Primary Mechanism Of Oligochitosan Induced Resistance To Fruit

The study on the induced resistance is one of the main reserch direction on the fruits controled postharvest diseases by biotechnological method. Oligochitosan with DP=4-11(Degree of Polymerization) was used as elicitor to research the induced resistance of jujube and peach fruits to Botrytis Cinerea in vitro and vivo, the relationship of resistant enzymes, antimicrobial substance and decay index was invesitigated in this paper to found the primary induced resistance mechnism of postharvest fruit.Oligochitosan has no inhibition effect on Botrytis Cinerea in vitro, it maybe work as an elicitor to induce potential resistance of fruit. The best induced condition of challenge inoculation jujubes as follows, the concentration of oligochitosan solution is54.2μg-mL-’, the maturity of jujubes is8, the induction time is25h, and the best induced condition of injury inoculation jujubes as follows, oligochitosan56.5μg-mL-1, maturity8, and induction time24h. The best concentration of oligochitosan solution acting on peaches is125.0μg-mL-1.The content of H2O2increased, on the contrary, activity of the eliminated enzymes of active oxygen such as SOD and CAT were restrained during the first period after inducing. During the last period, the activities of SOD and CAT were strengthened to remove excessive reactive oxygen and protective viable cell from injury.The survey about the relationship between related enzymes was able to explain that activities of the defense enzymes such as POD, PPO, PAL, GLU and CHT were higher than those of no induced jujubes, also maintained for a long time. The activity of PAL and GLU in induction and injury group was higher than that in oligochitosan induction group and that in injury group.The reasearch on peaches induced by oligochitosan showed, H2O2content appeared the peak time between the6th-8th day, the largest activity of PAL, GLU and CHT emerged at the8th day, the content of TSP got the maximum accumulation at the10th day, lignin content appeared the peak time at the12th day. All of these confirmed that biochemical metabolism of peaches was altered and accumulated more antimicrobial substance to against pathogens.Phytoalexin distilled from peaches induced by oligochitosan was studied by qualitative analysis and quantitative analysis after purification. The result showed that the major compotents in phytoalexin was flavonoid substances which can inhibit the growth of bacteria. The accumulation of it reached the peak time from the48th hour to the96th hour to resistant the bacteria effectively.