Genetically Improved Crops - The Oxford Topic of Food, Politics, and Society - page 68

Nitrogen fertilizer, through intemperate application, can also contribute to eutrophica-
tion at ground level, making its reduction desirable on several levels. However, nitrogen
is essential for crop production since it is quantitatively the most essential nutrient for
plants and a major limiter of crop productivity (Stewart et al. 2005, Erisman et al. 2008).
One of the critical factors limiting the efficient use of nitrogen is plants' ability to
acquire it from applied fertilizer. Therefore, the development of crop plants that absorb
and use nitrogen more efficiently can serve both the plant and the environment. Arcadia
Biosciences of Davis, California, developed nitrogen-efficient crops by introducing a
barley gene—AlaAT (alanine aminotransferase)—into both rice and canola. Arcadia's
nitrogen use efficiency (NUE) technology produces plants with yields that are equiva-
lent to conventional varieties but require significantly less nitrogen fertilizer because
the AlaAT gene allows more efficient use. Compared with controls, transgenic plants
also demonstrated significant changes in key metabolites and total nitrogen content,
confirming increased nitrogen uptake efficiency. This technology has the potential to
reduce the amount of nitrogen fertilizer lost by farmers annually due to leaching into the
air, soil, and waterways. In addition to environmental pressures, nitrogen can represent
a significant portion of a farmer's input costs and can significantly impact profitability.
Farmers spend $60 billion annually for 150 million tons of fertilizer (Svoboda 2008).
The technology has been licensed to Dupont for maize and to Monsanto for application
in canola.
One of the first commercialized products to have included a “yield gene” was
Monsanto's second-generation Roundup Ready 2 Yield Soybeans, which include both
the glyphosate-tolerant trait and one that was developed using extensive gene map-
ping to identify specific DNA regions that segregated with yield increase (Monsanto
2010). First-generation Roundup Ready varieties had demonstrated yield drag due to
the unfortunate insertion close to a gene that influenced seed size and co-segregated
with the transgene. This is a perfect example of the power of combining recombinant
DNA technology with genomics tools. The company claims that four years of field trials
across six US states showed 7 to 11% higher yields compared with the first-generation of
Roundup Ready soybeans, although there have been some problems with fungal (white
mold) susceptibility in certain regions. In August 2010, the National Technical Biosafety
Committee (CTNBio) in Brazil approved the Bt-enhanced version of this product for
planting in Brazil.
The second area where green technology can help in a changing climate is crop adap-
tation to environmental stress and changing niches. Under stress, plants will divert
energy into survival instead of producing biomass and reproduction; addressing this
impact should have a substantial effect on yields. In addition, improved stress tolerance
allows an expanded growing season—especially earlier planting—and further reduces
yield variability and financial risk to the farmer. The most critical of these stresses is
water. The physiological responses of plants to water stress and their relative importance
for crop productivity vary with species, soil type, nutrients, and climate. On a global
basis, about one-third of potential arable land suffers from inadequate water supply, and
the yields of much of the remainder are periodically reduced by drought. One of the