Genetic modification and biotechnology in...

Genetic modification and biotechnology in agriculture

Overview

While there is resistance on the part of some to genetic modification (we will use GM to

mean genetic modification or genetically modified as is common in the literature), and

hope in others, it is clear that there is no going back. The StarLink episode of 2000, in

which a genetically modified corn supposed to be used as animal feed turned up in a

multitude of products meant to be eaten by people, demonstrated that even farmers who

were organic growers for years had indications of StarLink corn in their crops. This

presumably occurred because corn pollen can travel through the air. The episode also

showed that the processing paths from field to end use are porous, with mixing

(“contamination”) occurring all the time.(107)

Fig. E24.3.1 The United States has the greatest crop area planted in genetically modified crops. (USDA, Ref. 108)

Energy, Ch. 24, extension 3 Genetic modification and biotechnology in agriculture 2

Biotechnology includes GM, but is broader, and deals with other techniques such as

cloning, doubling the number of genes in a plant, monitoring recombination in the

genome, or making selection work more efficiently because of a better understanding of

cell biology and heredity. While individual farmers could, and did in the past, carry out

improvements in crops, the ability of farmers to make the major changes necessary to

improve varieties is quite circumscribed.(109)

This has given an opportunity to both government-funded research and private

(corporate) research. In the middle of the last century, government-funded research was

the engine driving improvements in the United States. Seed companies adopted improved

varieties and delivered them to farmers, while supporting some private research. The

climate for “intellectual property rights,” by which is meant the ability to gain from the

creation of particular knowledge by keeping it to oneself through patents or licensing it,

has gotten markedly more supportive in the United States in particular.

Fig. E24.3.2 The number of patents issued for U.S. field crops in 1998.


(U.S. Department of Agriculture, Agriculture Information Bulletin 762, Ref. 107)

This has stimulated the companies to fund more research, pursue more patents (Fig.

E24.3.2), and put a much greater share of the funded research into private company

hands.(109) A similar phenomenon also occurred in Britain.(109) At the same time as

private funding has increased, public-sector research has begun to decline.(109)

While it can be seen from Fig. E24.3.2 that corn and soybeans, not wheat, has been the

focus of private-sector funding in the United States, it has been more important in

Europe. Much wheat planted in Europe does come from the seed companies. In the U.S.,

the area planted to companies’ seed is increasing.(109) This effort has led to higher yields

or lower costs for farmers, or both.

American farmers have eagerly adopted GM and by the beginning of the new century,

75% of GM crops were being grown in the United States. Argentina and Canada made up

virtually all the remainder.(108,110) Farmers primarily are interested in GM varieties

because they think their yields will increase and their pesticide costs will decrease (cited

by 85% of respondents to a survey).(111)

American and European seed companies have jumped into GM. A huge merger mania

and acquisition spree occurred in agribusiness in the 1990s, with concentration of

expertise and technology into just a few giant companies: Monsanto, DuPont, Syngenta

(the Novartis/AstraZeneca merger), Novartis, and (the lone Latin American giant)

Empresas la Moderna. This raises concerns about the untrammeled capitalist approach.

The seed monopolies could perpetuate the comparative disadvantages already present

between developed and the developing world.(110) The companies patent extensively


(this has been possible since the early 1980s) and make profits from selling their seed to

farmers.

Historically, farmers have preserved part of the current year’s crop for seed. In the past,

the seed companies have developed and deployed hybrid seeds. These seeds can be sown

again, but the second generation’s yields are inferior to that of the first generation. This

occurs because of “hybrid vigor,” for reasons that are still not known.(112-114) Therefore,

little by little, farmers in the developed countries have changed their custom of saving

“seed corn,” and bought seed from the seed companies for each year’s crop.

The less-developed world

To change this custom for good in America and elsewhere, seed companies are adopting

one of several possible technologies that force the farmer to pay each year for seed,

known collectively as terminator technology.(110,112,115) There are several forms of

terminator technology, which aims to prevent farmers from saving seed for the next

year’s crop from this year’s crop (therefore reducing income for the seed producer, while

reducing cost for the farmer). This may be done, for example in the patented TPS

(Technology Protection System) by making changes that require a certain chemical

treatment of the seed in order to make it germinate.(112) Terminator technology

eliminates farmer-developed variability of the gene pool. This is a loss in biodiversity.

There is some concern that this could circumvent environmental “canaries.”(110)

The agribusiness companies “follow the money” and devote most of their resources to

working on plants that are common in the temperate world. Much less work has been

done in support of improvements to varieties common in the tropical lowlands.(109) In


particular, little effort has focused on African crops. Benefits of patenting are “skewed to

markets of the rich and largely exclude the concerns of the poor.”(110)

World food prices have dropped in real (deflated) terms by 70% since the 1970s.(116)

This has helped the poor in the less-developed world. Direct food aid is less useful than

allowing poor farmers to feed themselves. Several agricultural economists have

suggested that production of hybrid seed for less developed regions be pursued instead of

terminator technology to allow farmers to reuse cropped seeds as necessary (with the

consequent penalty when “hybrid vigor” does not help push yields upward.(116) Perhaps

the most important additional thing the developed world can do is not to use GM to

“steal” tropical crops such as vanilla, cocoa, and sugar, and so rob farmers in tropical

countries of income.(117)

Worldwide, 80 million new babies are born each year—a population equivalent to adding

another Germany. Population pressure on agriculture is enormous in regions where the

population is growing rapidly. In fact, population is outracing farmland everywhere in the

world. The problem is particularly acute in Africa and west Asia, which are home to the

greatest population growth rates. Population puts pressure on land by making more

mouths to feed, by using it for housing instead of farmland, and by increased demand

causing the degrading of some cropland so that it becomes less productive and may be

taken out of service.

