盾状粉褶菌对难溶性磷的体外溶磷效应

Solubilizing effect of Entoloma clypeatum on insoluble phosphorus

摘要:

【背景】外生菌根真菌（ectomycorrhizal fungi，ECMF）能够促进植物吸收土壤中难溶性磷。【目的】评价不同难溶性磷源下盾状粉褶菌（Entoloma clypeatum）菌丝生长和溶磷特点，为该菌进一步研究和应用提供依据。【方法】对盾状粉褶菌进行组织分离纯化及内部转录间隔区（internal transcribed spacer，ITS）鉴定；于纯培养条件下测定卵磷脂、磷酸铝、植酸钙和磷酸铁对该菌菌丝生长、有效磷含量、溶磷率、pH、柠檬酸含量和酸性磷酸酶含量等影响。【结果】经鉴定供试菌株为盾状粉褶菌，其菌丝体在不同磷源固体和液体培养基均可正常生长，前者菌丝生长缓慢，而卵磷脂液体培养基中菌丝球干重最高；含植酸钙的发酵液中有效磷含量（75.029 mg/L）和溶磷率（9.31%）最高，卵磷脂最低（25.880 mg/L、0.55%）；各培养发酵液pH值均降低；4种磷处理发酵液中，柠檬酸含量以植酸钙条件下最高（19.4 mmol/L），卵磷脂最低（12.4 mmol/L），为对照组的1.9—5.1倍；酸性磷酸酶含量是对照的1.3—3.2倍，以植酸钙最高（0.006 7 U/mL），显著高于其他3种处理（P<0.05）；有效磷含量与酸性磷酸酶含量呈正相关，与溶磷率呈显著正相关（P<0.05），与柠檬酸含量呈极显著正相关（P<0.01），与pH和菌丝球干重呈负相关。【结论】盾状粉褶菌具有利用难溶性磷的能力，是减少磷肥使用的优良选择，这为开发利用盾状粉褶菌及进一步挖掘ECMF的溶磷机制提供了参考。

Abstract:

[Background] Ectomycorrhizal fungi (ECMF) can promote plants to absorb insoluble phosphorus in the soil. [Objective] To study the mycelial growth and phosphorus solubilization of Entoloma clypeatum with different insoluble phosphorus sources, so as to provide a basis for further research and application of the fungus. [Methods] An ECMF strain was isolated by the tissue culture method and identified based on the internal transcribed spacer (ITS) sequence. The effects of lecithin, aluminum phosphate, calcium phytate, and iron phosphate on the mycelial growth, available phosphorus content, phosphorus solubility, pH, citric acid content, and acid phosphatase content of the strain were determined under pure culture conditions. [Results] The strain was identified as E. clypeatum, and its mycelia grew normally in solid and liquid media with different phosphorus sources. The mycelial growth was slow in the solid media, and the dry weight of mycelial pellets in the liquid medium supplemented with lecithin was the highest. The available phosphorus content (75.029 mg/L) and phosphorus-solubilizing rate (9.31%) of the strain were the highest in the medium containing calcium phytate and the lowest (25.880 mg/L and 0.55%, respectively) in the medium supplemented with lecithin. The pH of each fermentation broth decreased over time. The citric acid content was the highest (19.4 mmol/L) in the medium supplemented with phytic acid calcium and the lowest (12.4 mmol/L) in the medium supplemented with lecithin, which were 1.9-5.1 times that of the control group. The acid phosphatase content in the media supplemented with different insoluble phosphorus sources was 1.3-3.2 times that of the control. It was the highest (0.006 7 U/mL) in the medium with calcium phytate as the insoluble phosphorus source, with significant differences from that in the other three treatments (P<0.05). The available phosphorus content was positively correlated with phosphorus-solubilizing rate (P<0.05) and citric acid content (P<0.01) and negatively correlated with pH and mycelial pellet dry weight. [Conclusion] E. clypeatum capable of solubilizing insoluble phosphorus serves as an excellent choice to reduce the use of phosphate fertilizer. The findings provide a reference for the development and utilization of E. clypeatum and further research on the phosphorus-solubilizing mechanism of ECMF.