Isolation And Identification Of Pathogen Of Peach Shot-hole Disease

Peach(Prunus persica L.)is an economically important fruit tree,which is cultivated all over the world.It is susceptible to different pathogens.Pathogens infection may cause some severe diseases,resulting in significant economic losses.In recent years,peach shot-hole disease occurred in some major peach production areas in China.With the global warming,the occurrence of this disease is increasing,and may cause significant economic losses.The pathogen of peach shot-hole disease include bacterial and fungal pathogen,and the causal agent of this disease in China are still unknown.This study conducted a survey of peach shot-hole disease in China,isolated and identified the pathogen of this disease.The results will be helpful for prevention and control of the disease.1.Collection of peach shot-hole disease samples.It was found that peach shot-hole disease occurred in eight peach production areas including Dalian(Liaoning),Pinggu(Beijing),Changli(Hebei),Taian(Shandong),Jiaxing(Zhejiang),Linhai(Zhejiang),Xi'an(Shaanxi),and Fuzhou(Fujian)in China.Symptomatic samples of peach shot-hole disease were collected from above areas.2.Isolation and identification of fungal pathogen.108 fungal strains were isolated and purified from samples.According to morphological features,ITS rDNA squences,108 fungal strains were classified into F1 ~ F6,and then identified as Alternaria sp.,Fusarium sp.,Colletotrichum sp.,Colletotrichum sp.,Diaporthe sp.,Phoma sp.,respectively.Pathogenicity test was conducted by inoculating F1 ~ F6 fungal strains on the detached peach leaves and twigs.The results showed that F1 ~ F6 fungal strains could not cause the symptoms of shot-hole diaease on peach leaves and twigs.3.Isolation and identification of bacterial pathogen.60 bacterial strains were isolated and purified from samples.According to morphological features,16 S rDNA squences,physiological and biochemical characteristics,60 bacterial strains were identified as Xanthomonas arboricola pv.pruni(Xap).Pathogenicity test was conducted by inoculating 60 Xap strains on the peach seedings.60 Xap strains caused hypersensitive response on tobacco,and the symptoms emerged on peach seedings were consistent with the naturally infected samples.Then the infected leaves of peach seedings were collected to be re-isolated and re-identified,it showed that re-isolated strains were identical to the inoculated strains based on morphology and 16 S rDNA squences.The above results revealed that Xap was the pathogen of peach shot-hole disease in China.In conclusion,this study found out the distribution of peach shot-hole disease in China,and it revealed that the peach shot-hole disease in some major peach production areas in China was bacterial shot-hole,which was caused by Xap.It provided a theoretical basis for prevention and control of peach shot-hole disease.