Effect Of Disease Control Treatment On Soil Microbial Community In Potato Root Zone And Isolation Of Strains Antagonizing Late Blight

Potato is the third largest food crop in the world after rice and wheat,and has important economic value.Potato late blight is recognized as the first potato disease in the world.The occurrence of late blight will cause large-scale potato deaths,cause serious economic losses,and greatly restrict the development of the potato industry.In recent years,chemical and biological control methods for potato late blight have been studied in terms of agricultural sustainability,reduction of pesticide residues,and physical health.However,there are few reports on the effects of these control methods on soil microbes in the potato root zone.This study mainly used field experiments to analyze the effects of biological control represented by Streptomyces 335920 and chemical control represented by mancozeb on potato late blight and yield.With the help of high-throughput sequencing technology,the effects of two control methods on soil bacterial and fungal communities in the potato root zone were studied.The strains that antagonize the Phytophthora infestans in the root zone of potato were screened through the flat-panel confrontation experiment,and further studies on the growth characteristics of the isolates with better antagonistic effects were conducted.The specific research results are as follows:(1)Streptomyces 335920 was identified,which was determined to be Streptomyces hygroscopicus.Streptomyces 335920 grows well on the culture medium ISP1-7 and has a certain tolerance to chemical pesticides.Streptomyces 335920 was used in field experiments,and three different treatments were set up: streptomyces,mancozeb,and control.Compared with the control,the streptomyces and mancozeb treatment showed a downward trend in potato late blight disease index during harvest The treatment with a low to high disease index is Streptomyces <Mancozeb <Control.The yield of potatoes treated with Streptomyces and mancozeb was slightly higher than that of the control.The treatment of potato yield from high to low was: mancozeb> streptomyces> control.(2)Streptomyces treatment significantly increased the total soil bacterial abundance in the potato root area,and had no significant effect on the abundance of fungi.The treatment with mancozeb on behalf of the population significantly reduced the total abundance of soil fungi in the potato root zone,and had no significant effect on the total abundance of bacteria.Pco A analysis and LEf Se indicated that the treatment of streptomyces and mancozeb affected the bacterial community structure of the potato root zone soil.It is the development of the stabilized microbial community structure of the main dominant flora.Among them,the indicator microorganisms treated by Streptomyces are more abundant at the species level.PICRUSt function prediction analysis showed that the treatment of streptomyces and mancozeb enriched genes related to amino acid transport and metabolism,and the OTU abundance of each treatment in the subfunction of amino acid metabolism was: streptomyces> mancozeb>CK.Compared with the control,the mancozeb treatment significantly reduced the total abundance of soil fungi in the potato root zone.Streptomyces treatment did not significantly affect the total abundance of soil fungi in the potato root zone.Beta diversity analysis showed that the fungal community structure in the soil responded significantly to the addition of chemicals or biocontrol bacteria.Lef Se analysis showed that the indicator fungal microorganisms treated by Streptomyces were more abundant at the species level,and most of them belonged to Tremellomycetes.Most of the indicated microbial species in the mancozeb treatment group belonged to Agaricomycetes,but they were less than those treated by Streptomyces.FUNGuild functional prediction analysis showed that the treatment of streptomyces significantly reduced the abundance of woody saprophytic fungi in the soil compared with the control,which was nearly half that of the control.(3)A total of 23 strains were isolated from the soil of the potato root zone treated with three different treatments.Through the plate confrontation experiment,10 strains with antagonistic effects on the late blight fungus were selected.The 7 isolates grew differently on different media.The growth conditions of 7 isolates under different growth conditions such as temperature,p H,salt concentration and heavy metals were studied.The results showed that 7 strains had good adaptability to the growth environment.