| Spot blight of Luobuma(Apocynum venetum)caused by Septoria apocyni is a fungal disease that seriously harms the yield and quality of A.venetum,and is also one of the main fungal diseases that restrict the industrialization of A.venetum in China.In this study,two strains of S.apocyni isolated from disease A.venetum in Gansu(GS)and Xinjiang(XJ)were used as test strains in combination with greenhouse and field experiments,and research on the biological characteristics of the pathogen,the disease loss assessment and the prevention and control technology of the disease in the field were carried out.In order to provide support for the sustainable use of A.venetum,the main results are as follows.(1)The biological characteristics of S.apocyni.The fungus did not produce spores on the 7 medium tested,the colonies could grow in the range of 10～30 °C,the optimal growth temperature was 25 °C,and they could grow in the range of p H 4～10,and the optimal growth p H was 5～5.5;the GS strain grew best on PDA medium,and the XJ strain grew best on 10% A.venetum juice + PDA medium,and when cultured in the dark at 25 °C for 20 days,the net growth diameter of colonies can reach 31.44 mm and 27.95 mm,respectively.Both XJ and GS could grow under 20～120 min of ultraviolet irradiation,and both strains grew best under alternating 12 hour light and12 hour dark conditions,and the net growth diameters of XJ and GS on PDA and 10%A.venetum juice + PDA medium were 15.8%,8.9%,13.8% and 9.8% higher than those on 24 h continuous light at 20 days,respectively,while there was no significant difference in the net growth diameter of colonies between different light treatments.(2)Effects of spot blight on leaf biomass and medicinal components of A.venetum.Spot blight significantly reduced the biomass and isoquercitrin content of A.venetum leaves,which were 2.0%～24.8%(P<0.05)and 25.8%～90.5%(P<0.01),respectively.While the total flavonoid content increased significantly compared to the control,increasing by 15.8%～40.5%(P<0.01),respectively.The contents of hyperoside,rutin,Fe and Cu showed a trend of increasing and then decreasing with the increase of severity of spot blight,and reached the highest level at severity level 3,with increases of 8.1%～17.7% and 4.0%～5.1%(P<0.01),5.7%～68.2% and33.3%～100.0%(P<0.05),respectively.Compared with the control,the content of hyperoside and rutin were the lowest when the severity was grade 6,which decreased by 38.1%～42.9% and 19.6%～19.8%(P<0.05),respectively.The content of 16 amino acids was significantly reduced,which was 39.3%～67.1% lower than the control,and the content was the lowest when the severity was grade 3 and 6,which were51.1%～67.1%(P<0.01)lower than that of the control.(3)Chemical control of S.apocyni spot blight in field.Four types of fungicides were sprayed in the field conditions.On the 15 th day of application,the relative prevention efficacy of the four types of fungicides in descending order were:chlorothalonil + fluopyram o trifloxystrobin complex > fluopyram o trifloxystrobin alone > chlorothalonil alone > methyl thiobacillam alone.The disease index were decreased by 38.1%～74.2% and 65.7%～77.3%(P<0.05)under the single application of fluopyram o trifloxystrobin and chlorothalonil +fluopyram o trifloxystrobin combination,respectively.And the relative control effects reached 68.0% and 71.2%,which were 43.4%～49.9% and 46.7%～53.1% higher than that of chlorothalonil and methyl thiobacillam alone,respectively.The leaf disease index of the leaves of the upper,middle and lower parts of the A.venetum plant increased sequentially,and the disease indices of the lower leaves were the highest,which were 3.0～6.7 times and23.0～51.3 times(P<0.01)higher than that of the middle and upper leaves,respectively.(4)Fungicide control effects on medicinal components of A.venetum leaves.The better the control effect,the higher the content of hyperoside,rutin,isoquercitrin and amino acids,which increased by 32.2%～90.8%,19.1%～39.7% and 18.7%～48.3%,respectively,while the changes of incidence and total flavonoid content were opposite,and the regression equations were y=0.307-0.298 x and y=6.591-2.108 x,respectively.The content of 17 amino acids increased by 0.005～5.387 mg/g compared with the control,which was 0.5%～178.6% higher than control. |
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