During the next 30 years, farmers must produce 70% more rice than the 550 millions tons produced today to feed the increasing population. Nitrogen (N) is the nutrient that most frequently limits rice production. At current levels ofN use efficiency, we will require at least double the 10 million tons of N fertilizer that are currently used each year for rice production. Global agriculture now relies heavily on N fertilizers derived from petroleUIll, which, in turn, is vulnerable to political and economic fluctuations in the oil markets. N fertilizers, therefore, are expensive inputs, costing agriculture more than US$45 billion annually. Rice suffers from a mismatch of its N demand and N supplied as fertilizer, resulting in a 50-70% loss of applied N fertilizer. Two basic approaches may be used to solve this problem One is to regulate the timing ofN application based on needs of the plants, thus partly increasing the efficiency of the plants' use of applied N. The other is to increase the ability of the rice system to fix its own N. The latter approach is a long-term strategy, but it would have enormous environmental benefits while helping resource-poor farmers. Furthermore, farmers more easily adopt a genotype or variety with useful traits than they do crop and soil management practices that may be associated with additional costs.

Inhalt

1. Introduction: Assessing opportunities for nitrogen fixation in rice - a frontier project.- 2. Fertilizers and biological nitrogen fixation as sources of plant nutrients: Perspectives for future agriculture.- 3. Isolation of endophytic diazotrophic bacteria from wetland rice.- 4. Isolation of endophytic bacteria from rice and assessment of their potential for supplying rice with biologically fixed nitrogen.- 5. Association of nitrogen-fixing, plant-growth-promoting rhizobacteria (PGPR) with kallar grass and rice.- 6. Occurrence, physiological and molecular analysis of endophytic diazotrophic bacteria in gramineous energy plants.- 7. Azoarcus spp. and their interactions with grass roots.- 8. Biological nitrogen fixation in non-leguminous field crops: Facilitating the evolution of an effective association between Azospirillum and wheat.- 9. Rhizobial communication with rice roots: Induction of phenotypic changes, mode of invasion and extent of colonization.- 10. Natural endophytic association between Rhizobium leguminosarum bv. trifolii and rice roots and assessment of its potential to promote rice growth.- 11. Interactions of rhizobia with rice and wheat.- 12. Interactions between bacterial diazotrophs and non-legume dicots: Arabidopsis thaliana as a model plant.- 13. Root morphogenesis in legumes and cereals and the effect of bacterial inoculation on root development.- 14. Strategies for increased ammonium production in free-living or plant associated nitrogen fixing bacteria.- 15. Genetics of Azospirillum brasilense with respect to ammonium transport, sugar uptake, and chemotaxis.- 16. Chitin recognition in rice and legumes.- 17. The role of phytohormones in plant-microbe symbioses.- 18. The impact of molecular systematics on hypotheses for the evolution of root nodule symbioses and implications for expanding symbioses to new host plant genera.- 19. Nif gene transfer and expression in chloroplasts: Prospects and problems.- 20. Enhancing biological nitrogen fixation: An appraisal of current and alternative technologies for N input into plants.