| The Garze tibetan autonomous prefecture located in the western Sichuan plateau is the transitional zone between Qinghai-Tibet plateau and western edge of Sichuan Basin,with complicated natural conditions and climate variability.Garze is the major medicinal plants-producing region in china,more than 800 species of rare medicinal plants were grown in this area.The medicinal plants which grown in extreme environment with high altitude,high radiation,large different in temperature provide a rich resources for screening endophytic actinobacteria.In this study,the medicinal plants growthing in Garze were selected to be studied.,using traditional isolation,antimicrobial activity screening and molecular biology technology to analyze the diversity of endophytic actinobacteria,antimicrobial and growth promoting activity.215 endophytic actinobacteria were isolated from 44 medicinal plant species.Based on the morphological characteristics and BOXAIR-PCR analysis,84 representative strains were further sequenced,which belonging to 8 genera:Streptomyces,Pseudonocardia,Brevibacterium,Kribbella,Amycolatopsis,Pilimelia,Microbacterium,Nocardia,Streptomyces is dominant genera.58.6%out of 84 representative strains showed antimicrobial activity against at least one of tested pathogenic organisms,while the best antagonistic effect is against Fusarium oxyspirum F sp niveum,while inhibition of Escherichia coli,Salmonella sp.and Klebsiella Pneumoniae were poor.The number of strains with PKS ?,PKS ?,NRPS,Halo,CYP,phzE,dTGD enzyme gene fragments matching the anticipated length were 37.5%?75%?38.9%?30.6%?54.2%?43.1%?40.3%16.7%,72.2%,25.0%,11.1%,with the highest rates observed in PKS ?.Phylogenetic tress were generated using the type ? PKS gene cluster KSa gene sequences,the strains were divided into two major clades:one included known spore pigment production-linked KSa gene and other sequences were linked to the production of different types of aromatic polyketide antibiotics.In terms of plant growth promoting ability,38.1%out of 84 representative strains showed ability to produce IAA,31.0%of isolates produced cellulases and chitinase,20.2%had the ability to produce protease,16.7%of isolates showed ability to produce siderophore,while only 15.5%of strains showed ability to solubilize phosphate.Based on the above results,medicinal plant Bletilla striata was selected to be tested the plant growth promoting ability of isolates 2,12,20,49,72,122,156,179 and 72+2 by pot experiment.In treatment,there were significant increase in shoot length and dry weight compare to the control.Strain 20 and 12 exerted the greatest influence on Bletilla striata and showed 117.55%and 86.47%increase in number of leaves,91.75%and 208.25%increase in root numbers,295.21%and 355.09%increase in root length,112.93%and 56.46%increase in stem length,320.75%and 186.17%increase in plant height and 234.04%and 140.43%leaf width,respectively,which revealed the plant growth promoting of the endophytic actinobacteria.In this study,combined with traditional isolation,bioactivity screening and molecular biological techniques to investigate the endophytic actinobacteria resources of medicinal plants in Garze.The results revealed the diversity of endophytic actinobacteria isolated from medicinal plants in Garze and most of them showed antimicrobial and plant growth promoting ability,which have potential to be utilized as biofertilizer and exploite noval antimicrobial agents,and provide a scientific reference for the research and exploitation of endophytic actinobacteria of medicinal plants. |
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