Studied On Effect Of Oligochitosan On Postharvest Disease Resistance And Storage Quality Of Apricot Fruit

In this study, effects of oligochitosan treatments on postharvest diseases resistance, storage quality and physiological metabolisms of apricot fruit were studied. Results from our studies will provide theoretical and practical information on how to reduce postharvest decay, improve storage quality of apricot fruit and provide alternatives to traditional applications of chemical fungicides on horticultural crops.(1)The Saimaiti apricot fruit (Prunusar meniaca L.) were treated by vacuum infiltration of0.25%,0.50%,1.00%chitosan solution (molecular weight:3000Da.,5000Da.,10000Da.), and stored stored at4℃,90%-95%RH.Among then,oligochitosan with molecular weight of10000Da. showed the most fungistatic property. The apricot fruit were treated with2.00%oligochitosan (molecular weight of10000Da.) solution.results that the nature decay incidence and disease progress in the apricot fruit inoculated with Alternaria alternate was effectively inhibited by the treatment with oligochitosan,The effect of2.00%oligochitosan treatment on ripening and the control of the disease of apricot fruit was less than that2.00%oligochitosan. The effect of oligochitosan by vacuum infiltration of postharvest apricot fruit was evaluated by rensponse surface method with different concentration, pressure and treatment time. Results indicated that oligochitosan solution and presurre were the keyfactors affecting disease and firmness,and significant effect on it. The optimum vacuum infiltration was solution0.50%,0.05MPa, and3min.(2)The influencing factors of the antifungal activity on the main postharvest disease-producing fungus (Penicillium expansum, Alternaria alternate, Rhizopus stolonifer) of apricot fruit by oligochitosan were studied. The effect of oligochitosan of different molecular weight and concentration on the colony growth were evaluated. The antifungal activity of10000Da was higher than that of the oligochitosan with molecular weight3000Da. The antifungal activity of the tested oligochitosan concentration has a concentration dependent manner. Among them,2.00%oligochitosan was the most effective. Different strains had different sensitivities to the oligochitosan.A.alternata and R. stolonifer were more sensitive to oligochitosan than P. expansum.(3)Oligochitosan treatment accelerated biosynesis of hydrogen peroxide (H2O2) and susuperoxide radicals(O2.-). Enhanced the activities of the defense-related enzymes,i.e.,superoxide dismutase (SOD),peroxidase(POD),ascorbate peroxidase(APX),catalase(CAT),polyphenol oxidase (PPO),phenylalanine ammonialyase (PAL),chitinase(CHT),β-1,3-glucanase(GUN) and lipoxidase (LOX).(4) The physiological metabolism and storage quality were studied of apricot fruit by oligochitosan.The result showed that the total phenolic content in the fruits were accumulates, respiration rate and decay incidence of the apricot fruit were significantly reduced by the oligochitosan treatment during storage. Therefore,the results suggested that the enhanced disease resistance in apricot fruits by oligochitosan treatment could result from the activation of the disease-related defense system.Firmness and the chlorophyll content of the apricot fruit were efficiently maintained and declining in titratable acidity, ascorbic acid were all effectively inhibited,but increase of total soluble solids and weight loss were retarded. The storage qualities of apricot fruit were efficiently maintained by the treatment of0.50%oligochitosan during storage.