Colonization dynamics of LuxAB gene-marked N2106-L in wheat rhizosphere.

Objective To study the autecology of wheat PGPR(plant growth-promoting rhizobacteria) and its colonization dynamics in wheat rhizosphere.Method LuxAB gene was transfered into Azotobacter N2106 strain by the tri-parent conjugation method to obtain the strain N2106-L labeled with luxAB.The survival of the strain N2106-L in sterilized and non-sterilized yellow cinnamon soil(YC),yellow fluovoaquic soil(YF),and red soil(RS) were studied after inoculation into the soils.Rhizoboxes were used to trace the colonization dynamics of the strain around wheat root.Result The labeled strain N2106-L had a high luminescence activity and resistance to km,str and tet,and was genetically stable.Strain N2106-L in these three sterilized soils were higher than those in non-sterilized soils,and decreased in the order of YCYFRS.The colonization density of N2106-L on wheat rhizoplane was higher than in wheat rhizosphere.In rhizosphere soil,the colonization density reached to maximum(2.17±0.25)×106CFU/g at the depths of 0～2 cm after wheat grew for 10 days,and(3.92±0.47)×105CFU/g at the depths of 2～4 cm after grew for 20 days.On wheat rhizoplane the colonization density of all root segments reached the highest level on day 10,with(3.60±0.60)×106CFU/g fresh root on the surface of 0～2 cm segment and(2.78±0.56)×104CFU/g fresh root on that of segments deeper than 12 cm.Conclusion The labeled strain could proliferate continuously with the growth of wheat roots and stably colonized in wheat rhizosphere.The results provided credible data for the study and application of wheat PGPR strains.