Identification And Detection Of The Pathogens Causing Peach Shoot Blight In Wuxi And Disease Cycle Exploration

Peach Shoot Blight is one of the most important diseases of peach,which results in circular brown spots on the root of new branches of peaches and serious damage on leaves.In recent years,domestic area and the incidence of the disease have been expanding year after year.Tree may subsequently become a weak grower.In order to control disease,disease trunks and branches were collected from region of incidence.We identified the causing agents by morphology and molecular biological methods.Furthermore,we established rapid detection method which could monitor disease timely,quarantine the pathogen and help us make preventive measures.Finally,this detection method was applied into the research of hibernacula of pathogens and disease dynamic.So we can confirm the hibernacula and preliminary dynamic of peach shoot blight,which is helpful to control the disease.The results we achieved are as follows:First of all,disease trunks and branches were collected from different peach orchards in Wuxi,Jiangsu.After isolation and culture,we obtained pure cultures.Through Koch’s Rule,we confirmed two kinds of pathogens.According to the morphological characteristics and multilocus sequence analysis(MLSA),we identified the pathogens as Phomopsis amygdali and Botryosphaeria dothidea,respectively.Secondly,the detecting system of P.amygdali was developed.We compared the pathogen with its closely related species and found that histone H3 of P.amygdali was more specific,so hi.stone H3 was a suitable target for molecular detection.The histone H3 gene of P.amygdali was selected as target gene for design of the specific primers and TaqMan probe,and the TaqMan Fluorescence Quantitative PCR Method(FQ-PCR)was established for the detection of P.amygdali.Results showed that the method established in this study was specific for P.amygdali detection.Furthermore,the FQ-PCR was more sensitive and faster compared to routine PCR.In the field,the positive detection rates of suspicious samples by FQ-PCR were highest.Finally,the occurrence and development of diseases were studied.The hibernacula is the initial infection sources of next season,so it could provide better measures on disease control when we study on hibernacula.This experiment applied established detection technology and tissue isolation to study on hibernacula of P.amygdali and B.dothidea,and we compared the growth speed of fungi colony at different temperatures and predicted the occurrence and epidemic period of disease.The result showed that P.amygdali and B.dothidea could be isolated and detected from buds and scabs,by the way,the detection rate of B.dothidea was higher in discolored xylem.So buds,scabs and discolored xylem provide ideal hibernacula for pathogen of peach constriction canker disease.The experimental results showed the optimum growth temperature of P.amygdali and B.dothidea was 25 ℃ and 30℃,respectively.The growth speed of P.amygdali was faster than B.dothidea at 5-20℃,however,when temperature rose to 30℃,the growth speed of P.amygdali became slower than B.dothidea.These results indicated that the infection time of P.amygdali was earlier than B.dothidea.Furthermore,the results were consistent with the occurrence of disease.The peach shoot blight caused by P.amygdali was more in early spring,but the occurrence rate caused by B.dothidea was significantly increased at high temperature in summer.