The Competitiveness Of Peanut Bradyrhizobial Strains Studied By Using LuxAB MarKer Technique

Four nitrogen fixing effective strains were selected out from 22 peanut bradyrhizobiai strains,which were isolated from the different cultivars and locations in sichuan, by observing nodule number, fresh nodule weight,amotmt of N fixed and peanut yields in N-free solution pot, soil pot and small scale field experiments. One strain Cspr7-1 with LuxAB gene marker was obtained trimphantly by thri-parental mating. Five iransformants, which named Cspr7-l- I, Cspr7-l-2, Cspr7-l-3, Cspr7-l-4 and Cspr7-l -5, were purified and tested for their marker stability, and competitive nodulation with soil indigenous bradyrhizobia in N-free solution pot amended with soil water extmctant under green-house condition, the results show as following: 1 .The LuxAB gene can express in Cspr7- 1. After continously transfering one hundred generations on YEM broth medium and in nodulation process, the characteristic of kuninescence still keep stabilizecL The main properties of symbiotic effectiveness and generation time were not changed significantly compared with the parent strain. 2.Applying the LuxAB gene marker technique to study the competitive ability of spr7- 1 strain, the results indicated that the competitive ability of spr7-l strain was higher than that of the soil indigenous bradyrhizobia. LuxAB marker technique is simple, reliable and veiy useful in assessing the competitiveness of rhizobial strains in rhizosphere. 3.Using the LuxAB marker to study competitive ability of peanut bradyrhizobia, four strains spr2-9, spr3-7, spr4-5 and spr7-1 were selected out, which have higher nitrogen fixing efficiency and stronger competitive ability then that of the soil indigenous bradyrhimbia. Their inoculation effectiveness needs to be finther conflnned under field conditions by considering different ecological factors.