| China is the largest producer of apple fruit and apple-derived products all over the world,and the quality and safety of apple and its derived products are important for the Chinese apple industry.Microorganism on the surface of fruit is the main factor affected the fruit quality and safety,and related with the occurrence of fruit disease,the accumulation of mycotoxin,and the contamination of food-borne pathogen.Specifically,Penicillium expansum(P.expansum)is one of the most concerned microorganisms on the apple surface,and it is a key factor endangering the quality and safety of apple and the derived products.This study will research on the fruit quality and safety related apple surface microorganisms and the blue mold disease with the application of omics technology.The main contents and results as follows:1.The apple surface microbes of samples from two main Chinese apple-producing regions,the Bohai Bay(BHB)and the Loess Plateau(LP),were investigated by microbiomic technology.BHB and LP apples contained significantly different bacterial and fungal communities,which were represented by11 fungal genenra and 12 bacterial genera.BHB apples had higher fungal diversity than LP apples,and had higher content of phytopathogenic fungal genera,indicating the higher phytopathogenic risks of apples from the BHB region.LP apples contained more bacterial genera identified as gut microbes,indicated the potential risks of contaminating apples with foodborne pathogens in the environment of the LP.This study indicated the environment-oriented microbial specificity on apples,and provided a basis for further investigation.2.The pathogens of apple blue mold disease were isolated from the main Chinese apple-producing regions.The changes of metabolite during the apple P.expansum infection were explored by metabonomics.Significantly metabonomic differences were observed between the control and P.expansum infected samples.A total of 485 differential metabolites were screened out.In these different metabolites,the majority of sugars were decreased during P.expansum infection,whereas the majority of organic acids,amino acids,phenolics and fatty acids were increased.Disturbed metabolic pathways in early infection were mainly secondary metabolite biosynthesis,ABC transporters,amino acid and carbon metabolism.The intergroup comparison obtained 140 differential metabolites to represent the core metabolic changes during infection.A total of 27 metabolites were strongly increased along with the disease process,which could aid the biomarker discovery for apple blue mold disease.This study highlights the different metabolites and metabolic pathways during the apple P.expansum infection,and provide a basis for further investigation.3.The metabolic mechanism of salicylic acid(SA)mediated apple resistant to P.expansum infection were explored by metabonomics.The different metabolite between samples were obtained,which reflected the process related to P.expansum invasion and SA treatment.Metabolic pathways for P.expansum invasion were mainly contained the TCA cycle,galactose metabolism,starch and sucrose metabolism,glyoxylate and dicarboxylate metabolism and carbapenem biosynthesis.Metabolic pathways related to apple natural response were mianly included the TCA cycle,amino acid metabolism and reactive oxygen metabolism,secondary metabolites biosynthesis and unsaturated fatty acids biosynthesis.The changes of amino acid metabolism were diverse,which could both reflected the consumption of amino acids for fungal proliferation and the biosynthesis of amino acids for disease resistance.Results indicated SA promoted multiply responses especially the biosynthesis of secondary metabolites and unsaturated fatty acids to improve fruit disease resistance.This study is beneficial to elucidate the mechanism of SA mediated apple resistant to P.expansum infection. |
