Annals of Arid Zone 47(3&4): 1-12, 2008

Crop Genetic Engineering Under Global Climate Change

Rodomiro Ortiz
Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT), Km 45 Carretera
México-Veracruz, Col. El Batán, Texcoco, Edo. de México, C.P. 56130, México

Abstract: Climate change may bring an increased intensity and frequency of storms,
drought and flooding, weather extremes, altered hydrological cycles, and precipitation.
Such climate vulnerability will threaten the sustainability of farming systems, particularly
in the developing world. Stress tolerant bred-germplasm, coupled with sustainable
crop and natural resource management as well as sound policy interventions will
provide means for farmers to cope with climate change and benefit consumers
worldwide. This article reviews advances in genetic engineering for improving traits
such as heat tolerance, water productivity, and better use of nutrients that may
enhance crop adaptation to the changing climate of the twenty-first century.
Key words: (Please supply)

Many crops are grown worldwide across Global Warming and Crop Yields
a range of climates, soils, and vegetations.
The total production of annual crops
Farmers and scientists are aware of the
will be affected by increases in mean
influence of climate and weather on crop
temperatures during the twenty-first century
adaptations and yield stability. Furthermore,
(Wheeler et al., 2000). Seed yields are
by using high resolution paleo-climatic data,
particularly sensitive to short periods of
Zhang et al. (2007) showed that in both
hot temperatures if they coincide with
Europe and China long-term weather
critical stages of crop development. Crop
patterns were strongly linked to the
yield variation across years may depend
frequency of wars from AD 1400 to 1900.
on growing-season weather, which also
Increasing carbon dioxide (CO2), rising influences how pathogens and pests affect
global mean temperatures, gradual rainfall crops and their host plant resistance. As
changes, more frequent intense weather indicated by Coakley et al. (1999)
extremes, and great weather variability are temperature is the single most important
occurring due to climate change (FAO, factor affecting insect ecology,
2008a). Such factors impact directly on epidemiology, and distribution, while plant
the health and well-being of crops, thereby pathogens will be highly responsive to
affecting small landholders, subsistence humidity and rainfall, as well as to
agriculture, and food security in the temperatures. CO2 may further promote the
developing world (Tubiello et al., 2007). rapid establishment of invasive insect
Hence, research advances in agronomy and species (Zavala et al., 2008).
breeding should translate into crop yield
gains to keep pace with predicted climate After analyzing spatial averages based
change. on the locations of each crop, Lobell and
Field (2007) indicated that temperatures and
2 ORTIZ

precipitation account for approximately life cycles associated with small plants and
30% or more of year-to-year variations in low yields. However, crop development
global average yields for the world’s six slows beyond each species-dependent
most widely grown crops. For example, optimum temperature. Moreover, longer
Argentina has had yield increases due to crop life cycles due to global warming
increases in precipitation, especially will need more water. Higher temperatures
between October and March, decreases in at the reproductive stage may also affect
maximum temperature and solar radiation, pollen viability, fertilization, grain filling,
particularly during spring and summer, and and fruit development, thereby reducing
increases in minimum temperature almost crop yield potential. For example, by using
year round. Yield increases occurred projected low, mid, and high global warming
especially in summer crops and in the semi- scenarios, Anwar et al. (2007) indicated
arid zone as shown by Magri et al. (2005), that median rainfed wheat yield may
who quantified the impact of climate on decrease by about 29% in southeastern
crop yields in the last decades of the Australia.
twentieth century. There was a negative The negative impacts of warmer
response on global yields of wheat, maize, temperatures on crop yields may be
and barley to increased temperatures (Lobell countered by the increased rate of crop
and Field, 2007): warming since 1981 growth at elevated atmospheric CO2
resulted in annual combined losses of about concentrations, at least when there is
40 million t or US$ 5 billion per year, sufficient water (Wheeler et al., 2000). C3
as of 2002, for these cereal crops. Peng crop species (e.g. rice or wheat) appear
et al. (2004) also showed that rice yields to be more responsive to CO2 doubling
decline with higher night temperatures, as than C4 crop species (e.g. maize or
a result of global warming. Rice grain yield sorghum). There are, however, serious
declined by 10% for each 1°C increase doubts on projections that rising CO2 will
in growing-season minimum temperature fully offset yield losses due to climate
in the dry season. change (Long et al., 2006). Crops may
Each crop has a base temperature for respond well to a CO2 increase but the
vegetative development when growth high temperature stress during the
commences, as well as an optimum reproductive stage may erase such a benefit,
temperature when the plant develops fast. which will depend upon other factors such
Optimum mean temperatures for grain as optimum breeding, irrigation, and
yields vary among the major crops [18-22ºC nutrients. Hikes in surface ozone (O3) can
for maize, 22-24ºC for soybean, 15ºC for also be a threat to crop yields and will
wheat, 23-26ºC for rice, 25ºC for sorghum, outweigh any benefits triggered by rising
25-26ºC for cotton, 20-26ºC for peanut, CO2 levels (Giles, 2005) because O3 creates
23-24ºC for dry bean, and 22-25ºC for reactive molecules that destroy Rubisco-a
tomato] (CCSP, 2008). An increase in very important enzyme for photosynthesis,
temperature often accelerates crop and makes leaves age faster. CO2 and O3
phenological phases that may lead to shorter can also affect crop water-use because of
 CROP GENETIC ENGINEERING 3

