Professor Richard Trethowan

In self-pollinated crops like wheat, it can take 6 to 7 generations to reach homozygosity, or to create a pure line, and it's these pure lines that are released to farmers. So in other words, what we plant breeders do is cross one line with another to create what we call an F1. That F1 is grown out and it's an F2 generation. We then select individual plants from that F2 generation based on the different traits that we're looking for, it might be disease resistance or maturity or height, and then we allow them to self. And we do the same thing in the F3 generation and onwards we go for about seven to eight generations. By that stage, we have reached homozygosity. Now think about it, each generation is a year in the field. That's a long time to make a homozygous line. We then take that homozygous line, and we test it broadly in the environment over years for yield and quality and disease resistance before that is ever released to farmers.

Now, what doubled haploid technology allows us to do is to jump to homozygosity, complete homozygosity in one single step. So, in a 12-month period, we can go from the cross to actually having seed of that homozygous line in our hands. That saves us an enormous amount of time. So, what is the process? Well, we make an emasculation of our target plant, and then we pollinate it not with pollen from wheat, but pollen from maize. So, in other words, we trick the wheat plant into thinking it's been fertilised and the embryo starts to grow. But of course in time, those maize chromosomes are eliminated and the embryo will shrivel and die. That's why we rescue the embryo and we grow it on media, and I've got some examples here of those embryos growing on media. And of course these only have half the number of chromosomes. So, these are what we call haploid plants and they're sterile.

Now, once that haploid plant has grown on and been transferred to a pot, it is completely sterile, remember, we then treat the roots with colchicine. And what colchicine does is double the chromosomes. So, we now have a fully fertile plant with a balanced miosis and this is our double haploid plant. Normally it takes 12 years or more to produce a wheat variety. With this technology, we can cleave up to five years off the process and we can go to the farmer with a new variety with enhanced traits within 7 years. That is a phenomenal advantage to we breeders of self-pollinated crops. The other issue that I didn't raise is the combining double haploid with other technologies like molecular markers. So, for example, we can screen our F2 generation using molecular markers for known traits. Once we identify a plant that has the traits that we want based on those molecular markers, we can then send that for double haploid and go to rapid fixation in a very short period of time. And that gives us a line with all those key genes that we want very, very quickly.

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Drew Penberthy – farmer

Drew Penberthy from between Narrabri and Moree, we’ve got a farm there, grow a multitude of crops I suppose. We’ve got baby beans, chick peas, wheat durum. Summer crops such as sorghum and cotton. I still farm with my younger brother and my parents at the moment and yeah.

I have been involved in the agricultural industry for a fair while now I suppose. I went to university, Gatton College up in Queensland. I went into a farm about five years after I finished there. So, I have a fair bit to do with the wheat breeding team at the Plant Breeding Institute here in Narrabri.

We have trials on our property every season where we see the new soon to be released commercial varieties and the new commercial varieties that are being released this season. We watch these coming through our trials and we get a good understanding of where they fit our farming system.

There’s been some real big inroads into breeding in the last probably five years where we’ve got some really good varieties coming through the system, varieties such as Suntop and Lancer and Spitfire and Sunguard. Those varieties have really taken off in our district. They’ve given us good disease tolerance – Yellow leaf spot and a few of those varieties have been quite good –Stripe Rust resistance.

So, the big issues we run into with our farming system now is because it’s zero till, there’s a lot of stubble in our system that’s not breaking down because of the dry summers. Some of these new varieties have got really good tolerance to Crown Rot and Nematodes which play a real role on our yield detriments I suppose through our system.

Moving forward in our farming system in the next ten years I suppose or further wheat breeding’s going to play an even more important role in our farming system. Our diseases are getting more and more rampant through the system, virulence is becoming stronger in Stripe Rust and maybe Leaf Rust coming through the system. So, we need to keep on top of these things, resistance is coming in with our fungicides and stuff like that through our system.

So, wheat breeding’s really a really important part of our system and if we drop the ball on the wheat breeding then obviously we’re going to run into issues down the track into resistance and then we’re going to be really caught, yields are going to drop dramatically. And then you move onto things like changes of a climate through our area that appears to be having some significant changes.

So CO2 levels and all that sort, temperatures are all things that we’re trying and Plant Breeding Institute’s doing a lot of work on that now, it’s preliminary data but hopefully we get some good stuff so as things change we can adapt with our farming system and our varieties quite quickly so we’re not dropping yield and profitability and even sustainability through our farming system.

