Study On The Growth Characteristic Of Hami Melon Postharvest Pathogen And Its Preliminary Study Pathogenesis

There were five types of infect pathogen including genus of Mucor,Penicillium,Fusarium,Alternariaand Aspergillus during the storage of Postharvest hami melon. The biggest bottleneck of the developmentof xinjiang hami melon industry was the rot problem of melon, while pathogen infection was the mainreason of postharvest melon rot during the storage.Different kinds of cell wall degradation enzymes, whichwas an important factor of Postharvest melon rot during the storage, would produce in the process ofpathogenic fungal infection on postharvest hami melon and many studies had shown that there were veryclose relationship between postharvest melon rot and those cell wall degradation enzymes. The hami meloncould produce different physiological and biochemical changes when pathogen infecting. It could provideimportant theoretical basis and practical guidance If we figure out these defense reaction changes in meloncells when resisting the pathogen infecting.This test isolated five strains of the main pathogens of hami melon named BJ-Q,BJ-M,BJ-M1,BJ--M2,BJ-M3,respectively. Cell wall degradation enzymes of these five pathogens were determined in vitroculture. Finally, One of these cell wall degradation enzymes, which might play a main role in the process ofhami melon rot, was select by orthogonal test analysis. Besides, Resistant enzyme activity was studied forthe main pathogens and electron microscope slices was also studied for the hami melon tissue afterinfection.The results were as follows:(1) BJ-M Mand B-M1strains belong to the genus of Fusarium,BJ-M2strains belong to the genus ofMucor, BJ-M3strains belong to the genus of Aspergillus and BJ-Q strains belong to the genus ofPenicillium through morphological, physiological, biochemical and molecular biology research means.(2) Penicillium and Fusarium grew well on PDA culture medium, while Mucor grew well on the seedculture medium; the best utilization of Carbon and nitrogen source were lactose and sodium nitrate forPenicillium and Alternaria, However, the best utilization of Carbon and nitrogen source for Mucor weresucrose and peptone respectively. The mainly three pathogens of hami melon grew well. The mainly threekinds of pathogen mycelium of hami melon grew well in the neutral and alkaline environment.(3) Cellulose degradation enzyme (Cx, β-glycosidase enzymes), pectin degradation enzyme (PMG,PG), PGTE and PMTE cell wall degradation enzymes were found in Penicillium and Alternaria duringvitro culture. The enzyme activity of PGTE and PMTE were very low.(4) The optimal conditions of Cx enzyme production of Penicillium were conformed by single-factorexperiments and orthogonal experiments, they were4days of culture time, initial pH6.5, concentration ofcarbon source was1.5%and nitrogen source was1.0%. In these conditions, the highest Cx enzyme activitywas358.12U/mg. The optimal conditions of Cx enzyme production of Alternaria were4days of culturetime, initial pH6.0, concentration of carbon source was1.5%and nitrogen source was1.0%. the highest Cxenzyme activity was385.67U/mg. The consequence on comparison of enzyme activity shows thatAlternaria might affect more on hami melon rot than Penicillium.(5) The Cx enzyme activity of two pathogens was significantly higher than other enzymes during vitro culture. Cx enzyme presumably played a very important role in the process of pathogen infection of hamimelon and had a huge influence on the rot of melon. However, The specific pathogenic mechanism of hamimelon had to be further syudied.(6) Results of resistant enzyme research showed that hami melon infection by pathogen had anobviously effect on the characters including the hardness, respiration intensity, weightlessness etc. Theenzyme activity change of protective enzyme system such as POD,CAT and PPO also showed that thepathogen infect speed up the rot rate of hami melon. Comprehensive analysis shows that the Alternariaplayed a main role in the process of hami melon rot and the relationship between the cell wall degradationenzymes and resistance of enzyme activity change may provide some scientific basis for the study ofspecific pathogenic mechanism of hami melon in the future.