Abstract: Compared to symbiotic nitrogen fixation in legumes, associative nitrogen fixation is widely existed in the rhizosphere of non-leguminous food crops such as rice and maize, which potentially plays major role in reducing the use of synthetic nitrogen fertilizer in agriculture and increasing plant yield. Pseudomonas stutzeri A1501,  a model associative/endotrophic nitrogen-fixing bacterium, was isolated from the rhizosphere of rice. Inoculation with wild-type A1501 could promote the growth of rice and maize plants. In order to further elucidate the relationship between the biological nitrogen fixation (BNF) in rhizosphere and the plant-growth promotion, an efficient associative nitrogen fixation system consist of excretion-ammonium mutant strain (1568/pVA3) and transgenic nitrogen efficient maize genotype was constructed, and used for the evaluation of promoting effect and BNF quantification under greenhouse condition. After 60 d, inoculation of two maize genotypes (transgenic nitrogen efficient maize and the control) with 1568/pVA3 and wild-type A1501 all significantly increased the plant biomass of aboveground and underground, compared with the control without inoculation. However, in all the conditions assayed, transgenic nitrogen efficient maize inoculated with 1568/pVA3 or wild-type strains showed no significant difference between plant biomass and the control genotype. In the efficient associative nitrogen fixation system,  the biomass of the transgenic nitrogen efficient maize inoculated with 1568/pVA3 significantly increased by 25.5%, compared with the N fertilization treatment control, 39% total N content compared with the control without inoculation. According to the estimation by 15N-isotopic dilution method, individual maize plant could obtain  N 0.8 g·plant^-1 from BNF. Meanwhile,  the biomass of the transgenic nitrogen efficient maize inoculated with wild-type A1501 significantly increased by 24.8%, compared with the N fertilization treatment control. Accordingly, individual maize plant could obtain  N 0.64 g·plant^-1 from BNF. Therefore, the efficient associative nitrogen fixation system used in this study contained transgenic nitrogen efficient maize genotype and associative diazotrophs especially the excretion-ammonium engineering bacteria performed better in terms of nitrogen fixation rate and plant biomass. It was estimated that 23% synthetic fertilizer could be reduced in this efficient associative nitrogen fixation system, against than 7.5% in the control system.

Key words: Pseudomonas stutzeri A1501, nitrogen efficient maize genotype, associative nitrogen fixation, biological nitrogen fixation rate, 15N-isotopic dilution method

摘要： 非豆科植物根际联合固氮作用广泛存在于水稻、玉米等根际，在农作物节肥增产方面具有巨大的应用潜力。施氏假单胞菌A1501是一株分离自水稻根际的模式联合固氮菌，接种该菌对水稻和玉米均具有良好的促生效果。为了进一步研究根际固氮与促生效果的关系，利用突变型泌铵固氮菌株（1568/pVA3）和转基因氮高效利用玉米品系共同构建高效固氮体系，并在温室条件下进行促生及生物固氮量评价。播种60 d后对玉米生长量和微生物固氮量进行分析，结果表明：固氮施氏假单胞菌接种后氮高效利用和对照玉米品系的地上和地下部生物量都显著高于不接种对照，但是固氮菌接种对氮高效利用玉米和对照玉米的总生物量没有显著影响。氮高效利用玉米接种1568/pVA3菌株后，植株生物量较施肥处理提高25.5%，全氮含量较不接种对照增加39%，15N同位素稀释法测定生物固氮量为0.8 g·株^-1；接种野生型后植株生物量较施肥处理提高24.8%，生物固氮量为0.64 g·株^-1。研究结果表明,通过将固氮菌尤其是泌铵工程菌与氮高效利用玉米建立联合固氮体系可以显著提高根际固氮量和植株生物量，据估算每公顷可节省化肥约23%，而对照体系为7.5%。

关键词: 固氮施氏假单胞菌A1501, 氮高效利用玉米, 根际联合固氮, 生物固氮效率, 15N稳定性同位素稀释法