Screening Of Functional Actinomyces Streptomyces Lycopersici RGN-GS-3 Against Vertucullium Wilt Of Tomato And Taxonomic Identification Of New Species

Verticillium wilt of tomato is a soil-borne disease caused by Verticillium dahliae and Verticillium alboatrum,which is widely distributed in all parts of the world,seriously affecting the yield and quality of tomato crops.At present,the control of tomato Verticillium wilt in our country is mainly focused on agricultural control and chemical control.Selection of high-yield varieties and application of pesticide fungicides have become the daily control methods.However,the large use of chemical pesticides not only poses a great threat to the environment,but also increases the drug resistance of crops.Biological control is safe and reliable,which can not only reduce the harm to the environment,but also ensure the quality of crops.Ther efore,it is of great significance to control the occurrence of Verticillium wilt of tomato by biological control.There are many kinds and large quantities of actinomycetes.Endophytic actinomycetes have the functions of preventing diseases,killing insects,weeding and promoting plants growth,and have diversity.In this study,screening of antagonistic actinomycetes against tomato Verticillium wilt from endophytic actinomycetes isolated from healthy and susceptible plants with tomato Verticillium wilt and to obtain dominant strains with better activity.The broad-spectrum activity of the dominant strains and the determination of the antibacterial activity of the fermentation broth were detected,and the antagonism of the active strains were verified by th e preliminary study on the control,colonization and growth-promoting mechanisms of tomato seedlings,and further provide strain resources for prevention and control of Verticillium wilt of tomato and commercial microbial agents.Simultaneously,a new strain of actinomycetes belonging to the genus Sphaerisporangium was identified by multiple taxonomic methods in order to discover and find new rare actinomycetes and enrich the resource base of actinomycetes.The main results are as follows:(1)A total of 512 actinomycetes isolated from healthy and susceptible tomato plants were rearranged to obtain 140 endophytic actinomycetes.There were 42 actinomycetes isolated from healthy plants,73 actinomycetes isolated from susceptible plants,and 25 strains of actin omycetes coexisting.The strains of susceptible plants have obvious advantages.(2)16 strains of actinomycetes were found to have broad-spectrum resistance in vitro antibacterial activity test,the inhibition rate is 6.15 ±0.02 %-67.86±0.01 %,among which 9 strains were isolated from infected plants and 7 strains were isolated from healthy plants.Strain RGN-GS-3 isolated from infected plants,which the spores and fermentation broth of strain RGN-GS-3 had the strongest antibacterial activity against the pat hogen of Verticillium wilt of tomato,the fungal inhibition rate reached 42.50±0.02 %-67.86±0.01 %,and the diameter of the bacteria inhibition zone reached 10±0.01-27±0.02 mm,and tesed fungi and bacteria also have strong inhibitory activity.(3)Spore suspension of active strain RGN-GS-3 can control the occurrence of Verticillium wilt of tomato.The incidence rate decreased from 83.56±0.91 % to 23.73±0.98 %,and the disease index decreased from 45.53±0.73 to 15.28±0.65.The application of the active strain RGN-GS-3 alone can promote the growth of tomato seedlings in terms of plant height,stem length,fresh weight and dry weight.A preliminary study on the growth promoting mechanism revealed that the strain could produce a variety of extracellular hydrol ase,and the strain could be stably colonized on the tomato root surface for a long time,and the colonization amount was 4.4 ×105±0.03 CFU/g.(4)The 16 S r RNA genome sequencing and phylogenetic analysis and morphological identification of the active strain RGN-GS-3 were carried out.The strain was initially identified as a specie of Streptomyces geuns,which was consistent with the basic characteristics of Streptomyces.(5)A new strain NEAU-mq3 T belonging to the genus Sphaerisporangium was identified by multiple taxonomic methods.Through phenotypic characteristics,molecular level characteristics,physiological characteristics,chemical classification characteristics and DNA homology analysis and comparison,the strain conforms to the characteristics of th e genus Sphaerisporangium,but is different from the first and second similar strains.Thus,the strain NEAU-mq3 T is determined to be a new species of Sphaerisporangium,named Sphaerisporangium rhizosphaerae.