Colonization and Nitrogen-Fixing Ability of Herbaspirillum sp. Strain B501 gfp1 and Assessment of Its Growth-Promoting Ability in Cultivated Rice

Abstract

The endophytic colonization, nitrogen fixation, and plant growth-promoting abilities of Herbaspirillum sp. strain B501 gfp1, which is a diazotrophic endophyte isolated from wild rice, were studied after infection (at 10² and 10⁸ cells ml^-1) of seedlings of cultivated rice Oryza sativa cv. Nipponbare. Both doses resulted in colonization of the roots and stem (basal stem and leaf sheath). No colonization of leaves was observed. Higher bacterial populations were observed in the roots than stems. The bacteria colonized the intercellular spaces of the root epidermis and the spaces at the junctions of the lateral roots. They also colonized the epidermis and pericycle of the basal stem and the sub-epidermal tissues of the dermal tissue system of the leaf sheath at later stages. The colonizing bacteria incorporated significant amounts of ¹⁵N₂ into the infected plants. The inoculated plants also had higher dry weights and fresh weights than the control (uninoculated) plants.