Speeding up rate of wheat genetic gain remains key focus

GRDC continues to invest in wheat grain gains

Cereals
Breeders are seeking to optimise wheat productivity in a range of trials, including this site on the Liverpool Plains, NSW.

Breeders are seeking to optimise wheat productivity in a range of trials, including this site on the Liverpool Plains, NSW.

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Pre-breeding research develops tools and technologies to fast-track new varieties.

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Speeding up the rate of wheat genetic gain remains a key focus of GRDC Managing Director, Steve Jefferies.

Dr Jefferies says pre-breeding research must focus on developing tools and technologies which enable breeders to increase the speed of variety development and the magnitude of yield, disease and quality improvement per breeding cycle.

GRDCs multi-pronged approach to pre-breeding involves focusing on the key pillars of:

  • Optimising the use of genetic variation for key traits such as improved heat and frost tolerance
  • Maximising effective population size to increase throughput
  • Improving the accuracy and precision of selection
  • Reducing cycle time for identification of elite parents and their re-use.

Dr Jefferies came to GRDC in 2016 from Australian Grain Technologies (AGT), Australias largest and market-leading wheat-breeding company. Prior to that, he was a University of Adelaide wheat breeder and senior lecturer.

Cracking wheat’s genetic code

GRDCs approach to wheat pre-breeding includes reducing the cycle time from 10 to six years.

GRDCs approach to wheat pre-breeding includes reducing the cycle time from 10 to six years.

Australian researchers were among 200 scientists from 73 research institutions in 20 countries that unlocked the complete wheat genome in 2018, after 13 years of collaboration.

The success, supported by GRDC, paves the way for accelerated development of wheat varieties with higher yields, enhanced nutritional quality and improved sustainability, that can better adapt to climate challenges.

Wheat is the staple food for more than a third of the worlds population. It accounts for almost 20 per cent of the total calories and protein consumed by humans.

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Due to its complex genetic make-up, genetic improvements to wheat varieties have been harder than in crops such as rice and corn.

The International Wheat Genome Sequencing Consortium says to meet a projected world population of 9.6 billion by 2050, wheat productivity needs to rise by 1.6 per cent a year.

Much of this increase must be achieved via crop and trait improvement to preserve limited natural resources.

It says the full genetic map of wheat will allow breeders to identify faster the genes and regulatory elements underlying complex agronomic traits, such as yield, grain quality, resistance to fungal diseases and tolerance to abiotic stress.

The wheat genome sequence lets researchers look inside the wheat engine and reveals tools to vary and adapt to different environments through selection, as well as sufficient stability to maintain basic structures to survive under various climatic conditions.

Partnership yields gains

The International Wheat Yield Partnership (IWYP) aims to raise the genetic yield potential of wheat by 50pc in 20 years.

GRDC is the lead Australian research funding partner in IWYP, which funds and co-ordinates international research to address urgent global production challenges.

At the fundamental level, this will be achieved by improving wheats ability to capture and process the suns energy, through photosynthesis, and making sure the captured carbon ends up in the wheat grain.

For example, wheat uses only about 1 per cent of sunlight to produce the parts humans eat, compared with maizes 4 per cent efficiency and sugarcanes 8 per cent efficiency.

Even increasing wheats photosynthetic efficiency from 1 to 1.5 per cent would allow growers to increase their yields on the same amount of land, using no more inputs.

IWYP targets six key research scope areas of:

  • Uncovering genetic variation that creates the differences in carbon fixation and partitioning between wheat lines
  • Harnessing genes from wheat and other species through genetic modification to boost carbon capture and fixation to increase biomass production
  • Optimising wheat development and growth to improve grain yields and harvest index
  • Developing elite wheat lines for use in other breeding programs
  • Building on discoveries in wheat relatives and other species
  • Fostering breakthrough technology to transform wheat breeding.

Protecting against heat

Periods of extreme high-temperature, in particular short periods of heat shock, are a major threat to wheat yield and grain quality throughout much of the Australian wheatbelt.

CSIRO projections of Australian climate change indicate heat waves and temperature variability will become more frequent and intense in coming decades.

Dr Juan Juttner, GRDC Senior Manager for Genetic Technologies, says heat stress in wheat is estimated to cost the Australian industry $1 billion a year.

Investments such as this will help breeders in converting genetic variation for heat tolerance into yield gain for Australian growers, he says.

Professor Richard Trethowan, of the University of Sydney, says it is vital new wheat germplasm with improved high-temperature tolerance, and molecular tags linked to this tolerance, are developed for use by commercial breeding programs.

While the effects of high-temperature on yield and grain quality are well known, those traits underpinning plant response to high-temperature and the inheritance of tolerance are less well understood," he says.

Professor Trethowan is leading a GRDC investment to undertake extensive phenotyping of wheat lines produced from a diverse range of international sources.

These wheat lines are being assessed for field response to high temperature using both traditional and new phenomic methods, he says.

We are also looking to calculate genomic breeding values for heat tolerance to select the best crosses to generate the next generation of lines."

A major stumbling block to the genetic improvement of all complex traits is accurate phenotyping and the lack of broad scale and relevant phenotyping strategies have historically limited genetic progress.

A critical element of this investment has been the development of accurate field-based heat phenotyping methods," Professor Trethowan says.

"These heat chambers can accurately apply heat to plants in the field.

The stage is set to now develop new and improved germplasm using the latest molecular tools and associated breeding strategies.

The investment is combining the developed phenotyping method, and diverse germplasm with state-of-the-art wheat DNA marker technology and genomic selection approaches, to significantly enrich wheat lines for heat tolerance."

Genomic selection is a breeding method that requires a reference population consisting of wheat lines that are phenotyped for the trait of interest and genotyped at many DNA markers distributed across the whole genome.

Various statistical methods are then used to estimate the effect of each DNA marker on the phenotype. The collection of all these DNA marker effects is called a prediction equation that predicts a genomic breeding value of a wheat line.

This prediction equation can then be used to predict new plants that are only genotyped and do not have a phenotype.

This allows for early selection of plants/lines without them having to be phenotyped, which can decrease breeding cycle times and increase genetic gain substantially.

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