Screening of efficient rhizobia from Vicia sativa L. in Guizhou

【Objective】To screen and obtain indigenous efficient strains of Vicia sativa L. rhizobia with strong nitrogen fixation ability and growth promoting effect and to provide high quality strain resources for soil improvement in karst area of Guizhou.【Method】Isolation and purification of V. sativa L. nodules in different ecological functional areas of Guizhou were isolated and cultured by Congo red YMA plate method，and bacterial species identification was carried out according to bacterium morphological structure and the 16S rRNA sequencing method. Then rhizobia and legume model plant Lotus corniculatus L. were employed for potted re-inoculation test，and the determination of the nitrogenase activity of the strains were combined to screen indigenous efficient rhizobia.【Result】From different ecological functional areas in Guizhou，53 rhizobia of different shapes，colors and sizes were isolated from V. sativa L. root nodule samples. After Gram staining，a total of 30 Gram-negative（G-）purified strains were obtained，of which 8 strains were identified as nodule endophytic bacteria，22 strains were Rhizobium and Pseudomonas. Rhizobium had the highest distribution frequency， reaching 91% and R.leguminosarum had the highest frequency of distribution，up to 27%，indicating that they were dominant genera and dominant species obtained through isolation，respectively. In potted re-inoculation test of different species of rhizobia from different regions and L. corniculatus L.，6 excellent nitrogen-fixing and growth promoting rhizobial strains were screened：XDVR141-4，ZJVR339-3，WEVR362-3，WXVR365-1，WLVR370-5，BQVR415-3. And enzyme activity and plant probiotic effect of WXVR365-1 strain were significantly different from those of the other 5 strains（P< 0.05），proving that it was the optimal growth-promoting rhizobium strain.【Conclusion】R. acidisoli isolated from V. sativa L. root nodules from different ecological functional areas in Guizhou belongs to rhizobial strain α-Proteobacteria with strong nitrogen fixation and growth-promoting effects，which can be used as a candidate strain resource for developing microbial fertilizer.