Download Research lifts early vigour and yields in wheat

Cropping
New varieties
Research lifts early vigour and yields in wheat
Grain growers continually seek new wheat varieties which are better adapted to Australia’s challenging farming systems.
Armed with advanced breeding methods and a better understanding of what limits wheat productivity, scientist Wolfgang
Spielmeyer details how a CSIRO Plant Industry research team is developing promising new wheat varieties.
uture wheat varieties will yield more with
less water, compete better with weeds and
have higher emergence rates.
CSIRO scientists are using molecular
marker technology to speed the development
of new wheat varieties.
By identifying specific markers on wheat
chromosomes, researchers can determine
quickly whether a newly emerged seedling
contains the desired genetic make-up.
The marker technology avoids the need to
grow plants to maturity before selecting them
for desirable traits.
Transpiration efficiency
Crops with high transpiration efficiency,
like the recently released Drysdale wheat
variety, yield more with less water.
While the method used to measure
transpiration efficiency in Drysdale is
effective, it is also expensive and
unfortunately cannot be automated.
To overcome these limitations, CSIRO
Plant Industry researchers are developing
molecular markers for transpiration
efficiency which will hasten the selection of
water-efficient wheats in plant breeding
programmes significantly.
The CSIRO research has shown certain
components of high transpiration efficiency
are highly heritable and can be tagged with
molecular markers.
In addition, the molecular marker
technology lends itself to automation,
potentially enabling hundreds of wheat lines
to be screened quickly.
At a glance
• CSIRO scientists are using
advanced genetic methods to
produce new wheat varieties.
• The new varieties will yield more
with less water, compete better
with weeds and have higher
emergence rates.
• Varieties with longer coleoptiles will
enable wheat to be sown deeper
and earlier in the season.
• Reduced tillering varieties will
produce larger kernels, reducing
the risk of screenings.
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Photos: CSIRO Plant Industry
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Using molecular markers, CSIRO scientists have identified wheat lines which yield more with less water,
compete better with weeds and can be sown deeper and earlier without affecting emergence rates.
The new varieties will go a long way to meeting the challenges faced by wheat growers, especially in many
drier areas.
Improving early vigour in wheat
Early growth and vigour of wheat is poor
compared with other cereals such as barley.
Slow growth limits wheat yield in southern
Australia. More vigorous wheat varieties
would shade the ground faster, reducing
evaporation from the soil surface.
These varieties would also compete more
effectively with weeds and suffer less yield
penalty when sown late.
Much of the water used by wheat crops in
southern and western Australia is provided by
in-season rainfall.
Yet as much as 50 per cent of this rainfall is
lost as water evaporation from the soil —
resulting in substantial water loss which, if
saved, could be used for crop growth.
Weed competition
The inability of young wheat plants to outcompete weeds results in reduced yields and
consequently more herbicide use.
Such high use of herbicides has led to the
serious problem of herbicide resistance in
some weeds such as ryegrass.
CSIRO scientists have identified a marker
linked to early vigour located on one of the
wheat chromosomes. This discovery is
significant because the marker now can be
used to hasten the selection of wheat plants
with good early vigour.
By screening breeding lines for the
marker, scientists expect to improve crop
establishment of future wheat varieties.
Dwarfing genes
All wheat varieties released in Australia
over the past two decades have short
coleoptiles — the sheath encasing the first
leaf which pushes the germinating seedling
through the soil to reach the surface.
Short coleoptiles are an unwanted
by-product of certain dwarfing genes in
the genetic makeup of wheat.
Long-coleoptile wheats containing alternative
dwarfing genes are less affected by deep sowing.
These varieties produce good stands and higher
grain yields than short-coleoptile wheats (for
example, Hartog as pictured).
