Phosphate-solubilizing function evaluation and taxonomic identification of endophytic fungi separated from roots of Amomum villosum / 中草药

ABSTRACT

Objective: To study the characteristics of endophytic fungi separated from the roots of Amomum villosum grown in Jinping County of Yunnan Province, including the culture, evaluation of phosphorus-solubilizing ability and taxonomic identification of target strains. Methods: Endophytic fungi in the roots of A. villosum were separated by culturing in the mediums of PDA and MEA, and purely cultured in PDA. The endophytic fungi with phosphorus-solubilizing ability were screened by solid and liquid mediums of Pikovaskaia’s (PVK) prepared with inorganic phosphorus source. Then, the phosphorus-solubilizing capacity and reasonable mechanism were analyzed by growth circle, biomass, effective phosphorus content, pH value, and phosphatase activity. Moreover, molecular identification of target strains with the capacity of phosphorus-solubilizing would be carried out by ribosome 18 S PCR amplification. Results: The results showed that 24 endophytic fungi were separated from the roots of A. villosum in total, 10 of which were dark septate endophytes (DSE). Eight strains could grow on PVK solid medium and produce phosporus-dissolved growth circle. The growth circle diameters of JP-20 and JP-23 were larger than others, and more than 9 cm, followed by JP-15 with the growth circle of 6.06 cm. Furthermore, it was shown that JP-23 had a strong ability of phosphate-solubilizing due to presenting a high biomass in the PVK liquid medium instead of the medium prepared by soluble phosphorus source. The content of effective phosphorus of JP-23 in PVK liquid medium was significantly increased with an obviously decreasing pH and a sharply rising of acid phosphatase (ACP) activity. Moreover, the strain JP-23 was preliminarily identified as Cladosporium sp. (GenBank: MK629004) by molecular identification. Conclusion: An assumption was concluded that strain JP-23 could decompose and use insoluble phosphorus sources by adjusting the pH value and secreting ACP in medium. Our findings would provide data support and theoretical basis for studying the phosphate absorption mechanism of plant-microbial symbiosis system and the ecological plantation of A. villosum.