After
my nervousness last week, I'm going to talk today about a more relaxed (sure?)
subject: genetic evolution of species. It is a general subject, valid for both
plant and animal species.
What
is it?
It’s
the various natural or artificial ways that cause the evolution of species. At
all times since the invention of agriculture, man has tried to adapt his
environment, and his agricultural activities to his needs. He has felt the need
to select species for their specific characteristics, thus providing
improvements to what had hitherto existed.
1-
SELECTION
It
is the most simple process that will be used either alone or in combination to
other methods.
It
simply consists in observing a population of the same species, and chose the
most interesting individuals to use them as parents, so try to transmit to
their progeny, characters for which they were identified. For example, in apple, an old and almost extinct
variety is Gala, bicolor variety that was achieved around 1920 in New Zealand.
It is a variety whose general characteristics are very interesting, but the
color does not correspond any more with current standards. In Gala orchards, trees producing the most colorful fruits were selected (in fact they are small
natural mutations affecting only the color) to get the current Royal Gala
variety. It is the same variety as Gala, but with a more intense red color. We proceed in the same way to select cows producing more milk, sheep producing
more wool, running faster horses, or cats or dogs whose characteristics are the
taste of the juries of beauty contests.
It is a very
old method, which has been all time used by farmers and gardeners around the
world, consciously or unconsciously.
2- MUTATION
This
is a natural process, which is a genetic change of one or more characteristics.
It is one of the main causes of the evolution of species.
It
is a common phenomenon in plants, where you will find in a field either a plant
or a branch with different characteristics. Thus it is usual, for example in my
peach orchards, find a branch of nectarine, or a twig with fruits of different
color or shape. It comes from a genetic change in the formation process of a
bud that develops different characteristics. This new feature is set into the
genome of the mutant individual or the mutant area and can then be transmitted
to its progeny. If the mutant feature is interesting, it may either be used unchanged
or it may be used as a parent in order to create a new progeny by a
hybridization technique.
It
is also possible to cause artificial mutations by controlled irradiation in
specialized laboratories.
3-
BREEDING
It
is a very old method, based on the observation of characters, and their ability
to combine to create a different characteristic. The breeding technique is
normally done by natural ways, not allowing the breeding of naturally
incompatible individuals. It is currently the main method for getting new
varietal characteristics. If you cross a yellow flesh, small and early nectarine,
with a late, white and bloody flesh flat peach, you will obtain a wide range of
diverse fruit, which will combine in all possible ways, the original characters
of parents. We generally consider that, in peach, a controlled crossing of two
specific varieties can give a variability of about 500 different types.
It
is in this way that, in recent years, appeared in the markets, flat peaches (paraguayo),
and flat nectarines (platerines). The origin of the flat character in peach
comes from a natural mutation, occurred 2000 years ago in China. Closer to us,
there is an old variety, cultivated for many years in the region of Murcia,
Spain, called Paraguayo, which is a small flat peach, rather shapeless,
greenish, white and bloody flesh, slightly sweet but very aromatic (a type of
vineyard peach, green and flat). It was used as parental in several breeding programs,
allowing the current varieties diversity.
The
technique is simple: you take a tree from a selected variety that will be the
female parent (the receiver), and you substitute the natural pollination
(normally made by bees) by a delicate fine
brushwork, throwing on each flower pistil, pollen grains of the variety chosen
as the male parent. It is also possible to proceed by isolating trees of both chosen
varieties under a fine mesh net, under which a beehive is placed. Bees have no
other choice but to interpollinate the two present trees.
Finally,
there is the natural pollination, without human intervention, which simply consists
of a carriage of pollen from a variety to the other, done by bees. This
technique is not normally used for breeding, but it is widely used for pollination
of self-sterile varieties, which means whose pollen is incompatible with its
own flower (usual case in apricot, cherry, plum, apple and pear, for example).
