Isolation and screening of multifunctional phosphate solubilizing bacteria and its growth‑promoting effect on Chinese fir seedlings

In this study, 7 endophytic phosphate solubilizing bacteria were screened out from Chinese fir,and were characterized for plant growth-promoting traits. Based on morphological and 16S rRNA sequence analysis, the endophytes were distributed into 5 genera of which belong to Pseudomonas, Burkholderia, Paraburkholderia, Novosphingobium, and Ochrobactrum. HRP2, SSP2 and JRP22 were selected based on their plant growth-promoting traits for evaluation of Chinese fir growth enhancement. The growth parameters of Chinese fir seedlings after inoculation were significantly greater than those of the uninoculated control group. The results showed that PSBs HRP2, SSP2 and JRP22 increased plant height (up to 1.26 times), stem diameter (up to 40.69%) and the biomass of roots, stems and leaves (up to 21.28%, 29.09% and 20.78%) compared to the control. Total N (TN), total P (TP), total K (TK), Mg and Fe contents in leaf were positively affected by PSBs while showed a significant relationship with strain and dilution ratio. The content of TN, TP, TK, available phosphorus (AP) and available potassium (AK) in the soil increased by 0.23–1.12 mg g− 1, 0.14–0.26 mg g−1,0.33–1.92 mg g−1, 5.31–20.56 mg kg−1, 15.37–54.68 mg kg−1, respectively. Treatment with both HRP2,SSP2 and JRP22 increased leaf and root biomass as well as their N, P, K uptake by affecting soil urease and acid phosphatase activities, and the content of available nutrients in soil. In conclusion, PSB could be used as biological agents instead of chemical fertilizers for agroforestry production to reduce environmental pollution and increase the yield of Chinese fir.

本研究从杉木（Chinese fir）中筛选得到7株内生解磷细菌（endophytic phosphate solubilizing bacteria，PSBs），并对其植物促生性状进行了表征。通过形态学观察与16S rRNA序列分析，将这些内生菌划归至5个属，分别为假单胞菌属（Pseudomonas）、伯克霍尔德菌属（Burkholderia）、副伯克霍尔德菌属（Paraburkholderia）、新鞘氨醇杆菌属（Novosphingobium）以及苍白杆菌属（Ochrobactrum）。基于促生性状表现，选取HRP2、SSP2与JRP22菌株开展杉木生长促效评估。接种后杉木幼苗的各项生长指标均显著高于未接种对照组。结果显示，与对照组相比，HRP2、SSP2及JRP22可显著提升杉木株高（最高达对照组的1.26倍）、茎直径（最高提升40.69%）以及根、茎、叶生物量（最高分别提升21.28%、29.09%与20.78%）。菌株接种可正向影响杉木叶片中的总氮（TN）、总磷（TP）、总钾（TK）、镁（Mg）与铁（Fe）含量，且该效应与菌株种类及菌液稀释比例呈显著相关性。土壤中总氮、总磷、总钾、有效磷（AP）与速效钾（AK）含量分别提升0.23–1.12 mg g⁻¹、0.14–0.26 mg g⁻¹、0.33–1.92 mg g⁻¹、5.31–20.56 mg kg⁻¹与15.37–54.68 mg kg⁻¹。HRP2、SSP2与JRP22可通过调控土壤脲酶与酸性磷酸酶活性，提升土壤有效养分含量，进而增加杉木叶片与根系生物量及其对氮、磷、钾的吸收量。综上，解磷细菌可作为生物菌剂替代化肥应用于农林业生产，以降低环境污染并提升杉木产量。