GM in Africa

While South Asia has a greater absolute number of hungry children, Africa has the

greatest number in proportion to its population. And model projections are that the

number will increase, despite a great predicted increase in the area of farmland in sub-


Saharan Africa.(117,118) Africa and west Asia have lost the greatest amount of farmland

per capita in recent years in the race to feed their populations because of unrestrained

population growth. Only bringing the fruits of GM and other biotechnology to Africa and

other less-developed regions seems capable of stalling the Malthusian forecast.(115-121)

This is part of the reason that the private foundations that supported the first “green

revolution” are turning their attention to Africa.

One particularly intractable problem in Africa is the lack of a good transportation

network.(117-119) This transportation net was important to the success of the “green

revolution” in Asia, and needs to be considered in the context of agricultural solutions for

Africa as well.

Another nearly intractable problem is witchweed, the common name for Striga

hermonthica and two close relatives, Striga asiatica and Striga gesnerodes.(115,121)

Witchweed feeds on the host plants, which include maize, sorghum, and a later-

developed liking for millet,(118) three of the most important African food crops. An

outbreak of witchweed in North and South Carolina cost millions and 40 years and still

may not have been eradicated. Each witchweed plant makes tens of thousands of seeds.

The seeds can remain dormant for up to 20 years, and come back to haunt a farmer who

dares plant a crop in a field that once harbored the witchweed, a plant that can activate

witchweed’s germination and parasitism through its detection of sorgalactone produced

by the growing crop plant.(115,121)

A Purdue University team developed a GM sorghum that is witchweed-resistant, and it

proved a tremendous success with African farmers. That’s only a partial answer because

of witchweed’s ability to switch hosts. The hope is for a herbicide-resistant crop, so that

the witchweed can be killed by a herbicide.


North Africa and the Middle East hosts broomrape, which has behavior similar to

witchweed.(115) It attacks vegetables and sunflowers.

One approach to improvement in both Africa and Latin America is to try to engineer

aluminum tolerance into plants, because so many tropical and subtropical soils are

lateritic (and have a high proportion of aluminum).(116,122) A collateral benefit of such

work on metals is also the possibility of breeding plants to concentrate metals and

therefore have available bioremediation of metal-contaminated sites all over the

world.(116,122,123)

On the bright side, African farmers in KwaZulu found success using Bt cotton. The

designation Bt refers to insertion of a gene from Bacillus thuringiensis to confer

resistance to insect damage. Records from a large sample (~1500 farmers) were studied

to identify differences between those who used Bt cotton and those who did not. Bt

cotton is used to prevent infestation by bollworms, a universal cotton pest. Prolonged use

of Bt cotton even seems to repress bollworm populations in regions where it is

predominant, as a decade-long study showed.(124) Comparable regions not grown in Bt

cotton did not exhibit the suppression. As the authors of Ref. 124 note, “Such long-term

suppression has not been observed with insecticide sprays, showing that transgenic crops

open new avenues for pest control.”

While the seeds were more expensive (by a factor of 2), the cotton yield was higher for

Bt cotton farmers, the pesticide costs were lower, and farmers using the GM crop earned

more than their compatriots using conventional cotton varieties.(125) It had been expected

that GM techniques would work best in the tropics and subtropics,(126) but as mentioned

above, African countries have resisted GM crops.


GM in Asia

Bt cotton has also been successful in India.(126,127) This success and that of golden rice

raises expectations for the applicability of GM all over Asia. Much of south Asia has

monsoon rainfall, and much of the region is subject to periodic, frequent droughts. There

is an opportunity to design GM crops that minimize the need for water.(128)

Rice is one of the most important crops in Asia, both in less-developed and more-

developed countries. A significant amount of work has been done with rice, both by

CIMMYT and the International Rice Research Institute in Los Baños,

Philippines.(112,129) Much of the rice genome has been determined.(130) However, for

Asia to feed itself, yields will have to rise substantially—from 5 to 8 t/ha.(131) The “green

revolutionary” plants just might eke this out—if all other conditions are right.(129) It

seems likely that some of that increased yield will have to come from improved plant

varieties. The worst problem may be finicky consumers. Asians are very particular about

the characteristics of the rice they eat.(112)

One problem with rice cultivation, as we saw in Ch. 15, is that it produces methane, a

greenhouse gas. In fact, 30% of the world’s annual methane emissions come from rice

cultivation. Unfortunately, enhancing rice yields with fertilizer increases emissions of

methane from the crop.(132) Further research has found that the greatest methane

emission comes from unfavorable moisture conditions during the wet season. This could

lead to ways to reduce emissions.(133)

One triumph of rice research is the production of “golden rice.” This is a form of rice that

can supply a human nutritional supplement, β-carotene, a precursor of vitamin


A.(130,134,135) Genes from daffodils and bacteria were used, since rice has no natural

genes for production of β-carotene.(135)

GM in Latin America

Latin America did well under the “green revolution.” The real standard of living

increased. It is still difficult to grow crops in some lateritic soils in the tropics, but work

continues. New improved GM crops include sweet potato,(136) cassava, palm oil, and

banana.(122)