direct effects on crop growth and leaf area, in maize production in Africa and Latin
alterations in leaf stomatal aperture (and America; i.e., a loss in maize grain worth
consequently their conductance for water approximately US$ two billion yearly.
vapor loss), and physical changes in the Climate change impacts on agriculture
vapor pressure inside leaves (CCSP, 2008). will vary by region because these are
Furthermore, rising atmospheric CO2 may influenced by the technologies used by
contribute to shrubland expansion, which farmers; i.e., technological sophistication
remains an important problem facing determines farm productivity far more than
rangeland managers and ranchers (Morgan climatic and agricultural endowments
et al., 2007). This process replaces grasses, (Brown and Funk, 2008). The productivity
the preferred forage of domestic livestock, of food staples, especially those grown in
with species that are unsuitable for domestic the developing world, will likely suffer
livestock grazing. without adaptation measurements to address
Nitrous oxide (N2O) is a potent global warming and water shortages. The
greenhouse gas generated through use of magnitude of climate change will influence
manure or nitrogen (N) fertilizer and crop prices elsewhere, which depend also
susceptible to de-nitrification (several on global market changes, thereby affecting
groups of heterotrophic bacteria use NO3- food affordability for poor people.
as a source of energy by converting it Recent estimates suggest an increase by
to the gaseous forms (N2, NO, and NO2). about 5 to 8% (60-90 million ha) of areas
Thus, N2O is often unavailable for crop with drought by 2080 in sub-Saharan Africa,
uptake or utilization (Smith et al., 1990). which contributed very little to climate
In many intensive cropping systems change (about 2% of the anthropogenic
common N-fertilizer practices lead to high CO2 (Fischer et al., 2008). Southern Africa
fluxes of N2O and nitric oxide (NO) (Matson may be severely affected with about 11%
et al., 1998). Reduced emissions (50% less) of its land at risk of being lost to crop
should be therefore a target for the intensive husbandry due to environmental constraints
agro-ecosystems of the twenty-first century, induced by climate change. Stige et al.
but without affecting crop yields, e.g., (2006) suggest that maize yields in Southern
through proper amounts and timing of N Africa are affected by the El Niño Southern
applications or by genetically enhancing Oscillation, which may be a likely scenario
crops with a better N use. with global climate change.

Targeting Priority Regions The favorable, high potential, irrigated

Indo-Gangetic Plains, which account for
Crop modeling shows that climate most of the rice and wheat production in
change will likely reduce agricultural South Asia will be likely affected by possible
production, thus reducing food availability climate shifts. For example 51% of its
(Lobell et al., 2008) and affecting food wheat-producing area might be reclassified
security (Schmidhuber and Tubiello, 2007). as a heat-stressed, irrigated, short-season
For example, Jones and Thornton (2003) production environment (Ortiz et al., 2008).
forecast for 2055 an overall 10% reduction This shift would also represent a significant
4 ORTIZ

reduction in cereal yields, unless appropriate Adapting Agriculture to Climate

cultivars and crop management practices Change through Plant Breeding
were offered to, and adopted by South
The Intergovernmental Panel on Climate
Asian farmers.
Change (IPCC) 4th Assessment Report
As a result of climate change, there indicates that crop yields may slightly
will be a decrease in water availability increase at mid to high latitudes for local
(expressed as runoff) of up to 40 mm per mean temperature increases of up to 1 to
year in the Middle East and North Africa 3°C depending on the crop, and then
(MENA); there will be twice the runoff decrease beyond that in some regions (IPCC,
in the Anatolian Plateau (FAO, 2008b). 2007). For example, at lower latitudes,
The number of dry days will increase especially in seasonally dry and tropical
whereas the number of frost days should regions, crop productivity is projected to
decrease and heat waves could increase decrease for even small local temperature
in the region’s more continental areas. The increases (1-2°C), which would increase
length of growing seasons should also the risk of hunger. The IPPC further states
decrease in MENA. Hence, crop yields in that crop and husbandry adaptations, such
this region will likely suffer losses because as altered cultivars and planting times,
of high temperatures, drought, floods, and respectively, may allow low and mid to
soil degradation, thereby putting food high latitude cereal yields to be kept at
security of the inhabitants under threat. or above baseline yields for modest
The Andes of South America are also warming, whereas frequent droughts and
highly vulnerable to climate change (Lagos, floods will affect local production
2007), which will aggravate challenges for negatively, especially in subsistence sectors
sustainable development of such a mountain at low latitudes.
region and will impact the ability of its
farmers to adapt to changing conditions The Stern Review on climate change
brought by global warming. By using a advocates for developing crops that can
multi-model of global warming simulations withstand heat, drought, and floods (http://
and analyzing observed rainfall trends, www.hm-treasury.gov.uk/independent_rev
Neelin et al. (2006) showed a significant iews/stern_review_economics_climate_
drying trend in the Caribbean/Central- change/sternreview_index.cfm. A recent
American region. Similarly, climate change assessment of the World Bank report on
scenarios suggest that the average annual climate change also points out that cultivars
temperature increase in China by the end with enhanced tolerance to heat, and water
of the twenty-first century may be between or plus salinity stresses are essential for
3 and 4°C (Erda et al., 2005). The models a long-term adaptation response to climate
suggest that climate change without CO2 change (E. Pehu, World Bank, personal
fertilization could reduce the rice, maize, communication). Not surprisingly,
and wheat yields in the country by up worldwide research recently focused on
to 37% in the next 20 to 80 years. generating plants with catch-all alterations
involving the signaling pathways and their
early responses that are common to several
 CROP GENETIC ENGINEERING 5

