permaculture

[Lawrence London <lfljvenaura@gmail.com>]

colonization of cereals and other crop plants by nitrogen-fixing bacteria
for reduced inputs of synthetic nitrogen fertilizers

   - Edward C. 
Cocking<http://link.springer.com/search?facet-author=%22Edward+C.+Cocking%22>,

   - Philip J. 
Stone<http://link.springer.com/search?facet-author=%22Philip+J.+Stone%22>,

   - Michael R.
Davey<http://link.springer.com/search?facet-author=%22Michael+R.+Davey%22>


http://link.springer.com/article/10.1007/BF03187127

Abstract

It has been forecast that the challenge of meeting increased food demand
and protecting environmental quality will be won or lost in maize, rice and
wheat cropping systems, and that the problem of environmental nitrogen
enrichment is most likely to be solved by substituting synthetic nitrogen
fertilizers by the creation of cereal crops that are able to fix nitrogen
symbiotically as legumes do. In legumes, rhizobia present intracellularly
in membrane-bound vesicular compartments in the cytoplasm of nodule cells
fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound
vesicular compartments, rhizobia are supplied with energy derived from
plant photosynthates and in return supply the plant with biologically fixed
nitrogen, usually as ammonia. This minimizes or eliminates the need for
inputs of synthetic nitrogen fertilizers. Recently we have demonstrated,
using novel inoculation conditions with very low numbers of bacteria, that
cells of root meristems of maize, rice, wheat and other major non-legume
crops, such as oilseed rape and tomato, can be intracellularly colonized by
the non-rhizobial, non-nodulating, nitrogen fixing 
bacterium,*Gluconacetobacter
diazotrophicus* that naturally occurs in sugarcane.*G.
diazotrophicus*expressing nitrogen fixing (
*nif*H) genes is present in symbiosome-like compartments in the cytoplasm
of cells of the root meristems of the target cereals and non-legume crop
species, somewhat similar to the intracellular symbiosome colonization of
legume nodule cells by rhizobia. To obtain an indication of the likelihood
of adequate growth and yield, of maize for example, with reduced inputs of
synthetic nitrogen fertilizers, we are currently determining the extent to
which nitrogen fixation, as assessed using various methods, is correlated
with the extent of systemic intracellular colonization by*G. diazotrophicus*,
with minimal or zero inputs.