Identification And Biological Characterization Of Wax Apple Soft Rot Disease Pathogen And The Research Of Pathogenic Mechanism Of The Pathogen

In this paper,‘Black Pearl' wax-apple fruits(Syzygium samarangense Merr.et Perry)were used as materials to cultivate in normal temperature until they going mouldy.The results show that,Wax Apple Soft Rot Disease seems to be the main disease of postharvest wax apple fruit.Then,isolate and purify the main pathogen of the disease as well as do rearsch about the pathogenicity of the isolatedfungus in order to find out the main pathogen that cause the wax apple soft rot disease.Morphological analysis and molecule biology identification of the certain fungus which isolated from soft rot disease wax apple was reported in this paper.In addition,we conducted research of pathogenicity and biological characteristics of the fungus.At last,take cell wall degrading enzyme as main points to investigate the pathogenic mechanism of the fungus.The cell wall enzymes contain PG,PMG,Cx,PGTE and PMTE.The results show that:The main disease of the postharvest ‘Black Pearl' wax-apple fruit is wax apple soft rot disease.The morphology of fungus is identified.The fungus acervulus is black,scattered,the conidia is elongated,with five cells separated by four lines.The size of acervulus is 11.97?m~26.60?m×6.65~10.64?m,the middle thress cells are coloured while the top two cells are dark.The top cell and the rear cell are both triangle as well as transparent.There are two to four ascomal hairs with the length of 10.64?m~21.28?m.There is one basal appendage.Then we conducted PCR amplification and sequencing of the sequence of the fungus' ITS4 and ITS6.The resulted base sequences were compare on the BLAST of NCBI.C hoose the strains sequences which more than 98% homology to establish the phylogenetic tree.The result shows that,the fungus is closest to Pestalotiopsis versicolor(accession number :AF405298.1).After made a general analysis of morphological analysis' result and molecule biology identification result,we identified the pathogen of wax apple soft rot disease is Pestalotiopsis versicolor(Fungi,FungiImperfecti,Coelomycetes,Melanconiales,Melanconiaceae,Pestalotiopsis,Pestalotiopsis versicolor).The fungus infect the fruits by wound infection.In vitro culture showed that the optimum temperature for the growth of hypha was 25?,and the optimum relative humidity was 75%~80%,the relative humidity has smallinfluence on the growth of the fungus.The p H ranged from 3~9 was suitable for the fungus while p H 5~6 was the optimum for it.The mycelia grew best on mediawith malt dust as its carbon soureces,on the contrary,mannitol was unfavorable for its growth.Peptone was the best nitrogen source for mycelia growth while carbamide inhibited its growth.The fungus was sensitive to light,complete dark was the best for mycelial growth.The lethal temperature for conidium was 55 ?,10 min.The result shows that the fungus is highly adaptable to the living environment.The fungus can product a series of cell wall degrading enzymes both in vivo and in vitro.It can induced the production of PG,PMG,C x in vitro while PG,PMG,PGTE in vivo.At the begin of few days,the enzymatic activity of diseased fruit is apparently higher than the healthy fruit.So,it is clear that,PG,PMG and PGTE play imoportant roles in the process of disease.While the enzymatic activity of PGTE is apparently lower than PG and PMG,so PG and PMG play leading roles in the disease.It is seems to be that,the fungus is able to product cell wall degrading enzymes as well as inducing fruits to produce enzymes.Thus,it helps the fungus to destroy the cell wall of the host fruites in order to intrude it.And the result shows that the fungus make no obvious effect on the cottony softening process of wax-apple.