Conway and Toenniessen assert that “Most of the ‘added value’ present in modern crops

has been accumulated over the centuries by farmers themselves as they selected their best

plants as the source of seed for the next planting.”(116) Simple justice should involve a

payback for all this effort throughout history. Food production must somehow be coupled

with poverty reduction in the poorer countries.(110) The environment of the less-

developed countries must also be preserved while this is happening.(110)

GM in North America

It appears that the countries in North America will adopt GM crops aggressively. The

legal system supports the seed companies’ patents. Many farmers have lost suits brought

by the seed companies for raising GM crops without paying for them, and have been hit

for $100,000 damages on average.(137)

The most prominent case involved a suit by Monsanto against Saskatchewan farmer

Percy Schmeiser. Schmeiser noted that some canola in his fields was unaffected by


herbicides. GM canola had apparently pollenated his plants, transferring their Roundup

resistance. Schmeiser saved the seed from his own fields, and planted those canola seeds

the following year. A Monsanto agent tested the canola, found it was Roundup-Ready,

and had warned Schmeiser not to plant. When Schmeiser planted anyway, Monsanto

sued. The suit asked damages from Schmeiser.

The case became well known because it tapped into farmers’ reservations about the seed

companies’ tactics. Schmeiser (age 73) became the poster boy for those with

reservations, but he also became an example of someone who refused to embrace the new

world of agriculture. As reporter Randall Palmer put it, “the issue has also divided

farmers. Some resent paying fees from their shrinking incomes to multinational

corporations, while others want to see investment in new and improved crops and support

GMOs.” (GMO means genetically modified organisms.)(138)

Schmeiser lost twice, originally and on appeal.(137,138) When the case ended at the

Canadian Supreme Court, Schmeiser lost there, too (in a 5 to 4 decision). However, the

Court vacated the $19,800 (Canadian) fine and the judgment that Schmeiser pay

Monsanto’s legal costs.(138)

Most data from GM agriculture comes from North America because it was embraced

here early in development. Much has been learned about gene transference (what

happened to Schmeiser’s canola). The case of canola has even been studied (although

that was in Australia). In Ref. 139, researchers found that herbicide resistance traveled to

five-eighths of surrounding fields, even as far as 3 km. The number affected in the fields,

however, was very small (under 0.1% on average). As Stokstad points out, though, “the

study underlines a clear risk: Once transgenes are introduced, they can’t be completely

controlled. That’s a problem for organic farmers.”(140)


Other research revealed that relatively large amounts of plant DNA can be transferred

from modified plants to wild (or domestic) relatives. There’s a probability of about 6 x

10-5 for transfer of chloroplast DNA into the nucleus, much larger than expected.(141)

Other research on gene flow involves studying sunflowers (Helianthus annuus). The

domesticated and the wild versions of the flower are found often to hybridize. A group of

scientists followed several fields of wild and hybrids of wild and domestic plants, and

found that they survived at similar rates, but that wild plants had more seeds and a higher

seed density than the hybrids.(142) Wild plants were found to be less attractive to birds

and butterflies than the hybrids. This experiment tested the flow of genes between wild

and hybrid sunflowers and allowed quantitative measures to be tested. Genes were found

to persist even though there were the reported differences in seed production.

The obvious next step would be to test the flow of “transgenes” between Bt sunflowers

and wild sunflowers. When this was done, the researchers found that Bt sunflowers had

enhanced survival. There was much less damage from butterflies on the Bt plants, and

they also found “no effect on fecundity, suggesting that it was not associated with a

fitness cost.”(143) They say “our study is the first to demonstrate that a transgene derived

from a crop has the potential to increase the fitness of wild plants, and thus increase in

frequency in wild populations.”(143) This suggests to the researchers that “[b]ecause the

rate of spread of an allele is controlled largely by its selective advantage, a Bt transgene

could spread quickly across wild sunflower populations.”(143)

That suggestion must of course be tested by further research. Unfortunately, Allison

Snow, the lead author on Ref. 143, has been unable to make that step. The seed

companies are “accused of hindering attempts to assess whether genetically modified

sunflowers can turn their wild counterparts into ‘superweeds.’”(144)


This mechanism was studied by another research group, which investigated that

“superweed” possibility for oilseed rape. In a similar type of experiment, oilseed rape

was given genes containing Bt. This was crossed to the wild (weedy) Brassica rapa, then

backcrossed. This “superweed” was released and followed and compared to natural

weeds in wheatfields. It was less successful than the wild weed.(145) In similar work in

the United Kingdom, hybridization was also found.(146)

A more threatening spread may have occurred in Mexico. While corn has no near relative

in the United States, corn was created in Mexico by farmers long ago; in fact, 4400 years

ago modern maize alleles were in the corn being grown.(147) There could be a cross

between a genetically engineered variety and a wild relative in Mexico.(115) A paper

published in Nature in 2001 asserted that the authors, Quist and Chapela, “report the

presence of introgressed transgenic DNA constructs in native maize landraces grown in

remote mountains in Oaxaca, Mexico.”(148)

The implication of their paper was that the genes moved around the corn genome

relatively freely. This set off something of a fued, with some scientists claiming the

research was not done correctly. However, a report from Secretariat of the Commission

for Environmental Cooperation of North America concluded the threat was of

concern,(149) and most scientists do not dispute the reality of the gene flow, but rather the

evidence amassed.

There have been suggestions for limiting gene transfer. One such is the “repressible seed-

lethal system.”(150) According to the researchers, their method “allows normal plant and

seed development but inhibits seed germination.” Their results support their claims; this

may be one way to approach the problem.


