| Phytophthora sojae Kauf.et Gerd. is an oomycete that causes Soybean Phytophthora Root Rot, a destructive disease on soybean, and it is an important quarantine pathogen in China. In this study, AFLP fingerprinting technique is used to find the molecular characters in P. sojea,. Based on the features of DNA of P. sojae an AFLP system is made for analyzing the molecular chracters between P. sojae and other oomycetes and fungi species. Using this methode a specific band was detected by AFLP and a maker of AFLP-SCAR was obtained for specific detection of P. sojae. The main results in this study are as follows:1. Using single spore isolating technique, 34 P. sojea strains were purified and then the virulence of the strains were identified. 9 specis belong to oomycetes and 23 specis of fungi, which are seed- and soil-borne pathogens in soybean were cultured as the references in analysis of molecular characters.2. An AFLP protocol for analyzing P. sojea was established. 56 pairs of primers are polymorphic amplification in strains of P. sojae. Some special fragment were found in amplifying by primer pairs E-CG/M-AG, E-TC/M-CC and E-AT/M-AC. A 660 bp clear band was amplified using primer pair E-CG/M-AG.3. The special fragment was recovered, cloned and sequenced. Based on the sequence a SCAR primer was designed for amplifying a singal band in isolates of P. sojae. It means that the specific AFLP marker was changed to a SCAR marker successfully.4. The SCAR primer was tested for its specificity, reliability and sensitivity. Using the primer a 280 bp band was amplified in all of the isolates of P. sojae but not in refenrence oomycetes and other fungi species. The sensitivity of the SCAR primer is on 10 pg of DNA concentration of P. sojae.5. A molecular detection protocol for P. sojea was established after selecting the condition of react systems.
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