ABSTRACT
Soybean is one of the major food crops. It supplies plant protein for human and animal consumption, but also vegetable oils. The study of plant genes involved in the symbiosis advanced rapidly with the introduction of molecular biological techniques. The most significant finding from the physical mapping study was the calculation that one centiMorgan in this region of the soybean genome was equivalent to about 500 kb of DNA. Nodulation and nitrogen fixation contribute substantially to the nitrogen balance of soybean crops. The plant analysis of nodulation has been restricted by the absence of sufficient genetic variation in the nodulation phenotype, and inaccurate methods for the quantitative measurement of nitrogen fixation in the whole plant. Nodulation analysis provides information which has relevance to the whole field of biological research. Fundamental processes like cell division control, tissue-specific gene expression and plant immune response are addressed by this type of research.
