Nodulation of the legume Pterocarpus indicus by diverse strains of rhizobia

Pterocarbus indicus (Leguminosae: Papilionoideae) is a tropical legume with potential for commercial forest plantation. A glasshouse experiment was undertaken to investigate the effects of inoculation of 18 strains of diverse rhizobia comprising species from four genera on P. indicus seedlings. Pterocarpus indicus was effectively nodulated by Bradyrhizobium elkani WSM 2096. These seedlings had a significantly greater plant yield compared with seedlings with other strains and the controls. Strain Bradyrhizobium sp. WSM 3712, originally isolated from P. indicus from Malaysia, formed many partially effective nodules. However, three other slow-growing strains, B. liaoningense WSM 2098, Bradyrhizobium sp. TAL 643 and Bradyrhizobium sp. TAL 651, ineffectively nodulated P. indicus. The moderately fast-growing strain, Mesorhizobium ciceri WSM 2100, and four fast-growing strains, Sinorhizobium meliloti WSM 2114, Rhizobium hainanense WSM 2106, Rhizobium gallicum R 602 and Rhizobium tropici WSM 2110, also formed ineffective nodules on P. indicus. Pterocarpus indicus appears to be a diverse and promiscuous host for nodulation but with a narrow range for effective N-2-fixing symbiosis. This information is useful for future inoculation programmes for P. indicus in containerized nurseries.