油茶根际溶磷细菌对不同红壤质地磷组分及磷素转化的影响

Effects of phosphate-solubilizing bacteria in the rhizosphere of Camellia oleifera on phosphorus fractions and phosphorus transformation in red soil with different textures

摘要:

目的 溶磷菌促进土壤不同磷素形态的相互转化是提高土壤有效磷的重要途径。然而，溶磷菌的溶磷能力发挥受土壤质地的影响。因此，研究溶磷菌在不同红壤质地梯度下磷素形态的变化特征，对土壤磷素的高效利用具有重要意义。方法 采集湖南浏阳4个油茶主栽品种(‘华硕’ ‘华鑫’ ‘华金’和‘长林40号’)的根际土壤，采用平板涂布法、透明圈法、钼锑抗比色法及16S rRNA基因测序等方法，对根际土壤中的溶磷菌株进行分离、纯化、筛选与鉴定，获得一批高效溶磷菌株，并探究这些所得菌株在不同磷源(磷酸铁、磷酸铝、磷酸钙和植酸钙)下的溶磷特性。将溶磷菌接种至珍珠岩添加比例为0、20%和40%的红壤质地中(0%PR、20%PR和40%PR)，明确不同红壤质地下磷形态的变化特征。结果 共分离获得57株溶磷能力稳定的菌株，其中菌株CL37、HS5和CL36的溶磷能力表现较为突出。对这3个菌株进行16S rRNA基因测序鉴定，分别命名为泛菌属(Pantoea sp.) CL37、伯克霍尔德菌属(Burkholderia sp.) HS5和Burkholderia sp. CL36。3个菌株在不同磷源下的溶磷能力差异显著，其中对植酸钙和磷酸钙的增溶能力最强。在20%PR和40%PR红壤质地梯度中，有效磷含量(available phosphorus, AP)比对照组(CK)分别提高了8.90%-54.60%和1.90%-56.00%。溶磷菌接种提高了土壤铁磷(Fe-P)、树脂磷(Resin-P)、碳酸氢钠提取态无机磷(NaHCO₃-Pi)和氢氧化钠提取态无机磷(NaOH-Pi)含量，并随着红壤质地梯度呈现先升高后降低的趋势；溶磷菌处理降低了稀盐酸提取态无机磷(HCl-Pi)和残留态磷(Residual-P)的含量，且HCl-Pi在20%PR红壤质地梯度中降幅比0%PR和40%PR的梯度更为明显。单接菌株HS5对土壤Fe-P、Resin-P、NaHCO₃-Pi和NaOH-Pi含量的增加总体高于其他处理。相关性分析和随机森林分析表明，AP主要受到Resin-P、铝磷(Al-P)、NaOH-Pi、土壤酸性磷酸酶(soil acid phosphatase, ACP)、土壤脲酶(soil urease, Urease)、pH和氢氧化钠提取态有机磷(NaOH-Po)的影响。结论 油茶根际溶磷菌在不同红壤质地下的溶磷途径不同，菌株HS5具有较强的磷素转化能力，且在20%PR红壤质地下更有利于促进磷素转化。

Abstract:

Objective Phosphate-solubilizing bacteria (PSB) can increase available phosphorus by promoting the transformation of different phosphorus forms in soil. However, the phosphate-solubilizing ability of PSB is influenced by soil texture. Therefore, we studied the changes of phosphorus fractions in red soil with different textures and treated with PSB, with the aims of improving the efficient utilization of soil phosphorus.Methods We collected the rhizosphere soil samples of four main Camellia oleifera varieties (‘Huashuo’ ‘Huaxin’ ‘Huajin’ and ‘Changlin No. 40’) in Liuyang City, Hunan Province. PSB strains were isolated, purified, screened, and identified by plate coating, transparent circle method, molybdenum-antimony anti-spectrophotometric method, and 16S rRNA gene sequencing, and a batch of highly efficient PSB strains were obtained. The phosphate-solubilizing abilities of the obtained PSB strains were investigated with different phosphorus sources (iron phosphate, aluminum phosphate, calcium phosphate, and calcium phytate). PSB were inoculated into the red soil samples added with 0, 20% and 40% perlite (0%PR, 20%PR and 40PR%) to clarify the changes in phosphorus fractions in the red soil samples with different textures.Results A total of 57 strains of PSB were isolated from the rhizosphere of C. oleifera, of which strains CL37, HS5, and CL36 exhibited stronger phosphate-solubilizing abilities. The three strains were identified by 16S rRNA gene sequencing and named Pantoea sp. CL37, Burkholderia sp. HS5, and Burkholderia sp. CL36, respectively. The three strains showed significant differences in their ability to solubilize different phosphorus sources, with the highest solubilizing ability for calcium phytate and calcium phosphate. Compared with CK, the inoculation of PSB increased the available phosphorus (AP) in soil by 8.90%-54.60% and 1.90%-56.00% in 20%PR and 40%PR, respectively. The inoculation with PSB increased Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi, which showed a tendency of first increasing and then decreasing along with the increase in the addition of perlite in red soil. Meanwhile, PSB decreased the content of HCl-Pi and Residual-P, and the decrease in HCl-Pi was more pronounced in 20%PR than in 0%PR and 40%PR. Of all treatments, the inoculation with HS5 led to the highest increases in Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi in the soil samples analyzed. Correlation analysis and random forest analysis suggested that AP was mainly affected by Resin-P, Al-P, NaOH-Pi, acid phosphatase, urease, pH, and NaOH-Po.Conclusion The phosphate-solubilizing pathways of PSB vary in red soil with different textures. Strain HS5 has a strong phosphorus-transforming ability and is more conducive to phosphorus transformation in the red soil with 20%PR.