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2-Plants: New Zealand study on role of flies in cross pollination

------------------------------- GENET-news -------------------------------

TITLE:  Flies show pollen power
SOURCE: Fairfax New Zealand Limited, by Tim Cronshaw /
        posted by Checkbiotech, Switzerland
DATE:   7 Oct 2005

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Flies show pollen power

The skills of native flies in pollinating South Island crops may shed
more light in evaluating the potential of cross contamination from
genetically modified plants.

A study by Crop & Food Research is monitoring the behaviour of native
flies in arable plants and has found they could be major pollinators.

Until now it was assumed bees do most of the crop pollination and arable
farmers have traditionally placed honey bee hives next to crops for this

Native flies have, however, been found in some crops carrying up to
19,000 pollen grains - as many as honey bees.

The observations are hoped to give greater knowledge of the pollinators
ability to move genes so scientists can accurately predict what would
happen if modified plants were at some stage commercially introduced into
the country.

"If New Zealand was ever to allow commercial transgenic crops we must
first examine any possibility of gene flow from these crops to other
crops, weeds and native flora," said Crop & Food Research entomologist Dr
Brad Howlett.

Over the last two summers he and fellow entomologist Melanie Walker have
spent 14-hour days watching bees, flies and other pollinators in fields
of onions and brassicas in Marlborough, Canterbury and Central Otago.

Definite patterns have yet to emerge, but they are surprised about
several findings, including the numbers of native flies in onion and
brassica crops.

Howlett said there were more native flies found to be carrying similar
pollen loads to honey bees in some areas. The bigger and hairier flies
carry the most pollen, while the small, less hairy ones carry fewer than
10 grains.

The range of pollinators in crops, however, varies widely even on sites
that are close together.

In Central Otago it was found that two onion fields about 17km apart
attracted completely different ranges of insects.

In one site where honey bees were introduced to help with pollination,
there were the same number of native fly pollinators as there were honey bees.

On crops of pak choi (Chinese cabbage) near Lincoln and Gore, a bibionid
fly was found in numbers 10 times more than honey bees and carrying the
same amount of pollen.

Howlett said it was unknown whether fly populations varied yearly and
more research was needed to monitor geographic variations.

Little was known about the role of native pollinators in transferring
pollen in crops before this study. Kiwifruit is the only other crop where
pollinators have been surveyed to a wide extent in New Zealand, he said.

While the research funded by the Foundation for Research Science and
Technology until 2008 is still at an early stage, scientists hope to
learn more about the potential of bees and flies to move pollen from
genetically modified plants to traditional plants.

Howlett said there was international concern that genes modified for
herbicide tolerance could be transferred to weeds or non-crop plants via
pollen and make control more difficult.

"But to evaluate the likelihood of the movement of transgenic genes via
pollen away from genetically modified plants, we must first understand
the mechanisms that cause pollen movement. That is what this research is
all about."

Over the next three years the research will attempt to confirm initial
observations by measuring the distance pollen is moved from crops and the
effectiveness of pollinators.

Howlett said the research could be useful if the varroa bee-mite disease
arrived in the South Island and native flies were found to be effective
as alternative pollinators.


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