Edible Grade Inhibitors Inhibit Blueberry Fruit Rot Caused By Alternaria Sp.

Blueberry has high nutritional and medicinal value.It can enhance immunity,improvevision,resist oxidation and delay senescence.It is known as one of the top five healthy foods.However,blueberry postharvest diseases are serious because of its juicy fruit and thin peel.Alternaria is the main kind of pathogen causing blueberry fruit rot in Liaoning and Shandong areas.In order to control fruit rot caused by Alternaria,edible inhibitors were screened through two level studies,including inhibitors agaist directly to Alternaria and inhibitors treating blueberry fruit to evaluate control effect to Alternaria fruit rot.The results are as follows:1.Three edible grade Inhibitors were screened out by plate inhibit test.Three targets of Alternaria species strains were used here,including A.alternata,A.tenuissima,and A.dumosa.A.dumosa was discovered as a new record species infecting blueberry recently.The plate inhibition test was as the way to screening.The result shows thatε-Polylysine hydrochloride,potassium cinnamate and chitosan were worked to Alternaria.The EC₅₀values ofε-polylysine hydrochloride against A.dumosa,A.alternata,and A.tenuissima respectively were 104.97,28.87,and 26.17μg/m L.As forε-polylysine hydrochloride,A.tenuissima is relatively the most sensitive strain,while A.dumosa the most resistant stain.The EC₅₀values of potassium cinnamate to A.dumosa,A.alternata,and A.tenuissima respectively were 133.13,75.08,and 34.91μg/m L.As for potassium cinnamate,A.alternata is relatively the most sensitive stain,while the A.dumosa the most resistant stain.The EC₅₀values of chitosan to A.dumosa,A.alternata,and A.tenuissima respectively were1260.03,653.76,399.69μg/m L.As for chitosan,A.tenuissima is relatively the most sensitive strain,while A.dumosa the most resistant stain.Base on the analysis,ε-Polylysine hydrochloride and potassium cinnamate had more inhibition to tested Alternaria strains than chitosan.It is also found that A.dumosa has 3～4 times resistant than the others.2.Three inhibitors effect the spore germination and cell membrane permeability of target Altenaria strainsSpore germination and cell membrane permeability were detected after treating by three inhibitors.It was found that they reduced the growth and development of target Altenaria strains.When the concentration of chitosan is around 400μg/m L,its inhibition rate of three strains were 92.9～98%,furher observision showed that the spore germinate were not changed for 3 days.However the concentration ofε-Polylysine hydrochloride and potassium cinnamate around 3200μg/m L had 97%inhibition to spore germination.Chitosan was superior toε-polylysine hydrochloride and potassium cinnamate in inhibiting spore germination.It is observed that potassium cinnamate andε-Polylysine hydrochloride can cause the leakage of nucleic acid and soluble protein of three strains of Alternaria sp.,which indicate that the cell membrane structure was destroyed.However,the leakage of nucleic acid and protein is not obvious after treating by chitosan.3.Effects of three inhibitor on blueberry fruit after inoculation AlternariaIncidence rate,secondary metabolite changes,H₂O₂content,enzyme activity and gene expression were analysis here.Based on incidence rate analysis,three inhibitor have good function.Secondary metabolites including total phenols,flavonoids and anthocyanins in blueberry fruits were all increased.the increasing of anthocyanin with chitosan treatment was more than the other treatments.The H₂O₂content of blueberry fruits decreased after treatment.The activities of peroxidase（POD）,superoxide dismutase（SOD）,ascorbic acid peroxidase（APX）andβ-1,3glucanase（GLU）in blueberry fruits are all significantly increasing in treatment groups.In addition,the gene expression of POD,APX,GLU and SOD is quantitatively detected by real-time fluorescence,which further verifie the change trend of enzyme level.The results show that three inhibitors can play roles on preventing blueberry fruit rot by Altenaria.Among of them chitosan is the best one.