Differential colonization of Azospirillum lipoferum on roots of two varieties of rice (Oryza sativa L.)

Summary Seedlings of rice (IR42 and IR50) were aseptically dipped into Azospirillum lipoferum strain 34H suspension under dark, and the presence of bacteria on the differentiating regions of rice roots was observed by scanning electron microscopy. The bacterium did not colonize the root tips of IR42, while it colonized this region in the case of IR50, within 24 h after inoculation. In the early stages, most of the bacteria were embedded in the ruptured mucigel below the root cap cells of IR42. Mucigel was hardly detectable in IR50. While the root hair primordia of IR50 were colonized heavily with the bacterium within 24 h, the root hairs of IR42 were colonized 48 and 72 h after inoculation. This phenomenon in relation to plant varietal differences was discussed.