Examination of witnesses (Questions 200
- 219)
TUESDAY 7 DECEMBER 1999
DR PHILIP
DALE and PROFESSOR
ALAN GRAY
200. I am just concerned about those growing
crops and the problem of pollen transfer. Now are there any crops
grown in the United Kingdom which do not have to flower before
they are harvested, so that they do not produce pollen?
(Dr Dale) Many of the vegetable crops are harvested
before flowering. If a cabbage flowers it is useless. So vegetable
crops principally would be harvested before flowering. If one
is producing a seed crop to produce seed that will sold to farmers
for growing cabbages or cauliflowers or so on, those are grown
specifically for seed production, so you would leave them and
let them provide seed heads.
Chairman
201. Professor Gray, we are grateful to you
for sharing the platform together. This is a relatively informal
session so if you want to chip in and amplify what Dr Dale has
said please feel free to do so at this stage.
(Professor Gray) I was going to add that, of course,
one possible source is that there may be in the soil of the field
in which that plant is grown, so-called volunteers from a previous
crop; so when the crop is growing in the ground, unbeknown to
us some seed from a previous year, or even several years before,
has been lying dormant in the soil.
Mr Mitchell
202. What are "volunteers"?
(Professor Gray) The plants that come up as weeds
in the crops in following years.
203. But they could also be debris, root structures
which are ploughed into the soil, could they not?
(Professor Gray) In some cases, in potato, that is
a common source of so-called volunteers. There is another technical
term for it which is "ground keepers". The potatoes
that get left and chopped up in the soil will appear sometimes
as small plants in the crop the following year. This is very common,
for example, in sugar beet crops. You often find there are volunteer
potatoes in your part of the world.
204. Is it also possible for GM to leach into
the soil through root structures?
(Professor Gray) No, not in the context of herbicide
tolerance, no, which is what we are talking about when we talk
about these things.
Mr Curry
205. Could I clarify. Nature has recently
published some material about maize found to excrete toxin. "Maize
engineered to resist insects has been found to excrete toxin into
the soil." Chapter New York University. "Toxin associated
with the plant passes into the soil where it may be active up
to 25 days. The team had not realised that such a large protein
could pass out of the root in such a way." Could you put
that in context for us?
(Professor Gray) It is not my area of science. I do
not know how having Bt toxin in the soil that has come from plants,
how it will affect the organisms that are there; but the particular
gene concerned, these toxins which are engineered—
206. It does not absorb genes from the soil,
does it?
(Professor Gray) No. It is usually bound on to clay
particles. This often happens in arable situations. But the actual
gene we are concerned with is targeted at particular insects which
it will kill and it is non-toxic to all others.
(Dr Dale) Most plants have substances in them that
act against micro-organisms. It is a natural defence mechanism.
In some cases, in rape seed for example, you would let the straw
lie on the surface of the ground for leaching to happen. That
is called biofumigation. It actually destroys pathogens, and perhaps
seeds to some extent, in the soil. This leaching is quite a natural
phenomenon. This is an important study. It is the kind of information
that we need to build into the assessment process to make it more
scientifically informed but it is a fairly natural phenomenon.
Mr Mitchell
207. Going back to those crops which flower
before they are harvested, do they have wild equivalents which
could be cross-pollinated?
(Professor Gray) Yes, most of them do. Perhaps the
best example is beet or sugar beet which normally does not flower
but, of course, in many fields you will find flowers, flowering
beet. These are "bolters". Instead of putting on a tap
root or just having leaves, for some reason they have been stimulated
to flower in their first year of growth. So that is one particular
example. The ones which I mentioned, all the brassica family,
cabbage, sprouts, kohlrabi, which in fact is the same species,
have a wild relative of the same species growing in the British
Isles on the coast in fairly restricted areas, (it is called wild
cabbage strangely). Many of our crops—in fact, many crops
around the world—have wild relatives growing alongside them.
Often these are the weedy antecedents of them. They may be different
species but they could have been used in the breeding. Oilseed
rape has a wild relative . . .
Mr Curry
208. It is a brassica as well, is it not?
(Professor Gray) Yes. But it is a different species
of brassica. It is actually cross-compatible with wild cabbage.
You could make that cross.
209. You should not grow Brussels sprouts in
your garden if you have rape in the next door field.
(Professor Gray) I do not think it makes any difference.
You will not normally have hybrids because your Brussels sprouts
will not flower.
Mr Mitchell
210. Going back to the volunteers which you
also mentioned in section 2, how prevalent are self-seeded volunteers
of agricultural products that flower before they are harvested?
(Dr Dale) It depends on the crop. Rape seed has lots
of seeds and often there is seed shedding at harvest. The thing
about most crops is that they do not have much of a dormancy period.
It is not only what seeds are in the soil but the length of the
life of those seeds once they are in there. Oilseed rape lives
possibly to the next year. It depends on how it is handled. If
it is buried deep, if you do deep ploughing, you can keep oilseed
rape seeds going much longer. But, generally, ones on the surface
germinate the same year, in the autumn of harvest or in the early
spring, but in our experience we do not get very much after that.
