Read more
Adequate nitrogen fertilization is needed to obtain maximum crop yields. Without sufficient nitrogen available to the plant, other inputs are wasted. There are great differences between developed and develop ing areas of the world with regard to nitrogen-fertilizer production and application, resulting in serious food deficits in some of the most needy areas. Although nitrogen fertilizer is an inexpensive input in comparison to the resulting yield increases, chemical fertilizers must be purchased and do represent a direct cash outlay, sometimes the only cash require ment for the peasant farmer, often an insurmountable obstacle in subsistence farming situations. If present economic trends continue, poor farmers may find it increasingly more difficult to pay for nitrogen fertilizers. Biological nitrogen fixation offers the most promising alternative or supplement to chemical nitrogen fertilizers. Furthermore, nitrogen fixation does not present any hazard to the environment which may be the case with excessive application of chemical nitrogen fertilizers. It is there fore of utmost importance to promote the use of nitrogen fixing crops, especially grain legumes which are also an important source of dietary protein. Although legumes only account for some 9% of the combined world dry matter yield of cereals and legumes, they con stitute as much as 24% of the total protein yield of these crops because of the high protein content in legumes.
List of contents
Efficiencies and inefficiencies in the legume/Rhizobium symbiosis - A review.- Improving nitrogen fixation in legumes by plant breeding; the relevance of host selection experiments in red clover (Trifolium pratense L.) and subterranean clover (T. subterraneum L.).- A multiple-trait breeding program for improving the symbiosis for N2 fixation between Medicago sativa L. and Rhizobium meliloti.- Selection for improved nitrogen fixation in Glycine max (L.) Merr. and Phaseolus vulgaris L..- Developing a breeding strategy to exploit quantitative variation in symbiotic nitrogen fixation.- Mutation breeding of grain legumes.- Gene centres, a source for genetic variants in symbiotic nitrogen fixation: The symbiotic response of the cultivated pea to Rhizobium leguminosarum strains from Europe and the Middle East.- Field evaluation of symbiotic nitrogen fixation by rhizobial strains using 15N methodology.- Rhizobium inoculation trials designed to support a tropical forage legume selection programme.- Breeding soybeans for the tropics capable of nodulating effectively with indigenous Rhizobium spp..- Effect of plant genotype and nitrogen fertilizer on symbiotic nitrogen fixation by soybean cultivars.- Quantitative assessment of symbiotic nitrogen fixation in diverse mutant lines of field bean (Vicia faba minor).- Host genes in Pisum sativum L. conferring resistance to European Rhizobium leguminosarum strains.- Modification of symbiotic interaction of pea (Pisum sativum L.) and Rhizobium leguminosarum by induced mutations.
