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Could these potatoes improve soil life?

Some will picture Germany as the world's centre of anti-technology campaigns

November 14, 2007
By Top Crop Manager


34aSome will picture Germany as the world's centre of anti-technology campaigns,
those who refuse to accept GMOs in their food or agricultural crops. But this
could not be further from the truth at the Technical University of Munich, where
Dr. Michael Schloter leads a project growing genetically modified potatoes.

"We are investigating the effects of these potatoes on the microflora
in the root area, on soil bacteria and soil fungi," explains Schloter.
"The microflora are affected by a number of factors like the time of year,
type of crop and method of cultivation. But excretions from the plant roots
also cause changes."

The excretions, technically called exudates, from the potatoes on the trial
field could differ from those in conventional varieties. These are so-called
zeaxanthin potatoes, a genetically engineered variety that accumulates zeaxanthin
in its tubers. Zeaxanthin is a substance that can prevent age related blindness.
"However, we are not only investigating differences between the transgenic
potatoes and their parent variety," stresses Schloter, pointing to the
cultivation plan.


"This trial is also recording, for the first time, what effect varietal
differences in general have on soil microflora. In addition to the two zeaxanthin
potato lines, which have been produced in different ways, the field also contains
the parent line Baltica and four other conventional varieties: Ditta, Désirée,
Sibu and Selma.

The activity of the soil organisms
The members of the joint research project are taking root samples of all seven
potato varieties. To do this they dig up individual potato plants, quickly remove
most of the soil and cut off the roots with sterile shears. The reason for the
hurry is not so much the heat, but rather the fact that the researchers are
also interested in seeing what bacterial mRNA is present in the roots and on
the root surface. Since the mRNA usually degrades within just a few minutes,
the samples are immediately frozen in dry ice. "The mRNA is interesting
because it shows us which genes are actually active," explains Schloter.
"When we analyze the DNA, we find out only what genetic potential is present,
but not which parts are really active. The genetic potential in the soil is,
incidentally, huge," stresses the soil ecologist and holds up a handful
of soil… "According to a conservative estimate, there are 10 thousand
species living in each gram of soil."

However, the five research groups from Germany and Austria working on the project
are not investigating the potato plants and their root areas (the rhizosphere)
just to focus on the species diversity. They are also interested in the nutrient
dynamics, which are inextricably linked to soil life and plant growth, and in
plant pests and their antagonists. "If a plant can be modified in such
a way that it favours the antagonists in its root zone, some chemical treatments
could become superfluous," says Schloter, explaining the reasoning behind
the analysis. But adverse effects cannot be ruled out.

His own attention is focussed on the nitrogen cycle. "Most of the bacterial
groups involved have been identified. Now we want to know which of their genes
are involved and how they are regulated."

For instance, he believes it is conceivable that plants could be modified through
breeding so that their root exudates affect soil bacteria in a way that improves
their digestion of nutrients bound in the soil, thereby making them available
to the plants. But that is all in the future. First of all, the trial is being
conducted for safety research purposes: to investigate whether the genetic modification
has a greater effect on soil life than would normally be expected as the result
of varietal differences.

Schloter stresses the fact that regardless of whether the zeaxanthin potato
will ever be grown commercially, this project will supply important findings
about the conversion of substances in agricultural soil, and will also provide
the basis for further safety research in the area of transgenic potatoes.

Zeaxanthin potatoes
Are these new potatoes a remedy for blindness in old age? The genetically modified
potatoes were developed a few years ago as part of a publicly funded research
project. Genetic modification of a metabolic pathway causes the carotenoid zeaxanthin
to accumulate in the tubers. The genetically modified potatoes have up to 130
times the zeaxanthin concentration of conventional potatoes. -30-

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