FA R M I N G A H E A D
No. 150
July 2004
New varieties
Cropping
FIGURE 1 Tiller inhibition gene reduces tiller numbers to lift yields
All Australian wheat varieties produce more tillers
than they can sustain until maturity. These
superfluous tillers represent a waste of water and
nutrients, which otherwise could be invested into
grain production. CSIRO scientists have identified
a gene responsible for inhibiting tillering and are
developing new wheat varieties, which produce
larger kernels and consequently reduced
screenings.
These dwarfing genes are primarily used to
reduce plant height — lowering the lodging
risk and lifting yields in modern wheats.
While the dwarfing genes provide
significant yield advantages, the short
coleoptiles of modern wheats deter growers
from deep sowing at the optimum sowing
time because of the risk of reduced seedling
emergence and vigour.
Instead, sowing is usually delayed until soil
moisture increases, forcing growers to accept
the likelihood of lower yields.
Reduced emergence is worse when
seed is sown deep, at higher temperatures
or where growth is impeded because of
compacted soil.
Seedling emergence of current varieties
is particularly disadvantaged in minimum
tillage as seedlings must emerge through
stubble or from hard seed beds.
CSIRO scientists have identified alternative
dwarfing genes which reduce plant height but
do not affect coleoptile length or early vigour.
The long-coleoptile wheats containing the
alternative dwarfing genes are less affected by
deep sowing. These varieties produce good
stands and higher grain yields than their
shorter coleoptile counterparts.
The CSIRO scientists are identifying
markers linked to these new dwarfing genes,
which will enable the genes to be transferred
into new, higher yielding wheat varieties.
Tiller number
All Australian wheat varieties produce
more tillers than they can sustain to grain
maturity (see Figure 1).
The superfluous tillers represent a waste
of water and nutrients which otherwise could
be invested into fertile heads to increase
grain yield.
CSIRO scientists have identified a single
gene which reduces tillering known as the
FA R M I N G A H E A D
No. 150
July 2004
Current varieties
Current varieties + tiller inhibition gene (tin)
Wasteful tillers
Fewer tillers
Larger ears
Larger grains
Source: CSIRO Plant Industry.
‘tin’ gene for tiller inhibition. The process of
tillering inhibition is not always complete
and it is possible to modify the expression
of the tin gene so fewer wasteful tillers
are produced.
Lines with the tin gene have been yield
tested in southern New South Wales over the
past three years.
Yields have, on average, been similar to
the commercial parents but under some
conditions yields are higher.
In all cases, kernel size has increased,
reducing the potential for screenings.
A marker linked to the tin gene is being
used to select for the presence of this gene in
breeding lines. This marker screening is
easier than relying on the often complicated
scoring procedure of tiller number.
For more information contact Wolfgang
Spielmeyer
wolfgang.spielmeyer@
csiro.au, phone (02) 6246 4934 or fax
(02) 6246 5000.
What is a molecular marker?
olecular marker technology enables
scientists to identify the presence of
particular genes within plants and animals.
M
The markers are small pieces of deoxy
riboneucleic acid (DNA) located near a
gene of interest, for example, a disease
resistance gene or a dwarfing gene.
The benefit of markers is they can be
detected more easily than the expression of
the gene they are near.
Before
marker
technology
was
developed, determining whether a wheat
variety contained, for example, a gene
for disease resistance involved growing
the plant and infecting it with the
disease in question.
If the plant became diseased, it was
identified as not carrying the resistance
gene and removed from the plant
breeding programme. The process took
considerable time and was relatively
expensive as resources were spent on
identifying unwanted as well as wanted
plant varieties.
Using molecular markers, scientists can
now simply look for the presence of the
marker DNA next to the gene in question.
The process of marker identification is
rapid and relatively inexpensive.
More importantly, marker identification
can be carried out at any stage during a
plant’s development.
For example, scientists can test a small
piece of seed for the presence of a marker
linked to a resistance gene and therefore
determine whether the plant will be diseaseresistant without even sowing the seed.
Used in this way, thousands of potential
new varieties can be tested cheaply and
quickly and new varieties can reach their
end user years earlier than with traditional
plant breeding methods.
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