Preferential occurrence of diazotrophic endophytes, Azoarcus spp., in wild rice species and land races of Oryza sativa in comparison with modern races

• DOI: 10.1046/j.1462-2920.2000.00078.x
• Publication Date: 2003-03-11T19:18:47Z
• Authors: Margret Engelhard; Thomas Hurek; Barbara Reinhold‐...
• Keywords: Oryza

Several diazotrophic species of Azoarcus spp. occur as endophytes in the pioneer plant Kallar grass. The purpose this study was to screen Asian wild rice and cultivated Oryza sativa varieties for natural association with these endophytes. Populations culturable diazotrophs surface‐sterilized roots were characterized by 16S rDNA sequence analysis, identified genomic fingerprints. A. indigens sp. group C detected only rarely, whereas D occurred frequently samples flooded plants: 75% rice, 80% land races O. from Nepal 33% modern cultivars Italy. putatively endophytic populations differed genotype. diversity cultured significantly lower than cultivars. In officinalis (from Nepal) minuta Philippines), predominant putative roots. contrast, their number , numbers other diazotrophs, such Azospirillum spp., Klebsiella sp., Sphingomonas paucimobilis Burkholderia Azorhizobium caulinodans increased. equally high; however, found high apparent numbers. Similar differences also observed a culture‐independent approach comparing ( ) modern‐type plant: clone libraries root‐associated nitrogenase nifH gene fragments, species. New lineages genes detected, e.g. one deeply branching cluster within anf (iron) nitrogenases. Our studies demonstrate that host range extends old being preferred over