樱桃根际产吲哚乙酸促生菌的分离、鉴定及功能特性

Isolation, identification, and functional characterization of plant growth-promoting rhizobacteria capable of producing indole acetic acid from cherry rhizosphere

摘要:

【目的】从东北山樱(Prunus sachalinensis)根际土壤中分离产吲哚-3-乙酸(indole-3-acetic acid,IAA)优势细菌，测定促生特性，通过反接种到甜樱桃常用砧木吉塞拉6号幼苗明确促生效果，为挖掘樱桃自身生物学潜力，建立良性根系-微生物互作关系，为解决根系发育较弱问题提供理论参考及实践途径。【方法】使用牛肉膏蛋白胨培养基分离根际土壤细菌，选择各类特异培养基筛选并测定细菌产IAA、固氮、溶磷、解钾和趋化性能力，通过16S rRNA基因序列的同源性分析构建系统发育树鉴定菌属，采用盆栽樱桃植株探究菌株的促生效果。【结果】从东北山樱根际土壤中筛选到5株产IAA菌株，其中菌株D46的IAA产量最高(53.10 mg/L)。通过16S rRNA基因序列分析将D5鉴定为普里斯特氏菌属(Priestiasp.)，D27和D46鉴定为肠杆菌属(Enterobactersp.)，D43和D79鉴定为芽孢杆菌属(Bacillussp.)。5株细菌均具有固氮能力，D27、D46和D79具有溶磷能力、D5和D43具有解钾能力。菌株D27、D46和D79对糖、有机酸和氨基酸的综合趋化性较强。盆栽促生试验显示，接种菌株D27、D43、D46和D79均显著提高了植株的根系活力。接种菌株D27后根系总呼吸速率较对照组(CK)显著提高了51.40%，并且根系糖酵解途径(glycolysis,EMP)、三羧酸循环途径(tricarboxylic acid cycle,TCA)和戊糖磷酸途径(pentose phosphate pathway,PPP)呼吸速率均显著提高。菌株D27显著改善了樱桃幼苗的根系构型。接种菌株D5后叶片净光合速率(net photosynthetic rate,Pn)较CK显著提高了58.82%，接种菌株D27对叶片水分利用效率(water use efficiency,WUE)提升最显著。菌株D27、D46和D79对植株生物量的综合促生效果较为显著。【结论】樱桃根际存在产IAA细菌，分离到的5株产IAA菌株兼具其他促生特性。菌株D27、D46和D79对樱桃幼苗的综合促生效果良好，后续可深入探究其促生对象的广谱性及环境耐受性，为发掘和丰富PGPR菌种资源提供理论基础。

Abstract:

[Objective] This study isolated the dominant indole-3-acetic acid (IAA)-producing bacteria from the rhizosphere soil of Prunus sachalinensis, determined their plant growth-promoting properties, and clarified the growth-promoting effect by inoculation to the seedlings of the common rootstock Gisela 6, aiming to provide theoretical reference and practical approaches for exploring the biological potential of cherry, establish a benign root-microbial interaction relationship, and solve weak root development. [Methods] We used the beef extract peptone medium to isolate bacteria from the rhizosphere soil and selected various specific media to screen the bacteria and determine the IAA-producing, nitrogen-fixing, phosphorus-solubilizing, potassium-solubilizing, and chemotactic abilities of the bacteria. Then, we constructed a phylogenetic tree based on 16S rRNA gene sequences to identify the bacteria. Finally, potted cherry plants were used to explore the plant growth-promoting effects of the strains. [Results] Five IAA-producing strains were screened from the rhizosphere soil of P. sachalinensis, among which strain D46 had the highest IAA yield (53.10 mg/L). D5 was identified as Priestia sp. D27 and D46 were identified as Enterobacter sp. D43 and D79 were identified as Bacillus sp. All the five strains had the ability to fix nitrogen. D27, D46, and D79 had the ability to solubilize phosphorus, and D5 and D43 had the ability to solubilize potassium. Strains D27, D46, and D79 showed strong integrative chemotaxis to sugars, organic acids, and amino acids. Pot experiments showed that the inoculation of strains D27, D43, D46, and D79 significantly increased the root activity. After the inoculation of strain D27, the total root respiration rate increased by 51.40% compared with that in the control group (CK), and the root respiration rates of glycolysis (EMP), tricarboxylic acid cycle (TCA), and pentose phosphate pathway (PPP) also significantly increased. Strain D27 significantly improved the root architecture of cherry seedlings. After inoculation of strain D5, the net photosynthetic rate of leaves significantly increased by 58.82% compared with that in CK, and the inoculation of strain D27 demonstrated the best performance in improving the water use efficiency of leaves. Strains D27, D46, and D79 significantly increased the plant biomass. [Conclusion] There were IAA-producing bacteria in the rhizosphere of cherry, and the five IAA-producing strains isolated had other plant growth-promoting properties. Strains D27, D46, and D79 demonstrated comprehensive plant growth-promoting effects on cherry seedlings. In the future, we can explore the spectra of plants with growth promoted by the strains and the environmental tolerance of the strains, providing a theoretical basis for mining and enriching the strain resources of plant growth-promoting rhizobacteria.