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July 11, 2002
Scientists have moved closer to
unlocking the genetic codes which could allow the worldıs major
food crops to cope better with drought, with the formal signing
of agreements which link the relatively small Australian sorghum
research effort with three major American universities.
The agreements between Queenslandıs Department of Primary
Industries and the Texas Tech, Texas A&M and Missouri
Universities centre on a characteristic called Stay-Green
discovered in some sorghum plants.
Stay-Green delayed leaf ageing and death is a trait which
helps the sorghum plant continue filling its grain in water
limited situations. It increases resistance to lodging and
improves stubble quality, ratooning ability and ground cover.
Research trials have shown hybrid sorghums incorporating
Stay-Green can outyield those without it by up to 25% under
water-limited conditions.
What excites scientists is the possibility of incorporating
Stay-Green genes once theyıre isolated and cloned into other
major cereals like wheat, barley, maize and even rice.
Successful transformation of these food crops with Stay-Green
could lead to greater drought resistance. The value of
Stay-Green genes in such a situation would be considerable.
The QDPI sorghum breeding program led by Dr Bob Henzell at the
Hermitage Research Station, outside Warwick has been working
for more than two decades on the development of the Stay-Green
characteristic for incorporation into commercial sorghum
varieties, where their use is now common.
The breeding program is supported by Australian growers and the
Federal Government through the
Grains Research & Development
Corporation (GRDC), as is a physiological study of
Stay-Green by Hermitageıs Dr Andrew Borrell.
Dr Borrell and Hermitage sorghum breeder David Jordan led the
negotiations to develop agreements with the US universities,
which he says recognise the excellence of the breeding and
physiological areas of Australian sorghum research
"The American universities do not have our capacity to test
sorghum germplasm in a wide range of environments, nor do they
have a strong physiology program, although their laboratories
and biotechnology facilities, particularly at Texas A&M, are
fantastic," Dr Borrell says.
"The Americans have supplied us with four different iso-genic
sorghum lines, each containing key chromosomal regions
associated with stay-green.
"We will be growing those lines
in the field sometimes under a rain-out shelter to determine
the function of each of these chromosomal regions. We may
discover genes associated with increased water use efficiency,
reduced rate of leaf senescence, higher leaf nitrogen status or
increased nitrogen uptake under drought conditions.
"All these traits will be be measured against a fully senescent
line one with no Stay-Green component for comparison
purposes.
"Weıll send the results of our work back to the US for them to
assist in the identification of candidate genes for stay-green.
RNA (ribonucleic acid) samples will also be sent to Texas A&M
University for micro-array analysis to determine which genes
have increased or decreased activity under drought
conditions."
Dr Borrell said at the same time Dr Jordan, would be developing
breeding material to assist in further testing the key
chromosomal regions associated with stay-green.
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