| Apples are known as the "king of fruits" and are among the most popular fruits.Apples are in great demand all over the world.However,due to improper post-harvest handling,apples are susceptible to pathogenic fungal infestation,which lead to quality loss and even decay,resulting in substantial economic losses.Blue mold decay caused by Penicillium expansum is one of the most common disease during post-harvest storage of apples.Chemical fungicides are commonly used to control the blue mold decay of apples,but the chemical residues cause adverse effects on the human body and environment.Hence,finding new methods with high safety and being environmentally friendly has become a hot research spot for controlling apple post-harvest diseases.Antagonistic yeasts have been proven to be the safest alternative to chemical fungicides.Moreover,effector-induced antagonistic yeast is an effective way to improve the biological control effectiveness of the yeasts.This thesis aimed to enhance the biocontrol efficacy of the antagonistic yeast Debaryomyces hansenii Y3 by alginate oligosaccharide(AOS)and to study its biocontrol efficacy on apple post-harvest blue mold decay and further investigate the mechanism of improvement biocontrol effectiveness.The main findings of the paper are as follows.(1)AOS significantly improved the biocontrol efficacy of D.hansenii Y3 on blue mold decay of apples,and the best effect was achieved at an AOS concentration of 0.5%(w/v).D.hansenii Y3 enhanced by AOS significantly reduced the natural decay of apples and had no adverse effect on the storage quality.(2)AOS significantly improved the inhibition efficacy of D.hansenii Y3 on the germination rate,germ tube length,and colony diameter of P.expansum;AOS increased growth and colonization ability of D.hansenii Y3 in apple wounds and surface;the activities of resistance-related enzymes(PPO,POD,PAL)and the content of total phenols and flavonoids in apple were induced by AOS-enhanced D.hansenii Y3,thus improving the disease resistance of apple.(3)Differentially expressed genes were screened and analyzed based on transcriptomic data of AOS-induced D.hansenii Y3.The differentially up-regulated genes mainly included: genes involved in DNA replication and mismatch repair;genes associated with cellular oxidative phosphorylation and purine metabolism;genes involved in carbon metabolism,biosynthesis of glycosylphosphatidylinositol anchors and N-Glycan biosynthesis;genes participated in cellular temperature,ion concentration and p H regulation.The differentially down-regulated genes mainly included: genes associated with blocking the suppression of yeast meiosis-related gene expression;genes involved in glycerolipid metabolism.(4)Differentially expressed proteins were screened and analyzed based on proteomic data of AOS-induced D.hansenii Y3.The differentially up-regulated proteins mainly included: proteins involved in yeast meiosis,nucleotide synthesis,and cell membrane production;proteins associated with yeast oxidative phosphorylation;proteins involved in pyruvate metabolism,methane metabolic pathway,amino and nucleotide sugar metabolic;proteins participated in yeast cell wall synthesis,oxidative stress protection,signal transduction. |
