Abstract:【Objective】Peach originated and has a long history of cultivation in China. In recentyears, a shoot blight disease that resulted in brown cankers around buds on shoots or twigs of peach trees has been widely observed in many orchards in Wuxi. This disease killed shoots and branches and resulted in high yield losses. Shoot blight has become a serious limiting factor in the growth of peach trees. In order to clarify pathogens causing peach shoot blight disease and evaluate the disease resistance of different peach varieties. 【Methods】Firstly, a field survey was carried out to determine the incidence of peach shoot blight in peach orchards, and types of symptoms were observed. Secondly, the disease samples were used as materials to isolate the pathogenic fungi by the methods of tissue block separation. Isolates were identified by morphological observation and combined with analysis of rDNA internal transcribed spacer (ITS), elongation factor 1-α (EF-1α) and beta-tubulin (TUB) sequences. And the pathogenicity of isolates was tested based on Koch postulates. Then, wound inoculation method used on detached twigs was used to identify and evaluate the resistance of 37 peach varieties (germplasms) to shoot blight caused by D. amygdali. And the system clustering method was adopted to identify the resistance of different peach varieties (germplasms) to shoot blight based on the disease lesion length data. 【 Results 】 The disease occurred initially on peach shoots that turned brown. Subsequently, reddish-brown cankers developed on the shoots, and resulted in shoot blight，the disease spot present gummosis sometimes. Total 54 isolates were obtained through tissue separation. All the isolates were identified as 3 species, including D. amygdali (35 isolates), D. eres (5 isolates) and B. dothidea (14 isolates) by morphological observation and multiple genes. The result of pathogenicity test showed that the isolates can induce lesions on shoots, and the pathogens isolated from the infected lesions after inoculation were identical with the inoculated isolates. The resistance determination results indicated that 37 peach varieties (germplasms) were divided 4 types based on the lesion lengths after 7 d inoculation with D. amygdali isolate by the cluster analysis. ‘Guhetao’, ‘Honghuashantao’, ‘Zhouxingshantao’, ‘Baigengansutao’ and ‘Honggenggansutao’ were classified into Group I. ‘Zhongyoupan No.9’, ‘Zhongyoupan No.7’, ‘Zhongyoupan No.16’, ‘Zhongyoupan No.13’, ‘Honghujing’, ‘Hujingmilu’, ‘Baihua’, ‘Zhongtaohongyu’, ‘Wanhujing’, ‘Zhongtaoziyu’ and ‘Qingshuibaitao’ were classified into Group Ⅱ. ‘Fenghuapantao’, ‘Jinghong’, ‘Xiahui No.5’, ‘Zhongpantao No.11’, ‘Xiahui No.6’, ‘Yuhualu’, ‘Wenzhoushuimi’, ‘Xiahui No.8’, ‘Zhanglingzaoyulu’, ‘Fenghuayulu’, ‘Chaohui’, ‘Muyangshuimi’, ‘Ri No.89’, ‘Gangshan No.500’ and ‘Yingzuitao’ were classified into Group Ⅲ. ‘Richuanbaifeng’, ‘Liutiaobaifeng’, ‘Dazenbaochiyue’, ‘Benbaifeng’, ‘Fenglu’ and ‘Baifeng’ were classified into Group IV. The resistance evaluation results indicated that ‘Guhetao’, ‘Honghuashantao’ and ‘Zhouxingshantao’ performed as immunity, ‘Baigengansutao’ and ‘Honggenggansutao’ performed as resistance, 11 cultivars performed as middle resistant, 15 cultivars performed as susceptibility, and 6 cultivars performed as high susceptibility.【Conclusion】 There were three pathogens (D. amygdali, D. eres and B. dothidea) associated with peach shoot blight in Wuxi. D. amygdali was the dominant pathogen of the disease, and the isolation frequency was 64.81%. And different peach varieties exhibited varying resistance levels to shoot blight disease. The percentages of total in levels immunity, resistance, middle resistant,susceptibility and high susceptibility accounted amount to 8.10%, 5.40%, 29.73%, 40.54% and 16.22% respectively.
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