Pathogen Genetic Diversity,Disease Occurrence Regularity And Control Of Peach Bacteria Shot Hole

Peach bacterial shot hole is an important disease that harms peach trees and seriously affects the health and sustainable development of peach industry.In order to effectively control the disease,the pathogen identity and genetic diversity of pathogen population,growth and decline regularity,and the fungicides screening and control in field of the disease were studied in this paper.The isolates were obtained by plate streaking method from the bacterial shot hole diseased leaves,twigs and fruits in peach orchards of the main peach production areas in China.According to colony,physiological and biochemical characteristics and 16S-23S rDNA ITS sequence analysis,51 isolates were identified as Xanthomonas arboricola pv.pruni.Using Rep-PCR and ISSR-PCR methods for cluster analysis of 51 isolates,this paper found that these isolates were homologous with a certain diversity,and their diversities had a certain degree correlation with geographic sources.Most of these isolates could cause symptoms on peach leaves and fruits,and could elicit hypersensitive response on non-host tobacco,but there were some differences in pathogenic response types and strengths between isolates.The field investigation for 2 consecutive years in Siqian village,Yangshan town,Wuxi city,Jiangsu Province showed that the diseased leaves appeared in the end of April and early May and the disease incidence rate rose rapidly from June to August,and then it tended to a steady state.According to the weather conditions,it was found that the severity of peach bacterial shot hole was closely related to humidity,temperature and especially rainfall.The higher the temperature and humidity were,the more severe the disease was.Heavy rainfall contributed to spread of bacteria.The weather of drought and high temperature was not conducive to disease epidemic and spread.The virulence of 7 biopesticides and 11 chemical fungicides against the pathogen was tested in the laboratory by inhibition zone method.Among biopesticides,tetramycin,streptomycin sulfate and zhongshengmycin had good inhibitory effects on the bacterial pathogen,with ECso values of 0.0651 μg/mL,0.0698 μg/mL and 1.2422 μg/mL,respectively.In the chemical fungicides,chlorobromoisocyanuric acid had the strongest virulence,with EC50 value of 0.0559μg/mL,and zinc thiazole,bromothalonil,benziothiazolinone and oxine-copper had better antimicrobial effects.The field control trials showed that iprodione and zinc thiazole were better to prevent peach bacterial shot hole in Wuxi,Jiangsu Province,and oxine-copper,streptomycin sulfate and zinc thiazole had better control efficacy in Dalian,Liaoning Province.The control efficacy of streptomycin sulfate was the best in Fuzhou,Fujian Province,followed by zhongshengmycin.There were differences in the control effects of fungicides between test sites from differernt peach-growing areas.