Effects Of Epicoccum Nigrum And Plant Extracts On Postharvest Preservation Of Blueberry

Blueberry is a kind of emerging fruit with extremely high nutritional and economic value.However,it is susceptible to postharvest pathogenic fungi infection,which causing fruit rot,mycotoxins residue,serious economic losses and food safety problems.Due to the lack of knowledge of blueberry postharvest pathogens and safe and effective control measures,there were many difficulties for blueberry preservation.In this paper,the postharvest pathogens of blueberry in Dalian were isolated and identified.The growth inhibition of the blueberry postharvest pathogens by Epicoccum nigrum and two kinds of plant natural extracts,Perilla frutescens extract?PFE?and pomegranate peel extract?PPE?,were determined.At the same time,the effects of PFE and PPE on the storage quality of blueberry were also analyzed.The results were shown as below:1.Using the tissue isolation method,twelve kinds of pathogenic fungi were isolated from the postharvest rot blueberry fruits.Morphology and molecular biology were used to identify the 12 fungal strains namely Aspergillus niger,Cladosporium tenuissimum,Chaetomium sp.,Alternaria tenuissima,Alternaria alternate,Phoma sp.,Pestalotiopsis sp.,Botrytis cinerea,Botryosphaeria dothidea,Fusarium sp.,Neopestalotiopsis foedan and Penicillium brevicompactum.Botryosphaeria dothidea was isolated from the rot blueberry in Dalian,which also can cause the diseases of blueberry leave and stems.The optimal culture conditions for the mycelium growth of B.dothidea were PSA,pH=5.0 at 25?.48?was the mycelium lethal temperature.50%carbendazim water dispersible granules had the greatest inhibitory effect(EC₅₀=0.01 mg/L)on mycelium growth in vitro.2.An endophytic fungus of blueberry with good antifungal activity was identified as Epicoccum nigrum.The results of dual culture assays showed that E.nigrum had good inhibitory effects on the growth of blueberry postharvest pathogenic fungi,B.cinerea,Pestalotiopsis sp.,B.dothidea,Alternaria sp.and Phoma sp.,and the inhibition rate reached66.47%,53.83%,47.59%,41.63%and 38.45%,respectively.The microscopic observation of the mycelial morphology revealed that E.nigrum can cause distortion,dissolution and breakage of the pathogenic mycelium.Further experimental results showed that the liquid and solid fermentation products of E.nigrum can increase the membrane permeability and membrane lipid peroxidation of pathogens,with good inhibitory effects on the pathogenic fungi.3.PFE and PPE had good inhibitory effects on five kinds of blueberry postharvest pathogenic fungi.After different concentrations of PFE and PPE treated,the fruits rot rate and weight loss rate of blueberry decreased significantly,and fruit firmness,the contents of main nutrients such as soluble solids,titratable acid,ascorbic acid,flavonoids and total phenolic were maintained at a higher level compared to the control.The activity of superoxide dismutase?SOD?,peroxidase?POD?,catalase?CAT?,phenylalanine ammonia-lyase?PAL?and?-1,3-glucanase?GLU?were also higher than the control group.This study confirmed that postharvest fruit rot of blueberry were caused by a variety of pathogenic fungi.Epicoccum nigrum and its fermentation products can inhibit the growth of many kinds of pathogenic fungi and reduce the incidence of postharvest gray mold caused by Botrytis cinerea.PFE and PPE achieved the preservation effect by reducing the damage of pathogenic fungi to blueberry and enhancing their own resistance of the fruit,and the preservation effects of 10 g/L PFE and PPE were better.