Agriculture Reference
In-Depth Information
varieties, synthetic and natural fertilizers, frequent pesticide applications,
and the use of irrigation. Developed mainly during the Green Revolution,
modern high-input agriculture provided new and convenient farming prac-
tices allowing for adequate production, significantly reducing world fam-
ine and malnutrition. The focus of this type of agricultural system has been
to create an environment that maximizes productivity and profitability,
along with providing a relatively inexpensive food supply.
Although high-input systems may provide large yields, they create
a fundamentally unsustainable environment that requires frequent and
heavy applications of water, nutrients, and disease/pest/weed controls. In
modern breeding programs, varieties are often developed by crossing pa-
rental genotypes possessing the most desired traits (e.g., yield, early fl ow-
ering, vigor, plant architecture), and selecting offspring are under optimal
growth conditions. The most successful individual plants are selected in
successive generations to ensure consistent uniformity [12], in the case
of self-pollinating crops (e.g., wheat, potato, pea). Even in outcrossing
crop species (e.g., maize, canola, cotton), for which heterozygosity con-
fers advantage through heterosis at the individual level, genetic variability
is restricted in the breeding program pipeline by using only a few elite
highly-inbred parental lines generated from distinct plant populations that
are fi nally combined to produce genetically homogenous hybrids. Modern
crop improvement programs generally select under optimal conditions,
therefore the focus is on genotypic selection based on increased yield per-
formance or fruit/grain weight. This method of artifi cial selection results
with a predictably uniform crop, in which genetic variability is restricted.
Due to the fi eld conditions provided by high-input production system, this
breeding regime has been the dominant approach during the last century.
Genotypes selected for high performance in high-input conditions likely
do not maintain those same high yields under low-input or stress condi-
tions due to the lack of natural genetic variation [13]. High-input systems
work mainly for producers in the developed world, where the heavy im-
portation of supplies and governmental incentives guarantee production
and competition. However, many of the food production systems around
the world are either low-input or under stress conditions and cannot de-
pend on the purchase of supplies or fi scal incentives for crop production,
