Agriculture Reference
In-Depth Information
key genetic elements (genes) and genetic variations (of coding or regula-
tory regions) that are benefi cial to drought tolerance.
HARDY
, an ethylene-
responsive transcription factor, is an example of a single gene identifi ed
from studies with the model species
Arabidopsis
that has been demonstrat-
ed in rice to confer enhanced drought (and salt) tolerance when a specifi c
mutant allele is overexpressed [51].
ESKIMO1
is another promising ex-
ample of a major genetic player affecting water economy (as well as cold
and salt tolerance), with lack-of-function
Arabidopsis
mutants show better
fi tness in drought conditions [52] by altering hydraulic conductivity in the
vascular tissues and increasing ABA levels [53]. Natural genetic variation
studies in crops [54,55] and model species [56] are also helping to unveil
alleles conferring drought tolerance traits, which can be used as powerful
tools on breeding programs via either traditional or molecular approaches.
11.4.3 ENERGY AND NITROGEN
Modern high-input agriculture is heavily reliant on energy, particularly
in the form of petroleum products like gas and oil. This dependency will
cause the energy demand of modern agriculture to increase approximately
45% over the next 20 years in order to supply food for the increasing pop-
ulation [20]. Although there are alternative forms of energy (solar, wind,
hydro, biofuel) to reduce the dependence on gas and oil, intense modern
agricultural systems require significant energy input. Large equipment
powered by fossil fuels are vital to today's crop production in order to
prepare, cultivate, and harvest the vast number of crops grown to provide
an adequate and nutritious food supply to people around the world. Petro-
leum supply, based on the production data, tends to follow a bell-shaped
curve. The amount of oil in any given region is finite and the production of
petroleum is quickly reaching its peak (Hubbert's peak), coinciding with
the midpoint in the depletion of the resource supply. The U.S. reached
its peak domestic oil production in 1970, and has since been importing
more oil than it is capable of producing [57]. As the world's oil produc-
tion peaks, maintaining high-input agricultural production systems will
become increasingly more difficult and less productive.
