Screening of plant-growth promoting rhizosphere actinomycetes in Xishuangbanna Reserve

Abstract:

[Background] Xishuangbanna Nature Reserve is rich in biodiversity, but few reports about plant growth promoting rhizobacteria especially actinomycetes in this reserve are found. [Objective] Screen the plant growth promoting rhizobacteria in Xishuangbanna Nature Reserve and test their growth-promoting ability. [Methods] Plant growth-promoting rhizobacteria was selected by five types of medium and followed by taxonomic identification based on 16S rDNA sequence analysis. The ability of obtained strains to produce IAA, siderophores, dissolved phosphorus, cellulase, and amylase activities were determined by Salkowski method, CAS method, molybdenum anti-chromogenic method, CMC-Na method and improved Young method, respectively. [Results] Fourteen strains of growth-promoting rhizobacteria, were isolated and purified from soil samples and identified as Streptomyces, Nocardia, Bacillus, Ensifer, Mesorhizobium, Azospirillum and Stenotrophomonas. Among the 14 strains isolated, strain B433 had the maximum capacity of indole acetic acid (9.23 mg/L) at 12 d. The strains of B351, B453 and B546 had strong iron siderophore production capacity, where the Su value were all >80%, and the maximum was 86.67%, with a strength of +++++. Strain B541 showed the strongest phosphorus solubility, and the concentration of dissolved phosphate reached 9.79 mg/L. The comprehensive cellulase production capacity of strain B442 was 31.86 U/mL. The amylase activity of strain B412 was 16.07 U/mL. [Conclusion] The rhizosphere soil in Xishuangbanna Nature Reserve contained a variety of growth-promoting rhizobacteria with strong and broad spectrum growth-promoting ability, which is valuable for research and exploitation. This study provides reliable basis of bacterial strain resource for the development of microorganism resource in Xishuangbanna Nature Reserve.

Key words:Xishuangbanna Nature Reserve, Rhizosphere, Bacteria, Screening, Growth promotion