abiotic stresses such as heat, cold, salinity conventional and molecular tools (including
or water scarcity, as pointed out by Tester the transgenic approach) are needed to
and Bacic (2005). develop such cultivars. However, as
indicated by Bonhert et al. (2006), abiotic
Innovations in crop genetic enhancement
stresses such as temperature extremes, water
will provide some of the best options for
scarcity, and ion toxicity (e.g. salinity and
farmers, especially in the developing world,
heavy metals) are difficult to dissect because
to cope with global warming and water
defense responses to abiotic factors require
scarcity, flooding, and salinity. Breeding
regulatory changes to the activation of
research to develop crops for the twenty-first
multiple genes and pathways. Nevertheless,
century should, however take into account
recent advances in genomics research
the fact that production environments will
address in a more integrated fashion the
be more variable and more stressful, yearly
multigenicity of the plant abiotic stress
climate variation will be greater, and field
response.
sites and environments for testing and
targeting crops will essentially be a rapidly Crops with a better use of N can reduce
moving target (Ainsworth et al., 2008). unneeded N-fertilizer inputs, saving farmers
Plant breeding, appropriate crop husbandry, money and protecting the environment by
sound natural resource management, and reducing trace gas emissions, thus mitigating
agricultural policy interventions will be climate change. Biological nitrification
needed to ensure food availability and inhibition (BNI) or suppressing nitrification
reduce poverty in a world affected by climate by releasing inhibitory compounds from
change (FAO, 2007; Howden et al., 2007; plant roots) may assist in this endeavor
Slater et al., 2007). (Subbarao et al., 2006). BNI genes are
available in some tropical grasses
Research Agenda to Address (Gopalakrishnan et al., 2007) and wild
Climate Change in Agriculture relatives of wheat (Subbarao et al., 2007)
through Plant Breeding and may pave the way for genetically
engineered BNI ability in other major food
To cope with the impacts of climate crops.
change, priority target breeding traits will
address crop responses to temperature, water Transgenic Crops for Farming
(drought and flooding) and nutrient stresses, under Climate Change
and elevated CO2 and O3 (Ainsworth et
al., 2008). Breeding new cultivars with As a science-based technology, modern
enhanced adaptation to high-temperatures, plant breeding brings innovations to farming
CO2 and O3, as well as cultivars that yield systems as a result of new findings and
well with lower water and nutrient inputs ensuing knowledge from research on the
will help farmers grow crops in stressful genetic enhancement of crops. Crop
environments of the twenty-first century. improvement could be accelerated by the
Such farmers which also be affected by genetic engineering of new traits,
limited resources for farming. Genetic particularly those that are not amenable
resources and breeding methods combining to conventional breeding (Jauhar, 2006).
6 ORTIZ

Transgenic alfalfa, canola, cotton, maize, to an enrichment of stress-adaptive alleles

