| Soybean, as one of major oil crops, is not only an important material but also is an extremely important crop in Agriculture. Compared with foreign, the soybean yield and quality of China are worse, which are mainly due to soybean diseases. At present, soybean diseases distribute widely and damage severely in China. It is of great significance to carry out pathogens identifying, resistance screening, and suitability analysis of potential distrabution, which can be conducive to control the spread of diseases, promot soybean production and improve the quality. The main results were as follows:1. First identification of Phomopsis longicolla isolated from Chinese soybean field. The infected seeds and stems were collected from Chinese soybean field in summer of 2005-2008. Using traditional and molecular techniques, P. longicolla, as the pathogen, was isolated and identified. This is the first report of this pathogen found in China.2. First report of Phomopsis longicolla can cause a new soybean stem blight. The pathogen mainly caused the Phomopsis Seed Decay and Soybean Stem Canker, but a new stem blight caused by the pathogen was found in Jiamusi, Heilongjiang. At the mid-and late growing period of soybeans, the lower part of stem was formating water and chlorotic spots, followed by dry, shallow color. The lesion expand upper and lower ring stem, cause plants severe wilting and dead. But the leaves don't fall off. The symptom caused by Phomopsis longicolla, which was a new disease, named Soybean Phomopsis stem blight.3. The pathogenicity of Phomopsis longicolla was of significant differences, but excellent resistance resources existed in China. Ten isolates of P. longicolla were selected to inoculate the seedlings and seeds to confirm the pathogenicity. The result indicated that the pathogenicity of the 10 isolates was different. Some strains were highly pathogenic; inoculated soybean began to death after one week and could see the black conidia of the pathogen. Infected seeds were not germination, 100 percent were rot more serious than what has been reported in other countries. That showed these strains of P. longicolla were more pathogenicity to seeds. PL12, the most pogenitic strain, was selected to identify the resistance of 285 soybean cultivates to Phomopsis longicollla. Seventy-four plant varieties were resistant, accounts for 26.0%. Fifty-three plant varieties were moderately resistant, accounts for 18.6%. The moderately susceptible to very susceptible plant varieties were 158, accounts for 55.4%. Forty-three soybean materials in 285 were of high resistance to P. longicolla, and the mortality rate approached to zero.4. Diaporthe phaseolorum var. caulivora can suit for growth in major part area of our country. The Northeast area, the Northern region and the Yunnan-Guizhou Plateau area are the highly suitable area. The potential distribution of D. phaseolorum var. caulivora in China has been analysed by using CLIMEX and GIS combination software.The results indicated that the Northeast area and the Huanghuai Haiti area, the main soybean production area, were the medium and high suitable area. It is urgently to establish early warning mechanism to prevent the pathogen invasing.5. Phytophthora sojae could grow in a broad scop of our country, moreover the risk is high. The whole East China area belonged to high stuitable area of the pathogen. Especially the wide areas included the Northeast area, Huanghuai area and South area of our country.6. Fusarium virguliforme was suitable to live in south our country. The global climate warming and soybean seed area increasing were favorable for the pathogen. Recognizing of its destructiveness to soybean, it should to arouse the regarding of the pathogen in Northeast area and Huanghuai area.
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