So they are there. It is a consideration. That is why one usually
has a rotation so you would have a break from a crop for, say,
three or four years. Again, if it is rape seed, you would have
a break for several years to clean the soil of that particular
crop.
211. Tell us what happens if pollen from a genetically
modified variety gets into a wild equivalent, or a volunteer,
or a conventional crop in a nearby field.
(Dr Dale) If that becomes established, if it flowers
at the same time, if it is sexually compatible and hybrids can
form, then there is a chance that a hybrid will form. Some crops
are outbreeding. Some crops are inbreeding. Many of the cereals
will self-pollinate preferentially, so you get very little cross-pollination.
With oilseed rape there is a certain proportion, 5 per cent sometimes,
of cross-pollination. This may well happen.
212. Will the trait that is being introduced
pass through subsequent generations in the normal way? Is there
a 50/50 chance of it being inherited or will it always be inherited?
(Dr Dale) If it is something like herbicide tolerance,
then the hybrids are quite likely to be herbicide tolerant. Now,
as you go through subsequent generations, some will be herbicide
tolerant and others will not. So it depends very much on whether
you have selection pressure. If that hybrid occurs in an environment
where you are spraying with herbicide, then you would select hybrids
that have that herbicide tolerant gene. So it depends on management.
In principle, hybrids and subsequent generations could carry the
introduced gene.
(Professor Gray) It is too difficult to lay down hard
and fast rules of how well genes will survive in the wild plants,
particularly since there may be quite a lot of differences between,
say, the arable environment and an environment which is not managed.
We have good evidence with hybridisations of wild turnip, which
occurs as an agricultural weed in some parts of Europe. This is
another brassica, brassica rapa. It occurs as a weed in
Denmark, quite a serious weed. It occurs as a weed in North Lincolnshire
actually but farmers do not get terribly worried about it. It
also occurs as a naturalised plant on river banks and canals,
where it is known as Bargeman's cabbage. What work has been done
on this suggests that if you get one or two wild turnips in a
field of rape, then you will get quite extensive hybridisation.
If you collect the seed from three or four plants that are in
the middle of an oilseed rape field, then up to 80 per cent of
the seed you collect from those plants, the father will have been
an oilseed rape plant, so there has been hybridisation. That was
known a long time ago—certainly in the 1960s—that
turnips and swede, which is what rape is really, will hybridise
in this way if you have a few of one in a crop of the other. Wild
turnip, when it grows outside of the crop—or even very close
to the crop, about a metre or a couple of metres apart, or if
it grows in these so-called natural populations; if it is growing
there with lots of its own species (and, as Philip Dale says,
wild turnip is actually self-incompatible—it cannot pollinate
itself). Therefore, when it is growing in oilseed rape, which
can pollinate itself, it can pollinate other things, so it will
hybridise. When it is growing nearby it is much more likely to
cross-pollinate other plants in that population. So with those
very difficult probabilities the end product has to be something
that has survived all that. The question to ask is how many surviving
individual hybrids do you get the following year or even the year
after that? That will tell you whether the trait you have put
into this plant improves its fitness; whether it is acting under
selection. The view about herbicide tolerance is that at best
it is neutral. Therefore, unless it was transferred in large numbers,
to a large number of plants, it would disappear or not be important
in wild populations. But something like resistance to a pest or
a virus or a fungus might have an impact on the wild population
because that wild population may be suffering from that pest or
virus and may suddenly get release from that. Part of assessing
risks is to find out what the role of these genes is, and how
important they are in controlling wild plants.
(Dr Dale) If I may add to that. These principles are
not unique to GM crops. People have been inserting virus resistance
measures by conventional breeding and it is important to ask these
questions of conventional varieties as well. In a sense, GM development
is requiring us to ask those specific questions about this set
of crops, and we are asking very few similar questions about conventionally
reared ones.
Chairman
213. This is a matter not so much of recessive
dominant genes but of natural selection?
(Professor Gray) Absolutely, as far as the natural
environment is concerned; and, indeed, as far as the farming environment
is concerned. Applying the herbicide would be the most powerful
selective force you could have for a plant which is tolerant to
herbicide, so that is the major force involved in all this, the
force of selection.
Chairman: I am going to ask one more question
myself and then bring in Mr Marsden to discuss the issues of segregation
distances, which is obviously very important. Then my colleagues
might wish to ask some further questions to follow up. Dr Dale,
in your memorandum you discussed ways of actually preventing gene
flow by pollination. This is in section 5. Now one of them you
say is not a workable system, which is terminator technology.
The other three you say are being considered. How widespread is
the use of these approaches?
Mr Curry: And what does "chloroplast"
mean?
Chairman
214. If you could give us a brief definition
of chloroplast transformation that would be great.
(Dr Dale) Chloroplasts are the green things in plants.
They contain green chlorophyll. Those are the little sacs within
plant cells that hold the green material. I will go through these.
The first one is removal of flowers. With some of our early release
field experiments we were required to remove flowers. That is
practical with a small-scale experiment where you perhaps have
a 30 by 30 metre plot. On a large scale it is not practical. The
second one is the production of sexually sterile—
Mr Curry
215. Even in a 30 by 30 plot there are a hell
of a lot of plants. Do you do this mechanically or by hand?