papaya, soybean, and squash with herbicide in the breeding populations.
and pest resistance have been successfully
deployed elsewhere (James, 2007). Farmers Drought stress
grew about 114.3 million ha of transgenic
crops in 2007 (with a growth rate of 12% Climate change will also be associated
vis-à-vis the previous year). with increased water stresses in many
regions due to changes in rainfall
As indicated in the previous section, distribution and because increased
abiotic stresses exacerbated by climate temperatures under low relative humidity
change pose a serious threat to the will result in greater evaporative demand
sustainability of crop yields and account thereby reducing water-use efficiency,
for substantial yield losses, particularly in particularly in drought-prone environments.
rainfed agriculture. Various research Bennett (2003) summarizes options for
domains including plant and cell physiology, water productivity enhancement through
molecular biology, genetics, and plant crop breeding and biotechnology, whereas
breeding will influence crop breeding in Ortiz et al. (2007) provide an overview
terms of how new cultivars can respond of transgenic research for drought-prone
to environments with abiotic stresses environments. Some highlights of the most
(Bhatnagar-Mathur et al., 2008). recent advances on genetically engineered
crops for drought-prone environments are
Successes in crop breeding to adapt new given below.
cultivars to such abiotic stressful
environments will depend on various A model plant such as Arabidopsis
research domains including plant and cell thaliana became a useful research tool for
physiology, molecular biology, genetics, functional genomics and also as a source
and plant breeding (Bhatnagar-Mathur et of alleles for improving crops in stressful
al., 2008). The modern tools of cell and environments. For example, the
molecular biology have shed light on control Dehydration-Responsive Element Binding
mechanisms for abiotic-stress tolerance, and gene 1 (DREB1) and DREB2 are
for engineering stress-tolerant crops based transcription factors that bind to the
on the expression of specific stress-related promoter of genes such as the
genes. This could accelerate the breeding dehydration-responsive Arabidopsis gene
of new cultivars. Nevertheless, rd29A, thereby inducing expression in
physiological knowledge of the processes response to drought, salt, and cold in some
of abiotic stress tolerance in crops continues crop species (Ortiz et al., 2007 and reference
to develop and guides conventional breeding therein). Similarly, the expression of the
and genetic engineering of new crop Arabidopsis’ HARDY (HRD) gene in
cultivars. Such physiological trait-based transgenic rice improved water-use
approaches to crop genetic enhancement efficiency and the ratio of biomass produced
will lead to target genetic manipulations to the amount of water used, by enhancing
(through crossing or transgenic approaches), photosynthetic assimilation and reducing
thereby resulting in desired genotypes due transpiration (Karaba et al., 2007). Rice
 CROP GENETIC ENGINEERING 7

plants that consumed less water exhibited CspA from E. coli, and CspB from Bacillus
increased shoot biomass under irrigated subtilis, promote stress adaptation in
conditions and an adaptive increase in root multiple plant species. They further stated
biomass under drought stress. This result that, expression of CSP proteins in maize
shows the usefulness of research undertaken is not associated with negative pleiotropic
in a model plant such as Arabidopsis for effects, indicating that stress tolerance does
improving water-use efficiency in a main not come at a cost to crop yield under
staple such as rice. limiting water.
Drought accelerates leaf senescence, Phosphatidylinositol-specific phospho-
leading to a decrease in canopy size and lipase C (PI-PLC) plays important roles
loss in photosynthesis, thereby reducing in various physiological processes that could
crop yields. A delay in drought-induced be activated by several environmental
leaf senescence could therefore enhance stresses. A phospholipase C1 gene
crop tolerance to water scarcity. Rivero (ZmPLC1) cloned from maize encoded a
et al. (2007), using tobacco as the model PI-PLC and up-regulated the expression
plant, showed that the suppression of in maize roots under dehydration (Zhai et
drought-induced leaf senescence led to al., 2005). Research results show that an
outstanding drought tolerance as measured enhanced expression of ZmPLC1 improves
by the vigorous growth of the transgenic drought tolerance in transgenic maize (Wang
plants after a long drought period that killed et al., 2008). Under drought stress, the
the control plants. Furthermore, the transgenic maize had higher relative water
transgenic tobacco plants maintained high content, better osmotic adjustment,
water contents and retained, although increased photosynthesis rates, lower
reduced, photosynthetic activity during the percentage of ion leakage, less lipid
drought period. Moreover, there was membrane peroxidation, and higher grain
minimal yield loss in the transgenic plants yield than the control. Recently, Nelson
when they were watered with only 30% et al. (2007) showed that an orthologous
of the amount of water used for the control maize transcription factor (ZmNF-YB2)
plants. confers improved performance under
drought. Transgenic maize plants with
Transgenic maize that expresses increased ZmNFYB2 expression show
Escherichia coli’s glutamate dehydrogenase tolerance to drought as measured by
(gdhA) gene (Lightfoot et al., 2007) will chlorophyll content, stomatal conductance,
be another potential avenue for breeding leaf temperature, reduced wilting, and
drought tolerance. Germination and grain maintenance of photosynthesis under
biomass production were increased in gdhA limiting water. Such stress adaptations will
transgenic maize in the field during seasons contribute to grain yield, when this maize
with significant water scarcity. Water deficit grows in drought-prone environments.
tolerance under controlled conditions was
also increased. Moreover, Castiglioni et al. The new generation of traits to counter
(2008) indicate that expression of related drought includes the use of RNA
cold shock proteins (CSPs) from bacteria, interference in which defense to stress will
8 ORTIZ

