Not available – first paragraph follows: Production of ammonia from atmospheric nitrogen by the Rhizobium-legume symbiosis offers opportunities for genetic improvement of both Rhizobium bacteria and host legume. Root nodules formed by rhizobia are the organs responsible for nitrogen fixation. California crops that might benefit most directly from such improvements are alfalfa, clover, common beans, lima beans, garbanzos, and blackeye peas. Additional nitrogen fixed, but not used, by those plants would be bound in an organic form that could carry over to benefit subsequent crops.