ISOLATION OF ENDOPHYTIC BACTERIA FROM RICE AND ASSESSMENT OF THEIR POTENTIAL FOR SUPPLYING RICE WITH BIOLOGICALLY FIXED NITROGEN

The extension of nitrogen-fixing symbioses to important crop plants su ch as the cereals has been a long-standing goal in the field of biolog ical nitrogen fixation. One of the approaches that has been used to tr y to achieve this goal involves the isolation and characterization of stable endophytic bacteria from a variety of wild and cultivated rice species that either have a natural ability. to fix nitrogen or can be engineered to do so. Here we present the results of our first screenin g effort for rice endophytes and their characterization using acetylen e reduction assays (ARA), genomic fingerprinting with primers correspo nding to naturally occurring repetitive DNA elements (rep-PCR), partia l 16S rDNA sequence analysis and PCR mediated detection of nitrogen fi xation (nif) genes with universal nif primers developed in our laborat ory. We also describe our efforts to inoculate rice plants with the is olates obtained from the screening, in order to examine their invasive ness and persistence (stable endophytic maintenance). Lastly, we revie w our attempts to tag selected isolates with reporter genes/proteins, such as beta-glucuronidase (gus) or green fluorescent protein (gfp), i n order to be able to track putative endophytes during colonization of rice tissues.