Bundoora, Victoria, Australia
April 17, 2007
Beer lovers and barley growers
could soon be raising their glasses to Australian scientists who
may have found a way to increase beer supply.
Researchers at the
Molecular Plant
Breeding CRC are looking for genes that protect barley from
pre-harvest sprouting, a grain condition that causes substantial
reductions in barley yield and significant economic losses for
farmers.
Under prolonged wet or damp conditions, barley grains begin to
germinate or ‘sprout’. Sometimes this happens while the crop is
still standing, before the barley is harvested.
Pre-harvest sprouted barley is useless for beer making because
the starch has been degraded and the grain can’t be malted.
Instead, farmers are forced to sell their grain in the
considerably less profitable animal feed market, and beer
drinkers are denied the ales and lagers for which Australian
barley is known.
Ms Yumiko Bonnardeaux, a PhD student at the WA Department of
Agriculture and Food, says that pre-harvest sprouting could be
eradicated by breeding barley lines that contain ‘dormancy
genes’.
Similar to the way bears hibernate in the winter and emerge in
spring when the weather is warmer and food plentiful, the seeds
of many plants have a mechanism which enables them to only
germinate when the conditions are favourable for growth.
“Warm temperatures or rain can act as cues for seeds, telling
them that the time is right for germination,” says Ms
Bonnardeaux.
“But dormant seeds are prevented from germinating, even under
the conditions that encourage germination.”
“The greater number of dormancy genes a barley plant has, the
greater its resistance to pre-harvest sprouting.”
“The challenge is to develop barley grain that is dormant enough
to withstand pre-harvest sprouting but not so deeply dormant
that the grain doesn’t germinate during the malting.”
Ironically, Ms Bonnardeaux says, pre-harvest sprouting is a
result of our own quest for the perfect beer.
“Over the years, farmers have continually selected and bred
varieties with lower seed dormancy to provide grain that will
germinate rapidly in the malthouse. As a result, malting
varieties often have low dormancy and are more susceptible to
preharvest sprouting.”
Ms Bonnardeaux has found pre-harvest sprouting to be a very
complicated trait controlled by multiple genes and environmental
factors.
“Depending on the environment, different genes controlling
dormancy get switched on. That’s why grain from the same barley
variety may have a different dormancy response depending on the
site that it’s grown on.”
“This is also why it’s difficult for breeders to reliably
predict which barley lines will have pre-harvest sprouting
tolerance, as this can change from year to year.”
As a part of her PhD research, Ms Bonnardeaux has located
regions of barley chromosomes that may contain previously
unidentified dormancy genes. These have been tested extensively
across different sites and over two seasons for pre-harvest
sprouting.
Using the well studied plant Arabidopsis, or ‘Thale cress’, as a
guide, she has identified several potential dormancy genes and
is now mapping these in the same barley population.
“The next step is to find out whether these genes are located in
chromosomal regions known to be involved in controlling dormancy
in barley. This would identify whether these are candidate genes
to do further research on.”
Once it is certain which genes confer the dormancy ability,
molecular tests can be developed that predict which varieties
have these genes. Plant breeders will then be able to develop
varieties that are tolerant to pre-harvest sprouting.
The Molecular Plant Breeding CRC is a Cooperative Research
Centre established under the Australian Government's CRC
Program. |
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