桃枝枯病病原菌鉴定及品种(种质)室内抗病性评价

Identification of the pathogen of peach shoot blight and indoor resistance evaluation of peach varieties(germplasms)

【目的】明确桃枝枯病的病原菌以及不同桃品种(种质)对枝枯病的抗性。【方法】观察桃枝枯病田间症状。通过组织分离法对病样进行分离培养,观察分离物的形态特征,通过扩增测序其ITS、EF-1α和TUB基因序列进行分子鉴定,并对分离物进行致病性验证。选取优势病原菌种类,采用离体有伤接种枝条的方法测定37个桃品种(种质)对其的抗性,并根据病斑长度利用系统聚类方法对不同桃品种(种质)对枝枯病的抗性进行分级和评价。【结果】通过组织分离和纯化,获得54株分离物,经形态学观察和多基因系统发育分析结果显示,这些分离物有3个种,其中:35株为桃拟茎点霉(Diaporthe amygdali),5株为甜樱间座壳(Diaporthe eres),14株为葡萄座腔菌(Botryosphaer dothidea)。致病性测定试验表明,对接种后发病的病斑再分离鉴定,均能得到与原病原菌一致的菌株。抗性测定结果表明,根据病斑长度利用聚类分析将37个桃品种(种质)分为4类,类型Ⅰ有5个、类型Ⅱ有11个、类型Ⅲ有15个、类型IV有6个。抗性评价结果表明:供试品种(种质)中,免疫3个(光核桃、红花山桃和帚形山桃),占8.10%;抗病2个(白根甘肃桃和红根甘肃桃),占5.40%;中抗11个,占29.73%;感病15个,占40.54%;高感6个,占16.22%。【结论】无锡桃枝枯病的病原菌有3种分别为:D.amygdali、D.eres和B.dothidea,其中D.amygdali为优势种,分离频率为64.81%,不同桃品种(种质)对桃拟茎点霉菌的抗性不同,筛选到2个免疫品种(种质)、3个抗性品种(种质)。

【Objective】Peach originated in China and has been cultivated for a long time.In recent years,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 could kill shoots and branches and resulted in high yield losses.The study aimed to clarify the pathogens causing peach shoot blight disease and evaluate the disease resistance of the different peach varieties(germplasms).【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.The isolates were identified by morphological observation combined with analysis of rDNA internal transcribed spacer(ITS),elongation factor 1-α(EF-1α)and beta-tubulin(TUB)sequences.And the pathogenicity of the isolates was tested based on Koch postulates.Then,wound inoculation method used on detached twigs was used to identify and evaluate the resistance of the 37 peach varieties(germplasms)to shoot blight caused by Diaporthe amygdali.And the system clustering method was adopted to identify the resistance of the different peach varieties(germplasms)to shoot blight based on the disease lesion length data.【Results】The disease occurred initially on peach shoots and caused brown canker.Subsequently,the reddishbrown cankers developed on the shoots,and resulted in shoot blight,the disease spot presented 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 Botryosphaer dothidea(14 isolates)by morphological observation and multiple genes.The result of pathogenicity test showed that the isolates could induce lesions on the 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 into 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 GroupⅠ.Zhongyoupan No.9,Zhongyoupan No.7,Zhongyoupan No.16,Zhongyoupan No.13,Honghujing,Hujingmilu,Baihua,Zhongtaohongyu,Wanhujing,Zhongtaoziyu and Qingshuibaitao were classified into GroupⅡ.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 GroupⅢ.Richuanbaifeng,Liutiaobaifeng,Dazenbaochiyue,Benbaifeng,Fenglu and Baifeng were classified into GroupⅣ.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.The different peach varieties exhibited varying degree of resistance to the shoot blight disease from immunity to high susceptibility.