中国核桃炭疽病病原菌种类及潜在侵染源研究

Walnut anthracnose is one of the most devastating diseases in the walnut production areas in China. Up to 30% of the walnut fruit can be lost as a result of walnut anthracnose, which seriously affects the yield and quality of walnut. Colletotrichum gloeosporioides was regarded as the only Colletotrichum species to infect species of Juglans regia based on morphology and sequence data of the internal transcribed spacer region. However, it has been well recognized that C. gloeosporioides represents a species complex. The pathogens of anthracnose disease have not been only C. gloeosporioides. We have isolated six strains from walnut leaves, which are taxonomically different from C. gloeosporioides and other Colletotrichum species reported from walnut. Therefore, it is necessary to confirm the pathogens of walnut anthracnose and potentially novel pathogens. Accordingly, the healthy and infected walnut fruit, leaves and branches would be collected from the major walnut growing areas in China during June to September. Strains were isolated from collected material.It would be revealed that the pathogens of walnut anthracnose and potential pathogens by morphological character, cultural character, multilocus phylogenies and pathogenicity testing. Results would allow us to better understand the epidemiology and management of anthracnose and yield useful information for disease resistance breeding.

核桃炭疽病是我国核桃生产中的主要病害之一，发病严重时可引起减产30%以上，严重影响核桃的产量和品质。前人通过形态学和ITS序列分析认为我国核桃炭疽病的病原为胶孢炭疽菌，但最近有研究发现胶孢炭疽菌为复合种，许多植物炭疽病病原菌并非仅仅为胶孢炭疽菌。且申请人前期从核桃上分离到不同于胶孢炭疽菌的刺盘孢属菌株。因此关于我国核桃炭疽病病原菌种类和潜在致病菌种还有待于进一步探讨。基于以上分析本研究拟在核桃炭疽病发生高峰期(6-9月份)，从全国各核桃主产区采集健康和疑似炭疽病果实、叶片和枝条，对病原菌进行分离，通过形态学、培养性状、多基因分子系统学分析和致病性测定相结合的方法，明确我国核桃刺盘孢属中潜在的致病菌种类和炭疽病致病菌种类。本项目的实验结果将为核桃炭疽病的发生规律和有效防治，以及抗炭疽病育种的研究奠定基础。

核桃炭疽病是我国核桃生产中的主要病害之一，发病严重时可引起减产30%以上，严重影响我国核桃产业的发展。本项目对我国核桃主产区河北省、山东省、河南省、陕西省、四川省、云南省以及北京等7个省份16个采样地点进行了系统的病害调查和样品采集。通过常规组织分离法分离病原菌，扩增菌株的ITS区域，并结合形态学特性，获得720株刺盘孢属菌株；通过扩增100个代表性菌株的ITS、TUB2、CAL、GAPDH、GS和CHS-1区域，构建多基因系统进化树，并结合形态学特性、培养性状和致病性测定鉴定胶胞刺盘孢复合种中病原菌种类；通过扩增代表性菌株的ITS、TUB2、GAPDH和CHS-1区域，构建多基因系统进化树，并结合形态学特性、培养性状和致病性测定鉴定尖胞刺盘孢复合种中病原菌种类；通过致病性测定，明确内生刺盘孢属中潜在致病菌种类；采用ITS序列，针对河北省、陕西省、山东省、北京地区，选择不同地区内包含所有基因型的代表性菌株，进行序列比对，并进行系统发育分析，阐明了我国核桃炭疽病优势致病菌Colletotrichum gloeosporioides的遗传多样性。结果表明：（1）我国核桃产区河北省、山东省、河南省、陕西省、四川省、云南省以及北京地区核桃炭疽病的病原菌为C. gloeosporioides、C. siamense、C. fructicola、Colletotrichum aenigma、Colletotrichum godetiae以及Colletotrichum属的一个新种(暂时命名为Colletotrichum juglansense)，其中C. gloeosporioides为优势致病菌，C. aenigma和C. godetiae在中国首次报道引起核桃炭疽病；（2）通过致病性测定发现从健康组织中获得的C. siamense和C. fructicola具有致病性；（3）核桃炭疽病优势致病菌C.gloeosporioides具有丰富的遗传多样性。其中在河北省和山东省遗传多样性较高，山东省种群与北京地区种群遗传分化极大。研究成果不仅将为进一步探讨刺盘孢属真菌系统进化、遗传多样性和致病性的理论奠定基础，该研究也将为病害的发生规律和防治技术，以及有效防治核桃炭疽病和核桃抗炭疽病育种奠定坚实的基础。