Effect of rhizobium japonicum mutants with enhanced nitrogen fixation activity on nitrogen transport and photosynthesis of soybeans during vegetative growth glycine max cultivar wells

Thomas, R.J.; Jokinen, K.; Schrader, L.E.

Crop Science 23(3): 453-456


ISSN/ISBN: 0011-183X
Accession: 005267078

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The effects of 2 mutant strains of R. japoniucum with enhanced capacitites for N2 fixation, ureide and transport photosynthesis, root respiration, and growth in soybeans [G. max L). Merr. Wells] were examined during vegetative growth. Three-week-old plants inoculated with the mutants were larger and had higher rates of acetylene reduction, photosynthesis, xylary ureide transport, leaf allantoinase activity and higher concentrations of ureides in shoot tissues than did plants inoculated with the wild-type strain. The relative composition of xylem sap N was unaffected by Rhizobium strain. Ureides comprised over 90% of the sap N in all treatments. After 5 wk of growth, however, there were no statistically significant differences among treatments in rates of the physiological processes and growth parameters examined. Cross contamination of nodules containing the mutant strains with the wild-type strain was not responsible for the apparent loss of the initial advantages to the host plant (in terms of N2 fixation and growth) brought about by the use of the mutant strains. The use of modifications in Rhizobium genetics for improving the dependency of the host plant on N2 fixation of its N requirements is briefly discussed.