The Research That Oligosaccharide Induce The Alternaria And Inhibit The Toxins

Oligochitosan(OTS) is a kind of soluble saccharides with good biocompatibility, and non-toxicity to humans and animals, which has broad application prospects in plant disease control, food preservation and healthcare. Recently, mechanisms by which oligochitosan elicits the defense response of plant have been intensively studied. However, little attempt has been made to elucidate the mechanisms of antifungal activity of oligochitosan. Alternaria pathogenisis is a wide infected fungal, which generate multiple mycotoxins when causing damage, tomato fruit can be subjected and infected black mold.The effects of oligosaccharide on biological traits of Alternaria were investigated. The different concentration of oligosaccharide strongly inhibited the mycelium growth and spore germination,500 μg/mL is the best and the inhibition rate reached 55.56%, spore germination inhibition rate is 78%. Scanning electron microscopy observed that different treatment group damaged the mycelium and spores, the form of mycelium was fuzzy, roughness, and even melted. Equal to the spores, which was ruptured, deformed completely and protoplasm overflowed.Oligochitosan induced apoptosis of Alternaria was investigated. It was found that oligochitosan had the lethal effects on the protoplasts. Mitochondrial membrane potential was decreased and ROS levels increased, indicating that oligochitosan can promote apoptosis.Through the CLSM observed fluorescent-oligosaccharide combined with mycelium and spores. Both of them dyed uniformly, but the fluorescence was breakaged on the membrane, indicating that diaphragm is undyed. Infered the oligosaccharide may enter the interior of the cell and combine with its DNA, and testified it by gel retardation experiment.Extracted the toxin of Alternaria to confirm the further mechanism, making the toxin and oligosaccharide interact with tomato cells and calculate the survival rate. The cell viability of oligochitosan treatment group was equal to the control group, however toxin-treated group appeared plasmolysis, the survival rate was less than 5%. When combined oligosaccharide with toxin and interacted with the cell, there was no shrinkage phenomenon in cell nucleus, survival rate reached 90%, indicating that oligochitosan inhibited the toxin infected tomato cells to some extent.The effect of oligosaccharide on the quality of postharvest tomato was also studied. It reduced the incidence, inhibited the spot expanding, delayed fruit softening and sweetness changes, kept the color and ascorbic acid content, increased the total phenolic, which conducive to improve taste and good flavor.