Harvested
fruits will be the same as the female original variety, because genetic changes
are taking place in the seed, thus immediately invisible. It’s necessary to
take all seeds and place them to germinate. Each seed has a set of combined
characters from both parents.
The
two most common breeding types are:
-
Intraspecific breeding, which means crossing two varieties (in plants) or two
breeds (animals) of the same species. This is for example, crossing a Golden
apple with a Granny Smith apple or a German shepherd dog with a boxer dog. In
humans, the process is called miscegenation.
-
Interspecific breeding, which means crossing two related and compatible
species. In plants, it is a cross between wheat and rye (triticale) or
clementine and tangerine (clemenvilla) or apricot and plum (aprium or pluot).
In animals, there are many cases. The best known is the mule, a cross between
horse and donkey, but it is quite common in cats, or in open air pig farms, where
sometimes introduce boars.
Remains
the problem of F1 hybrids, concerning annual crops seeds. These seeds are
produced by first generation artificial pollination whose agronomic
characteristics are known, and generally interesting. But the progeny of these
F1 hybrids (F2 hybrids) is very different. The farmer is forced to buy seeds
every year to maintain the properties of the variety. Seed companies were
accused of abusing the system. Although this is partially true (these are
for-profit corporations), it should however be said in their defense, that the
qualities of F1 hybrids are very difficult to obtain by other ways (stable
varieties usually have lower agronomical performance and tend to degenerate
over generations), in the other hand, varietal research is very expensive, and it
is a way to get the investment back. Seed prices are calculated for mutual profit
otherwise seeds companies could not sell anything. Farmers are not stupid,
anyway.
4-
GMOs
It
is a technique that can be applied both to animals and plants. It consists in
the laboratory, to make an artificial modification on a specific gene, to
change the behavior of the original organism. The technique allows us to
imagine almost any modification or crossing, impossible in nature, especially
interspecific crosses, unimaginable by natural ways.
It
is obvious that there can be a serious ethical problem using this technique. Moreover,
some companies used it as a very powerful economic weapon. It must also be said that the first
GMOs varieties, commercialized on a large scale, were for the resistance to
herbicides, sometimes causing overconsumption of these herbicides, and
environmental problems. Ecologist organizations took it as a symbol of struggle
against GMOs, without considering the potential benefits of the method. The anti-globalization
organizations, for their part, combined the refusal of GMOs with the fact that these
varieties are hybrid F1 too, to violently attack the seed companies, without
trying to see the positive aspects of the system. Films have been made on this topic,
and political campaigns as well, but without objectivity, playing on the fear
of the unknown risk, and using perfectly the power of modern communication. And we know very well, from dictatorships to main political and
economic crises, how high is the power of the mass media, and how easy it is to
manipulate public opinion by shocking images.
However,
it should be noted that this technique allows us to imagine some interesting
solutions in specific conditions. For example, there are significant works in
progress to create, by this method, crops adapted to saline soils of some
regions of the world (and currently prohibiting any type of agriculture), or
resistant to severe drought conditions, just to give two examples.
One
of the main problems encountered since the first sale of GM crops, is the
modification of some proteins in the plant, giving them a sometimes dangerous
character to human health. But it seems clear, that if suitable work is done,
researchers learn to control these risks. Investigation works are currently in
progress in this way.
The
technique has probably an important future, in the inevitable goal of feeding
the world in the centuries to come, but it is essential to regulate its use.
"Science
without conscience is but the ruin of the soul," wrote François Rabelais
in 1532 in "Pantagruel". The formula is a bit dated, but it is really
current in its meaning. Any new technique can lead to abuses. This is the case
with GMOs. The first GM crops have flaws that emerged after their sale. That is
not why we must drop the technique, especially because, as it is known, it will
inevitably be recovered by not necessarily scrupulous people, who will make it a
personal enrichment or domination tool.
However,
this technique can provide very interesting answers, to many currently
unresolved problems, and for the good of humanity.
It is therefore preferable to continue working
on it, to use it in a controlled way, but while establishing the political and
legal means to prevent abuses.
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