Grain growers, advisors and research scientists from
either side of the Queensland New South Wales border travelled to Goondiwindi
for the 2020 GRDC Grains Research Update.
Many attending this Update session rely on wheat for their livelihood.
Whether they breed it or grow it. At the University of Sydney Plant Breeding
Institute at Narrabri cutting edge wheat pre-breeding work has
been conducted by scientists such as Richard Trethowan
and Rebecca Thisethwaite and at this Update Richard gave a
presentation on breeding for heat tolerance.
Now we all know that high temperatures impact
crop yields we know that and at Narrabri over the past eight years we've been
running extensive dates of planting experiments and these
extensive experiments have allowed us to estimate yield loss.
And we estimate that for every one degree rise in average maximum
seasonal temperature we're seeing between 250 and 400 kilogram
yield loss. And when we see heat shocks at meiosis to flowering we see a
reduction in grain number as most people it makes sense that that
would be the case and when we see heat shocks during the
grain filling period we see a reduction in grain weight we need to
have a relevant and effective and repeatable phenotyping
strategy. Absolutely fundamental without that we
go nowhere and I emphasize the relevant here. So we
developed over a period of time a three-tiered
scheme for phenotyping for heat tolerance.
Stage 1 involves date of planting trials and to ensure these lines are only
impacted by heat stress and not water stress irrigation is used.
Stage 2 sees those lines that show a level of heat tolerance
exposed to a temperature shock delivered by
heat chambers to confirm the initial response.
Stage 3 involves the application of a controlled heat stress in the glass
house to understand what's happening.
We calibrated this over a three year period using a fixed
set of germplasm and these are the results. We ran these
experiments in triplicate plots that were replicated
and what we found and this is very pleasing
a consistent reduction in yield under the heat chamber
but no difference between the ambient and the plot that did not have a chamber.
It also told us that what was driving this was grain number.
There was a significant reduction over that period in grain number and that was
largely driving this change in yield.
Now when once we've been through the heat chambers we go off to the control
environments and we look at floral biology we look at
the impacts of temperature on pollen in particular.
Heat stress can have an enormous impact on pollen.
In this example a heat susceptible variety
exposed to heat shock had two-thirds of its pollen
rendered non-viable. If we can introduce a gene for enhanced pollen viability
under heat tolerance, if we can induce introduce another gene
that let's say maintains grain weight under high temperature
then all of a sudden that sowing window just gets a little wider
even though the conditions are becoming tougher
for the grain grower. Update delegates were also told
the success of this phenotyping strategy was also due to
a genomic selection strategy for heat tolerance
and the formula looks like this so we have reduced the cycle time from cross
to cross from six to seven years to two to three
years. So all of this depends on our training
population absolutely and fundamentally if we don't get the training population
right that initial population upon which we base all our predictions
then we're going to go nowhere fast. Now because we have an extensive genetic
profile of all that material we can combine the genetics
and the field responses and the chamber responses and the greenhouse responses
to calculate a genomic estimated breeding value.
So this is a the value of that germ plasm
to a plant breeder who's interested in heat tolerance if you like.
So how are we estimating our genomic breeding values.
There are two models there's a baseline model but there is a more sophisticated
model and this is where Hans Daetwyler and his group
they've integrated a genotype by environment interaction term
into the estimation of genomic values and
we then look at predictability simply as the correlation between the GBV
and yield. We then take those lines with the highest breeding values
and we test them in Western Australia and in Victoria
just to confirm that these responses are transferable across environments on the
basis of that breeding value. And what we see
is a predictability when you look at that correlation of
between 0.3 and 0.5 and that is good and what is also interesting is this
more sophisticated model almost in every instance it gives us a
better predictability. Better predictions, better germplasm.
A weighted index that includes these predicted yields
and other data is used to screen and select from these
pre-breeding lines. Lines that perform very well when you sow them
optimally and maintain a yield when temperatures are high
that's what we're looking for that's the focus of our program. This is
from last year 2019 and we're looking at yield under late sowing at Narrabri
versus yield under optimal sowing and what I've done
here I've put in green the lines these are the new lines that for the first
time are in trial were in trial last season
that came through our crossing program that was based on
GEBV alone these have never been phenotyped
these lines have never been phenotyped they were developed simply
and selected simply on the basis of GBV remember that
and yet up here in the top quadrant we have a number of these lines that are as
good as or better than the varieties and they've never been selected for a
phenotype just developed on the basis of the breeding values. I think it's working.
Based on the data collected Richard
Trethowan has rated the trials cultivars in order of heat tolerance. Based on our
experience and our dates of sowing our multi-environments our heat chambers
come up with this type of ranking. So some key messages here i actually
think that Australian wheat cultivars wheat varieties are already heat
tolerant. Wheat breeders over many years of just
through empirical selection in the environment have produced heat tolerance
in our material but we've identified stuff that's even
better and that's what our wheat breeders need to access.
What we're seeing works in other parts of Australia and I think that's a really
key issue and genomic selection combined with a broader plant-breeding strategy a
pre-breeding strategy is effective in identifying new material.
And I'd just like to acknowledge a bunch of people who have helped out here
including AGT and Integrain who have helped with
identification of some of the materials and
have helped with some of the testing. Thank you very much.
Richard Trethowan from The University of Sydney's Plant Breeding Institute at
Narrabri. And this video is one in a series of
Update videos recorded at the 2020 GRDC Grains Research Updates.
Go to the description bar below for the latest information, links and resources.