| The gusA and celB genes were introduced by conjugation into three peanut bradyrhizobiol strains , Spr3-5, Spr 3-7and Spr 4-5 respectively. Testing for gusA and celB activity showed the gusA and celB genes in Spr3-5, Spr 3-7and Spr 4-5 could express.Using any maker gene system for ecological studies the effect on recipient strains must be evalucated. The generation time of marked and parental strains demonstrated there was no significant difference between them,which indicated their growth rate was the same.In N-free solution pot experiment the nodulating competitive ability of parental and marked strains and their nitrogen fixing efficiency were tested. Coinoculating parental and marked strains at a 1:1 ratio their competitive ability was tested. The results showed the proportion of blue nodules didn't differ significantly from 50%.It indicated the competitiveness of maked strains was not changed significantly compared with the parent strains.To study nitrogen fixing efficiency of marked and parental strains , the symbiotic shoot dry weight, total nitrogen and contents of chlorophyll of marked and parental strains were tested, and the result showed there was no significant difference between them., which indicated the nitrogen fixing efficiency of marked strains didn't differ from parental strains markedly in different ways.The correlation coefficients among shoot dry weight, total nitrogen and contents of chlorophyll were 0.864 (P<0.01), 0.809 (P<0.01) and 0.854 (P<0.01) respectively, which indicated they were reliable indexes reflecting nitrogen fixing efficiency of Eradyrhizobiwn sp.(arachis).The results of soil pot experiment showed that three peanut bradyrhizobial strains, Spr3-5, Spr 3-7and Spr 4-5,had higer nitrogen fixing efficiency and stronger competitive ability than indigenous bradyrhizobia.Besides,it indicated that use of gusA or celB genes in competition studies of rhizobium is simple,reliable and the nodules occupied by gusA-marked strains or those occupied by celB -marked strains cound be observed intuitionisticly.However.the cost of gusA marker was lower than that of celB marker. |
