Isolation And Identification Of Bio-control Agent And Its Effect In Controlling The Pathogeny Of Citrus Huanglongbing

Huanglongbing is a one of serious disease that damages the citrus industry.In this study,We use biological fungicides to irrigate citrus,aim to carrying out the pathogen of huanglongbing.Providing a basis for the breeding of citrus virus-free seedlings.On the basis of the effective NO.2 was isolated and purified,and the isolated single strain was identified by multiple taxonomies combined with morphological observation,physiolog-ical and biochemical index detection and genetic information comparison.1.I tested the pathogen concentration of huanglongbing after 20 th and 23 th respectively treated by NO.2,NO.6(the concentration of the first 10 treatments was 1.0g/L and 1.5L/plant,and then it was increased to 1.67g/L and 1.5L/ plant)and water.The real-time fluorescence quantitative PCR combined with conventional PCR method was used to analyze the result.The results showed that we use NO.2 for 20 times,the positive detection rate from 100% to 66.7%.After 23 treatments,the positive detection rate was only 16.67%.The results showed that we use NO.6 for 20 times,the positive detection rate from 100% to 50%.After 23 treatments,the positive detection rate was only 0%.2.I measured some physiological and biochemical dates after treated 23 times such as chlorophyll content,photosynthetic rate,soluble sugar content,starch content,the results showed that citrus treated by NO.2,NO.6 which leaf soluble sugar content and starch content were significantly lower than control group.The chlorophyll content in the leaves of samples treated with NO.2 and NO.6 was significantly higher than the control group.There was no significant difference in leaf photosynthetic rate between NO.2,NO.6 and control group.3.I analyzed the activities of PPO,POD,PAL,SOD and Trx R.The results showed that the activity of five enzymes of citrus treated with NO.2 and NO.6 increased significantly after 0 h-36 h compared with the control group.4.I analyzed the expression levels of PAR1,NHO1,HSP90 and STG1 by the real-time fluorescence quantitative PCR.The results showed that the expression levels of four resistance genes treated by NO.2 and NO.6 were significantly increased after 0 h～36h compared with the control group.5.I divided effective NO.2 into the 2-1 and 2-2 strains and then classify into the bacillus through observing the morphological characteristics,physiological and biochemical characteristics of the bacteria.Then we compared 16 S rDNA,recA and recN3 genes sequences of the strain,The results showed that sequences of 2-1 recA and recN were 99% and 100% similar to bacillus velezensis LD02,so it could be considered that the 2-1 strain might be bacillus velezensis.The results showed that sequences of 2-2 recA and recN were100% similar to bacillus amyloliquefaciens ws-8,so it could be considered that 2-2 strain might be bacillus amyloliquefaciens.