I think this study has significance beyond telling us something we already
know... or more to point, telling something people farming canola think
they know. There has been a significant shift in canola cropping systems
since a lot of the canola pollination work was last done. The canola
industry still operates under the paradigm of these studies - ie Brassica
napus does not benefit from supplemental honey bee pollination. This
study suggests there may be need to revise this paradigm now that they
largely farm GM.
The paper describes a significant pollination deficit in Round-Up Ready
fields arising from fewer pollinators (~1.5 times greater yield compared
to a coventional field and ~6 times greater compared to an organic field).
What does a ‘pollination deficit’ mean in the context of this study? It
means a difference in the average number of seeds per fruit between
supplementally pollinated (what would happen if you had unlimited
pollinators) and open-pollinated flowers. Overall GM seedpods had around
6 fewer seeds per seedpod when open-pollinated compared to being
supplementally pollinated, whereas in organic fields the difference was
just 1 seed per seedpod. Clearly the GM fields would benefit from having
more pollinators.
I am not sure GM canola, as a rule, run pollination deficits compared to
conventionally grown canola... this requires additional study. If it
turned out to be true, might it not offer beekeepers an opportunity to
revaluate their relationships with their canola-growing neighbours?
Currently Canadian beekeepers are not paid to put bees on production
canola fields, only in the fields used to produce hybrid seed for
planting. A persistent pollination deficit in GM fields would no doubt be
a potential boon for beekeeping. Rather than write the study off as being
common sense, I think it should be repeated.
I think this was a nicely-done study. It was conscice, well executed and
conducted one of Canada's most significant crops (argueably the most
imporant honey bee forage). I agree with Peter and Allen that it was a
shame that it got yanked out of context and used to make the case for GM
crops repelling bees from fields. This careless arguement distracted from
the very carefully laid and supportable case that the yield increases from
Round-Up Ready canola cropping systems may be subverted by their inability
to sustain large populations of pollinators.
For anyone who is still interested (and I doubt there are many) I have
attached a summary of the state of knowledge on this issue as of 2001 from
a Bee World review by Don Nelson and Lynn Westcott (sorry for
the spaces). In the Morandin study, the organic field was B. rapa (ie the
self-sterile cultivar) whereas the conventional and GM fields were B.
napus (ie self-pollinating).
Regards,
Adony
The need for insect pollinators in canola and rapeseed crops.
It is generally considered that cultivars of B.
rapa are self-sterile and require insect crosspollination
to set seed11,19,28,42,92, but there are
conflicting views on the need for insect pollination
in B. napus. Brassica napus is considered
self-fertile and produces good seed
yields without insect pollination19,23,92.
Despite their assertions that insect pollinators
are not necessary for good seed yield
in B. napus, Free & Nuttall reported a 13%
seed yield increase in B. napus plots with
bees compared to those without bees23.
They did not feel that this was a large
enough increase to justify the use of bees
for pollination23. Downey et al. reported that
B. napus is 70% self-pollinated, but this presumably
leaves the remainder in need of
insect- or wind-mediated cross-pollination19.
Canola and rapeseed have sticky pollen typical
of plants requiring insect pollination20,
which suggests that wind activity is not the
only means of B. napus pollination. Windpollinated
species usually have smooth, dry
pollen grains that are readily dispersed
through the air. Eisikowitch found that B.
napus cv. Maris Haplona pollen adhered to
the flowers’ anthers under wind velocities
as high as 5.0 m/sec20. He suggested that selfpollination
must be the result of direct contact
between the long anthers and the stigma
with little pollen transfer through the
air20. He concluded that insect pollination is
important in setting seeds in this particular
B. napus cultivar.
Many researchers have concluded that
insect pollination of B. rapa and B. napus is
necessary to provide high seed-meal lipid
concentration78, higher seed set and
yield43,45,58,78, higher numbers of seeds per
pod and higher numbers of pods41,92, earlier
pod formation21,96, earlier cessation of flowering
58,96, faster and more uniform seed maturation
46, and increased germination of
seeds39. All of these factors may contribute
to a higher-quality crop that ripens more
evenly and is easier to harvest95. Most of the
canola hybrids and open-pollinated cultivars
currently produced and sold to Canadian
growers are B. napus. Farmers who purchase
and grow these hybrids may be interested
to understand the pollination requirements
of their crop, especially if B. rapa
hybrids are developed and become commercially
available within the first decade of
the 21st century50. Canola growers may find
it beneficial to work co-operatively with
beekeepers to maximize their seed yield.
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