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Dr Angela Pattison

Plant breeder, University of Sydney, Narrabri

Another really important focus for wheat breeders is breeding in resistance to diseases. Like all living things wheat plants are susceptible to diseases and particularly fungal diseases – Stripe Rust and Stem Rust and Leaf Rust, three particularly damaging diseases that can very much limit the yield ability of a wheat plant.

The rusts infect the various parts of the plant and desiccate or dry out the parts of the plant that they infect limiting the plant’s ability to function normally to photosynthesise and to fill grain and create yield. The diseases continue to develop and evolve just like the wheat plants do.

So, while breeders may be able to create a wheat plant that has resistance to a particular disease that disease continues to evolve so that over time it may beat the resistance that the breeders have developed for the plant. So, continuing breeding for disease resistance is a really important part of protecting yield in wheat.

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Associate Professor Richard Heath

Farm manager, University of Sydney, Narrabri

Another really important focus for wheat breeders is breeding in resistance to diseases. Like all living things wheat plants are susceptible to diseases and particularly fungal diseases – Stripe Rust and Stem Rust and Leaf Rust, three particularly damaging diseases that can very much limit the yield ability of a wheat plant.

The rusts infect the various parts of the plant and desiccate or dry out the parts of the plant that they infect limiting the plant’s ability to function normally to photosynthesise and to fill grain and create yield. The diseases continue to develop and evolve just like the wheat plants do.

So, while breeders may be able to create a wheat plant that has resistance to a particular disease that disease continues to evolve so that over time it may beat the resistance that the breeders have developed for the plant. So, continuing breeding for disease resistance is a really important part of protecting yield in wheat.

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Associate Professor Richard Heath

Farm manager, University of Sydney, Narrabri

My name’s Richard Heath and I’m the Farm Manager of the University of Sydney’s north west farms. One of the most important advancements in wheat breeding in the last fifty years has been the creation of semi dwarf wheat varieties or the shortening of wheat varieties.

The original wheats were between a metre and a metre and a half tall and as the yields were increased through breeding and there was a lot of weight at the top of the plant. The tallness of the plant and the thinness of the stem meant that the stems couldn’t support that weight of the grain and they tended to fall over or lodge as the wheat plant matured.

The Green Revolution of the 1950s with Dr Norman Borlaug created semi dwarf varieties which reduced the height of the wheat plant typically to around sixty to eighty centimetres. And that reduced height also created a thicker, stronger stem which meant that it could support the weight of the grain in the top of the plant as the yields continued to increase.

The difficulty with wheat plants that fall over water can’t move up to the grain and so it limits the ability of the plant to fill the grain and create yield. So, as we continue to create more and more yield it still remains a priority that the strength of the stem and the ability for the wheat plant to stand upright as it matures is an important breeding target.

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Dr Angela Pattison

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My name is Doctor Angela Pattison and I work on drought tolerance in wheat. The name of my research project is the Managed Environment Facility or the MEF as it’s conveniently acronymed. The Managed Environment Facility is looking at drought tolerance in wheat and it’s a large standardised field based agricultural experiment which is comparing different genera types or breeding lines for their capacity to grow well in drought situations.

The MEF has three sites around Australia – here in Narrabri, then also down south at Yanco and over in Western Australia at Merredin. All three sites operate under standardised experimental protocols to make sure that we can compare the results of our experiments under drought conditions. The aim of the MEF is to be able to compare breeding lines which have some weird and wonderful traits for drought tolerance.

For example reduced tillering, reduced awns or no awns at all, higher waxiness on the leaves or better carbohydrate storage in their stems which allows the grain to feel better once it’s flowered. These traits are placed in using plant breeding into various different genetic backgrounds so that they can be compared in something that’s relevant to Australian conditions.

The Managed Environment Facility was set up with good controls which means that not only do we have our experimental lines in the trial but we also compare them to standard varieties such as Hartog or Janz which are a bit older plus some of the new wheat varieties like Suntop. This allows our experiment to be compared to modern day growing conditions. The entire trial is well randomised. We have about eight hundred breeding lines in the trial and these are scattered throughout the field. To make sure that they’re not all just concentrated down the bottom or up the top.

The MEF area is about three hectares and there is possibility that there’s going to be variation in the soils or in the water across the field. By randomising we can make sure that the plots down the bottom aren’t necessarily all going to be from the same breeding group and therefore have biased results. We replicate our experiment not only between the three sites but also within the same site.

