Studies On The Pathogens Causing Angelica Sinensis Root Rot

Using Chinese traditional medical herb Angelica sinensis in Minxian county of Gansu Province as material, the pathogens causing A. sinensis root rot were isolated and identified. Based on this, biological characteristics of the pathogen was studied, and then field fungicide screening and virulence evaluation experiment were also done in order to select efficient, low poisonous and low remaining fungicides to control the pathogens causing A. sinensis root rot, ensuring their yield and qulity in the industrialized production. The main study results are as follows:1.The chief pathogens causing A. sinensis root rot were F. solani (Mart.) Sacc, F. oxysporum Schlecht and F. redolens Wollenw. F. solani and F. oxysporum had strongly nosopoietic ability with isolation frequencies of 36.0%-48.0% and 26.3%-32.0% respectively. The incidence of the root rot after inoculation pathogens by goring radicles were significantly higher than that by non-goring, indicating the wound is helpful for the pathogens to infect the plants. It suggests that the transplant and cultivation should be careful to keep the plant integrality.2.The best carbon sources was sucrose and the best nitrogen sources was sodium nitrate for F. solani. Darkness condition could promote their mycelia growth but restrain their sporulation. The mycelia get optimal growth and sporulation at pH=6. The optimal temperature was 25-30℃. Sucrose was also the best carbon source for F. oxysporum pathogen growth; sodium nitrate was the best nitrogen resources for pathogen growth; whole darkness condition could promote sporulation, however, 2 h of ultraviolet irradiation under dark was helpful for mycelia growth. The optimal pH was 6 for mycelia growth and was 5 for sporulation with optimal temperature of 25-30℃. The best carbon sources was glucose and nitrogen sources was ammonium nitrate for F. redolens. The darkness could promote mycelia growth with optimal pH of 6-7 and temperature at 25℃.3. Using water as CK, five kinds of general fungicide were selected from nine and the seedling dipped with those medicaments showed good appearance in the plant growth and low incidence rate of root rot, which were significantly lower than that in CK. The control effects from high to lower were 70% Topsin M, 70% Mancozed, 50% Crarbendazim, 50% Daconil respectively in turn. 72% Metalaxy mancozeb's prevention and control had the best effects in contrast, the incidence rate reduced by 44% and yiled got at the highest of 2532.44 kg/hm~2 with better root rot prevention.4. According to the field screening test result, five kinds of fungicides were selected and their virulence were measured. The result showed that 70% Topsin M, 75% Daconil and 70% Mancozed showed better inhibition effect on the A. sinensis root rot. The EC50 were 0.37, 1.17 and 48.59 mg/L for F. solani respectively; 4.75, 0.12 and 0.001 mg/L for F. oxysporum; 0.004, 0.0005 and 0.0001 mg/L for F. redolens. All the relative coefficiency were above 0.9000, indicating high estimated dependability.