Authentication of putative competitive bacterial endophytes of rice by re-isolation and DNA fingerprinting assay

The plant-growth-promoting putative competitive endophytes offer significant benefits to sustainable agriculture. The unworthy opportunistic and passenger endophytes are inevitable during the isolation of putative competitive endophytes. This study aimed to discriminate the putative competitive endophytes undoubtedly from the opportunistic and passenger endophytes.

The newly isolated endophytes from field-grown rice were inoculated to 5-days old rice seedlings under gnotobiotic conditions. Re-isolation of the inoculated strains from the root surface, inner tissues of the whole plant, root and shoot was performed after 5-days. All the re-isolated colonies were compared with native isolates for homology by BOX-A1R-based repetitive extragenic palindromic-PCR (BOX-PCR) and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) DNA fingerprints. The results revealed that the putative competitive endophytes (RE25 and RE10) showed positive for re-isolation and BOX and ERIC fingerprints for the whole plant, root and shoot. The opportunistic (RE27 and RE8) and passenger endophytes (RE44 and RE18) failed in re-isolation either from root or shoot. The epiphytes (ZSB15 and Az204) showed negative for endophytic re-isolation and positive for surface colonization.

This modified procedure can discriminate the putative competitive endophytes from others.

Eliminating the opportunistic and passenger endophytes and epiphytes early by this method would help develop endophytic inoculants to enhance rice productivity.