GM in Europe

Gene flow research was done in Europe, too (see a few examples above). As was found

in the United States and Canada, gene flow was seen. One study of sugar beets (Beta

vulgaris ssp. vulgaris) found evidence of such gene flow.(151) Another study found

significant savings in cultivation of transgenic sugar beets.(152)

Until 2004, the European Union made planting of GM crops very difficult and

discouraged importation of GM plants. Members of the general public give different

answers to what experts see as the same question, as is well-known. However, European

and American publics give different answers to something perceived as the same

question by both. Just as American farmers have embraced GM technology for a variety

of reasons (most of them having to do with money), American consumers have accepted

GM foods without much protest. European consumers have been more vocal in

opposition.(153,154)

Apparently, one reason for American complacency is ignorance. Over a third of

American respondents responding to a question about GM foods did not think they were

being sold. Altogether, 60% did not know or did not think GM foods were being

sold.(153) European press on GM technology was more positive than in the United States,

but despite this, more opposition has arisen in Europe.(154) Perhaps this was due to more

threatening images of the future in Europe, since Europeans scored higher on knowledge

than Americans but tended to be more opposed to GM foods.(154) Apparently, more

Europeans think that eating GM foods (“Frankenfoods”) will cause a person to be

infected with GM organisms, that GM animals always outweigh normal ones, and that

GM foods are the only ones with genes.(154) Perhaps this was due to more trust of

government agencies that regulate food in America.(153,154) Perhaps this is due to the


epidemic of “mad cow” disease in Europe, which may have sensitized Europeans to fear

of infection of any kind.(153)

The most striking finding of Ref. 136 is that Europeans are much less confident than

Americans about the regulators and their work. Only 4% of Europeans saw their

governments as reliable sources of information about GM issues. The American

regulatory bodies, the Food and Drug Administration and the Department of Agriculture

were seen as believable by a majority of American respondents.

The British government, intending to allow introduction of GM plants, ran “debates,”

with uninspiring results.(155) Despite the high level of public opposition,(156) the

government went ahead and allowed (with restrictions) GM crops to be grown in

Britain.(157)

Some believe that GM is the solution to the hunger crisis in Africa. Africa was the only

region of the world to see a decrease in crop production between 1985 and 2000.(158)

Proponents believe that local farmers will save money and be able to grow more of the

crop as a result of the fine tuning possible.(159) However, African countries have resisted

imports of GM foodstuffs even when their citizens were starving (in the case of

Zimbabwe). There is a fear (rightly or wrongly) that allowing GM crops into these

countries will make it impossible to sell their export crops in Europe.(158,160)

GM risks

Scientists are concerned about superweed release and other problematic aspects of the

GM revolution. Some have thought seriously about risks of GM agriculture. Ellstrand

suggests considering six lessons learned about gene flow when assessing risk: “it is not


unusual for crops to mate with their wild relatives; ... gene flow, in itself, does not

necessarily create problems, ... natural hybridization occasionally results in problems in

terms of increased weediness or invasiveness; ... natural hybridization occasionally

results in negative impacts in terms of increased extinction risk to wild relatives; ... gene

flow varies tremendously, both between species and within species; [and] ... typically,

intraspecific gene flow occurs at surprisingly high rates and over surprisingly high

distances.”(161) This seems to sum up the experiments described above.

Hancock considered the various possible classes of risk and cross-correlated them to the

classes of plants to assess which treatments should be of concern and which not.(162) He

notes that invasiveness of plants is connected to weediness. One could determine which

plants (or classes of plants) are at high risk of spreading altered versions by examining

such traits. Hancock claims that “[w]hen the biology of the crop is known and the nature

of the transgene is understood, low- and high-risk categories can be clearly identified

without additional experiments.”(162) Hails notes that the risks are simiular to those of

invasive species (see Ch. 26), and the measures appropriate to one apply also to the

other.(163) A true risk assessment should include all “externalities,” or connected factors

(assuming these could be identified).

There are possibilities of risks to animals; indeed, one report suggested the Monarch

butterfly would be endangered by treatment of corn with Bt, as pollen would contain the

gene.(164) It now appears that that is not the case.(165) The effect of Bt on a bird showed

no harmful effect.(166) At least one European study suggests that the results of embracing

GM agriculture will be beneficial: “if biodiversity is to be conserved in farmland habitats,

the negative effects of farming technology need to be halted, and GM crops may be the

place to start.”(167)


Why consider GM as a solution? Why not “more of the same”?

The success of the “green revolution” is apparent. Major changes were made in many

crops through painstaking breeding measures. One problem with agriculture is that it

relies on growing plants! This is a problem because much energy absorbed from the sun

must go into the plant’s metabolism, and much of the growth of the plant goes to support

the plant infrastructure, not the grain. Human breeding with natural wild plants over the

course of millennia coaxed plants that were crops into committing about 25% of their

weight to grain (it is far less in wild plants).(129) In the “green revolution,” intensive

breeding succeeded in raising the “theoretical” maximum grain productivity (called the

harvest index) to about 50% of crop weight. This doubling of crop weight has had a

tremendous economic impact on poor farmers in Latin America and South Asia. It is

obvious that another doubling cannot occur.

