| In order to explore the the pathogens for root rot disease of Mongolia Astragalus and revealing the harm root rot disease brings. Pathogen species, different physiological characteristics under different culture conditions are studied in this thesis. In addition, in this study,3 different kinds of bacteriostatic agents are chosen to explore their control effect for Astragalus root rot disease. Giving preliminary analysis for the content difference of active ingredients between healthy Astragalus and those have root rot disease. All the studies aim to initially identify major species of Astragalus root rot disease pathogens,to explain the reasons for plant disease, to find the optimum growing condition for Astragalus and to confirm the best fungicides. Providing theoretical basis for Astragulus planting and root rot disease prevention and cure in Longde county, Ningxia province. The study results are as follows:(1) The experiment of studying the main pathogens for root rot disease of Astragalus shows that: the major pathogens are 3 kinds of Fusarium, Fusarium oxysporum,Fusarium solani and Fusarium moniliforme. The separation frequency for Fusarium oxysporum is 53.33%, 65%and72% for each 3 times. For Fusarium solani, the frequency is 26.7%,15% ,20%, and for Fusarium moniliforme the number is about only 5%. The result shows Fusarium oxysporum is the main pathogen for root disease in Ningxia while the Fusarium moniliforme is an unique pathogen in this area. The disease incident of the Astragalus whose epidermis is stabbed is 65.07% while for those is not stabbed, the incident is only 34.92%. This indicate epidermal damage is a main factor that will induce root rot disease.(2) The physiological characteristic of main pathogens under different culture conditions shows that:the best living temperature for Fusarium oxysporum and Fusarium solani is 20-30 ℃, the average colony diameter is 79.47mm and 75.44mm. The best temperature for Fusarium moniliforme is 25-30 ℃, when it is over 35 ℃ the growing rate for all 3 pathogens slow down,when it is over 40 ℃, all pathogens stop to grow. The influence different pH brings differs from each other. When the pH is 5-9, Fusarium solani grows well, Fusarium oxysporum grows slower when it is in alkaline condition, Fusarium moniliforme grows slow in neuter and alkaline condition, the average diameter is about 25mm for Fusarium oxysporum when pH is 5-9, Fusarium solani’s is 62mm and Fusarium moniliforme is about 25mm. With the growing number of pH,alkaline condition suppress the the growing of Fusarium moniliform. When Fusarium oxysporum is under the lighting condition of 24h lighting, the growth speed is 11.33/d and Fusarium solani’s is 11.08mm/d, for Fusarium moniliform the number is 1.67mm/d. Under the lighting condition of 12h lighting and 12h dark, the speed is 10.75mm/d and for Fusarium solani it is 9.52mm/d, and it is 3.75mm/d for Fusarium moniliform. Under the condition of 24h total dark, the growth speed is 10.83mm/d, and it is 15.95mm for Fusarium solani, for Fusarium moniliform it is 4.41mm/d. In conclusion, the growing speed of Fusarium oxysporum is suppressed in the condition of 24h darkness, the speed for Fusarium solani is slightly suppressed under the condition of 12h’s lighting and 12h’s darkness. In the environment of 24h"s lighting, Fusarium moniliform suppressed to grow larger.(3) The chemical control experiment shows that:Astragalus which are processed by different antiseptic all have a better growth during their different growth periods compared to those only processed by water. The combination agents group Gaoqiao+Rui Miaoqing with the concentration of 15007.5g/ha-1 and 22512g/ha-1 both have a good root rot disease control effect. The combat rate is 30.25% and 32.40% for each. The combat rate for Thiophanate-methyl with a concentration of 700.5g/ha-1 is 34.11% and the rate for Hymexazol(560g/ha-1) is 36.21%. Though Hymexazol feels like to have the highest combat rate, Gaoqiao+ Rui Miaoqing has a far more reliable control effect among all three antiseptic. In conclusion, antiseptic Gaoqiao+Rui Miaoqing is the best choice for Astragalus root rot disease prevention and cure.(4) The research about testing the difference active ingredient content between sick Astragalus and healthy ones shows that:Astragalus root rot disease has a significant influence for the content of Asreagaloside. Healthy Astragalus has about 14.16% more than sick ones. Because Astragalus saponins is widely distributed in xylem and phloem root rot disease only has a slight influence for the content of Saponins in different part of Astragalus. Polysaccharides mainly distribute in xylem, sick Astragalus has 0.12% fewer polysaccharides than healthy ones, because polysaccharides is rarely presented in Astragalus, root disease significantly reduce the content of polysaccharides in Astragalus. |
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