Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/17/1999
Publication Date: N/A
Citation: Interpretive Summary: The ability of soybean to take atmospheric nitrogen and convert it to ammonia for use by the plant (termed symbiotic nitrogen fixation) is an important biochemical pathway which eliminates the need for application of fertilizer nitrogen. This manuscript describes the genetic control of two hypernodulated soybean lines which are being used in crosses with normally nodulated lines in an attempt to enhance symbiotic nitrogen fixation. It was confirmed that a single recessive gene is responsible for this trait and that this trait is easily transferred to other soybean lines by genetic crossing and selection. Understanding symbiotic nitrogen fixation is important to soybean production and understanding the genetic control of the nodulation process, which is responsible for converting atmospheric nitrogen to ammonia, will allow better manipulation of the process. These results will be of benefit to farmers and the environment.
Technical Abstract: Genetic analysis of the hypernodulating NOD mutants and the En6500 supernodulating mutant has shown that they were genetically controlled by single recessive mutant genes. But, it remained unclear whether there was an additional mutant gene independent of rj7 as previously speculated to be present in the NOD2-4 mutant. In addition, in our previous work, the NOD3-7 mutant line was not successfully characterized because of apparent seed contamination. The present study was carried out to investigate the inheritance of mutant gene(s) conferring the hypernodulating trait, and to determine whether there exists an additional mutant gene in NOD2-4. A normally nodulating Harosoy 63 cultivar was crossed to the mutants to produce F1 hybrids and F2 progeny. The hypernodulating lines exhibiting purple hypocotyl, isolated from F2 segregants of the crosses with cv. Harosoy 63, were used as male parents for crossing to the hypernodulating NOD lines with green hypocotyls for allelism analysis. The hypernodulating phenotypes were visually evaluated at 14 d after planting in the greenhouse. Genetic analysis confirmed that a recessive mutant was involved in the hypernodulating lines. Subsequent allelism analysis revealed that although the hypernodulating mutants were isolated from discrete mutational events, there was a single recessive mutant gene (rj7) controlling the phenotype, and the mutant genes in the NOD mutants and the En6500 mutant are allelic.