still be maintained, but without impairing express different types of Rubisco in sunlit
the growth of the plant. Bayer CropScience and shade leaves.
report yield increases of up to 40% using
A strategy to increase crop tolerance
this approach in transgenic canola after
to O3 might involve reducing stomatal
field testing in Canada (http://www.
conductance (Lin et al., 2001), whereas
checkbiotech.org/green_News_Genetics.a
other approaches for improving crop
spx?infoId=15836). Other scientists are
tolerance to O3 may rely on improving
investigating the ability of the South African
detoxification of O3-induced reactive
resurrection plant, (Craterostigma
oxygen species (Fiscus et al., 2005).
plantagineum) for withstanding drought. In
Ainsworth et al. (2008) also indicate that
this plant, a number of genes are only
components of the O3 sensing and signaling
read during a water shortage, while others
pathways are potential targets for crop
are completely turned off at the same time.
engineering under high O3. However, any
Researchers from the University of Bonn
attempts for breeding crop tolerance to O3
(Germany) isolated the detoxification
by altering sensing, signaling, or regulatory
enzyme aldehyde dehydrogenase (ALDH)
pathways should not disrupt other vital
from this resurrection plant and inserted
processes in the plant.
it in Arabidopsis. The transgenic
Arabidopsis withstood periods of drought
longer (>40%) vis-à-vis wild-type plants. Better N use
Improving the nitrogen-use efficiency
High CO2 and O3
(NUE) of crops will be a key factor for
Rising atmospheric CO2 and O3 are reducing N fertilizer pollution as well as
broadly acknowledged as important to crop for improving yields in N-limiting
production, but little genetic research environments. Shrawat and Good (2008)
investments are given to improve crop give a brief summary of crop genetic
responses to such factors. Ainsworth et al. engineering for enhancing NUE.
(2008) provide an overview of potential Engineering plants with transport gene
biotechnological targets for improving systems, glutamine synthetase and
yields in high-CO2 and O3 cropping systems. glutamate synthase gene systems, gene
The main challenge for crop genetic systems regulating N metabolism or
enhancement will be to breed crops that manipulating N remobilization are among
maximize the advantages of rising CO2. the ongoing NUE research undertakings.
For example, Ainsworth et al. (2008) Research suggests it could be possible to
suggest that substituting current Rubisco enhance or manipulate N metabolism and
for Rubisco from other species, particularly crop growth. However, knowledge of the
non-green algae, which has a markedly mechanisms involved in N remobilization
lower specificity and higher catalytic rate, during leaf senescence is still preliminary
could dramatically increase C gain at current and further research will provide new
and elevated CO2 levels, whereas Zhu et insights for transgenic approaches to
al. (2004) indicate that further gains could enhance NUE. In this regard, Yanagisawa
be maximized by engineering plants to et al. (2004) advocate that transcription
 CROP GENETIC ENGINEERING 9

factor might be a powerful approach to make the same choices about the advisability
modification of metabolism for a generation of genetically engineered crops for
of crops having superior characteristics consumption, because different people have
because a single transcription factor different values.”
frequently regulates coordinated expression The authors of the International
of a set of key genes for respective pathways. Assessment of Agricultural Science and
In their research the plant-specific Dof1 Technology for Development (IAASTD)
transcription factor induced the found that transgenic crops are appropriate
up-regulation of genes encoding enzymes in some contexts, unpromising in others,
for carbon skeleton production, a marked and unproven in many more (Kiers et al.,
increase of amino acids, and a reduction 2008). The potential of transgenic crops
of glucose in transgenic Arabidopsis. to serve the needs of the subsistence farmer
Furthermore, the N content increased in was also recognized, but the IAASTD
the Dof1 transgenic plants (~30%), which authors claim that this potential remains
indicated the promotion of net N unfulfilled. As stated recently by the German
assimilation. The Dof1 transgenic plants Advisory Council on Climate Change
exhibited improved growth under a low (2007), “ …without resolute counteraction,
N. climate change…could result in
destabilization and violence, jeopardizing
Outlook
national and international security to a new
It takes about a decade and US$ 100 degree.” Indeed, falling crop yields will
million to breed a new transgenic crop block development and raise poverty,
cultivar and for it to become available to thereby escalating the risk of conflicts. Crop
farmers (E. Sachs, Monsanto Co.). The genetic engineering should therefore
development of a successful transgenic contribute to global security and peace by
cultivar starts from trait discovery and ensuring food security and improving the
undergoes, after the proof of concept, several livelihoods of both farmers and consumers
development phases (including those in the twenty-first century.
needing field testing), and requires a
regulatory phase for assessing risks to Acknowledgement
human health, the environment, and The author thanks Ms. Allison Gillies
biodiversity. Some farmers and consumers (CIMMYT, Mexico) for her language
are already planting and eating foods from editing of an early version of this manuscript.
these crops, while others are raising issues
related to food and environmental safety. References
Lemaux (2008) provides updated responses Ainsworth, E., Rogers, A. and Leakey, A.D.B. 2008.
to these issues using the most recent Targets for crop biotechnology in a future
peer-refereed literature. As she points out, high-CO2 and high-O3 world. Plant Physiology
147: 13-19.
her article presents “ as accurate a scientific
Anwar, M.R., O’Leary, G., McNeil, D., Hossain,
picture as possible, although this does not
H. and Nelson, R. 2007. Climate change impact
imply that people possessing the same on rainfed wheat in south-eastern Australia. Field
scientific understanding will necessarily Crops Research 104: 139-147.
10 ORTIZ

