基于根际营养竞争的植物根际促生菌的筛选及促生效应研究

Screening of plant growth-promoting rhizobacteria based on rhizosphere nutrition competiveness and investigation of their promoting effects

[目的]优良菌种是微生物肥料的基础,根际竞争能力是微生物肥料菌株发挥作用的前提,本研究主要基于根际营养竞争能力筛选植物根际促生菌.[方法]利用玉米、黄瓜、番茄3种作物的根系分泌物为初筛培养基的营养源,从相对应作物的根际土壤样品中分离筛选能利用根系分泌物快速生长的菌株,通过测定所筛菌株的促生特性,进一步结合平皿幼苗促生试验复筛优良菌株,并通过盆栽试验评价促生效果.[结果]初筛所得24株菌株,均可在以植物根系分泌物为唯一营养来源的培养基上迅速生长,具有溶磷、产NH3、产IAA及产嗜铁素等一种或多种促生性能,其中具有产氨能力的14株,占所筛菌株的58.3%;可产IAA的20株,占所筛菌株的83.3%,菌株JScB的IAA产量最大,达到了73.28 mg·L^-1;可产铁载体的12株,占所筛菌株的50.0%;具有溶解有机磷能力的15株,占所筛菌株的62.5%;所筛各菌株均有一定的溶解无机磷的能力,但差异很大,溶磷量范围为19.14-200.05 mg·L^-1.结合平皿幼苗促生试验,最终筛选出12株菌株用于盆栽试验.接种所筛菌株于相应作物后,其株高、生物量、根系形态（总根长、根表面积等）和叶绿素含量等均高于不接菌对照.经16S rDNA鉴定序列同源性,5株为芽孢杆菌属（Bacillus）,3株为剑菌属（Ensifer）,2株为根瘤菌属（Rhizobium）,1株为苍白杆菌属（Ochrobactrum）,1株为微杆菌属（Microbacterium）.[结论]基于根际营养竞争筛选的植物根际促生菌具有良好促生效果,为筛选作物专一性、高效根际促生菌提供了策略.

[Objectives]Excellent microbial strain is the basis of microbial fertilizer,and rhizosphere competitiveness is the prerequisite for the performance of plant beneficial roles of the bacterial strains in fertilizer. Plant growth-promoting rhizobacteria（PGPR） was screened in this study mainly based on rhizosphere nutrition competiveness. [Methods]The root exudates of maize,cucumber and tomato were used as the sole nutrient source of the screening medium,respectively,to isolate the fast growing PGPR from the corresponding plant rhizosphere. Their plant growth-promoting characteristics were determined and further verified by petri dish seedling promoting assay,finally,the screened strains were evaluated in greenhouse pot experiment. [Results]All the 24 strains isolated from the first round screening could grow quickly in the screening medium using root exudates as the sole nutrition source,and had one or more of the following abilities：phosphate solubilization,production of NH3,IAA and siderophores. 14 strains were capable of producing ammonia,accounting for 58.3%;20 strains could produce IAA,accounting for 83.3%,JScB strain had the highest production of IAA,reaching 73.28 mg·L^-1;12 strains could produce siderophores,accounting for 50.0%;15 strains were capable of dissolving organic phosphorus,accounting for 62.5%;all strains had ability of dissolving inorganic phosphorus,but the difference was extensive,ranging from 19.14 to 200.05 mg·L^-1. 12 strains,which performed well in the petri dish seedling promoting assay,were eventually selected for pot experiment. After inoculation of them to the corresponding crops,the plant height,biomass,root morphology（total root length,root surface area,etc.）and chlorophyll content were higher than those of control. Through 16S rDNA identification of the sequence homology,five isolates were Bacillus genus,three isolates were Ensifer genus,two strains were Rhizobium genus,one strain was Ochrobactrum genus,and one strain was Microbacterium genus. [Conclusions]Isolated strains based on rhizosphere nutrition competitiveness had excellent plant growth-promoting effects,which provided the preliminary screening strategy for crop specific PGPR.