Screening,preliminary Application And Biocontrol Mechanism Of Antagonistic Yeasts Against Peach Anthracnose

Peach is one of important fruits in China,but due to the immature technology in picking,transportation and storage,and the infection of pathogenic,it causes serious loss of peach after harvest.A large number of reports have confirmed that antagonistic yeast can safely and effectively inhibit the postharvest diseases of fruits and vegetables.This project mainly screened an antagonistic yeast that effectively inhibited peach anthracnose,explored its biocontrol mechanism,and used its freeze-dried powder in storage period of peach.The main research findings were summarized as follows:(1)Screening of antagonistic yeast from peach orchard,the method of in vitrol screening and in vivo screening were used to obtain an antagonistic yeast named Y23,yeast Y23 could effectively control peach anthracnose caused by Colletotrichum gloeosporioides;through the tests of molecular characteristics,according to the identification results,yeast Y23 was identified as Kloeckera apiculata.(2)According to the in vivo experiment,the optimal concentration of K.apiculata Y23 in inhibiting C.gloeosporioides was 1×10~8 cells/mL.After co-culture in PDB,it was found that K.apiculata Y23 could significantly inhibit C.gloeosporioides spore germination,and yeast Y23 might be attached to the pathogenic fungal hyphae;In antagonistic experiment,K.apiculata Y23 could secrete anti-fungal substances to inhibit the mycelial growth of C.gloeosporioides,and could reduce the quantity and quality of spores produced by C.gloeosporioides;Through the back-off experiment,it was found that K.apiculata Y23 could produce volatile anti-fungal substances to inhibit the growth of C.gloeosporioides,and the anti-fungal substances were determined by GC-MS;After apiculata Y23 treatment,the defense enzyme activities,total phenols and flavonoids content of peach were increased,indicating that increasing the defense response was one of its biocontrol mechanisms.(3)By co-cultivation of K.apiculata Y23 with cellulase,we presumed K.apiculata Y23 could secrete proteases to degrade cellulase,and grew and multiplied as a nitrogen source,then inhibited cellulase activity,thereby slowed the destruction of host cell walls by pathogens and increased the storage period.The results showed that K.apiculata Y23 degradation of extracellular enzymes was a new biocontrol mechanism.(4)The conditions for obtaining the highest centrifugal yield of the yeast cells were 8000 r/min and 20 min,and the centrifugal yield under this condition was 86.6%.Among the single protective agents,inulin,sucrose and sodium glutamate has the best effect.The optimal combination of protective agents was 10%inulin,5%sucrose and7.5%sodium glutamate.Under this condition,the freeze-dried survival rate was85.32%;It was found that-20°C was more suitable for preservation of K.apiculata Y23,and the survival rate was still 50.06%at 6th months.(5)After rehydration of the yeast freeze-dried powder,the peach fruits were treated by immersion and spray respectively.The effects of the two methods on the storage and preservation of peaches were studied.The results showed that the two methods could obviously inhibit the rot of peaches during storage and reached the decay index of 3..42%and 5.61%respectively on the 7th day after storage.Moreover,Weight loss rate,hardness,soluble solids content,pericarp cell membrane permeability,vitamin C content and total acid content all played a positive role.The results showed that the yeast freeze-dried powder has a positive effect on the postharvest storage and preservation of postharvest peach fruit.