Isolation, Identification And Antibacterial Activity Of Endophytic Actinobacteria And Rhizosphere Soil Actinobacteria In Several Medicinal Plants

With a special ecological environment in Ganzi, Sichuan province, a wide variety of medicinal plants grow there. This article studied the diversity of endophytic and rhizospheric actinomycetes isolated from 24 medicinal plants collected from different environments in Ganzi, using culture-independent and culture-dependent methods, and the antibiotic activities of actinomycetes against Pathogenic bacteria or fungi with confrontation tests.The results showed that, there were many factors to affect actinomycetes’ distribution, growth and isolation. Both soil organic matter and sampling altitude were negatively related to the number of actinomycetes; Soil moisture and the number of actinomycetes were positively correlated; Soil pH was negatively related to the number of endophytic actinomycetes while positively related to that of rhizospheric actinomycetes. The statistics showed obvious differences in quantity of isolated actinomycetes from different media:citrate medium did the maximum number, No.5 and gauze No.1(GA) medium followed. The distribution of endophytic actinomycetes was also different among the plant tissue parts:the largest number was found in root, then in stem and leaf, respectively.This article made a preliminary study of the diversity of actinomycetes with weighted calculation, based on 7 phenotypic characteristics of them. Value G and Value C of 225 actinomycetes were different, respectively. The scatter distribution was concentrated in (Value G, Value C) coordinate system. ARDRA-RLFP analysis of endophytic and rhizospheric actinomycetes indicated that the macrorestriction maps of 94 rhizospheric actinomycetes and 131 endophytic actinomycetes had some differences. The diversity of actinomycetes was some abundant, but the clustering distribution was uneven. Phylogenetic tree of some sequenced strains indicated that there were 2 genera and 7 species among sequenced strains, of which about 85% belonged to Streptomyces. The denaturing gradient gel electrophoresis(DGGE) method was applied to investigate the diversity and community structures of the endophytic actinomycetes isolated from different tissue parts of Melissilus ruthenicus. The results indicated that the diversity and community structures of the endophytic actinomycetes were significantly different among different tissue parts. The highest diversity index(H) and richness(S) were found in the plant flower.According to the screening of antagonistic actinomycetes against Pathogenic bacteria or fungi, different actinomycetes had different inhibition. On the whole, inhibitory effect on Fusaium oxysporum was the best. The inhibitory effect of SCAUSN-2 was better than any other actinomycete, especially against Fusaium oxysporum. Pot experiment indicated that watermelon seedlings grew differently under different treatments. Statistical analysis showed that the index of A treatment, which only sprayed a certain concentration of Fusarium pathogen bacteria was on a low level, and had significant differences from others. On the contrary, the index of C treatment, which sprayed a certain concentration of SCAUSN-2 was on a high level, with the intervention coefficient IC>0.5, promoting the growth of watermelon seedlings greatly.