London (1.1.09)
– For thousands of years, plant breeding depended on selection of the
best plants and intercrossing between related varieties in attempts to retain
the best characteristics of available crop plants and eliminate the worst.
By the middle of the 20th century there was a growing understanding of genetics
which lead to the idea that if one could provoke change and reassortment of
the genes of a particular type of organism it was possible that, by chance,
strains with more desirable properties might emerge which could then be developed
for commercial use. Enough was known of genetics to understand that such random
genetic changes could be effected by agents which produced mutation, alterations
in the genetic material. Although there was at that time no knowledge of what
they might mean in molecular terms, it was realised that treatment with certain
chemicals (ones, for example, known to cause certain cancers in humans) or
by high energy radiation (which can also result in human cancers) might yield
such random genetic changes.
A technique of “mutagenesis breeding” accordingly developed in
which seeds were treated in these ways. Some of them became too badly damaged
to survive but, by chance, some did show useful new or enhanced characteristics
which eventually made them valuable crops in agriculture. There are estimates
that some 70% or more of our current crop plants have such a mutagenic event
in their histories. Among those food plants are apples, barley, cherries,
grapes, navy beans, oats, onions, potatoes, rice, soybeans, string beans,
wheat, “golden promise” malting barley and many others. We have
earlier noted this technique and some of its implications (1, 2).
Although the many possible consequences of such action were – and remain
– unknown, there are no regulatory requirements to test these crop products
either for effects they may have on human health or on “the environment”.
Seeds produced like this are regarded just like those made by traditional
crossing procedures. They have to be tested in the field, not for safety or
effects on the environment but to make sure they meet the commercial “DUS”
requirements”: that they are distinct, uniform and stable so that a
farmer buying such seeds knows what he is getting and can rely on what it
says on the label.
It is, of course, interesting to contrast those procedures with crops produced
with precision using the most modern techniques of genetics: those termed
“GM” or “genetically modified” although, of course,
they are no more and no less genetically modified that a plant produced by
mutation breeding or, indeed, by conventional crossing. GM crops are subject
to extensive and elaborate regulatory control with batteries of testing required
and, even when all those requirements are satisfied, in many parts of the
world (with the European Union the prime example) they are subject to endless
political argument and wrangling.
But the uncertainties of mutation breeding appear to worry nobody. Indeed
the International Atomic Energy Agency based in Vienna is advocating a wider
use of mutation breeding with radiation in order, they say “to improve
food crops…(to)…help fight global hunger” (3).
Examples of how this technique has resulted in new and better strains include
rice in Vietnam, wheat in Kenya, barley in Peru and cassava in sub-Saharan
Africa as well as ongoing projects in Algeria, China, Costa Rica, Egypt, Ghana,
India, Italy, Japan, Nigeria, Pakistan, Philippines, Scotland, Sierra Leone,
South Africa, Sudan, Turkey, USA, Zambia and Zimbabwe. One of the benefits
of using this random, uncontrolled way of generating new crop plants which
then require no testing other than for DUS properties is that “…unlike
genetic modification, which introduces new material into a plant’s genetic
makeup, induced mutation simply accelerates the natural process of spontaneous
changes occurring in plants” (sic!). It is particularly interesting
that Italy and Scotland are countries in which these mutation breeding activities
are going on since both claim (officially) to be vehemently against the genetic
modification of crop plants.
Chikelu Mba, head of the plant breeding laboratory outside Vienna run jointly
by the IAEA and the U.N. Food and Agriculture Organisation (FAO), said that
induced mutation" exposes a plant to radiation to speed up natural changes
to its genetic code, which might normally take millions of years, to resist
evolving threats like disease, pests, saline soil or drought. The method is
safe and cost-effective, requiring no notable upgrade in infrastructure beyond
investment in training people in the method in needy countries” (4).
Pierra Lagoda who heads the IAEA's plant breeding and genetics section said
"It's non-hazardous, it's low-cost and it has proven its effectiveness.
It's about using the right tool in the right way", while Jacquelyn Yanch,
professor of nuclear science and engineering at the Massachusetts Institute
of Technology, agreed that the technique was safe: The new plant variants
are not made radioactive by the process" (well, thank heavens for that)
(5) – and indeed they are right to make those statements.
So it was not surprising for the pressure groups to jump on the bandwagon
and grab hold of something – anything – to enable them to maintain
their anti-GM stance (5). Thus, Jan Beranek, nuclear energy project leader
at the environmental group Greenpeace, largely echoed Yanch's comments: "As
long as the radioactive material is properly managed in laboratories, there
are no significant risks," he said. "It certainly does not lead
to wide contamination of the plants". Wise man.
To put all that in perspective, a recent paper, one with real science and
subject to peer review, found that plant mutagenesis may induce more changes
than transgene insertion (i.e. “genetic modification”) (6). The
authors refer to the controversy regarding GM plants and their potential impact
on human health which they contrast with the tacit acceptance of other plants
that were also modified but not considered as GM products (e.g. varieties
raised through conventional breeding such as mutagenesis). They ask what is
beyond the phenotype of these improved plants and whether mutagenised plants
should be treated differently from transgenics.
Evaluating the extent of transcriptome modification occurring during rice
improvement through transgenesis versus mutation breeding, they found that
the improvement of a plant variety through the acquisition of a new desired
trait, using either mutagenesis or transgenesis, may cause stress and thus
lead to an altered expression of untargeted genes. In all of the cases studied,
the observed alteration was more extensive in mutagenised than in transgenic
plants. The authors accordingly proposed that the safety assessment of improved
plant varieties should be carried out on a case-by-case basis and not simply
restricted to foods obtained through genetic engineering.
Good idea but will politics again get in the way?
Sources:
1. Uncomfortable genes (29.11.06). CropGen (http://www.cropgen.org/article_96.html)
2. Messing with Mother Nature: regulations and pledges (24.8.07).
CropGen (http://www.cropgen.org/article_123.html)
3. Nuclear science for food security – IAEA says plant breeding
technique can help beat world hunger (2.12.08). International Atomic
Energy Agency (http://www.iaea.org/NewsCenter/PressReleases/2008/prn200820.html)
4. IAEA says irradiated crops could ease food crisis (2.12.08). Reuters
(http://africa.reuters.com/top/news/usnJOE4B10BP.html)
5. IAEA wants more money for nuclear crop breeding (2.12.08). International
Herald Tribune (http://www.iht.com/articles/ap/2008/12/02/news/UN-Nuclear-Agency-Food-Security.php)
6 Rita Batista, Nelson Saibo, Tiago Lourenço and Maria Margarida Oliveira
(4.3.08). Microarray analyses reveal that plant mutagenesis may induce
more transcriptomic changes than transgene insertion. Proceedings of
the National Academy of Sciences of the United States, 105(9), 3640-3645 (http://www.pnas.org/content/105/9/3640.abstract)
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