(Dr Dale) By hand. We employ students.
(Professor Gray) These trials have to stay small,
of course.
Chairman
216. Commercial apple growers will routinely
go around removing flowers from a number of their trees to enable
proper growth, so on quite a large scale you will get flower removal
from crops.
(Dr Dale) We went through every day and removed them.
That is practical for small-scale experiments and it may be considered
in the experimental releases that we have just heard about. The
second one I have here is the production of sexually sterile plants.
There is work, mainly in trees that may live a hundred or so years,
to produce sterile lines; and many of them can be vegetatively
propagated. That is a way forward with certain crops, vegetative
propagated ones, where the inserted gene is considered to have
some potentially undesirable environmental impact. The chloroplast
transformation: when you insert genes, normally you put them into
the nucleus. In the nucleus these are inherited by all of the
offspring. If they are put into the chloroplast, they are inherited
principally through the female side and not through the pollen.
So the idea there is that an inserted gene would be quite effective
but it would not be transmitted by pollen. It is not an absolute
rule. There is a small amount of pollen transmission—it
depends on the species again—but as a general principle
these chloroplasts are not transmitted through pollen. Technically
it is very, very difficult. I think the application of chloroplast
transformation is very limited for all kinds of reasons. There
may be applications but it is going to be difficult. The final
one here is terminator technology. Again, that is very topical.
This is where you have gone through the patent stage, so the principle
has been patented. There are three elements to it that have never
been put together as a package to get it to work but essentially
it is a means of modifying crops so that you buy the seeds, grow
the crop, and the seeds produced from that crop will not germinate.
So it is terminated at that stage. Now much of the debate and
the press interest in terminator, and the concern expressed by
some, is about its use to prevent farmers saving their own seed,
particularly in the developing countries. Traditional practices
may be compromised in that sense. Here we are looking at it from
a different point of view. It would be a way of stopping gene
transfer. It would be a way, if any hybrids form, then these would
not be viable.
Mr Curry
217. This is just what Monsanto said it is not
going to do?
(Dr Dale) Yes.
Chairman: Thank you. That will help us very
much. Mr Marsden.
Mr Marsden
218. I would like to talk about segregation
distances. I am not a scientist. I enjoy science but when it gets
to the Trivial Pursuit part of the science questions I
always flinch, so forgive me, please bear with me, and let us
try and keep it as simple as possible. Any mechanism to allow
consumer choice between GM, non-GM, (and organic, for that matter),
requires that all of those can be identified and adequately guaranteed.
The Soil Association proposes a six-mile notification zone, based
on the distance bees can travel, and on wind contamination. So
my question is this, does a crop being self-pollinating or pollinated
by insects affect the distance over which pollination can occur?
(Professor Gray) I will pick this up because I did
mention, in general, in the note I have prepared for you, that
it does indeed. In general, in wild populations, although insects
can travel considerable distances, there is much more variation
in the average distance that pollen travels. In effect, insects
tend to pollinate near neighbours of plants; and their transmission
of pollen to other plants beyond a fourth, fifth, sixth plant
they visit is often very low because they have picked up pollen
en route. So insects often confine pollination to small
groups of plants, whereas wind pollination can sometimes, particularly
if it is acting as a vortex, move pollen considerable distances.
On the other hand, of course, bees can catch trains, as it has
been said, and you could have some spectacular pollen movement.
One of the problems is that there is a clear difference between
the pollen travelling and it making an effective cross-pollination.
This will vary enormously between crops and enormously between
plants. It depends on how viable pollen is of a particular plant
and how easy it is for the bee to deliver pollen to that plant.
So if you take something like corn, for example, which was particularly
controversial in the context of organic issues, we know that bees
can travel considerable distances. They do not, as a matter of
course, pollinate corn but they will be found on corn occasionally.
It is actually very difficult to get maize to cross-pollinate.
If you have ever grown any in your garden you know you have to
shake it out. It is not a thing which effectively cross-pollinates
over considerable distances. But it can—and this is the
problem that I was trying to raise—enormous distances can
be achieved by vectors of pollen, whether it is wind or whether
it is bees. Particularly if you are growing the crop year after
year in a patchwork, and sometimes the fields are quite close
together; and particularly if you have these volunteers that we
have heard about, and also feral rape, which is wild populations
growing on the roadside; you have the wherewithal to connect genetically
plants at quite considerable distances. The problem is that these
are very rare events.
219. I take the general thrust of what you are
saying. There are obviously exceptions. There is no such thing
as zero risk. I appreciate that. Let me quote from the Soil Association
submission to the Committee: "On the basis of the information,
we concluded that there should not be an organic and GM site in
the same three-mile radius around a bee hive." So do you
think that is scaremongering and simply unacceptable?
(Professor Gray) It is not based on science in the
sense that you might expect to be worried about the gene being
found in sweetcorn. It is based on the view that GM and organic
should be totally separate. It would be an issue for things like
sweetcorn but not an issue for things like oilseed rape where
I understand there are no organic versions.
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