Whether the “theoretical” maximum that exists for a given crop is attained will depend

on local conditions. Is there the proper irrigation? Is the amount of fertilizer applied just

right? Can insect pests and weeds be kept at bay? Some progress can undoubtedly be

made by improving conditions, but theoretical harvest index maxima have not budged

since the “green revolution.”(168,169) The maximum yield for rice has been unchanged

for 30 years.(168)

Perhaps plants’ “theoretical maximum” harvest index might eventually be raised from

around 50% to 60%, but it is difficult to see how to get it much higher than that.(129)

Plants must have roots and leaves to capture sunlight and support the grain on stems. The

“easy” part of increasing yields has been done—it was the “green revolution.” To do

better, to get from the 50% to the 60% harvest index, will take more than just breeding.


There is interest in promoting a “doubly green revolution,” one that is sustainable

environmentally and increases the plant’s yield.(110)

In order to be able to see what is involved with genetic engineering, let us look at the way

agronomists formerly made progress (the sort of progress that led to the “green

revolution”). The traditional method used might be termed “Look for the

phenotype.”(170) A phenotype consists of the constellation of visible attributes of the

organism. So, one examines the plants (we will focus mainly on crops here) available to

identify a line with desired characteristics, then crosses it with an “elite” cultivar. After

this has been done, many seedlings exhibiting a range of possible changes reflecting the

sexual exchange of genetic material come up. To see what will happen under various

conditions, one must inoculate hundreds or thousands of plant seedlings and see which

exhibit resistance to a given disease or insect.(170) This method, based on the farmer’s

traditional method of altering crops, works best when a single gene controls the behavior

desired.(170)

Only a small part of the actual genetic variation of the plant is exploited by this

process.(170) It is quite likely that there are possibilities for beneficial alleles at many

places in the genome of the plant. (Alleles are alternative forms of a gene.) Many

beneficial characteristics that could be used are lying buried in gene banks, and are not

easily accessible using this method.(170) Normal crossing may take 10 generations and

thousands of crossings. This entire process could take up to 15 years to produce a new

variety.(132) Corn brings additional difficulties; the need to breed recessive or

semidominant traits into both inbred parent lines.(171) This is a devilishly complex

problem. Conventional agronomy has not been very successful in exploiting the seed

(genetic) resources available.(170) This is partly because it is difficult to see which plants’


crosses with crop varieties can be helpful, or, as Tanksley and McCouch say,”[t]he

phenotype of exotic germplasm is a poor predictor of its genetic potential.”(170)

One problem with traditional breeding methods is that farmers have continued to make

changes in the same varieties of seeds. As a result, most crops have a slender genetic

base. All the soybeans planted in the U.S. come from a small area of northeast China.

American wheat comes from just two genetic lines from Poland and Russia. This makes

them more vulnerable to disease epidemics and insect predation.(170) After the attack of

the 1970s corn blight, the National Academy of Science recommended that seeds be

collected and preserved in seed banks. That recommendation was heeded. Now 700 seed

banks hold 2.5 million seed varieties worldwide.(171)

It would be nice to be able to increase the efficiency of photosynthetic production. The

enzyme known as RuBisCO (ribulose-1,5-biphosphate carboxylase-oxygenase) is the

most inefficient enzyme in the primary metabolism. RuBisCO turnover as low as 2 to 3

reactions per second.(172) From 20% to 50% of photosynthetically-fixed carbon is lost to

photorespiration.(172) The problem of utilizing light is difficult, partly because the plant

using sunlight can also be damaged by too much light.(173)

If the photosynthetic process could be made more efficient, less fertilizer might be

needed; much of a plant’s nitrogen requirements come from need to make RuBisCO.(172)

There are two basic ways for plants to photosynthesize. C4 plants fix CO2 and jam it into

cells, blocking the oxygen reaction. The C3 plants are more effective below 28 °C, while

C4 plants are more effective above it.(172)

In addition to the problems with the narrow genetic resource of crops, there are still many

unknowns. Little correlation has been observed between photosynthesis and yield, so


even if photosynthesis is made more efficient, it is not clear that it will contribute to

increased yield.(172) Yields can only be raised by getting closer to theoretical maximum

harvest index, by developing of strains resistant to pests, disease, or stress, or by raising

the ceiling.(168)

Genetic engineering 101

This is where the possibility of genetic engineering steps up to the plate. The genetic

modification approach might be termed “Look for the genes.”(170) Most complex traits

are controlled by genes acting at more than one place (or locus), and the effects of the

loci are not equal. While good crops obviously have beneficial alleles at many loci, there

are almost always places where an “inferior” parent could contribute a superior

allele.(171)

It is likely that sampling of wild species will lead to new discoveries. The most promising

possibility for making improvements in crops is finding the wild relatives of crop species

and investigating their genetic resource.(135,171) It is important to find seeds of species

farthest removed from modern cultivars.(171) It is interesting that the genetic variation in

tomatoes in one valley in Peru is larger than the variation shown in all the world’s

commercial varieties.(134) One researcher, Steven Tanksley of Cornell used small, green,

bad tasting tomatoes to improve red varieties. Small wild tomato crosses made big

tomatoes bigger.(135) According to Tanksley and McCouch, the lesson they learned from

this work is that “[e]xotic germplasm often contains genes that are capable of improving

traits important to humans.”(171)

How can we find out about the genes and the loci to make such improvements? That is

the focus of research. There are many methods used to try to determine the genes and


their functions. There are four major ways to learn about the genes: (1) consulting a

database that already has information on gene sequences (and phylogenomics—

exploiting extant evolutionary information to assign gene function);(114,174) (2)

exploiting similarities among plant genomes; (3) making changes and seeing what

results; and (4) tracking the protein and metabolic expressions of cells.(174) This may not

be as simple as it sounds because “minor changes in the structure or expression of a gene

may lead to major changes in phenotype. ... [A]s few as four amino acid substitutions can

convert a desaturase to a hydroxylase.”(114)

