| Soybean root rot is a world wide disease. At the same time, it is also one of the universal occurrence and seriously damaged disease in soybean production of Xinjiang. Previous studies have shown that the soybean root rot was attacted by multi-pathogens and it was generally believed that the soybean root rot was more difficult to control, because of the features such as soil-borne pathogens mixed infection and early concealed disease. To further analyze the mixed infection regularity of the pathogens, the rDNA-ITS analysis method has been used for validating7pathogens of the disease in this paper. The biological characteristics of pathogens have been carried out by conventional biological methods. The pathogenic role of the main pathogens were analyzed by multiple-pathogens cross-inoculation and specific primers have been used for molecular marker to establish the molecular discrimination system and molecular detection of population dynamics of major pathogens on the plant and the monitoring results of molecular dynamics of pathogens have been compared with the conventional monitoring results of dynamics of mixed infection pathogens and analyzing the infection regularity of soybean root rot.The results of pathogencity test have shown that Rhizoctonia solani, Pythium aphanidenatum, Fusarum oxysporum, Fusarum graminearum, Fusarum avenum, Fusarum solani and Fusarum solani var. coeruleum (sacc.) Booth could all cause soybean root rot among them while Fusarum oxysporum, Rhizoctonia solani and Pythium aphanidenatum were stronger in pathogenicity.The identification results of six of seven pathogens were validated by the rDNA-ITS sequence analysis soybean root rot.The research results of biological characteristics of the seven major pathogens have shown that Rhizoctonia solani, Pythium aphanidenatum, Fusarium oxysporum mold all were able to grow under20～30degrees centigrade and optimum temperature was25degrees centigrade, which is coincide among them. Rhizoctonia solanii were suitable for growth in the neutral acidic and dark conditions. Pythium aphanidenatum were suitable for growth in acidic to neutral and light conditions. Fusarium oxysporum are suitable for growth in the weakly acidic to alkaline, light and dark alternating condition.Cross-inoculation test proved that Rhizoctonia solani played a leading role in multiple-pathogens pathogenic process.The specific primers of each pathogen could obtain target band by PCR and the molecular discrimination system of multiple-pathogens of soybean root rot has been initial established by optimization of PCR system and sensitivity detection.The detection results of30samples of soybean collected in peak incidence of soybean root rot have shown that the detection rates of Rhizoctonia solani, Pythium aphanidenatum were70.0%,10.0%, and6.7%respectively. The result proved that Fusarium spp. had played a dominant role in the composite pathogenic process.The dynamic monitoring results which obtained by traditional isolated identification and molecular identification has shown that the results of molecular analysis were the same as the traditional separation. Fusarium spp. has the highest separation ratio and shown a up-trend during the whole growth period. Rhizoctonia solani has a lower separation ratio, but the separation ratio is relatively high during the seedling stage while the separation ratio of Pythium aphanidenatum is the most lowest and there were little changes during whole growth period. This is also proved that the Rhizoctonia solani have played a forerunner role in composite pathogenic process, and Fusarium spp. has played a leading role in composite pathogenic process.Mixed infection regularity analysis shows that Fusarium spp. is a predominant pathogenic species and dominant factor in local of soybean root rot in multiple-pathogens infection soybean process. Rhizoctonia solani is predominant, pathogenic species in seedling stage and played a forerunner role and Pythium aphanidenatum played a secondary role in pathogenic process. |
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