Isolation,identification,bacteriostatic activity of the biocontrol Actinomycete Sc-7 and its growth-promoting effect on rice
In order to screen out Actinomycetes which can significantly inhibit Xanthomonas oryzae pv.oryzae(Xoo),and X.oryzae pv.oryzicola(Xoc),this study collected soil from various plant rhizospheres and isolated 60 strains of Actinomycetes using the dilution-spread and streak-plate isolation methods.Through the co-culture and the oxford cup methods,one of the 60 strains of Actinomycetes,strain Sc-7,which has significant inhibitory effects against Xoo and Xoc was obtained.Based on morphological and microscopic observations,physiological and biochemical experiments,and polygenic cluster analysis,a phylogenetic evolutionary tree was constructed and this strain Sc-7 was identified as Streptomyces lavendulae.The potting experiment demonstrated that spraying 2-fold fermentation dilution of strain Sc-7 before pathogen inoculation had prevention control efficiency of 74.57%and 65.33%on rice BLB and BLS,respectively,and the lengths of the lesions were significantly shortened.The treatment with fermentation filtrate of strain Sc-7 made Xoc and Xoo cells extensively lysed,crumpled,and perforated,and increased cell membrane permeability and decreased extracellular polysaccharides.In addition,germination promotion assays demonstrated that different dilutions of strain Sc-7 fermentation broth could promote the growth of rice seed buds and roots.Compared with sterile water treatment,the treatments with fermentation at 10-fold and 50-fold dilutions increased the shoot length by 32.79%and 37.70%and root length by 75.00%and 97.00%,respectively.Tube-based seedling assays showed that 10-fold and 50-fold dilutions of strain Sc-7 fermentation increased plant height by 16.68%and 10.53%,respectively.Salt stress alleviation experiments exhibited that the treatment with 10-fold fermentation dilution of strain Sc-7 alleviated the rice symptoms caused by salt stress to a certain extent.The above results indicate that strain Sc-7 has the potential to promote plant growth and prevent diseases and is expected to be developed as a biopesticide and biofertilizer.
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