Study On Pathogen Identification And Molecular Detection Technology Of Soybean Root Rot

Soybean root rot, a common disease occurring in soybean growing areas has caused economic losses in the main growing areas. After infected by soybean root rot pathogen, the leaves gradually turned yellow, susceptible plants dwarfed,pods reduced, the tips of lateral root of the under-ground part were infected firstly and then brown stripe fleck appeared on the underside of taproot, the darkening at the epidermis and cortex, the under part of taproot entirely rot, and the whole plant death gradually, directly affected on the soybean yield.Four hundred and twenty five isolates were identified by different selective culture medium cultivating diseased-partition,cut and divided from 302 samples collected from fields of Burjin County in Xinjiang during different growth stages, and the Fusarium were 307 strains, Rhizoctonia were 84 strains, Pythium were 21 strains, the separation ratio are 72.2 %, 19.8% and 4.9%, respectively. Phytophthora was not found in these isolates. This result preliminarily shows that soybean root rot in this region is Fusarium.root rot, and the main types of pathogens include Fusarium, Rhizoctonia and Pythium.By single-spore isolating of 307 Fusarium strains, the results of species identification showed that: these Fusarium belonged to five species and a variation, their respectively is: F.oxysporum Schlecht, F.solani (Mart.) Sacc, F.graminearum.Schwabel, F.solani var.coeruleum (Sacc.) Booth, F.avenum(Corda&Fr.)Sacc. and F.merismoidescorda Corda.The isolation frequence is as the following: the highest occurence frequency of F.oxysporum Schlecht, F.solani (Mart.) Sacc followed by the second, F.merismoidescorda Corda were the lowest.The discriminate result of species and anastomosis groups (AGs) shows that all of these 84 isolates of Rhizoctonia DC. were identified as Rhizoctonia solani and these isolates can be categorized as follows:AG1, AG2 and AG4.Three anastomosis groups,isolation frequence is as the following:AG4, AG2, AG1. Compared the Affinity of different groups there are differences between the same similarity group and the different groups. 21 Pythium isolates were identified as Pythium aphanidermatum.Based on the pathogenicity Comparison of Fusarium, Rhizoctonia solani and Pythium aphanidermatum, the results showed that: Rhizoctonia solani had most virulence; Fusarium oxysporum had most virulence in Fusarium.spp and the Fusarium solani followed by the second, Pythium has some pathogenic.Use of rDNA ITS-RFLP technology to analysis the pathogenic bacteria and the three non-pathogenic bacteria,s ITS restriction endonuclease analysis, established the molecular markers of Fusarium oxysporum, Rhizoctonia solani and Pythium, and studied on the molecular detection techniques of Fusarium species, and to lay a foundation of established the molecular detection methods of soybean root rot pathogen.