Isolation And Identification Of Pathogenic Fungi From Postharvest Pitaya And Antifungal Activity Of Quaternized Chitosan

The invasion of pathogen in the Postharvest of pitaya leads to fruit decay and deterioration,which brings significant losses.In this study,the common tissue isolation method was used to isolate strains from postharvest storage of naturally occurring fruit of Pitaya.After pathogenicity identification,the taxonomic status of the fungi was determined according to the morphological characteristics and rDNA-ITS sequence of the strains.At the same time,determination of the inhibitory effect of quaternized chitosan on the pathogenic fungi of Pitaya,so as to provide theoretical basis for the identification and control of Postharvest fungal diseases of Pitaya.The results are as follows:1.Four pathogenic fungi were isolated from postharvest fruits of pitaya,which were Bipolaris cactivora,Fusarrium incarnatum,Aspergillus tubingensis and Gilbertella persicaria by the method of morphology and rDNA-ITS sequence.Moreover Aspergillus tubingensis were the first reported as pathogenic fungi of postharvest pitaya.2.The antifungal activity of quaternized chitosan on the pathogenic fungi of Postharvest pitaya was carried out.The results showed that quaternized chitosan had a strong inhibitory effect on the mycelial growth of Bipolaris cactivora,Fusarrium incarnatum and Gilbertella persicaria,the virulence regression equation was y=5.9383x-10.21,y=2.6213x-2.5103,y=8.8701x-22.623.But quaternized chitosan has not nhibitory effect on the mycelial growth of on Aspergillus tubingensis.3.Microscopical observation showed that quaternized chitosan could inhibit the germination of spores.It was found by fluorescent staining that quaternized chitosan could destroy the permeability of cell membrane,stimulate the accumulation of reactive oxygen species,and make cell apoptosis.