Endophytic colonization and <i>in planta </i>nitrogen fixation by a diazotrophic <i>Serratia </i>sp. in rice

Abstract

Nitrogen fixing endophytic <i>Serratia </i>sp. was isolated from rice and characterized. Re-colonization ability of <i>Serratia </i>sp. in the rice seedlings as endophyte was studied under laboratory condition. For detecting the re-colonization potential in the rice seedlings, <i>Serratia </i>sp. was marked with reporter genes (<i>egfp </i>and <i>Km′</i>)<i> </i>using transposon mutagenesis. The conjugants were screened for re-colonization ability and presence of <i>nif </i>genes using PCR. Further, the influence of flavonoids and growth hormones on the endophytic colonization and <i>in planta </i>nitrogen fixation of <i>Serratia </i>was also investigated. The flavonoids, quercetin (3μg /ml) and diadzein (2 μg/ml) significantly increased the re-colonization ability of the endophytic <i>Serratia, </i>whereas the growth hormones like IAA and NAA (5 μg/ml) reduced the endophytic colonization ability of <i>Serratia</i> sp. Similarly, the <i>in planta </i>nitrogen fixation by <i>Serratia </i>sp. in rice was significantly increased due to flavonoids. The inoculation of endophytic diazotrophs increased the plant biomass and biochemical constituents.