农田环境中固氮菌的促生潜能与分布特点

【目的】了解小麦、水稻、玉米、蔬菜等作物根际固氮菌的优势种群、固氮菌菌株的固氮、抗病、促生潜能以及菌株在系统发育地位和来源作物种类上的分布特点。【方法】采用无氮培养基培养固氮菌，乙炔还原法测定菌株固氮酶活性，平板对峙法测定菌株拮抗病原真菌性能，ACC（1-氨基环丙烷-1-羧酸）唯一氮源法定性测定菌株产ACC脱氨酶特性，比色法定量测定ACC脱氨酶活性，通过16S rDNA序列测定和相似性分析研究菌株的分类地位。【结果】94株供试菌株的固氮酶活性在0.99-180.59 nmol C2H4/h•mg蛋白，其中大于10 nmol C2H4/h•mg蛋白的菌株有42株，占全部供试菌株的44.7%；类芽孢杆菌属（Paenibacillus)和芽孢杆菌属（Bacillus）是主要类群，分别占供试菌株总数的33.0%和26.6%，且不具有寄主专一性。供试菌株中有6株分别对核盘菌（Sclerotinia sclerotiorum）、玉米赤霉菌（Gibberella zeae）和大丽轮枝菌（Verticillium dahliae）3种植物病原真菌表现出拮抗作用，占菌株总数的6.4%，抑菌率为23.9%-65.9%。有20株固氮菌能够产生ACC脱氨酶，占全部供试菌株的21.3%，活性在0.33-21.98 µmol α-丁酮酸/h•mg蛋白，主要分布在芽孢杆菌属、类芽孢杆菌属和根瘤菌属（Rhizobium）。【结论】小麦、水稻、玉米、白菜、芹菜等作物根际以及农田环境中固氮菌的优势种群为类芽孢杆菌属和芽孢杆菌属，多数固氮菌菌株具有较高的固氮潜能，部分菌株具有ACC脱氨酶活性和促生潜能，少数菌株具有抗病潜能；固氮、抗病、促生潜力菌株主要分布在类芽孢杆菌属、芽孢杆菌属和根瘤菌属，随作物分布广泛，无专一性。

Growth Promotion Potential and Distribution Features of Nitrogen-Fixing Bacteria in Field Environments

【Objective】 The objective of this experiment is to determine the dominant species and phylogenetic position of nitrogen fixing bacteria in crop rhizosphere and field environments, and to screen for nitrogen-fixing bacteria with growth promotion potential. 【Method】Nitrogen-free medium was used to culture nitrogen-fixing bacteria and nitrogenase activity was determined with acetylene reduction assay. Confrontation method was used to test antagonistic bacteria against plant pathogenic fungus. ACC (1-aminocyclopropane-1-carboxylate) nitrogen source was used to test ACC deaminase. 16S rDNA was amplified by PCR and 16S rDNA sequence was analysed with MEGA software. 【Result】 Nitrogenase activity of the 94 tested strains ranged from 0.99 to 180.59 nmol C2H4/h•mg protein. Fourty-two strains accounting for 44.7% of the tested strains showed nitrogenase activity above 10 nmol C2H4/h•mg protein. Paenibacillus and Bacillus were main groups, and their percentages were 33.0% and 26.6% of the tested strains, respectively. Six strains accounting for 6.4% of the tested strains showed antagonistic actions against plant pathogenic fungi Sclerotinia sclerotiorum, Gibberella zeae and Verticillium dahliae with the inhibitory rate from 23.9% to 65.9%. Twenty strains accounting for 21.3% of the tested strains produced ACC deaminase with activity ranging 0.33 to 21.98 µmol α-ketobutyric acid/h•mg protein, which were identified as Bacillus, Paenibacillus, Rhizobium, and extensively distributed in crop rhizosphere and field environments.【Conclusion】The dominant species of nitrogen-fixing bacteria in crop rhizosphere and field environments belong to the genus Paenibacillus and Bacillus. Most of the nitrogen-fixing bacterial strains possess strong potential for nitrogen fixation, part of them possess potential for growth promotion, and a few of them possess potential for disease resistance. The potential strains belong to Paenibacillus, Bacillus and Rhizobium, and extensively colonized in crops with no specificity.