Opportunities for Biological Nitrogen Fixation in Rice and Other Non-Legumes: Papers Presented at the Second Working Group Meeting of the Frontier Pro: 75 (Developments in Plant and Soil Sciences) - Tapa blanda

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.

New frontiers of science offer exciting opportunities to stretch rice research horizons. Recent advances in understanding symbiotic Rhizobium-legume interactions at the molecular level, the discovery of endophytic interactions of nitrogen-fixing organisms with non-legumes and the ability to introduce new genes into rice through transformation have created an excellent opportunity to investigate the possibilities for incorporating N2 fixation capability in rice. During a think-tank workshop organized by IRRI in 1992, the participants reaffirmed that such opportunities do exist for cereals and recommended that rice be used as a model system. Subsequently, IRRI developed a New Frontier Project to coordinate the worldwide collaborative efforts among research centers committed to reducing dependency of rice on mineral N resources. An international Rice Biological Nitrogen Fixation (BNF) working group was established to review, share research results/materials, and to catalyze research. This volume contains the deliberations made at the second working group meeting, held 13-15 October, 1996 at the National Institute of Biotechnology and Genetic Engineering (NIBGE) in Faisalabad, Pakistan. The papers presented in the meeting deal with the recent findings on different approaches related to the establishment of endophytic association, development of N2-fixing nodules similar to legumes and transfer of nif genes to rice.