Journal Article

Isolation of endophytic diazotrophic bacteria from wetland rice

Revilla, L., Barraquio, W.L., Ladha, J.K.

1997

Overview

Endophytic nitrogen-fixing bacteria are believed to contribute substantial amounts of N to certain gramineous crops. We have been interested to find (a) a diazotroph(s) in rice which can aggressively and stably persist and fix nitrogen in interior tissues and (b) unique rice-diazotrophic endophyte combinations. To achieve these objectives, it has been essential to find an efficient method to surface sterilize rice tissues. The method described here consists of exposing tissues to 1% Chloramine T for 15 min followed by shaking with glass beads. It has proven very efficient since (a) surface bacterial populations on the root and culm were found to be reduced by more than 90%, (b) the number of the internal colonizers was found to be significantly higher than the number of surface bacteria, and (c) colonization of root but not subepidermal tissue by gusA-marked Herbaspirillum seropedicae Z67 bacteria was found to be virtually eliminated. Nitrogen-fixing putative endophytic populations (MPN g dry wt⁻¹) in the root (7.94 × 10⁷) and culm (2.57 × 10⁶) on field-grown IR72 plants grown in the absence of N fertilizer was found to be significantly higher near heading stage. The corresponding total putative endophyte populations in the tissues of 25 highly diverse genotypes of rice and their relatives was found to range from 10⁵-10⁸ and 10⁴-10⁹, in the roots and culms, respectively. Generally, the resident bacteria were found to be non-diazotrophic, although in isolated cases diazotrophs were found, for example in the roots and culm of IR72 rice plants, or the culm of Zizaniopsis villanensis plants. The size of populations of diazotrophic bacteria in different rice genotypes was found to be 10³-10⁷ for the roots and 10⁴-10⁶ for the culms, respectively. The rice genera-related plants Potamophila pariffora and Rhynchoryza subulata showed the highest levels.

• Publisher: Kluwer Academic Publishers,Springer,Springer Nature B.V
• Subject: Agronomy. Soil science and plant productions / Bacteria / Biochemistry and biology / Biological and medical sciences / Biotechnology / Chemical, physicochemical, biochemical and biological properties / Chloramines / Economic plant physiology / Endosymbionts / Fundamental and applied biological sciences. Psychology / Genotypes / Microbiology / Nitrogen fixation / Physics, chemistry, biochemistry and biology of agricultural and forest soils / Plant roots / Plants / Rice / Roots / Soil science / Stems / Sterilization / Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...) / Tissues / Wetlands