GENET archive


2-Plants: News on drought-resistant GE plants

                                  PART I
-------------------------------- GENET-news -------------------------------

TITLE:  Drought-resistant corn sprouts
SOURCE: USA Today, by Elizabeth Weise
DATE:   26 Jul 2005

------------------- archive: -------------------

Drought-resistant corn sprouts

As high temperatures continue to scorch large swaths of the USA, tiny
plots of corn and soybeans around the country are growing green and
strong while their neighbors shrivel up and die.

Through what some describe as the wonder and others the scourge of
biotechnology, the plants carry a trait that has long been the Holy Grail
of crop breeders: drought resistance.

The world's two largest seed producers, Pioneer Hi-Bred International and
Monsanto, both have drought-tolerant corn and soybeans growing in test
plots. Corn is furthest along, perhaps five to six years from commercial

"Under severe drought conditions we were able to see 20% yield
improvement with those plants with the drought gene," Monsanto's Robert
Fraley says.

Both companies are experimenting with using bio-engineering to put
drought-tolerance genes from other plants and microbes into corn and soy.

For areas where farmers use irrigation to grow crops, the drought-
tolerant trait would allow them to lower their water usage and cut costs,
Fraley says.

But the technology is problematic, says Michael Hansen of the Consumer
Policy Institute. "A genome is like an ecosystem. When you introduce new
things, it can have not so much of an impact or (it can have) a
catastrophic impact," he says. "Scientists have no control over where the
genes go, which can cause all sorts of disruption."

The plants still must face years of testing and regulatory studies, plus
review by the Environmental Protection Agency, the Food and Drug
Administration and the Department of Agriculture.

                                  PART II
-------------------------------- GENET-news -------------------------------

SOURCE: ISB News Report, USA, by Alessandro Pellegrineschi, M Pulleman,
        S Sullivan, R Trethowan, and M Reynolds
DATE:   Jul 2005

------------------- archive: -------------------


The emergence of the agricultural biotechnology industry at the end of
the 20th century brought with it products that fall into two basic
categories: herbicide resistant and insect resistant crops (i.e., maize,
soybean, and cotton). In the late 1980s and the 1990s, attempts were made
to develop a range of other products whose qualities were to include
improved fungal disease resistance, starch composition, fruit quality,
and so on.

As the agricultural biotech industry matured, standard product
development processes were adopted. For agricultural products, the
commercialization of initial discoveries generally takes 8-12 years, from
gene discovery to target validation. As genomics applications emerged,
the agricultural biotechnology industry recognized the potential to
identify candidate intervention points for commercial traits.

In reaction to stresses, plants adjust themselves at the levels of
morphology, phenology, physiology, and biochemistry. Because these
responses are presumed to be regulated by genes, efforts in recent years
have focused on the isolation and characterization of genes induced by
stresses. Among stress-induced genes isolated to date, several major
groups have been targeted for improving abiotic stress resistance in
plants. These include genes encoding enzymes for the biosynthesis of
compatible compounds, enzymes for scavenging active oxygen species, heat
shock proteins (HSPs), late embryogenesis-abundant (LEA) proteins,
enzymes modifying membrane lipid saturation, transcription factors, and
proteins required for ion homeostasis.

Among abiotic stresses, drought is the most important from an economic
standpoint and likely the most intractable to breeders' efforts.
Difficulties in breeding for drought tolerance are compounded by an
incomplete knowledge of the genetic and physiological bases of yield in
water-limited conditions. To overcome the minimal response to direct
selection for yield under drought conditions, substantial efforts have
been directed toward manipulation of morpho-physiological traits that
influence drought adaptation through escape, avoidance, and/or tolerance
mechanisms. However, this indirect selection strategy has been successful
in only a limited number of cases. More positively, in recent years
several genes that are responsible for different traits associated with
drought tolerance have been isolated and characterized.

