Stimulated nodulation of soybeans by Rhizobium japonicum mutant (B-14075) that catabolizes the conversion of tryptophan to indol-3yl-acetic acid
1985
Kaneshiro, T. | Kwolek, W.F.
Nodulations of Glycine max L. seedlings by parental Rhizobium japonicum (USDA strain 26) and a tryptophan catabolic mutant (tan 4b, NRRL strain B-14075) were evaluated for effectiveness. Seedlings grown in plastic pouches were compared based on increases in root weight (wt.), nodule volume (vol.) and acetylene-reducing (AR) activity. The tan 4b mutant, which can produce extracellular indol-3yl-acetic (IAA) and indol-3yl-pyruvic (IPA) acids asymbiotically, enhanced nodulation significantly. Nodulation by strain 26 was most effective when a basal nutrient was supplemented with sucrose, CaCO3, EDTA, nicotinic acid and glutamate. In contrast, effective nodulation by tan 4b did not require an exogenous glutamate (0.34 mM)-nicotinate (81 μM) combination. Like strain 26 inoculum supplemented with exogenous IAA (0.1 mM), taproot formation associated with unsupplemented tan 4b was inhibited by exposure to direct light.
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