【作者】 章建国；

【导师】 周俊初；

【作者基本信息】 华中农业大学 ， 微生物学， 2004， 硕士

【摘要】 根瘤菌与豆科植物形成的共生固氮体系在农业生产中具有重要作用。使用根瘤菌剂接种豆科作物可以大幅减少化学肥料的施用量，降低环境污染。已知菌剂的接种效果在从未种植过豆科植物的新区明显高于长期种植豆科植物的老区，菌剂在老区的接种效果又明显取决于其土著根瘤菌数量，因此不对土著根瘤菌资源进行调查而普遍施用根瘤茵剂具有很大的盲目性，难以达到理想的增产效果。 本研究用MPN法测定了广西、安徽、江苏、贵州和重庆5省市15份大豆种植土样中土著大豆根瘤菌的含量和快、慢生型大豆根瘤菌数量的比例。结果表明：老区土样中土著大豆根瘤菌的数量明显高于新区土样：传统当地栽培大豆品种的结瘤能力高于外地品种；在pH4.0-8.0范围内，pH值对土壤中快、慢生型土著大豆根瘤菌的比例没有显著影响。 高效根瘤菌剂施用后的增产效果，还取决于自身的竞争结瘤能力，已知影响根瘤菌竞争结瘤能力的因素有外在的，也有内在的。本研究参考已发表的大豆慢生根瘤菌(Bradyrhizobium japonicum)nolA基因序列，设计并合成了一对保守区特异性引物和一对全长基因引物，采用PCR的方法，以从广西和重庆土样中分离的30株费氏中华根瘤菌(Sinorhizobium fredii)的总DNA为模板，从费氏中华根瘤菌HH21中扩增出预计大小的DNA片段，进一步的测序结果表明，HH21和B．japonicum USDA110两者中的nolA基因序列具有90％以上的同源性，初步证明了nolA基因在费氏中华根瘤菌中的存在；随后的结瘤抑制实验结果表明：含有nolA基因的费氏中华根瘤菌也有种群密度依赖调节方式的结瘤抑制现象，本结果对提高商品化根瘤菌剂的竞争结瘤能力具有重要的参考价值。更多还原

【Abstract】 The symbiosis formed by rhizobia and legume host plays an important role in agriculture. The application of rhizobia inoculant can drastically reduce the dose of chemical nitrogen fertilizer and decrease the environmental pollutions. It’s well known that the application effect of rhizobia inoculant in soybean-uncultivated field is more significant higher than that in soybean-cultivated farm. The application effect of rhizobia inoculant in soybean-cultivated soil is determined, in most extent, by the nusmber of indigenous rhizobia population. So it is difficult to reach the ideal aim and also is blind if we did not investigate the resource of indigenous rhizobia before the application of rhizobia inoculant.The number of indigenous soybean rhizobisa was measured and the proportion of fast- and slow-growing soybean rhizobia was determined from the 15 soil samples collected from Guangxi, Anhui, Jiangsu, Guizhou provences and Chongqing City. The results showed that (1) The number of indigenous soybean rhizobia in soybean-cultivated soil was significantly higher than the one in soybean-uncultivated soil; (2) In comparison with the nodulation ability, the local cultivar was higher than the foreign cultivar; (3) The proportion of fast- and slow-grower was affected weakly by the pH value of soil when the pH value was ranged from 4.0 to 8.0.High effective rhizobia should also have strong competition ability. The factors that influence the competition ability of rhizobia come from not only environment, but also rhizobia itself.A special pair of conservative primers and a pair of complete gene primers were designed based on the released nolA gene (Genbank Accession No. AF322013) sequence of Bradyrhizobium japonicum. PCR and sequencing results showed that Sinorhizobium fredii strain HH21 contained nolA gene, too. Nodulation repression was also proved in S. fredii strain HH21 by both of pot and test tube plant nodulation experiments. This character is triggered by the expression of nolA gene in B. japonicum and controled by the pathway of population density-dependent regulation. These results offer a hint to improve the competition ability for commercial rhizobia inoculant.更多还原