Antagonism Of Soil Streptomyces Against Phytophthora Infestans And Their Growth-promoting Properties

Potato is the fourth largest food crop in the world and the main food crop in Inner Mongolia,China.Late blight is one of the most serious diseases in potato production,and its pathogen is Phytophthora infestans.At present,the main method against potato late blight is to use chemical pesticide control,but the long-term application of chemical pesticides destroys the ecological environment,and the pathogenic bacteria gradually develop resistance.Therefore,the selection of efficient and environmentally friendly biological control methods has become a research hotspot at this stage.Actinomycetes are recognized as the most valuable class of biocontrol bacteria,and are good biocide screening resources.Among them,streptomyces has attracted much attention,and it has antibacterial,fungal,viral and anticancer activities.In addition,some plant endophytes can promote plant growth through various functions such as nitrogen fixation and phosphorus dissolution.However,in recent years,the growth-promoting research on Streptomyces mostly comes from plant endophytic actinomycetes.The growth-promoting ability of Streptomyces in soil is relatively rare.Therefore,it is of great value and significance to study the antagonistic and growth-promoting properties of soil Streptomyces.Inthis researsh,eight strains isolated from soils in different regions of Inner Mongolia were used to study their physiological and biochemical properties and their molecular identificationTheir antagonistic and growth-promoting abilities were tested.The results are as follows.1.Physiological and biochemical characteristics detection and molecular identification results showed that eight strains were all streptomyces.2.The fermentation supernatant and the disrupted solution of eight strains have good antagonistic effect on Phytophthora infestans,and the antagonistic activity of bacterial cell disruption is the strongest.WH4-57 and WH4-58 exhibited broad-spectrum resistance to Escherichia coli,Staphylococcus aureus,Bacillus subtilis,and Saccharomyces cerevisiae.3.The fermentation supernatant and bacterial cell disruption of eight strains can effectively reduce the lesion area of potato leaves inoculated by Phytophthora infestans.4.The bacterial cell disruption of eight strains showed strong inhibitory effects on human granulocyte leukemia cells and glioma cells.5.Eight strains have the abilities to produce ammonia,produce urease,iron-producing carrier and can produce ACC deaminase.The yield of indole acetic acid is between 13.01-66.93 ?g/mL,and the phosphate-dissolving ability is between 2.34-20.22 ?g/mL.6.Eight strains could promote the growth of potato seedlings,and all of them could effectively promote the seed germination of the Lycopersivonesculentum Mill.WH4-58 can effectively inhibit the germination of Echinochloa crusgalli L.Beauv and Poa annua L.