In another branch of the biotech discipline, an increasing number of
studies have strived to map quantitative trait loci (QTL) affecting
drought-related traits and yield in major crops exposed to water deficit.
In a limited number of cases, marker-assisted selection (MAS) has been
used as an integral component of breeding strategies to incorporate
target traits and to increase tolerance to drought1. More recently,
bioinformatics and the flood of information generated by genomics
platforms have added new dimensions for understanding the role and
function of genes governing the response to drought. Despite these
impressive technological breakthroughs, the overall impact of MAS and
genomics on the release of drought resilient cultivars has thus far been

Possible impact of transgenic drought tolerant crops

As water shortages approach critical levels around the world,
particularly in developing countries where more than 60 percent of the
inhabitants already live under precarious conditions with no access to
safe sources of fresh water, we clearly need to provide quick solutions
to the multi-faceted dilemma of water shortages. One promising approach
is to integrate useful drought tolerance traits through genetic
engineering (transgenic intervention points) into lines or varieties at
the advanced breeding level for drought tolerance. Genes carrying these
traits are now coming on line and, applied together with conservation
agriculture techniques, may offer developing world farmers a response to
water-limited conditions that is sustainable, economical, and readily

Transgenic intervention points and comparative advantages

The use of transgenic intervention points is based on the following premises:

More information about inducible promoters The most widely used promoters
in development of transgenic plants are constitutively expressed, i.e.,
they are turned on all the time and throughout the plant. In cases where
gene expression needs to be tailored to a specific organ or a specific
time, such a promoter is not a good choice, especially for the stress-
induced genes. This is because the constitutive expression of a stress-
induced gene may have serious penalties with respect to energy loss or
other adverse side effects. Thus, a stress-inducible promoter should be
considered when the transgenic plants are targeted to deal with abiotic
stresses. Study of the cis-elements responsible for stress induction is
necessary to temporally and spatially target the transgenes. Several
studies provide successful examples of the use of an inducible promoter.

Ability to test transgenic plants under field conditions Overexpression
of stress-related genes has afforded some stress protection in transgenic
plants2. However, the results are not always consistent and can even be
conflicting. Due to the multigenic nature of stress tolerance,
comprehensive physiological and biochemical testing of transgenic plants
under stress conditions must be conducted, which requires a careful
evaluation of the methods for assessing stress tolerance, especially
osmotic stress. Desiccation and salt stresses applied by most researchers
are 'shock' treatments. For most crops, drought tends to develop slowly
as the soil dries. Plants that are subjected to drought conditions in
this gradual manner accumulate solutes that maintain cell hydration and
undergo complex adjustments in their morphology and photosynthetic
characteristics. Thus, to ensure that the responses of the transformed
plants to water stress treatments are agronomically relevant, plants must
be subjected to the same drought regime that crops experience in the field.

Ability to transfer multiple genes While introduction of the key abiotic
stress resistance/tolerance genes into plants increased their stress
resistance in some recent experiments, simultaneous transfer of several
genes will be the likely next step to achieve practical levels of plant
resistance/tolerance. As abiotic stress resistance is polygenic, plant
engineering will require manipulation of complex metabolic or regulatory
pathways involving multiple genes. If, for example, osmoprotectant-
producing, transcription factor-expressing, ion homeostasis-maintaining,
in the case of salt, and antioxidant enzymatic activities are all
incorporated into a single cultivar, there is a strong possibility that
they could work in concert to overcome concurrent abiotic stresses. This
could be achieved either by transformation with multiple genes or by
crossing plants containing different stress tolerance genes.

Developing sustainable agriculture systems

Agronomic measures to reduce yield losses related to drought stress are a
key aspect of an integrated set of technologies called conservation
agriculture (CA). The overall objective of CA is to increase yields and
sustain crop production and environmental quality through more efficient
use of natural resources and chemical inputs. International and national
research has contributed to the development and testing of CA
technologies suitable for local agroecological and socioeconomic
conditions in Africa, Asia, and Latin America, and a lot of expertise is
available. To optimally exploit the combined benefits from agronomic and
GE technologies to reduce yield losses due to drought stress,
collaborative efforts between genetic engineers, breeders, physiologists,
and agronomists are required. Moreover, integration between agronomic and
GE approaches is pivotal to ensure the sustainability of the technologies
with respect to the conservation of soil fertility and natural resources
in the long term. Three basic principles of CA are: (i) zero or reduced
tillage; (ii) retention of soil cover with crop residues and/or cover
crops that form a barrier to water loss by evaporation and runoff; and
(iii) crop rotations including, where possible, biological nitrogen-
fixing crops. Such systems are increasingly adopted to stop or reverse
soil degradation resulting from unsustainable management practices. Today
CA is used on more than one-third of the cropped areas in Brazil and
Argentina, and about 70 million hectares worldwide. CA systems
demonstrate clear benefits in terms of reduced labor and/or fuel inputs.
Other advantages include reduced soil erosion, improved water
infiltration and soil structure, increased soil fertility, soil organic
matter accumulation, carbon sequestration, soil water-holding capacity,
water-use efficiency, soil biodiversity, and resilience to climate
change3. The combined effect of all these factors is claimed to increase
and sustain agricultural productivity with lower water, energy, and labor
inputs. Increased adoption of CA technologies, therefore, not only
enhances food security for millions of smallholders in the developing
world, but also reduces detrimental environmental effects.

