REGULAR ARTICLE Enhancement of rice production using endophytic strains of Rhizobium leguminosarum bv. trifolii in extensive field inoculation trials within the Egypt Nile delta Youssef G. Yanni & Frank B. Dazzo Received: 24 October 2009 / Accepted: 26 May 2010 / Published online: 9 June 2010 # Springer Science+Business Media B.V. 2010 Abstract This study assessed the ability of biofertilizer inoculants containing Rhizobium leguminosarum bv. trifolii to enhance production of rice (Oryza sativa L.) under actual agricultural conditions in the Nile delta. Large-scale field experiments evaluated 5 rice varieties inoculated with 7 endophytic rhizobial strains during 5 growing seasons, including at sites ranked as the world’ s highest in rice production. Inoculation with single strains or multi-strain consortia significantly increased grain yield in 19 of the 24 trials. By combining superior rhizobial inoculants with agricul- tural extension training, grain yield increased up to 47% in farmers’ fields, with an average increase of 19.5%. Data on rice straw production, harvest index and the agronomic fertilizer N-use efficiency also indicated positive agronomic benefits of rhizobial inoculation. These results establish the merit of deploying our biofertilization strategy using selected rhizobial strains to promote rice production capacity while reducing the need for additional chemical N- fertilizer inputs to maintain agricultural sustainability and acceptable production economy. Technology trans- fer of this important translational research can signif- icantly help to alleviate hunger and meet the nutritional needs of many people in developing countries. Keywords Biofertilizer . Consortia . Endophyte . Field inoculation . Inoculant . Rhizobium . Rice Abbreviations bv biovar CFU colony forming units FAO Food and Agriculture Organization IRRI International Rice Research Institute PGPR plant growth-promoting rhizobacteria YEM yeast extract mannitol Introduction On June 19, 2009, the Food and Agriculture Organi- zation of the United Nations (FAO) announced that “more than ever before, one sixth of humanity is undernourished as world hunger reaches a historic high of 1,020 million people going hungry every day in 2009” (http://www.fao.org/english/dg/2009/index. html). The scope of this study addresses how biofertilizer inoculants developed by agricultural Plant Soil (2010) 336:129–142 DOI 10.1007/s11104-010-0454-7 Responsible Editor: Peter A.H. Bakker. Electronic supplementary material The online version of this article (doi:10.1007/s11104-010-0454-7) contains supplementary material, which is available to authorized users. Y. G. Yanni(*) Sakha Agricultural Research Station, Kafr El-Sheikh 33717, Egypt e-mail: yanni244@yahoo.com F. B. Dazzo Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA