采用2个大豆品种Hutcheson和Archer,通过温室一系列试验研究了水淹和终极腐霉（Pythium ultimum）对大豆的影响。一个试验是,大豆种子播种到经过灭菌土壤中,一部分土壤里接种沙子-玉米面的终极腐霉接菌体使之侵染,另一部分未接种病原菌;水淹处理是分别在出苗期水淹2 d、4叶节期（V4）水淹5 d,在每个试验中Hutcheson

The effect of conservation tillage on crop growth and soil microbial community play an important role in soil management.A long-term tillage experiment was conducted at Hailun Agro-Ecological Experiment Station of the Chinese Academy of Sciences.Tillage systems included no-tillage(NT),reduced tillage(RT)and rotary tillage(ROT).The study was to determine soybean growth and yield under conservation tillage,and analyze soil microbial diversity with Real-time QPCR and denaturing gradient gel electrophoresis(DGGE).NT and RT inhibited soybean growth and increased the disease severity of root rot at seedling stage.Soybean growth and yield was significantly increased under NT and RT compared with ROT at maturing stage.The highest yield of 2 507.3 kg·ha-1 was obtained under RT,which was increased by 3.9% compared with ROT.The three tillage systems had no significant effect on the amount of bacteria,and the amount of fungi was NTRTROT(P0.05).The colony forming units(CFU)and the genomic DNA quality of soil fungi were increased by 31.9% and 13.3% under NT compared with ROT,respectively.The ratio of bacteria and fungi was increased significantly under RT and ROT.DGGE fingerprint showed that the soil bacterial diversity had no significant difference under three tillage systems,however,NT and RT increased soil fungal diversity.Principal component analysis(PCA)of DGGE banding patterns indicated that the bacterial community structure had a higher similarity under RT and ROT,and significant differences were observed on the fungal community structure under three tillage systems.

Species of the genus Pythium are distributed worldwide important phytopathogens,in recent years,the diseases of Pythium has increasing frequent.The article summarized the newest research about the decline of Pythium morphological,taxonomic species,the kinds of plant diseases,the methods of identification and management.It discussed the development and research in the further.The objective is to provide a theory for study of the identification and prevention of Pythium diseases.