【摘要】 本实验通过质粒pSUP5011及其辅助质粒RP4将Tn5-Mob随机插入苜蓿根瘤菌(Rhizobium meliloti 042B)的基因组中,得到86株接合子SR。随机选取4株SR,通过辅助质粒R68.45的三亲本杂交,将它们的DNA片段引入慢生型大豆根瘤菌(Bradyrhizobium,japonicum USDA 110),获得106株接合子BSR。大部分BSR菌株获得了生长快速的特性和耐盐性,一般能耐0.3—0.5mol/L NaCl,其中有些菌株能产生黑色素。将90株BSR回接大豆和苜蓿植株,发现47株能在大豆和苜蓿植株结瘤,但在苜蓿上无固氮活性;26株只能在大豆植株结瘤固氮;13株只能在苜蓿植株结瘤而不固氮;4株在大豆和苜蓿植株均不结瘤。其中,获得了4株耐盐性和固氮酶活性强的接合子。更多还原

【Abstract】 Rhizobium meliloti 042B is a fast-growing, salt tolerant and high efficient nitrogen fixing symbiont with alfalfa. Bradyrhizobium japonicum USDA110 grows slowly, and cannot grow in YMA medium containing 0.1mol/L NaCl, but nodulates and fixs nitrogen efficiently with soybean. 86 transconjugants, called SR, were obtained by inserting Tn5-Mob randomly into genomes of 042B using pSUP5011 and helper plsamid RP4. Selecting 4 SR strains randomly, and introducing DNA fragment of SR into USDA110 with helper plsamid R68.45 by triparental mating, 106 transconjugants, called BSR, were constructed. Most of BSR strains had the fast-growing phenotype and could tolerate 0.3—0.5 mol/L NaCl generally.Some of them produced melanine. When inoculated to soybean and alfalfa, 47 out of 90 BSR were found to nodulate in both of these plants, but no nitrogenase activity was observed with alfalfa; 26 strains could only nodulate and fix nitrogen in soybean; 13 strains could nodulate in alfalfa but not fix nitrogen; 4 strains failed to nodulate in either soybean or alfalfa. Among them, 4 transconjugants which tolerated high salt and fixed nitrogen more efficiently in soybean were constructed。更多还原