Acronyms rule the literature of GM: People discuss ETSs and QTLs. These are ways of

tracking larger stretches of the genome. QTL stands for quantitative trait loci, which are

stretches of genome that control traits. EST stands for expressed sequence tag, which

indicates a region that is associated with a given trait. In both QTLs and ESTs, maps of

locations can be made and should be entered into the bioinformatics database, the first of

the four ways to learn about genes indicated above.(175,176) Both QTLs and ESTs can be

used to identify candidate genes, and extensive EST information should allow probable

gene function to be identified.(114) About half of ESTs can be identified by DNA or

protein homologies.(171) These databases will give us insights into the genes that control

complex responses, and allow knowledge of functional information from genes of

otherwise unknown function.

Consider the methods based on the second method above. The most important thing to

realize is that all the cereal grains (oats, triticeae, maize, pearl millet, sorghum, sugar

cane, foxtail millet, and rice, in order from largest to smallest genome) have a genome

organization that is highly conserved (many differences come from repetitive sequences),

that is, genes devoted to particular functions, such as leaf development, tend to cluster in


the genome. This is known as synteny. Figure E24.3.4 shows the synteny of the common

crop grains.(119)

Gale and Devos write: “Conservation of gene orders, but not intergenetic sequences, over

millions of years appears to be the rule within plant families.”(119) The reference to

intergenetic sequences is to the extra base pairs alluded to above. If rice is related to

wheat, which has 50 times as many base pairs, how can that be? The extra base pairs turn

out to be mainly repetitive sequences that are placed between genes (what used to be

called “junk DNA”).

So some knowledge of the organization of all similar grains is gained from learning about

any one of them—knowing genes responsible for traits in one cereal should reveal the

same information about others.(114) The existence of synteny should ultimately allow

breeders to identify and use alleles from one species in another.(119) Genetic databases

listing various similarities will become ever more important as more data are gathered

(method 1). This should help in building the genetic “grammar” of the gene

expressions.(177)

Now consider the third of the methods for identifying genomic information. The QTLs

and ESTs are markers of interesting regions on the gene; marker-assisted breeding tests

for genes already in a plant or animal and allows crosses to be made more efficiently.

This idea was first developed in the 1980s. Crossbreeding assisted by markers is still

inferior in many ways to pure GM because it is limited to traits already found (or at least

existing) in the species. It does allow avoiding the regulatory review required of GM

foods, which is an advantage because the regulatory process is generally an extended

one.(135)


In addition, marker-assisted breeding allows testing of plants much more quickly than in

traditional agronomy. The plants containing the marker can be identified at once.(135,171)

One problem is often that the plants’ genes have not been fully identified. Markers can be

used even if the genes have not been identified. The major drawback is currently the

expense—tests of the markers are expensive, about $1 each.(135)

Germ plasm screening and DNA-based markers accelerate the breeding process.(170) In

using QTLs, maps are made of the positions of alleles from wild species that appear in

the cultivars. Lines of specific QTLs from wild species can outperform “elite” cultivars,

for example, in Tanksley’s work with the tomato Lycopersicon hirsutum. Over 50% of

beneficial QTLs found were unique to the wild species tested. These QTLs were then

located in an advanced backcross generation. New lines were selected that exhibited

specific QTL alleles from wild species.(171) The QTL backcross method as applied to

rice identified 2 QTLs that each led to an almost 20% yield increase. The use of wild

alleles have far fewer negative effects than conventional agronomy.(171)

A more active version of the third method involves making plants genes change on

purpose. Molecular biology is isolating, characterizing, and modifying individual genes,

transforming the plant. (170) For example, insertion of alien genes or mutants allows the

function of a gene to be determined (we discuss various methods of doing this

below).(114) Researchers can use transposable elements (small pieces of DNA) to

generate many mutant plants that can be screened for useful traits.(174) Mutating plant

genes to see what happens can give information on the effect of the gene on the plant.

This works reasonably well for corn, but not for other plants.(174)

There are several other methods for non-corn plants that work to make changes.

Activation tagging works with stretches of DNA that can turn genes on when they are at


one of the ends or near the ends of the gene.(174) There is virus-induced gene silencing,

in which the plant surveillance system acts as an invader and suppresses the gene in

itself, which may be useful in suppressing gene function.(114) It has been suggested that

“plant artificial chromosome” libraries for plants with small genomes could help identify

interesting regions of chromosomes of higher plants through subsequent insertion

techniques.(114)

The earlier in plant development the measurement of properties of the changed gene can

be identified, the cheaper and more efficiently the knowledge is gained.(135,170) One

method is gene replacement, but this requires regenerating plants from single cells. This

is relatively slow.(114) Gene chips and microarrays are arrays of DNA sequences from an

organism on miniature supports. It can generate extensive data on the response of the

sequences to external stimulus. From microarrays, quantitative information will be

obtained about the degree to which genes respond to pathogens, pests, drought, cold, salt,

growth regulators, herbicides, and other chemicals. Original genes and mutants may be

compared to try to identify differences. Arabidopsis plants with a single foreign gene

from a higher plant may be investigated to see the gene’s functions, although these

results are sometimes hard to interpret. Also, the genome of the higher plant might be

chopped into many large pieces and inserted to see what traits result.(114) The chips are

currently expensive, but costs are expected to drop as experience is gained. The results

are obviously entered onto databases (and so contribute in the future to success of the

database search method).(114)