CA management practices for rain-fed conditions have been developed and
their effects investigated in some well-designed studies. For example,
results from the long-term management trials of CIMMYT in the subtropical
highlands of Central Mexico indicate that small-scale maize and wheat
farmers in this region may expect yield improvements of 67 and 84 percent
for wheat and maize, respectively, after adoption of zero tillage,
appropriate rotations, and retention of sufficient residues as compared
to current practices of heavy tillage, monocropping, and burning or
removal of residue.

An additional CA technology generating considerable interest is raised
permanent beds, where the benefits of zero-tillage are combined with a
bed and furrow system. The practice of planting crops on beds/ridges that
are formed between furrows used to supply irrigation water is widely
applied in many (semi)arid regions under irrigated agriculture, although
generally beds are tilled and reshaped before each crop cycle. However,
permanent bed systems have also been shown to be a promising technology
in water-limited, rain-fed environments, because they tend to conserve
rainfall, prevent runoff, and provide time for water to infiltrate, with
the surplus advantage that more varied weeding and fertilizer application
practices are possible3,4.

Concluding Remarks

Use of transgenics is a large challenge for public breeding programs, but
also one of the biggest opportunities. A more efficient and sustainable
agriculture depends on plant varieties and cropping systems with
increased resistance to diseases, pests, and other environmental
stresses. Transgenics are a robust source for these traits, although
target traits should be identified in close collaboration with
agronomists. CA technologies aimed to establish sustainable, water-
conserving cropping systems may require specific tolerances/resistances
or traits, for example herbicide resistance or tolerance against plant
pathogens and drought that are favored in zero-till systems.

In addition, transgenic breeding can provide plant varieties with new or
improved nutritional qualities and plants that will produce renewable
industrial products. Such novel varieties are relevant for environmental
conservation both in industrial and developing countries, and for food
security and poverty reduction in the developing world. Moreover, the
unique and diverse expertise available within CIMMYT and sister CGIAR
centers provides an environment that fosters collaboration among genetic
engineers, breeders, physiologists, and agronomists. Only through such a
joint effort can a broad-based systems approach be developed that
incorporates the benefits offered by GE crops and CA systems, and indeed
enhances them, for the good of both farmers and the environment.


1. Nguyen TT, Klueva N, Chamareck V, Aarti A, Magpantay G, Millena AC,
Pathan MS & Nguyen HT. (2004) Saturation mapping of QTL regions and
identification of putative candidate genes for drought tolerance in rice.
Mol. Gen. Genet. 272, 35-46

2. Govaerts B, Sayre KD, & Deckers J. (2005) Stable high yields with zero
tillage and permanent bed planting? Field Crops Research (in press)

3. Pellegrineschi A, Reynolds M, Pacheco M, Brito RM, Almeraya R,
Yamaguchi-Shinozaki K & Hoisington D. (2004) Stress-induced expression in
wheat of the Arabidopsis thaliana DREB1A gene delays water stress
symptoms under greenhouse conditions. Genome 47(3), 493-500

4. Sayre KD. (2004) Raised-bed cultivation. In: Lal, R. (Ed.),
Encyclopedia of Soil Science. Marcel Dekker, Inc. eBook Site Online
publication 04/03/2004

Alessandro Pellegrineschi Genetic Engineering Laboratory CIMMYT -
International Maize and Wheat Improvement Center Houston, Texas web: email:


European NGO Network on Genetic Engineering

Hartmut MEYER (Mr)
In den Steinäckern 13
D - 38116 Braunschweig

P: +49-531-5168746
F: +49-531-5168747
M: +49-162-1054755
E: coordination(*)
W: <>

   GENET-news mailing list