Future prospects and challenges
A big challenge in this century is to develop technologies leading
to a sustainable agriculture. The use of chemical fertilizers
cannot be eliminated without drastically decreasing food
production. At the same time, there is an urgent need to lower
the adverse environmental impacts of agricultural fertilizers.
Different initiatives are in progress aiming to improve N nutrition
and NUE in plants, such as the manipulation of plant
N metabolism. BNF is a promising alternative to improve
N nutrition, as the use of inoculants of diazotrophic bacteria
in agriculture has been proven to enhance N availability
and uptake, to promote plant growth, to increase biomass,
and to keep the plants healthy (Kloepper et al., 1999; Vessey,
2003; Adesemoye and Kloepper, 2009). The associative and
endophytic diazotrophic bacteria naturally colonize and contribute
with fixed N to several economically important plant
species, comprising a natural system to be explored. However,
the mechanisms regulating this particular type of plant–bacteria
association are still not clear; thus, a better understanding
of the mechanisms is necessary to allow improvement and
manipulation of this association, and possibly an extension
of it to non-natural hosts.