Bennett, J. 2003. Opportunities for increasing water FAO 2008b. Climate Change: Implications for
productivity of CGIAR crops through plant Agriculture in the Near East. Cairo. Twenty-ninth
breeding and molecular biology. In Water FAO Regional Conference for the Near East.
Productivity for Agriculture:Limits and ftp://ftp.fao.org/docrep/fao/meeting/012/
Opportunities from Improvement (Eds. J.W. k1470e.pdf (9 September 2008).
Kijne, R. Barker and D. Molden), pp 103-126,
Fischer, G., Shah, M., and van Velthuizen, H. 2008.
Wallingford, CAB, UK.
Climate change and agriculture in Africa.
Bhatnagar-Mathur, P., Vadez, V. and Sharma, K.K. Options Summer 2008: 16-17.
2008. Transgenic approaches for abiotic stress http://www.iiasa.ac.at/Admin/INF/OPT/
tolerance in plants: Retrospect and prospects. Summer08/ opt-08sum.pdf (9 September 2008).
Plant Cell Reports 27: 411-424.
Fiscus, E.L., Booker, F.L. and Burkey, K.O. 2005.
Bohnert, H.J., Gong, Q., Li, P. and Ma, S. 2006. Crop responses to ozone: Uptake, modes of
Unraveling abiotic stress tolerance mechanisms action, carbon assimilation and partitioning.
– getting genomics going. Current Opinion in Plant, Cell & Environment 28: 997-1011.
Plant Biology 9:180-188.
German Advisory Council on Climate Change 2007.
Brown, M.E. and Funk, C.C. 2008. Food security World in Transition: Climate Change as a
under climate change. Science 319: 580-581. Security Risk – Summary report for policy
Castiglioni, P., Warner, D., Bensen, R.J., Anstrom, makers. http://www.wbgu.de.
D.C., Harrison, J., Stoecker, M., Abad, M., Giles, J. 2005. Hikes in surface ozone could suffocate
Kumar, G., Salvador, S., D’Ordine, R., Navarro, crops. Nature 435: 7.
S., Back, S., Fernandes, M., Targolli, J.,
Dasgupta, S., Bonin, C., Luethy, M.H. and Heard, Gopalakrishnan, S., Subbarao, G.V., Nakahara, K.,
J.E. 2008. Bacterial RNA chaperones confer Yoshihashi, T., Ito, O., Maeda, I., Ono, H.
abiotic stress tolerance in plants and improved and Yoshida, M. 2007. Nitrification inhibitors
grain yield in maize under water-limited from the root tissues of Brachiaria humidicola,
conditions. Plant Physiology 147: 446-455. a tropical grass. Journal of Agriculture and
Food Chemistry 55: 1385-1388.
Coakley, S.M., H. Scherm, and Chakraborty, S. 1999.
Climate change and plant disease management. Howden, S.M., Soussana, J.-F., Tubiello, F.N.,
Annual Review of Phytopathology 37: 399-426. Chhetri, N., Dunlop, M. and Holger, Meinke
2007. Adapting agriculture to climate change.
CCSP (Climate Change and Science Program). 2008. Proceedings of the National Academy of Sciences
The effects of climate change on agriculture, (USA) 104: 19691-19696.
land resources, water resources, and biodiversity.
A Report by the U.S. Climate Change Science IPCC (Intergovernmental Panel for Climate Change)
Program and the Sub-committee on Global 2007. Climate Change 2007: Synthesis Report
Change Research. U.S. Environmental – Summary for Policy Makers. Valencia, Spain.
Protection Agency, Washington, DC, USA. http://www.ipcc.ch/pdf/assessment-report/ar4/
syr/ar4_syr_spm.pdf (9 September 2008).
Erda, L., Wei, X., Hui, J., Yinlong, X., Yue, L.,
Liping, B. and Liyong, X. 2005. Climate change James, C. 2007. Global Status of Commercialized
impacts on crop yield and quality with CO2 Biotech/GM Crops: 2007. ISAAA Brief
fertilization in China. Philosophical Summary 37. International Service for the
Transactions of the Royal Society B 360: Acquisition of Agri-Biotech Applications,
2149-2154. Ithaca, New York.
FAO (Food and Agriculture Organization of the Jauhar, P.P. 2006. Modern biotechnology as an
United Nations). 2007. Adaptation to climate integral supplement to conventional plant
change in agriculture, forestry and fisheries: breeding: The prospects and challenges. Crop
Perspective, framework and priorities. Rome. Science 46: 1841-1859.
FAO 2008a. Climate change and food security: A Jones, P.G. and Thornton, P.K. 2003. The potential
framework document. Rome. ftp://ftp.fao.org/ impact of climate change on maize production
docrep/fao/010/i0145e/i0145e00.pdf (9 in Africa and Latin America in 2055. Global
September 2008). Environmental Change 13: 51-59.
 CROP GENETIC ENGINEERING 11