Every breeding line is planted at least twice in the same treatment to make sure that we have two opportunities to get good results and these results are averaged to produce what we hope is the best representation of how that plant would grow under a drought or a well-watered condition. We make sure we standardise the conditions in the Managed Environment Facility best we can to reduce any chances that part of the field is going to be compromised or have a lower yield than other parts of the field.

This means we standardise things like plant intensity, like weed control, like the way that we till the fields and the way that we treat it with chemicals so that everything is even across the field.

So, for example if in just part of the field we see that there’s a little bit of wheat rust we will still spray the entire field to make sure that all the conditions are standardised so that nothing can hinder our results.

The final part of an experiment is being able to statistically compare our results because just since one line has a higher average doesn’t necessarily mean that that line is always going to perform the best. We need to be able to use a test of significance which allows for an objective comparison between two different lines or two different treatments.

A test of significance might be a T-test which involves the standard deviations of the lines or it might be other statistical tests which are a little bit more complicated but all of them are based on the variability that you’ve seen in the experiment trying to find out whether the variability was by chance producing something higher than it should have been in the field.

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Associate Professor Richard Heath

Farm manager, University of Sydney, Narrabri

Australia is one of the driest and hottest places on the planet where wheat is grown as a staple crop. Breeding wheats that are tolerant of drought and heat is obviously then an important part of breeding for the Australian environment. Even though countries such as England and throughout Europe grow enormous yields a lot of the time their total rainfall is actually the same as what falls in Australia.

The reason that we can’t convert that rainfall into yield is that in those countries that have much higher yields the temperatures that the grain is being produced in or the plant is filling the grain is generally around you know fifteen to even twenty degrees lower than what we have in Australia.

The University of Sydney we have a large research focus on looking at traits that cope with the extreme heat that we have in Australia when the plant’s at a critical stage where it’s trying to fill the grain to make yield.

We do this by screening diverse germplasm from all around the world from really hot climates like India and Africa and we actually have heat chambers out in the field where we have a little glasshouse essentially that’s hooked up to a heater and we subject the wheat plant to really high temperatures when it’s flowering and when it’s trying to fill the grain and we see which sets of germplasm can cope with that and yield better.

And by doing that we can hopefully find material that is more suitable or more adapted to the Australian environment.

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Associate Professor Richard Heath

Farm manager, University of Sydney, Narrabri

One of the most critical phases for a wheat plant in terms of getting yield is the period between when the plant flowers and while it’s filling grain.

In Australia that’s a real limiting environmental factor because we have a very short amount of time between the last frost of winter and excessive heat. The wheat plant doesn’t cope with frost when it’s flowering. If it incurs frost when it’s flowering it essentially sterilises the flowers and the grain doesn’t fill.

And once we hit extreme temperatures the grain also doesn’t fill. So, that period of time is very short and if we could have wheat plants flowering earlier when it’s cooler and not susceptible to frost we’d have a lot longer time period for the plant to fill grain in the cool weather and maximise yield.

So, looking for germplasm that is tolerant to frost and is able to cope with frost when it’s flowering is extremely difficult because there on all the evidence so far not a lot of germplasm anywhere that is able to cope with frost. But potentially a very high reward if we can find that.

So looking for plants that are tolerant to frost at flowering is one of the Holy Grails of wheat research.

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Dr Phil Davies

Plant pathologist, University of Sydney, Narrabri

My name’s Phil Davies, I’m a plant pathologist and plant breeder here at the University of Sydney and my main responsibility is for breeding for resistance and tolerance to Crown Rot.

So, Crown Rot’s a disease of wheat in the northern region, so northern NSW and southern Queensland. It’s a disease where the seedlings become infected by a pathogen. That pathogen then proliferates up and down the stem and stops water moving to the heads.

So, at harvest time what we see is heads that have ripened prematurely and either have no grain or very small grain. And that obviously has impacts on yield, reduces yield and also quality of the grain. So, it’s a huge emphasis for scientists in the northern region to try and reduce the impact of this disease.

So, we can do this in a number of ways, the main emphasis that we’re working on is breeding for resistance. So, making varieties that don’t suffer the yield loss associated with Crown Rot. On top of that we can also use other strategies in an integrated approach, things like rotation away from susceptible hosts. What happens with this disease is the pathogen survives in stubble from the previous crops. So, as long as you’ve got stubble remaining from previous seasons you’ll have inoculum ready for infection for the following crop.

