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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #69672
Title: RECIPROCAL GRAFTING AND BACTERIAL STRAIN EFFECTS ON NODULATION OF SOYBEAN GENOTYPES

Author
item ABD-ALLA, MOHAMED - U OF ILL, URBANA
item Harper, James

Submitted to: Symbiosis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Symbiotic dinitrogen fixation occurs in legume plants following successful infection of the root by a specific bacterial strain and development of a nodule (a tumor like structure) which houses the necessary components to covert atmospheric dinitrogen into a form usable by the plant. It is desirable to enhance capability of soybean and other legumes to symbiotically fix dinitrogen to alleviate the need for as much fertilizer nitrogen. Understanding the control points of the development of nodules is essential to enhance progress in improving symbiotic dinitrogen fixation. This study showed that the root itself is capable of restricting nodule development when specific bacterial strains are applied to roots of specific soybean lines. In contrast, the shoot also exercises control of enhanced nodulation, termed hypernodulation. Thus, both the root and the shoot contribute to overall control of nodule initiation and development. The observation that restricted nodule development is primarily a root controlled phenomena, while subsequent development and nodule function is primarily shoot controlled, provides direction for future studies on nodulation control.

Technical Abstract: It is known that the soybean (Glycine max [L.] Merr.) genotype PI 417566 has restricted nodule development when inoculated with Bradyrhizobium japonicum strain USDA 110 and grown at low temperature. The current experiments were conducted to determine if the restricted nodulation of PI 417566 roots could be overcome by grafting them to a hypernodulated shoot, since it is known that grafted shoots of hypernodulated mutants induce hypernodulation on roots of normally nodulated soybean. Reciprocal- and self-grafted NOD1-3 (a hypernodulation mutant) and PI 417566 (a plant restricted nodulation genotype) plants were evaluated for nodulation in a growth chamber at constant 20 deg C. Seedling roots of self-grafted PI 417566 were normally nodulated when inoculated with USDA 123, while USDA 110 resulted in restricted nodulation. Grafting of NOD1-3 shoots to PI 417566 roots did not enhance nodulation when inoculated with USDA 110, but did enhance nodulation when inoculated with USDA 123. It appears that the shoot of NOD1-3 has the ability to alter autoregulatory control of nodulation of the PI 417566 genotype only when challenged with a compatible rhizobial strain. The shoot of PI 417566 significantly inhibited nodule formation on NOD1-3 roots when inoculated with either USDA 110 or 123. The restriction of nodulation on the PI 417566 roots inoculated with USDA 110 appears to be primarily controlled by root factors. It was concluded that restricted nodulation and autoregulatory control of nodulation appear to be separate phenomena.