Ascending endophytic migration of locally isolated diazotroph, Enterobacter sp. strain USML2 in rice

Abstract

The aims of this study were to isolate endophytic diazotrophs from leaf tissues of oil palm (Elaeis guineensis Jacq.) and to understand the endophytic migration and colonization ability in a selected host plant (rice seedlings; Oryza saliva var. MR.220). Moreover, observing the production of plant-cell wall degrading enzymes would aid in the understanding of the endophytic migration. These enzymes are vital for endophytes invasion and spread within the host plant. The endophytic diazotrophs were isolated and identified via partial 16S rDNA sequence analyses. The N2-fixing ability and IAA production of the isolates were determined by Acetylene Reduction Assay (ARA) and Salkowski's colorimetric test. A total of six isolates were tested positive forN2 fixation potential (2.5×1CT10 to 8.5×1CT7 umol C 2H4 cfu-1l-1) and IAA production. The isolates were identified as Enterobacter sp., Acinetobacter sp., Azospirillum sp., Gluconacetobacter sp. and Phytobacter sp. Ascending migration of the endophyte from roots to leaves of the host was also proven via microscopic observation of Green Fluorescent Protein (GFP)-tagged Enterobacter sp. and production of plant-cell wall degrading enzymes. Thus, this study successfully proven occurrence of culturable endophytic diazotrophs in leaf tissues of oil palm. The endophytic diazotrophs were also classified as high-potential plant growth enhancers through the ability to fix nitrogen, produce phytohormone and the potential for endophytic migration and colonization inside the host plants. © 2011 Asian Network for Scientific Information.