So, if you can rotate away from these susceptible hosts, so all of the winter cereals so wheat, barley, oats and triticale that will allow the level of inoculums to break down and crops be grown without disease. So, crop rotation is a big factor.

Along with that we can actually do what’s called inter-row sowing, so where growers plant their wheat between last year’s cereal crop residue and that just reduces the amount of inoculum available to infect the following seedlings. And so using varieties that are resistant to Crown Rot, rotating away from susceptible hosts and using management strategies like inter-row sowing you can reduce the impact of this disease in a farmer’s field.

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Dr Tom Buckley

Senior lecturer, plant physiology, University of Sydney, Narrabri

When trying to isolate the best varieties of wheat that will be able to tolerate the conditions of the future in terms of environmental change, elevated CO2, warmer temperatures and so forth we have to take a multi-pronged approach. This involves making measurements out in the field and field trials where we can actually measure the amount of yield that each variety will produce.

The difficulty with field trials is that it’s next to impossible to control and even in some cases to precisely measure the environmental conditions that really matter. And so in order to get better measurements and more precise control of those environmental conditions we often replicate our trials in the glasshouse.

In the glasshouses we have the ability to control temperatures and humidity to a very precise degree. And we also have the unique ability in these glasshouses at Narrabri to control CO2 concentration. This can be done in the field but it’s an awful lot more costly and more difficult to carry out.

So, by combining field trials and glasshouse measurements we can get a pretty good handle on exactly how all of the many different varieties of wheat will respond to the conditions of the future and then find the best ones for farmers to grow.

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Dr Tom Buckley

Senior lecturer, plant physiology, University of Sydney, Narrabri

My name is Tom Buckley, I’m a Senior Lecturer with the University of Sydney in the faculty of Agriculture. And my research is mostly in Plant Physiology, Environmental Plant Physiology, studying how plants interact with their physical surroundings.

And most of my work involves identifying the traits that help wheat plants survive in harsh environments like we have here in northern NSW so that breeders can then isolate varieties that have those traits and deliver them to growers.

Wheat is a very typical monocot, like all grasses as a monocot wheat has parallel veins. It tends to have very long narrow leaves. Its root system is very fibrous as opposed to having a single large tap root with many smaller roots growing off of that, wheat has a fibrous system with many individual roots coming out of the base of the plant. Wheat leaves are also empty stomatas, they have stomata pores that let gas into and out of the leaf on both surfaces of the leaf. And wheat like other grasses also has intercalary meristems, these are areas of tissue at the base of the leaf that produce new leaf tissue and allow the leaf to continue growing even if the end of the leaf has been damaged or consumed by a herbivore.

Wheat as a monocot differs from dicots which tend to have tap root systems as I mentioned. They tend to have reticulate or net like vein systems in the leaves, usually broader leaves.

So, as distinct from a typical dicot crop like fava beans, fava beans would have a branched stem with very prominent and clear distinctions between the leaves and the stem. And a great deal of the tissue would be in the stem.

In wheat plants most of the plant that you see is actually in the leaf, that’s where most of the water conduction takes place. Wheat plants and other grasses reproduce vegetatively by tillering that is they grow horizontal stems just above or below the soil. And that enables them to grow and expand into new areas quite rapidly. And the amount of tillering is a measure that we use of how healthy a wheat plant is in particular environments.

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Dr Tom Buckley

Snr lecturer, plant physiology, University of Sydney, Narrabri

Another way in which the wheat plant is quite distinctive is its pattern of reproduction. Wheat is a flowering plant although its flowers are not terribly visible to the naked eye. You’d have to pry apart a young flower of a wheat plant to recognise that it is a flower. Wheat plants tend to pollinate themselves whereas most sexually reproducing organisms and other flowering plants pollinate one another.

Wheat plants pollinate themselves which means it’s quite a lot easier with a plant like wheat to get homozygous or genetically uniformed varieties which is very conducive to breeding efforts.

With plants that do not self-pollinate what you tend to see if you compare individuals out in nature is an enormous amount of genetic variation. Of course that’s the point of sexual reproduction. That variation makes it difficult to breed plants and so wheat because it self-pollinates and tends to have homozygous lines as a result is quite a bit easier to work with as a breeder.

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