Karaba, A., Dixit, S., Greco, R., Aharoni, A., Matson, P.A., Naylor, R. and Ortiz-Monasterio, I.
Trijatmiko, K.R., Marsch-Martinez, N., 1998. Integration of environmental, agronomic
Krishnan, A., Nataraja, K.N., Udayakumar, M. and economic aspects of fertilizer management.
and Pereira, A.2007. Improvement of water use Science 280: 112-115.
efficiency in rice by expression of HARDY,
Morgan, J.A., Milchunas, D.G., LeCain, D.R., West,
an Arabidopsis drought and salt tolerance gene.
Proceedings of the National Academy of Sciences M. and Mosier, A.R. 2007. Carbon dioxide
(USA) 104:15270–15275. enrichment alters plant community structure and
accelerates shrub growth in the shortgrass steppe.
Kiers, E.T., Leakey, R.R.B., Izac, A.-M., Heinemann, Proceedings of the National Academy of Sciences
J.A., Rosenthal, E., Nathan, D. and Jiggins, (USA) 104: 14724-14729.
J. 2008. Agriculture at a crossroads. Science
320: 320-321. Neelin, J.D., Münnich, M., Su, H., Meyerson, J.E.
and Holloway, C.E. 2006. Tropical drying trends
Lagos, P. 2007. Peru’s approach to climate change in global warming models and observations.
in the Andean Mountain Region: Achieving Proceedings of the National Academy of Sciences
multidisciplinary regional cooperation for (USA) 103: 6110-6115.
integrated assessment of climate change.
Mountain Research and Development 27: 28-31. Nelson, D.E., Repetti, P.P., Adams, T.R., Creelman,
R.A., Wu, J., Warner, D.C., Anstrom, D.C.,
Lemaux, P. 2008. Genetically engineered plants and Bensen, R.J., Castiglioni, P.P., Donnarummo,
foods: A scientist’s analysis of the issues. Annual M.G., Hinchey, B.S., Kumimoto, R.W.,
Review of Plant Biology 59: 771-812. Maszle, D.R., Canales, R.D., Krolikowski, K.A.,
Dotson, S.B., Neal Gutterson, Ratcliffe, O.J.
Lightfoot, D.A., Mungur, R., Ameziane, R., Nolte,
and Heard, J.E. 2007. Plant nuclear factor Y
S., Long, L., Bernhard, K., Colter, A., Jones,
(NF-Y) B subunits confer drought tolerance
K., Iqbal, M.J., Varsa, E. and Young, B. 2007.
and lead to improved corn yields on water-limited
Improved drought tolerance of transgenic Zea
acres. Proceedings of the National Academy
mays plants that express the glutamate
of Sciences (USA) 104:16400–16455.
dehydrogenase gene (gdhA) of E. coli. Euphytica
156: 103-116. Ortiz, R., Iwanaga, M., Reynolds, M.P., Wu, H.
and Crouch, J.H. 2007. Overview on crop genetic
Lin, D.I., Lur, H.S. and Chu, C. 2001. Effects of
engineering for drought-prone environments.
abscisic acid on ozone tolerance of rice (Oryza
Journal of Semi-Arid Tropical Agricultural
sativa L.) seedlings. Plant Growth Regulation
Research 4 http://www.icrisat.org/journal/
35: 295-300.
SpecialProject/sp3.pdf (9 September 2008).
Lobell, D.B., Burke, M.B., Tebaldi, C., Mastrandrea,
Ortiz, R., Sayre, K.D., Govaerts, B., Gupta, R.,
M.D., Falcon, W.P. and Naylor, R.L. 2008.
Subbarao, G.V., Ban, T., Hodson, D., Dixon,
Prioritizing climate change adaptation needs for
J.M., Ortiz-Monasterio, J.I. and Reynolds, M.
food security in 2030. Science 319: 607-610.
2008. Climate change: Can wheat beat the heat?
Lobell, D.B. and Field, C.B. 2007. Global scale Agriculture, Ecosystems & Environment
climate–crop yield relationships and the impacts 126:45-58.
of recent warming. Environmental Research
Peng, S., Huang, J., Sheehy, J.E., Laza, R.C., Visperas,
Letters 2 digital object identifier
R.M., Zhong, X., Centeno, G.S., Khush, G.S.
(doi):10.1088/1748-9326/2/1/014002.
and Cassman, K.G. 2004. Rice yields decline
Long, S.P., Ainsworth, E.A., Leakey, A.D.B., with higher night temperature from global
Nösberger, J. and Ort, D.R. 2006. Food for warming. Proceedings of the National Academy
thought: Lower-than-expected crop yield of Sciences (USA) 101:9971–9975.
stimulation with rising CO2 concentrations.
Rivero, R.M., Kojima, M., Gepstein, A., Sakakibara,
Science 312: 1918-1921.
H., Mittler, R., Gepstein, S. and Eduardo
Magrin, G.O., Travasso, M.I. and Rodríguez, G.R. Blumwald. 2007. Delayed leaf senescence
2005. Changes in climate and crop production induces extreme drought tolerance in a flowering
during the 20th century in Argentina. Climatic plant. Proceedings of the National Academy
Change 72:229-249. of Sciences (USA) 104: 19631-19636.
12 ORTIZ