Infection with the bacterium Agrobacterium tumefaciens is the usual means of

introducing foreign genes for dicots.(75,114) Some researchers have used a “gene gun,” in

which the DNA is put onto small metal spheres and shot from a pistol, for monocots,

which do not respond well to bacterial methods. The gene gun is used to put DNA coding


for an enzyme that gives corn herbicide resistance, for example.(178) Tobacco mosaic

virus is also being used to place foreign genes into plant cells.(174) In addition,

electroporation techniques (using almost anything to break down pore structure and allow

DNA to leak through and possibly be transferred) are used.(179) Most current GM crops

are the product of single-gene transfers carried out by these methods (and others

discussed below).(168) Double mutants will not usually happen by normal plant gene

recombination techniques.(114)

The fourth method of learning about genes and their functions focuses on the protein and

metabolic outcomes of changes made by the methods outlined above. Proteins are

followed by means of pictures of two-dimensional gels. Patterns result from the ways

protein is used in the cell, and comparisons give information about the mechanisms

within the cell. Likewise, genetic changes can change metabolic pathways in cells, and

identifying the changes also gives information on how the change affects cells.(174)

An undoubted triumph of the biotechnological era for crops is the sequencing of the rice

genome. Syngenta announced its achievement in January 2001.(180) The information is

proprietary, but a public consortium is also identifying the rice genome. It will cost $100

million and be completed in 2004. Rice has the smallest number of base pairs in its

genome, about 430 million, compared, for example to 3 billion for corn and 16 billion for

wheat.(175) The cost of sequencing maize is going to be about the same as the cost of

sequencing the human genome, that is, to run into the billions of dollars.(114)

The plant Arabidopsis thaliana is the model organism of choice for basic plant research.

Its genome was published in December, 2000.(180) Though the plant has no commercial

value, it is related to many food species (mustard, cabbage, etc.). Arabidosis is the

template for examining dicots, while rice is the template for monocots.(119) The


information on Arabidopsis and rice is so important because the databases gain

information that can be fed back to gain knowledge of other food plants.

Benefits and risks

A. Benefits

Table E24.3.1 lists some possible benefits from GM I have been able to identify from the

literature.

TABLE E24.3.1

Possible Benefits of Genetic Engineering in Agriculture

Reduced amount of pesticides applied Reduce water loss through stomata to reduce irrigation water needed Reduced soil loss Increased harvest index Increased yield through more efficient photosynthesis Crop disease resistance enhanced Expansion of genetic base of a crop Increase in range of soils that crops can grow on Drought tolerance enhanced Frost tolerance enhanced Shorter period of growth Supply of vitamins and minerals to humans enhanced Better nutritional value to crop Delay in ripening of fruit Improved storage behavior, shelf life Phytoremediation (removal of pollution through plants) Provision of ingestible vaccines for human diseases Cosmetic appeal enhanced Flavor, taste, texture enhanced Industrial feedstock produced (use of plants as chemical “factories”) Intrinsically low-calorie sugar produced Natural decaffeination of coffees and teas Production of animals with less fat Replacement of animal prophylactic treatment with antibiotics as animals engineered stronger Source: Refs. 110, 111, 116, 120, 122, 123, 135, 136, 168-173, 176, 181, 182


People need a minimal amount of the macronutrients (carbohydrates, proteins, and fats)

to live at all. But human beings also need 17 minerals and 15 vitamins, dubbed

micronutrients, for continued healthy life.(176,183) The food of the “hidden hungry,” at

least 800 million poor people,(110,117,118,160,176) perhaps as many as 1.2 billion

people,(183) worldwide does not contain the micronutrients they need for health. The flip

side of this problem is the explosion in obesity in the developed countries, but just

because some have too much to eat does not also mean they are getting the proper

micronutrients. The United Nations estimates that 80% of all people alive suffer from

iron deficiency.(183)

Plant secondary metabolism must be better understood in making changes in food crops

that will make more of these micronutrients available to the people who need them. This

process has begun. Soybeans have been modified to reduce levels of oligosaccharides,

stachyose, raffinose, and galactose.(171) Soybeans’ polyunsaturated fatty acids

decompose when they are heated slightly, and the research has worked to get the plants

themselves to produce monounsaturated fatty acid oleic acid (the proportion has been

raised from 25% to 85%). This allows discontinuation of industrial processing of soybean

oil that produced unhealthy trans fatty acids.(171) The creation of plants containing these

healthier oils would have been impossible without use of GM.(135) Other genes for

enhanced nutrition need to be found.

If these changes are to be made, it is very important to make sure there are no negative

health issues that result. There must be research into the safe upper limit for the intake of

nutrients so that people are not harmed by eating the enhanced foods.(176) This is quite a

challenging job because of the extreme biochemical diversity of the crop plants.(176)


Production of industrial feedstocks and polymers is another area of opportunity for

genetic technology.(171) One effort that succeeded at DuPont was the use of soybeans to

produce vernolic acid and ricinoleic acid (derivatives of oleic acid that are used as

hardeners in paints and plastics). The genes used to modify the soybeans were derived

from Vernonia and castor bean seeds and were transferred into the soybean genomes.(176)

B. Risks

Table E24.3.2 lists some possible risks I was able to identify from the literature. It has

been seen in the case of Hawaii that introduced invading species can affect nontarget

species. So the question of whether crops can hybridize with weeds is a good one.

