Studied On The Pathogen Of Flax Wilt In Dingxi

1. The structure of Fusarium on the root of flaxThere were 101 Fusarium strains, which belonged to 5 species including F.oxysporum, F.solani, F.moniliforme, F.semitectium and F.lateritium via purification and identification on the root of flax in Dingxi, Gansu, China.87 isolates of F.oxysporum were gotten and its isolate frequency was 86.1%, 7 isolates of F.solani were gotten and its isolate frequency was 6.9%, 5 isolates of F.moniliforme were gotten and its isolate frequency was 5.0%, and 1 isolate of F.semitectium and F.lateritium, and the isolate frequency was 1.0%.The isolate frequency of Fusarium varies when the flax was in different season, but F. oxysporum's always was the highest.2. The pathogen of flax wiltAccording to Koch's postulate, the pathogen of flax wilt was F. oxysporum in Dingxi, Gansu, China..3.The pathogenic diversity of FusariumThe pathogenic diversity of Fusarium was remarkablely. All of 36 strong pathogenic isolates were F. oxysporum, 30 middle pathogenic isolates were 29 F. oxysporum and 1 F.solani. 16 weak pathogenic isolates were 14 isolates of F. oxysporum and 2 F.solani. 19 no-pathogenic isolates were 8 isolates of F. oxysporum, 4 isolates of F.solani 5 isolates of F.moniliforme, 1 isolate of F.semitectium and 1 isolate of F.lateritium.The pathogenic diversity of F. oxysporum .: There were 36 strong pathogenic isolates, 29 middle pathogenic isolates, 14 weak pathogenic isolates and 8 no-pathogenic isolates in 87 isolates of F. oxysporum.4. The growth condition of F. oxysporum and its toxin filtratesBy the choices of culture liquids , temperature, time, model, pH of liquids, and sunlit or not, it was found that PD liquid was suitable for pathogen growth, and the optimum culture condition was 25℃, darkness, shock for 12h/d, pH=7 and 24d.. New-Czapek liquid was suitable for toxin growth, and the optimum culture condition was 25℃, light, continuous shock, pH=7 and 14d, pH was no significant effect on toxin production.5. The harm of F. oxysporum toxin filtrates to radicle of flax and seedling of flaxThe toxin of F. oxysporum depressed the flax's radicle growth remarkably, and high concentration meant strong depression. Different treatment caused the seedling of flax wilt in different degree. Be treated after 24h, the 100% and the 50% both caused light-reaction, be treated after 48h, the 100% caused mid-reaction, and the 50% caused light-reaction all the same, be treated after 72h, the 100% caused heavy-reaction, the 50% caused mid-reaction, and the CK is normal.