Robust biological nitrogen fixation in a model grass–bacterial association

Abstract

These authors contributed equally to this work. SUMMARYNitrogen-fixing rhizobacteria can promote plant growth; however, it is controversial whether biological nitrogen fixation (BNF) from associative interaction contributes to growth promotion. The roots of Setaria viridis, a model C 4 grass, were effectively colonized by bacterial inoculants resulting in a significant enhancement of growth. Nitrogen-13 tracer studies provided direct evidence for tracer uptake by the host plant and incorporation into protein. Indeed, plants showed robust growth under nitrogen-limiting conditions when inoculated with an ammonium-excreting strain of Azospirillum brasilense.11 C-labeling experiments showed that patterns in central carbon metabolism and resource allocation exhibited by nitrogen-starved plants were largely reversed by bacterial inoculation, such that they resembled plants grown under nitrogen-sufficient conditions. Adoption of S. viridis as a model should promote research into the mechanisms of associative nitrogen fixation with the ultimate goal of greater adoption of BNF for sustainable crop production.

Corn Yield and Foliar Diagnosis Affected by Nitrogen Fertilization and Inoculation with Azospirillum brasilense

“…This leads to greater growth of plant shoots, more water accumulation, and less stress from C accumulation and metabolism, and more nutrients are taken up by the plant (Pankievicz et al, 2015). Bashan et al (2004) noted that bacteria of the Azospirillum genus produce plant hormones such as indole-acetic acid (IAA), which play an essential role in plant growth.…”

“…Increases in photosynthetic pigments such as chlorophyll a and b, and auxiliary photoprotective pigments such as violaxantine, zeaxantine, ateroxantine, lutein, neoxantine, and beta-carotene, which result in greener plants without water related stress, were verified by Bashan et al (2006). When studying BNF with ammonium release by diazatrophs in the root system of Setaria viridis, Pankievicz et al (2015) verified an increase in root development and greater CO 2 fixation. When A. brasilense was introduced, plants grown in an environment with limited N developed in a manner similar to plants with sufficient N.…”

“…This happens because crops that have been inoculated with A. brasilense have greater CO 2 fixation, improving the ability of some mutant strains to increase BNF and positively influence the C metabolism of C4 plants, which is closely related to the N assimilation metabolism in the plant. However, it is essential to study the effect of different A. brasilense strains and corn genotypes in order to deepen discussion in regard to this subject (Pankievicz et al, 2015). .…”

Ammonium excretion, auxin production and effects of maize inoculation with ethylenediamine-resistant mutants of Pseudomonas sp.

“…Moreover, they altered morphology and growth of the root system, suggesting a phytohormonal effect on wheat growth. As reported earlier, ammoniumexcreting mutants of A. brasilense can supply all the nitrogen requirement of Setaria viridis (Pankievicz et al 2015). Besides the Azospirillum genus, diazotroph mutants of other PGPB species obtained either by induced mutagenesis or genetic transformation showed greater plant-growth promoting capacity than their wild-type strains.…”

Does it take a community to raise a plant? A summary of the Canadian Crop Microbiome Workshop

“…Gary Stacey (National Center for Soybean Biotechnology, University of Missouri, USA) gave a broad overview of the inoculant industry highlighting crop biologicals such as lipo-chito-oligosacharide technologies (such as Optimize™ and Torque™) that were derived from basic research (Sanjuan et al 1992) and are currently being used commercially, as well as the potential of associative nitrogen fixation to improve crop yields within nonleguminous plants as opposed to adapting symbiotic nitrogen fixation (Pankievicz et al 2015).…”