Schmidhuber J. and Tubiello, F.N. 2007. Global change. Proceedings of the National Academy
food security under climate change. Proceedings of Sciences (USA) 104: 19686-19690.
of the National Academy of Sciences (USA)
Wang, C.-R., Yang, A.-F., Yue, G.-D., Gao, Q.,
104:19703–19708.
Yin, H.-Y. and Zhang, J.-R. 2008. Enhanced
Shrawat, A.K. and Good, A.G. 2008. Genetic expression of phospholipase C 1 (ZmPLC1)
engineering approaches to improving nitrogen improves drought tolerance in transgenic maize.
use efficiency. ISB Report May 2008. Planta DOI 10.1007/s00425-007-0686-9.
http://www.isb.vt.edu/news/2008/ news08.may.
htm#may0801 (9 September 2008). Wheeler, T.R., Craufurd, P.Q., Ellis, R.H., Porter,
J.R. and Prasad, P.V. 2000. Temperature
Slater, R., Peskett, L., Ludi, E. and Brown, D. 2007.
variability and the yield of annual crops.
Climate change, agricultural policy and poverty
Agriculture, Ecosystems and Environment 82:
reduction – how much do we know? Overseas
159-167.
Development Institute, Natural Resource
Perspectives 109: 1-6. Yanagisawa, S., Akiyama, A., Kisaka, H., Uchimiya,
Smith, S.J., Schepers, J.S. and Porter, L.K. 1990. H. and Miwa, T. 2004. Metabolic engineering
Assessing and managing agricultural nitrogen with Dof1 transcription factor in plants:
losses to the environment. Advances in Soil Improved nitrogen assimilation and growth under
Science 14:1-43. low-nitrogen conditions. Proceedings of the
National Academy of Sciences (USA) 101:
Stige, L.C., Stave, J., Chan, K.-S., Ciannelli, L.,
7833-7838.
Pettorelli, N., Glantz, M., Herren, H.R. and
Stenseth, N.C. 2006. The effect of climate Zavala, J.A., Casteel, C.L., DeLucia, E.H. and
variation on agro-pastoral production in Africa. Berenbaum, M.R. 2008. Anthropogenic increase
Proceedings of the National Academy of Sciences in carbon dioxide compromises plant defense
(USA) 103: 3049-3053. against invasive insects. Proceedings of the
Subbarao, G.V., T. Ban, M. Kishii, O. Ito, H. National Academy of Sciences (USA) 105:
Samejima, H.Y. Wang, S.J. Pearse, S. 5129-5133.
Gopalakrishnan, K. Nakahara, A.K.M. Zakir
Hossain, H. Tsujimoto, and W.L. Berry W. Zhai, S.M., Sui, Z.H., Yang, A.F. and Zhang, J.R.
2007. Can biological nitrification inhibition 2005. Characterization of a novel
(BNI) genes from perennial Leymus racemosus phosphoinositide-specific phospholipase C from
(Triticeae) combat nitrification in wheat Zea mays and its expression in Escherichia
farming? Plant Soil 299:55-64. coli. Biotechnology Letters 27: 799-804.
Subbarao, G.V., Ito, O., Berry, W., Sahrawat, K.L., Zhang, D.D., Brecke, P., Lee, H.F., He, Y.Q. and
Rondon, M., Rao, I.M., Nakahara, K., Ishikawa, Zhang, J. 2007. Global climate change, war,
T. and Suenaga, K. 2006. Scope and strategies and population decline in recent human history.
for regulation of nitrification in agricultural Proceedings of the National Academy of Sciences
systems – challenges and opportunities. Critical (USA) 104:19214-19219.
Review of Plant Sciences 25: 1-33.
Zhu, X.G., Portis, A.R. and Long, S.P. 2004. Would
Tester, M. and Bacic, M. 2005. Abiotic stress tolerance transformation of C3 crop plants with foreign
in grasses. from model plants to crop plants. Rubisco increase productivity? A computational
Plant Physiology 137: 791-793. analysis extrapolating from kinetic properties
Tubiello, F.N., Soussana, J.-F. and Howden, S.M. to canopy photosynthesis. Plant, Cell &
2007. Crop and pasture response to climate Environment 27: 155-165.