小麦白粉病菌群体对温度的适应性研究

As the climate change and global warming, the incidence of wheat powdery mildew has continuously expanded northward. The disease occurrence frequency and severity presents ascendant trend. In contrast to this phenomenon, minimal elevation for wheat powdery mildew survives the summer is lower than previous record, which is therefore presumeed that the population of Blumeria graminis f.sp. tritici （BGT）has formed some adaptive mechanism to higher temperature. This project is planning to study the temperature sensibility and parasitic fitness of BGT samples from different wheat areas. Attempt to understand the status of sensitivity of BGT population to high temperature, and establish a model between temperature and parasitic fitness for simulation of the dynamic trends of the pathogen populations. The program will also attempt to explain the relationship between the BGT sensibility to temperature and the genetic diversity and the virulence of the pathogen. The HSP70 gene of wheat powdery mildew will be cloned and the impact of high temperature on the the expression of it studied. The expected results will help to reveal the effects of global warming on the BGT population evolution and to demonstrate the macroscopical and microcosmic adaptive mechanism of population of BGT to temperature. This will provide theoretical basis for disease forecasting and sustainable management of the disease.

随着全球气候的变暖，小麦白粉病的发生范围不断向北扩展，病害发生的频率和严重度也呈现上升趋势，但小麦白粉病越夏的海拔下限却呈现下降趋势，推测可能小麦白粉病群体已形成了某种对温度适应性机制。针对出现的这一现象，本项目拟以我国不同麦区的小麦白粉菌为研究对象，开展我国小麦白粉菌群体对温度敏感性以及不同温度敏感性菌株的寄生适合度研究，摸清我国小麦白粉菌群体对温度的敏感性状况，建立温度与寄生适合度的关系模型，模拟病菌群体的变化趋势；研究小麦白粉菌群体温度敏感性与遗传多样性和毒性关系，克隆小麦白粉菌的HSP70基因，并研究温度对其表达的影响；通过这些研究来揭示小麦白粉菌群体对温度的宏观和微观适应性机制，为小麦白粉病中长期预测预报和可持续治理提供理论依据。

对采集自四川、北京、甘肃、河南、浙江等10省市的小麦白粉菌标样，分离得到的139个单孢堆菌株的温度敏感性进行的测定结果表明，供试的139个菌株平均ET50为23.14℃，其中ET50最高为24.46℃，最低为21.34℃；58.76%的ET50值在23℃和24℃之间，仅有2.03%的供试菌株的ET50≥24℃。正态检验结果发现，自然环境中小麦白粉病菌群体已受到温度的选择压力。对温度敏感性不同白粉病菌株对其各流行组分测定的结果显示，对温度低敏感性的菌株与其它菌株相比在高温条件下具有相对较短的潜育期、相对较高的侵染几率、相对较快的病斑日扩展面积、相对较大的单病斑累积产孢量和相对较高的寄生适合度。对温度不同敏感性菌株的寄生适合度（Y）与温度（X）关系的分析发现，Y= (28.4-X)ˆ3.27、Y= 0.81(24.8-X)ˆ3.27和Y=0.798(23.7-X)ˆ2.457的方程形式可以对低、中和高敏感型菌株进行很好的拟合。基于以上模型，采用CMIP3和CMIP5模拟的结果表明，不同气候变化情景下抗高温小麦白粉病菌比例不同，抗高温菌株的比例将逐渐增大。利用RT-PCR和RACE技术克隆得到了小麦白粉菌HSP70基因cDNA 序列全长，GenBank 登录号为：JQ917466。该基因全长2216bp，编码648个氨基酸。对小麦白粉菌在28℃热激不同时间后HSP70的表达量结果表明，热激30min，HSP70的表达量即显著性上升，60 min时达到最高峰，随后表达量下降，且60 min时对温度低敏感性的菌株其HSP70表达量最高。小麦白粉菌群体对温度敏感性与毒性多样性相关性分析结果表明，ET50与毒性多样性（H和I 值）间存在显著的负相关。此研究结果揭示了小麦白粉菌群体对温度的宏观和微观适应性机制，为小麦白粉病中长期预测预报和可持续治理提供了理论依据。