Nitrogen fixation for cereals
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CTA. 1995. Nitrogen fixation for cereals. Spore 55. CTA, Wageningen, The Netherlands.
Permanent link to cite or share this item: http://hdl.handle.net/10568/49564
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Rhizobial bacteria living in nodules on the roots of leguminous plants such as peas and beans fix nitrogen from the air and make some of it available to the host plant. Plant breeders have long wanted to be able to transfer this trait to cereals,...
Rhizobial bacteria living in nodules on the roots of leguminous plants such as peas and beans fix nitrogen from the air and make some of it available to the host plant. Plant breeders have long wanted to be able to transfer this trait to cereals, such as wheat and rice, but until recently, this remained only a remote possibility. However, the possibility may soon become a reality as researchers have brought together rhizobia and cereals that are compatible. In 1991 British, Australian, Chinese and Mexican scientists formed the International Rice Nodulation Group which was funded by the Rockefeller Foundation and the UK's Overseas Development Administration (ODA). The task was to make rice behave like the legumes and 'fix' its own nitrogen. The group began by looking at all the strains of rhizobia world-wide. The strain that caught their attention was the rhizobium associated with the tropical legumes of the genus Sesbania. These plants have nitrogen fixing nodules on their stems, as well as on their roots. The rhizobia enter Sesbania plants by what is termed 'crack entry'. When lateral roots emerge, the rhizobia gain access through the crack in the root skin and, because they are invasive and tolerant of oxygen, they can penetrate further into the root and become established. The root then thickens and turns into a nodule. Research by Professor Ted Cocking at Nottingham University has shown that these rhizobia use 'crack entry' to invade the roots of rice, wheat, maize and oilseed rape and, once in, they form a symbiotic association. Tests in the laboratory have shown that the rhizobia will fix as much nitrogen in rice and wheat roots as they do in Sesbania. The next test will be to see how this symbiotic association works under field conditions. The first field trials will be with wheat in Egypt at the beginning of 1995, followed by trials with rice in India and maize in Mexico. The bonus is that there is no genetic engineering or new technology involved. All that will be required is for cereal seed to put with, or inoculated with, the appropriate rhizobia. Inoculation of legume seed with the right rhizobia is well known, so transferring it to cereals will not be difficult. It seems likely that the technology will be easily transferable to resource poor farmers. Professor Ted Cocking Department of Life Science Nottingham University Nottingham NG7 2RD- UK
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