茶白星病病原及其致病条件研究

Tea white scab is one of the most serious fungus disease in high altitude tea plantations around the world.Although the pathogen was identified as likely Phyllosticta theaefolia Hara or Elsinoe leucospila Bitancoum Jinkins by domestic and international researchers,The separating experiment and artificial infection test can not be repeated.The uncertainty of pathogen results in the severe hysteresis in the research on tea white scab.Our research has shown that Guignardia mangiferae is the dominant fungal from infected leaves and also widely exists in healthy leaves.Symptoms disappered when infected tea tree was transplanted from high altitude to low one,However,symptoms would appear when healthy tea tree was transplanted from low altitude to high one,With G.mangiferae existing in the process of transplanting all the time.Therefore,we proposed that G.mangiferae was an endogenous opportunistic pathogens of tea white scab.we would obtain endophyte-free tea plants through seeds disinfection,aseptic seedling and chemical treatments.Moreover,G.mangiferae was inoculated in tea plant in both high and low altitude tea plant garden respectively and its infection and pathopoiesis process were explored by technologies such as phytopathology,molecular biology and plant anatomy. we aimed at analyzing the environmental factors and physiological mechanism which trigger and fulfil the transition between harmless endogenous and pathogenic parasitic ,researching systematacially the rule of disease caused by endogenous opportunistic pathogens,providing a sound theoretical basis for ecological prevention and control of tea white scab.

茶白星病是世界各产茶国高海拔茶园最严重的真菌病害之一，国内外分别认为其病原为叶点霉属菌或茶疮痂菌，但在回接或分离实验上均不能被重复。由于病原的不确定性，导致了有关该病的研究严重滞后。本项目申请者前期研究表明，芒果球座菌是茶白星病样中的优势菌，但该菌也广泛存在于健康无症茶叶中，高海拔的发病茶树移植低海拔后即无症，而低海拔的无病茶树移植高海拔后即发病，且移栽过程中始终含有芒果球座菌。因此，我们提出芒果球座菌是引致茶白星病的内生条件致病菌的假说，本项目拟通过种子灭菌、无菌隔离育苗及药剂处理等措施获得无内生菌的实生茶苗，分别在高、低海拔环境下人工接种芒果球座菌株，采用植物病理学、分子生物学及植物解剖学等技术，检测该菌的侵染及致病过程，解析其实现无害内生与致病寄生之间转换的环境诱因及生理机制，系统研究内生条件致病菌引致病害的致病规律，为茶白星病生态防控提供理论依据。

茶白星病一直是全球高海拔茶园最严重的真菌病害之一，也是我国高海拔茶园的主要病害。其病原在我国曾认定为叶点霉菌Phyllosticta theaefolia Hara，但普遍发现难以回接显症，本项目将病斑浸泡接种法分离的真菌经过柯赫氏法则及分子鉴定，首次厘定我国茶白星病的病原为茶疮痂菌Elsinoe leucospila Hara，与日本等国的茶白星病病原为同种真菌，其生物学特性表明，茶疮痂菌在温度26℃、 pH7的PSA培养基上生长速度最快，28d菌落生长直径l达2.79cm，最适宜生长的碳氮源为蔗糖与甘氨酸，通过显微观察明确该菌的侵染途径为上下表皮及导管，同时应用病菌回接的转录组测定，分析得出病菌入侵茶叶后的差异基因富集表现为“活性催化”的上调与次生代谢产物生物合成途径，与田间病害入侵从叶面局部分布至全叶，而且斑点都局限在2mm大小的发生特点表型一致，从而明确了茶白星病病原及发病条件。由于感官审评茶白星病致苦特征突出，通过各种理化测定，明确其中与发病率呈正相关的游离氨基酸、EC、ECG、r-氨基丁酸、丝氨酸、丙氨酸、苯丙氨酸，其中疏水性氨基酸含量与致苦具有相关性，本研究在厘定我国茶白星病病原的基础上，不仅从细胞、分子水平阐述茶白星病的发生特点，也为明确茶白星病的致苦致病机理提供理论依据。