Genetic engineering in plant breeding: benefits for whom?

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10 Δεκ 2012 (πριν από 4 χρόνια και 7 μήνες)

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Genetic engineering
in plant breeding:
benefits for whom?

Prof. Kristofer Vamling









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 Plant breeding
 Main technologies to add new genes/traits
 Possibilities and limitations with different techniques
 BIT- Biological Information Technologies
 Plant breeding with GMP material
 Antisense: a technology to switch off a gene
 New potato starch quality
 Advantages for the market
 Designer crops by genetic engineering
 Why use genetic engineering in plant breeding?




Work group: Lucia D‘Urbano and Tommaso Zanella
A history of genetic manipulation.
We know that genetic manipulation has existed since 1500 B.C. when in the Tehuacan
Valley in Mexico the Teosinte plant used to grow. Through natural genetic manipulations
in 1500 A.D. in the same valley another plant used to grow, it was the Corn plant.
Plant breeding takes hundreds of years using hybridisation, but if you use genetic
engineering the process to obtain a new plant variety only takes about 15 years.


Plant breeding gene recycling system.
If you have to design a new crop for a market, first of all you must consider the market
demands and then add new genes or traits through hybridisation or genetic engineering
and then combine and select the genes or traits. In this way you obtain a new plant
variety. The genes can be recycled for a new cycle.
This gene recycling system can exploit two techniques: hybridisation and genetic
engineering. Each of them offers some possibilities, but also some limitations.

Hybridisation
It’s limited to closely related species and it implies the transfer of whole “blocks”
containing many genes, of many non characterised genes and of a difficult selection
process. It’s a low cost and well known technology and it’s often used.

Genetic engineering
It has no species barriers. It implies the transfer of few genes, of only well characterised
genes and of an extensive selection process. It’s a high cost technology, it’s new and it
offers new possibilities (with risks also).

Biological information technology
If we take a cell from a plant and examine the chromosomes in its nucleus we see that
they contain DNA which is composed by many genes that code for different proteins. On
DNA just next to the gene there is a protein called Promoter that starts the gene coding
process and next to the gene on the other side there is another protein called Terminator
that stops the process.
DNA is isolated from an organism, then a gene, a promoter or a terminator is cut out with
some enzymes. We can then proceed to the gene construct by adding to our DNA a
different gene, promoter or terminator. We must then create a gene vector to transfer the
new DNA in another organism to obtain a novel trait, so we insert the new DNA in an
bacterium.

Plant breeding with GMP material
In the laboratory we must construct a new gene and insert it in some plants through
transformation. We must then analyse and select the traits we obtain to find the best
event. We can then proceed to the first field trial, that implies a selection in the plants
until we find the élite event. Once we have an élite event there is a crossing work to be
done and after this the second field trial, that implies the élite line selection to find the
second élite event. At this stage we have obtained a new plant variety that we can use for
seed production.

Field trials in Sweden 1998-2001
The field trials in Sweden between 1998 and 2001 concerned initially (98-99) mainly the
potato starch and seed production, but also other cultures (sugar beet, oilseed rape,
turnip rape and more). Now the hectares assigned to these cultures are hardly any.

Potato starch
What both Svalof Weibull and Lyckeby Starkelsen wanted to obtain was a new potato
starch variety that suited the needs of the paper industry.
In 1985 the first discussions started, in 1987 there was a joint venture between the two
companies and Amylogene HB was born. In 1988 the lab work started and 1990 the
researchers were looking for some existent genetic variation. In the next two years the
two methods of hybridisation and genetic engineering proceeded in parallel. In 1992 there
was the first field trial and in 1995 the multiplication of the gene placed in the correct
position in the potato. In August 1997 there was the national notification application and
i n December the company obtained the national approval. In May 1998 there was a
notification for placing the new starch variety on the EU market.

Antisense: a technique to “switch off” a gene
In DNA every single gene codes for a protein through sense RNA. But if we invert a gene,
it won’t code for a protein because antisense RNA will be transcripted.

New potato starch quality
Ordinary potato starch is composed by two molecules, one is amylose (25%) which is
linear and the other one is amylopectin (75%) which is branched.
Through genetic engineering now we have obtained amylopectin starch which is
composed by amylopectin (100%). This kind of starch has benefits for the paper industry:

improved runnability
easier to achieve high porosity and better stability
decreased starch addition with 20-30%
mantained strength properties
easier to take away water from the paper during the production process.
We have also obtained amylose starch which is composed by 75% amylose and 25%
amylopectin. We can make films out of amylose starch, but it still isn’t water resistant
so it still can’t be used for juice cartons for e.g.

Barley starch
Barley starch can be useful for the food industry. Ordinary spring barley starch is
composed in the same way as potato starch, but we have obtained some new varieties
that are different.
Amylopectin barley starch is composed of 95% amylopectin and only 5% amylose. It has
excellent freeze and thaw properties.
Amylose barley is still under development. At the moment it’s composed of 45% amylose
and 55% amylopectin and it has a slow degradation, it can be useful for preventing
diabetis.

Designer crops by genetic engineering
Designer crops by genetic engineering produces resistance traits and herbicide tolerance
like input traits.
In most cases it also reduces herbicide usage, it facilitates no-ploughing cultivation, and
new herbicides replace older, and more environmentally damaging ones.
For what concerns the resistance, we have different kinds of it for each case: we’ll have
insect, nematode, fungal and viruses resistance.
Designer crops by genetic engineering is useful to improve present quality and to add new
quality traits.
It can help human beings reducing toxins, allergens and heavy metal, and adding vitamins
and proteins. We can also obtain new and useful pharmaceutical products.
Eventually, it’ll be better to analyse how the crop is shared.
As we can see by the following graphic, in a global area of 271 million ha (consider that
agricultural land in Sweden consists of 2,7 million ha) most of the fields are cultivated with
corn, then a smaller part with soybean, and, at last, with cotton and oilseed rape.