外源质粒（基因）导入花生根瘤菌的行为分析

利用二亲本或三亲本杂交的方法，将携带有共生固氮基因的外源重组质粒或外源载体质粒导入慢生型花生根瘤菌［Ｂｒａｄｙｒｈｚｏｂｉｕｍｓｐ．（Ａｒａｃｈｉｓ）］１４７－３和快生型花生根瘤菌［Ｒｈｉｚｏｂｉｕｍｓｐ．（Ａｒａｃｈｉｓ）］８５－７中。探讨了转移接合子中外源质粒在人工培养条件下和共生条件下的稳定性，发现外源质粒在花生根瘤菌中的稳定性与质粒的类型、受体菌的特性和环境条件有关。同时还探讨了外源质粒上的共生基因对受体菌１４７－３共生固氮效率的影响。结果表明，外源共生基因对共生固氮能力的影响是复杂的，既可以产生正效应，也可以产生负效应。

Behaviours of Exogenous Plasmids(Genes)in Peanut rhizobia

Exogenous recombinant plasmids carrying symbiotic genes were introduced into Peanut rhizobium 147-3 and 85-7.The stability of foreign plasmids in transcojugants was analysed under culture and symbiotic conditions.The results indicated that the stability of foreign plasmids was dependent on the characteristrics of exo-plasmids and the recipient as well as the environmental conditions.Under culture conditions,pRaZ15,pRmSL26 and pHN32(derivatives from pLAFR1)were unstable,pMN53(based on pMN2)was stable in 85-7,but not in 147-3,while pCK3 was variable either in 147-3 or 85-7;only pKT230(a widehostrange vector)was inherited stably. After symbiosis with peanut plants, pLAFR1 showed a high elimination frequency in 147-3,while pMN53 and pCK3 were more stable than in vitro and pKT230 remained stable.The effects of foreign symbiotic genes on nitrogen fixation of 147-3 was also tested in pot experiments.Judged by plant nitrogen content,transconjugants 147-3(pRaZ15) and 147-3(pMN53)were obviously lower than 147-3 at the 10% statistics level and the nodulation was significantly delayed with 147-3(pMN53).The nitrogen fixation ability of 147-3 was improved by the introduction of pHN32, but the difference was not significant.The nodule weight,shoot dry weight and nitrogen content of the plants inoculated with 147-3(pCK3)were significantly higher than those of 147-3.The results indicated that the effects of exogenous plasmids on the symbiotic nitrogen fixation efficiency of Bradyrhizobium sp.(Arachis)are very complicated and futher studies are needed.