU/ml were inoculated on the kiwifruit cv.Hongyang and stored at 25 oC.The incidence rate was43.33%,40% and 30% respectively.The incidence in control group was 100%.Li 1,Pu 1and Shan 2 had significant inhibitory effect on Botrytis cinerea,the incidence rate was30%,23.33% and 30% respectively,and the incidence rate in control group was 100%.Li1,Pu 1 and Shan 2 had significant inhibitory effects on Alternaria alternata,the incidencerate was 6.67%,6.67% and 10% respectively,and the incidence rate in control group was100%.These results indicated that the biocontrol yeasts,Li 1,Pu 1 and Shan 2 had obvious inhibitory effect on blue mold,gray mold and black spot on Chilean kiwifruit.The incidence rates were 80%,80%,86.67%,53.33%,56.67%,60%,16.67%,16.67% and16.67%,respectively.The incidence rate in control group was 100%.the biocontrol yeasts,Li 1,Pu 1 and Shan 2 had obvious inhibitory effect on blue mold,gray mold and black spot on green apple.The incidence rate was 20%,10%,10%,6.67%,10%,10%,10%,10% and10% respectively.The incidence rate in control group was 100%.4.The population growth rate of antagonistic yeasts: antagonistic yeasts Li 1,Pu 1and Shan 2 can grow and colonize rapidly in the fruit wound with or without the action of blue mold,gray mold and black spot.Yeast inoculated on kiwifruit quickly propagated in the first day and tended to be stable in the later period.5.Antagonistic yeasts Li 1,Pu 1 and Shan 2 at 1 × 10~7 CFU / m L could induce the activity of CAT(catalase),SOD(total superoxide dismutase),POD(peroxidase)and total phenol enzyme of kiwifruit were detected at 0 h,12 h,24 h,48 h,72 h and 96 h,respectively.It showed that the three yeasts can induce kiwifruit to produce disease resistance.