Experts had expected such hybrids to be sterile, but an experiment showed that Arabdosis

thaliana (a study species, a variety of wild mustard), were twenty times more likely to

cross than natural mutants.(184) European beets mixed (without human assistance) with a

wild relative and produced a farmer’s nightmare, a woody root that damages farm

machines.(115) Roundup Ready canola cross-pollinated with a related weed species just

one year after its release, producing an herbicide-tolerant weed.(185)

TABLE E24.3.2

Possible Risks of Genetic Engineering in Agriculture

Genes that jump from a transgenic plant to another plant Release of invasive change in a crop plant to a related wild weed species Herbicide- or insect-resistant weeds (superweeds) Unintended effects on beneficial organisms Indirect effects on species that depend on pests controlled by GM Generation of novel diseases Longterm dangers of ingestion of foods spiked with pesticides and alien genes Source: Refs. 115, 123, 129, 169, 182, 184


Perhaps most worrisome, wheat has been found to cross with bearded goatgrass, and the

two plants have a different number of chromosomes! With the ubiquity of bearded

goatgrass, even a cross that has only a low a priori probability of occurring could

occur.(115)

GM and insecticides

Resistance genes can be cloned and given to other plants. Introduction of tobacco mosaic

virus into cells confers resistance to virus invasion later.(186) Insect resistance can be

introduced using insect control proteins from the soil bacterium Bacillus thuringensis.

This bacterium is now used by agribusiness by insertion of some Bt genes into bacteria

active in the plant itself.(187) The Bt interferes with insects’ guts. It binds to gut

membrane cells and causes them to burst. Adding pest resistance does not increase the

plant’s yield.(169) For example, such Bt proteins protect corn against the corn borer and

the pink (cotton) budworm.(188) This is an environmental gain, because it allows fewer

chemical pesticides to be applied, though some have argued that not much pesticide is

targeted to the corn borer while others have disagreed.(189,190) All observers agree that

targeting the corn rootworm with Bt insecticide will greatly reduce pesticide use (perhaps

as much as 50%),(165) and be a great environmental gain.

It was originally hoped by some that the insects targeted by Bt would not become

resistant; this was a vain hope. By 2001, after 5 years of use, it was clear that some target

species such as the diamondback moth (cabbage and other cruciferous crops) and the

tobacco budworm (cotton) are already Bt resistant. Some target insects apparently have

proteins that can bind to Bt, rendering it ineffective, and these insects jump in numbers as

nonresistant insects are killed.(191) It appears that resistance by loss of carbohydrate

modification in the affected insects plays an important role.(192)


Pessimists have pointed out that this could be a sign that use of modified crops could lead

to the situation in which Bt is ineffective and the crop cannot be planted. In order for Bt

to continue to be used, the origins of the resistance must be identified. It is hoped that

that will allow prediction of resistance and heading off its development. A start has been

made and it appears that a DNA test that can identify developing Bt resistance in local

insects has been developed. This would allow farmers to switch back to chemical

pesticides for a time and prevent overwhelming the nonresistant population.

Summary

It seems that the only way we can find that will provide enough food to keep Malthusian

hunger at bay in the future, because the current agronomic practices are running out of

improvement room, is the use of genetic engineering to cause genetic modification. There

are risks associated with the use of GM, but the risks of not using the technology might

be starvation of many human beings. In addition, there are clear gains to be made in

many areas of health and nutrition as well as ability to enhance yields and prolong

viability of the foodstuff. The promise of future food security will come from

comparative genetics and genetic modification,(119) and from genomics-guided

transgenes, borrowing related genes from closely related species to modify the target

species.(193)

However, as we are aware of risks, we must make every effort possible to prevent the

escape of resistant genetic information into the wild. Every effort should also be made to

protect the environment as much as is possible while feeding the multitudes.


In the developed world, consumers who are rich enough to do so may choose to reject the

benefits of the genomic revolution. They should be allowed to have the right to choose

between GM and non-GM foods.(116)

In addition, equity and justice for the farmers in the developing world needs to be part of

the calculus applied to GM developments. These farmers have provided many of the

pieces of genetic information on which advance is based from time immemorial

(Newton’s “standing on the shoulders of giants” metaphor is appropriate here). They

have developed folk wisdom that produced crops in the first place. That means also that

everyone should support the effort to make sure that seeds are the dowry for the entire

planet. Undeveloped countries have begun to withhold seeds from researchers because

they do not think they will ultimately benefit from the fruits of the research.(194)

The International Treaty on Plant Genetic Resources, which mandates the free exchanges

of seed among plant breeders from 35 major crops (for example, rice and wheat) and sets

up a royalty fund for use of seeds from public seed banks that will support maintenance

of biodiversity,(194,195) should be adhered to in order to encourage continued free

exchange of seeds among nations (the U.S. declined to sign in order to protect

companies’ patent rights on individual genes).(195)

It is encouraging that over 100 countries negotiated and signed the treaty, and that it does

not ban patents totally (as some countries fought for).(195) It is discouraging that so many

crop varieties (soybeans [China demurred], tomatoes and peanuts [Latin American

countries demurred]) are still not among those included in the treaty.(195)

In any case the use of terminator technology in the developing world needs to be

eliminated.(116) Farmers need to be able to replant, even if the yield is inferior, as farmers


close to the poverty line might well not have financial resources each year to buy the

seeds.

Finally, since use of antibiotic resistance genes to select transgenic plants is so

controversial, and since other ways exist to achieve the same ends, its use should be

phased out.(115)

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