Submitted to: Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/17/2003
Publication Date: N/A
Citation: Interpretive Summary: Legume plants include many species that are used for food and fodder such as: bean, pea, lentil, peanut, alfalfa, clover, and trefoil. They are second only to the grass family in importance to humans. Grain and forage legumes are grown on some 400 million acres, which amounts to about 12% of the Earth's agricultural land. They account for 27% of the world's primary crop production and contribute 33% of humankind's dietary nitrogen needs. The high nitrogen (N) content of legume leaves and seeds make them important throughout the world. The reason legumes have such high nitrogen in seeds and leaves is because they can provide their own nitrogen requirements through a process called symbiotic nitrogen fixation (SNF). The process of SNF occurs on small wart-like structures on roots called nodules. Bacteria, collectively known as rhizobia, live inside the nodule and convert atmospheric N2 gas into fertilizer N. The fertilizer N produced by the nodule bacteria is donated to the plant, while the plant gives the bacteria sugars for growth. It is difficult to find in a single publication information on the importance of legumes, SNF, and constraints to legume production. This publication describes the importance of legumes, their potential for SNF, and research areas that need attention. The information will be useful to crop scientists, policy makers, and producers who are seeking a general overview of the importance of legumes.
Technical Abstract: Legumes play a critical role in natural ecosystems, agriculture, and agroforestry, where their ability to fix nitrogen in symbiosis makes them excellent colonizers of low N environments, and economic and environmentally friendly crop, pasture, and tree species. Unfortunately, legume yields continue to lag behind those of cereals. A research orientation that better balances the needs of third-world or sustainability-oriented agriculture with the breakthrough technologies of genomics and bioinformatics is needed. It requires stronger and more adventurous breeding programs, better use of marker-assisted technologies, and emphasis on disease resistance, enhanced nitrogen fixation, and tolerance to edaphic soil constraints. It also requires extension of existing low-cost technologies, such as rhizobial inoculation, to the small farmer. To paraphrase a comment by Catroux et al. (2001) "we enter the era of biotechnology knowing more and more about the growth of legumes at the gene level, but except for some producers in developed countries, unable to effectively translate these into major gains in productivity."