| Phytophthora Root Rot caused by Phytophthora sojae Kaufmann & Gerdemann, is one of the most destructive disease in soybean and also the quarantine pathogens for P. R. China. Phytophthora sojae could be spread as oospores carried in soybean seed, as well as oospores existed in soil and disease soybean residues. Since more and more soybean was imported into China, and most native soybean cultivars were sensitive to P. sojae, so the root rot caused by P. sojae is being a serve threatment to the soybean production in P.R.China. The development of the technique for rapid pathogen detection from the imported soybean will be very important for the controlling of Phytophthora root rot on soybean in P.R.China.Firstly, In this work, twelve Phytophthora strains were isolated from the soil residue carried in the soybean imported from USA by soybean leaves baiting, amongst them, 6 isoates were chosen for identification. The morphological characteristics, pathogenicity, host range. Based on its abundant, rounded hyphal swellings in chains, right-angle and shrinking in branch, non-papillate, ovoid sporangium, internal proliferation of sporangiophore, zoospores formed within sporangium, homothallism, rounded oogonia and paragynous antheridium as well as its narrow host range , the symptom of soybean blight after inoculation, the pathogen was identified as Phytophthora sojae. A couple of primer specific to Phytophthora sojae was used for further identify. All 12 isolates resulted a specific band with size about 330bp.The results indicated that these strains were Phytophthora sojae.Secondly, the other work aims to find pretreatment deadly temperature for exterminating Phytophthora sojae in imported seeds of soybean. It showed that, under the condition of 60 ℃ and keeping 20min, germination rate of oospore was 0%, and death rate was 100%.
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