Screening,identification,and activity assessment of endophytic actinomycetes from tomato plants against Botrytis cinerea

In this study,the endophytic actinomycetes in tomato plants in the farmlands in Huaibei City of Anhui Province were isolated and screened,and the bio-activities of the actinomycetes against pathogenic fungus Botrytis cinerea were determined.The population density of the actinomycete in the tomato roots,stems,and leaves were 5.66×104,0.67×104,and 0.39×104 CFU·g-1 fresh weight,respectively.According to the isolation position and phenotype characteristics,a total of 93 endophytic actinomycete strains were isolated from different tissues of healthy tomato plants,and,by using dual culture technique,7 strains with antagonistic activities against B.cinerea were screened,accounting for about 7.5% of the endophytic actinomycetes isolated.Among the 7 strains,the HNU-EA27 isolated from tomato roots had the best inhibition effect,with a formed inhibition zone of 28.3 mm.Based on the morphology,cultural characteristics,physiological and biochemical properties,chemotaxonomy,and 16S rDNA sequencing,the HNU-EA27 was identified as Streptomyces toxytricini.The culture filtrate of HNU-EA27 could inhibit the mycelium growth and spore germination of B.cinerea.The higher concentration the culture filtrate,the stronger the inhibition activity was.30% culture filtrate of the HNU-EA27 could completely inhibit the mycelium growth and spore germination of B.cinerea.Pot experiment showed that the prevention efficiency and cure efficiency of 30% HNU-EA27 culture filtrate against tomato gray mould were 80.6% and 73.8%,respectively,being superior to those of the 600-fold dilution of 50% badistan.It was suggested that the strain HNU-EA27 could be valuable in the bio-control of tomato gray mould.