Isolation And Identification Of Root Rot Pathogen Of Phoebe Zhennan And Its Antagonistic Bacteria And Analysis Of Resistant Physiological Index

Phoebe zhennan,a rare species,is the second important protected plant in China.It is also famous overseas.Its major distribution areas are Hubei,Guizhou,Sichuan and Chongqing in China.The artificial cultivation of Phoebe zhennan has been a new economic growth point,because its wild resource almost depletion,caused by the immoderately logging in Qing dynasty.In recent years,the root rot of Phoebe zhennan first appeared in Chengdu area.The pathogenic fungus was isolated and indentified from root rot of the big leaf type Phoebe zhennan in Chengdu.Its biological characteristic was also studied in this present work.The disease resistance of two types(large leaf and small leaf)of Phoebe zhennan was compared as well.2 kinds of bacillus with a good disease resistance were screened to investigate their antimicrobial characters,in order to select disease resistance materials.This work will provide a valuable basis for the development of biological control.The main results are shown as follows:1.According to Koch's postulates,the pathogenic fungus,L20170401,was determined to be same as the one from the plant affected by root rot.It was determined the Fusarium oxysprum is the pathogenic bacteria(L20170401)using the methods of morphological observation molecular biological identification.2.The most suitable substrate for the mycelial growth of pathogenic fungus and production of spore were PDA and PSA,respectively,by studying the pathogenic fungus characteristics.And the most suitable temperature were 25? and 30?,respectively.However,Alternating light and dark treatment had a certain promoting effect on the production of spore,and had little effect on mycelial growth.The pH value of 7 was the best for the pathogen mycelial growth and spore production.Pathogenic lethal temperature was for 54?.Moreover,the range of optimal humidity spore germination range is 95%~100%.3.The dynamic changes on the organic solutes and defensive ferments active in different state were measured after the types of Phoebe zhennan infected by pathogenic bacteria.The results indicated that the chlorophylls of two types of Phoebe zhennan decreased after the pathogen infected.The values of PPO,POD,SOD,MDA and soluble sugar content in two types of Phoebe zhennan increased first and then decreased.The value of MDA in large leaf trees were lower than that of small leaf trees.The values of soluble sugar content in large leaf trees had a faster growth speed than small leaf trees,and the PPO,POD,SOD,MDA had a larger rangeability than those of small leaf trees.Comprehensively,large leaf trees had a better disease resistance than that of small leaf trees.4.By screening 2 strains of bacillus with a good resistance to pathogenic fungus,the antibacterial properties were analyzed in this work.The result revealed that B04 was the Bacillus myloliquefaciens,and B02 was Bacillus subtilis.2 strains of bacillus had a better inhibiting effects on mycelial growth of pathogenic fungus and spore germination than the control group.B04 had a better inhibitory effect than B02.