Sheet n°311 - Febrary 2009
A new study highlights the way pollinators
can move genes
© IRD-ICIPE / Emeline Oudin
Cultivation of a
genetically modified
crop is likely to induce
an escape of the transgene into wild relative
populations if there are
wild relatives in the area.
Research undertaken by
IRD and icipe - African
Insect Science for Food
and Health - in Kenya
provides new information related to gene
escape risk. Using large
carpenter bees and minute radiotransmitters,
scientists were able to
follow the movements
of a solitary bee for the
first time. Bees can fly
up to 6 km from their
nest in order to collect
nectar and pollen from
cowpea flowers. As wild
and cultivated cowpea
are present in all subSaharan lowlands, the
goal was to assess potential contamination of
wild plants and landraces through pollen movement if GM-cowpea
was deployed in Africa.
The risk does exist,
although pollen movement is very low beyond
a short distance.
Therefore this should be
balanced with the potential benefits of a cowpea
resistant to Maruca, a
major pest of cowpea
which, during worst
years, can destroy up to
95 % of the harvest and,
therefore, of the protein
supply of a large part of
the African population.
Carpenter bee with a radiotransmitter affixed foraging on a cowpea flower.
Thanks to their waggle dance which
indicates where to find food, honey
bee foraging distances are well
known and usually do not exceed
10 kilometers. However, similar
work with solitary bees had never
been achieved. This new study
undertaken in Kenya by scientists from IRD and icipe - African Insect Science for Food and
Health - in Nairobi brings detailed
information on these pollinator
journeys. Entomologists glued
radiotransmitters on more than a
hundred of Xylocopa flavorufa, a
widespread African carpenter bee.
These large bees (weighting around
125 mg, far more than an inch long)
are able to fly easily while carrying
a 35 mg radiotransmitter affixed to
the back of their thorax. Thanks to
these minute devices, bees and
bee nests were easily located. For
the first time, entomologists were
able to follow directly the flight of
solitary bee. During a first phase,
134 bees were followed from flower
to nest. When weather and flower
supply were good, bees were foraging on average 2 kilometers from
their nest. The highest flower-nest
distance recorded was 6 kilometers.
During a second phase, the whole
foraging trip (from nest departure to
nest arrival) of three bees was recorded. The foraging trips were plotted
on a map of wild cowpea patches
and cowpea fields. During each
foraging trip bees visited at least
two wild cowpea patches and one
cowpea field. Therefore, bees can
move pollen from cultivated cowpea to wild cowpea. However, when
wild cowpea patches and fields are
more than 50 m apart, as was the
case when the tracking was done,
the probability of effective pollen
transfer is very low, though not nil.
Institut de recherche pour le développement - 44, boulevard de Dunkerque, CS 90009
F-13572 Marseille Cedex 02 - France - www.ird.fr
Retrouvez les photos de l'IRD concernant cette fiche, libres de droit pour la presse,
sur www.ird.fr/indigo
CONTACT :
RÉMY PASQUET
Adress :
ICIPE - IRD
PO Box 30772
Nairobi
Kenya
Tel: +254 (0) 721 338 569
+254 (0) 721 491 430
rpasquet@icipe.org
REFERENCE :
Pasquet R., Peltier A.,
Hufford M. B., Oudin E.,
Saulnier J., Lénaic P. ,
Knudsen J. T., Herren H.
R. and Gepts P., Longdistance pollen flow
assessment through
evaluation of pollinator
foraging range suggests
transgene escape distances, PNAS, vol. 105,
no. 36: 13456 13461, 2008
Bees from genus Xylocopa are the
main pollinators of legumes with large
flowers like cowpea. Cowpea is a legume crop which provides proteins to half
of the inhabitants of sub-Saharan Africa. The study undertaken on Xylocopa
flavorufa foraging behaviour is part of a
larger project to assess possible gene
escape from a genetically engineered
cowpea with a Bt gene, which is currently under development. Thanks to
the efficacy of Bt-toxin against Maruca
vitrata, which can destroy up to 95 %
of potential harvest during the worst
years, this major cowpea pest would
not be a problem anymore. As this behavioural study confirms results from
wild and cultivated cowpea population
genetics, it confirms that the Bt-gene
will move to wild plants if Bt-cowpea is
provided to African farmers. However,
as the Bt-gene is very specific and targets only few Lepidoptera, scientists
are now looking at the fitness advantage that the Bt-gene could give to
wild plants.
If the wild plants were not able to take
advantage of the Bt-gene and would
not become more weedy, African
farmers using Bt-cowpea could increase their harvest security, and
therefore their incomes. This is why
this study is part of a larger project
aiming at assessing all the components of the ecological risk linked
with the deployment of Bt-cowpea
in Africa.
DIC - Grégory Fléchet
Doi : 10.1073_
pnas.0806040105
KEY WORDS :
Pollination, leguminous
plant, transgene.
VINCENT CORONINI
+33 (0)4 91 99 94 87
presse@ird.fr
INDIGO, IRD
PHOTO LIBRARY :
DAINA RECHNER
+33 (0)4 91 99 94 81
indigo@ird.fr
www.ird.fr/indigo
© IRD-ICIPE/Rémy Pasquet
PRESS OFFICE :
© IRD-ICIPE/Rémy Pasquet
Sheet n°311 - Febrary 2009
For further information
Cowpea is a legume crop which is the main protein provider for numerous
African farmers. During worst years, a moth larvae (Maruca vitata) can destroy up to 95 % of the harvest.
Gaëlle Courcoux, coordinador
Délégation à l’information et à la communication
Tél. : +33 (0)4 91 99 94 90 - fax : +33 (0)4 91 99 92 28 - fichesactu@ird.fr