【摘要】 重要粮食作物水稻生产过程中大量施用氮肥会造成严重的环境污染，而利用内生固氮菌能有效减少作物氮肥的施用，并促进作物生长。为探究紫玉米内生微生物对水稻氮肥高效利用的促进作用，本研究从紫玉米中筛选根系内生固氮菌，经革兰氏染色、扫描电镜（SEM）和16S rRNA基因测序对固氮菌进行形态观察和分子鉴定；通过乙炔还原法评估固氮菌的固氮酶活性；对菌株产生长素吲哚乙酸（IAA）和1-氨基环丙烷-1-羧酸（ACC）脱氨酶以及溶磷和解纤维素等促进作物生长的活性和能力进行测定；检测菌株在水稻根中的定殖，验证不同氮浓度下固氮菌对水稻的促生作用。结果表明，从紫玉米根中分离到的2株固氮菌（CY60和CY101）均具有固氮酶活性。CY60和CY101均为革兰氏阴性菌，短棒状，分别为假单胞菌属（Pseudomonas）和肠杆菌属（Enterobacter）菌株；CY60具有固氮、解磷及产生长素和ACC脱氨酶能力，CY101具有固氮、产生长素和降解纤维素能力。2株菌均能成功定殖于水稻根内，接种后15 d在低氮和高氮条件下均可显著促进水稻的生长和叶绿素含量的提升。CY60和CY101可作为利用内生固氮菌减少水稻氮肥施用的候选菌株。本研究可为水稻氮高效固氮菌剂资源的开发与应用提供菌种资源与理论支持。更多还原

【Abstract】 Rice, one of the most important grain crops, requires a lot of nitrogen(N) fertilizer in the agricultural production process, which has caused serious environmental pollution. The use of endogenous Nfixing bacteria on crops can effectively reduce the application of N fertilizer and promote crop growth. To investigate the role of endophytic microorganisms from purple corn in enhancing the N utilization efficiency in rice, this study screened endophytic N-fixing bacteria from the roots of purple corn(Zea mays L.),morphological observation and molecular identification of N-fixing bacteria were performed by Gram staining,scanning electron microscopy(SEM) and 16S rRNA gene sequencing. Nitrogenase activity of N-fixing bacteria was evaluated using the acetylene reduction method. Indole-3-acetic acid(IAA) production and 1-aminocyclopropane-1-carboxylic acid(ACC) deaminase activity were measured, as well as inorganic phosphorus solubilizing and cellulose degrading abilities of the strains. The colonizations of bacterial strains in rice roots were detected and the promoting effect on rice growth under different N concentrations were verified. The results showed that, two strains of N-fixing bacteria(CY60 and CY101) were isolated from the root of purple corn, both of which had nitrogenase activity. CY60 and CY101 were both Gram-negative bacteria, short rodshaped, Pseudomonas and Enterobacter strains respectively. CY60 had the ability to fix N, hydrolyze phosphorus, and produced auxin and ACC deaminase, while CY101 had the ability to fix N, produced auxin,and degraded cellulose. Both strains of bacteria were able to successfully colonize rice roots. After 15 days of inoculation, rice growth and chlorophyll content were significantly promoted under both low and high N conditions. CY60 and CY101 could be used as candidate strains of endogenous N-fixing bacteria to reduce N fertilizer application in rice. This study provides strain resources and theoretical support for the development and application of N-fixing bacterial agents for high N efficiency in rice.更多还原