From ENVIROWEED list.


SCIENTISTS DEVELOPING A 'CONDOM' FOR WEEDS


Australian scientists are working on a world-first method for
achieving
contraception in plants.

In what promises to be a major advance in the control of noxious weeds
and other unwanted or invasive plants, researchers in the Cooperative
Research Centre for Australian Weed Management are exploring two
unique
ways to prevent plants from being fertilised.

If successful the research will contribute to increased food
production
and grain exports, and reduce herbicides in agriculture and the
environment.

A CRC team led by Associate Professor Ed Newbigin, of Melbourne
University , and CSIRO's Dr Andrew Young and Dr Steve Swain, is
exploiting a phenomenon known as "self incompatibility" (SI) to
create a
possible plant contraceptive.

SI is a biological system that prevents certain plants from
fertilising
themselves with their own pollen. By applying substances based on the
naturally occurring molecules used in SI, the team aims to fool the
plants into thinking that compatible pollen is actually incompatible -
and rejecting it.

"We're not out to kill weeds, which is the conventional approach, but
rather to cut back their production of fertile seed, so that over time
the weed population dwindles and becomes unviable," Prof. Newbigin
explains.

"This is not a magic bullet or cure-all for weeds. It is intended to
be
used with other methods of control. But over time we'd expect to
reduce
the weed seed-bank in the soil, so that farmers will then have to
spray
far less."

The team is exploring two separate approaches:
- the so-called "chemical condom" in which a natural substance
prevents
compatible pollen from being accepted by the plant
- use of compounds based on natural plant molecules to block the
transfer of the pollen's sperm to the plant's egg cells - a concept
akin
to a human vasectomy..

"Our research to date gives us good reason to believe that one or both
of these approaches will be a feasible way to prevent seed production
in
plants which have self-incompatibility," says Prof. Newbigin.

These include plants such as wild radish, one of the worst weeds of
the
Australian grain industry, costing well over $70m a year in lost grain
yield and as much again to control, and which is rapidly becoming
resistant to herbicides.

The research is using wild radish - from a family of plants known as
crucifers - as its initial target for proving that a contraceptive
approach works. If it succeeds, the work will then extend to
identifying
similar contraceptive substances in other major problem plants such as
perennial ryegrass.

"Crucifers like wild radish are SI plants, whereas wheat, barley and
most grain crops are neither crucifers nor SI plants - so the use of
the
contraceptive substance in or near a grain crop will have no effect on
the crop.

"We also think that the molecules which plants use to switch their
pollen reception on and off may be unique to particular species - and
are environmentally benign. So there should be no side-effects from
using them. But, of course, we are going to test this," Prof. Newbigin
says

"The beauty of this new approach is that it attacks a stage of the
plant's life cycle that isn't affected by current weed control methods
and it should be very hard for plants to develop resistance to it.
Because self-incompatibility is such a basic biological system, it
will
be extraordinarily difficult for SI plants to evolve around it," he
adds.

Crop weeds are the biggest limit to Australian food production and
cost
the economy about $1.2 billion a year. Weeds also have a major adverse
impact on the natural environment of the continent, infesting over 25
million hectares. The total annual national weed bill is over $4
billion
a year to agriculture alone.

Prof. Newbigin and his team are optimistic that their new approach
will
apply to a wide range of SI plants - though specific 'contraceptives'
will probably need to be developed for each species.

The CEO of the Weeds CRC, Dr Rachel McFadyen, says this is one of the
most far-reaching research projects ever undertaken by the CRC in its
5-year war on invasive plants. Its benefits could potentially amount
to
hundreds of millions of dollars.

"It is a highly original solution which has substantial implications,
not just for Australia, but for world food supplies and for the
environment in general," she says. "It's the kind of research that
will
build the scientific reputation of this country globally - and it
shows
the value of getting the best brains in the country to co-operate on a
particular challenge."

More information:
Assoc. Prof. Ed Newbigin, University of Melbourne, 03 8344 4871
Email: edwardjn@...

Dr Rachel McFadyen, Weeds CRC, 0409 263 817
Peter Martin, Weeds CRC, 08 8303 6693 or 0429 830 366

www.weeds.crc.org.au