高寒草地耐低温植物根际促生菌的筛选鉴定及特性研究

Screening, identification and characteristics of low-temperature-tolerant plant growth promoting rhizobacteria in alpine meadow

为获得优良植物根际促生菌(PGPR)并明确其促生特性,以红原地区广泛分布的3种高寒草地优势植物为材料,采用选择性培养基从3种高寒植物根际分离、筛选具有固氮、溶磷、分泌植物激素能力的耐低温植物根际促生菌,并进行16S rRNA分子生物学鉴定。结果表明:毛稃羊茅、洽草、紫穗鹅观草植物根际分布着大量根际细菌,且PGPR在根际不同部位的数量呈现出根系表面(RP)>根表土壤(RS)>根内(HP)的分布规律。经筛选共获得76株PGPR菌株,其中固氮菌30株,其固氮酶活性为124.61~311.04 nmol C_(2)H_(4)·h^(-1)·mL^(-1);溶解无机磷菌株24株,溶解有机磷菌株22株,溶磷量分别为249.85~558.07μg·mL^(-1)和52.25~158.77μg·mL^(-1)。挑选固氮酶活性较高、溶磷能力较强的27株PGPR菌株进行分泌植物激素能力测定,26株菌株具有分泌赤霉素(GA_(3))的能力,分泌量为0.60~52.91μg·mL^(-1),分泌吲哚-3-乙酸(IAA)菌株18株,分泌量为0.11~1.53μg·mL^(-1),分泌玉米素(t-Z)含量均小于0.31μg·mL^(-1)。筛选出综合性能优良的菌株14株,经鉴定分别属于假单胞菌属、不动杆菌属、假节杆菌属、贪噬菌属。研究结果可为研制适合高寒地区植被恢复的微生物肥料提供宝贵的菌种资源及理论基础。

The study aimed to isolate and screen low-temperature-tolerant plant growth promoting rhizobacteria(PGPR)from the rhizosphere of the dominant plant species in alpine meadows,with a view to using the PGPRs in restoration of grassland degradation.Nitrogen-fixing,phosphorus-dissolving and phytohormone secreting bacterial species were screened by selective media and subsequently the superior strains were identified by 16S rRNA molecular biology techniques.The results indicated large numbers of bacteria in the rhizosphere of Festuca kirilowii,Koeleria cristata and Roegneria purpurascens.The quantitative distribution of bacteria exhibited a strong rhizosphere effect,with bacteria numbers on the rhizoplane or surface of roots(RP)>on soil adhering to roots(RS)>histoplane or interior of roots(HP).In total,we obtained 76 strains of PGPR,of which 30 were nitrogen-fixing bacteria with their nitrogenase activity ranging between 124.61 and 311.04 nmol C_(2)H_(4)·h^(-1)·mL^(-1).A further 24 strains were active in dissolution of inorganic phosphorus(249.85-558.07μg·mL^(-1) in test solution),while 22 strains could dissolve organic phosphorus 52.25^(-1)58.77μg·mL^(-1) in test solution).Of the strains of PGPR with high nitrogenase activity or phosphate-solubilizing ability 27 strains were further selected for determination of plant hormone secretion.Results indicated that 26 strains of PGPR secreted GA_(3),with the secretion amounts ranging from 0.60 to 52.91μg·mL^(-1) of test solution.Meanwhile,18 strains of PGPR secreted IAA with the levels in test solution ranging from 0.11^(-1).53μg·mL^(-1),and all strains secreted t-Z at less than 0.31μg·mL^(-1).Preliminary identification of 14 superior PGPR strains using phylogenetic analysis determined that these belong to the bacterial genera Pseudomonas,Acinetobacter,Pseudarthrobacter and Variovorax.The superior PGPR strains detected in this study are potentially valuable bacterial resources that could be used for the development of microbial fertilizers suitable for vegetation restoration in alpine regions.