From single seed to pure breed
Legumes contain about twice the amount of protein found in whole grain cereals and play an important role in food security in most developing nations. Pulses, the edible seeds from legumes, have also been shown to help reduce the incidence of cancer, diabetes and heart disease.
Australia produces around 2.25 million tonnes of pulses annually, of which over 90% are exported. Pulse crops are valued for farming sustainability – as disease breaks and weed control options. Pulses also convert nitrogen in the air to the soil, allowing for reduced running costs for the next crop.
Changes in the production environment such as climate, new pests, water shortages and higher farming costs have led to pulse breeders looking for better strategies to ensure their crop material can adapt to changing conditions.
Dr Janine Croser is a farmer and a scientist. She and her team of researchers at UWA’s Centre for Plant Genetics and Breeding, including Dr Federico Ribalta have developed a novel rapid generation turnover process to help meet changing needs. Their platform speeds the development of purebred seed lines for pulse breeders with improved crop quality, predictability and resilience of offspring in harsh climate conditions.
As we move into more instability in our regions, we will be able to respond more quickly to emerging issues.
Sowing the seeds for change
Traditionally, plant improvement requires time as seed lines resulting from a cross between two parents need to return to a stable, pure breeding line before they can produce predictable offspring. This can take 5-6 generations of inbreeding. The most widely used method is the single seed descent (SSD) protocol. One seed is used to produce the next generation, in a glasshouse, enabling up to three generations per year.
Whilst methods exist for faster laboratory-based generation of pure breeding lines of wheat and canola crops, they are ineffective when applied to the main legumes: chickpea, lentil, field pea, faba bean and lupin.
In 2014, with co-investment and support from UWA and the Grains Research and Development Corporation (GRDC), the team began their research into a novel pulse platform.
Their goals were to develop a system that:
- speeds up the rate of generation turnover in pulses;
- includes the ability to select key traits in seed lines; and
- creates meaningful impact as part of national pre-breeding and breeding programs.
The team work with chickpea, lentil, field pea, faba bean and lupin.
Keeping a finger on the pulse
Their novel technology, the accelerated-Single-Seed-Descent platform (aSSD) was first in transforming the speed of delivery of pure seed lines, to pulse breeding programs in Australia.
The platform achieves five to eight generations per year in the major crop legumes. The benefit for plant breeders is a ready supply of new varieties to the farm gate much faster than previously.
By incorporating existing techniques such as gene discovery and selection, the aSSD platform can promote the favourable traits desired by plant breeders. Traits such as an ability to cope with climate and environmental stress and herbicide resistance to new pests and diseases present breeders with a competitive edge.
The predictability of offspring provides breeders with confidence to provide farmers with cultivars at a commercial scale. Farmers benefit with resilient crops that offer consistent yield at harvest time, fewer chemical treatments and reduced running costs. For consumers, a pure line seed results in food that is healthier and better tasting.
Working in close collaboration with breeders means that there is a faster release of novel varieties to the farmers.
Dr Federico Ribalta tending herbicide resistance lines as part of the chickpea breeding program.
An industry measure
The team began delivering the platform to industry in 2016. By 2019, an estimated 50,000 plants had passed through the system. Australian pulse breeding programs have been great supporters of the team’s research.
This work has been outstanding and one of GRDC’s investment success stories with practical impact on the ground.
Four national breeding programs and a number of research bodies currently use the platform, including:
- GRDC via their Pulse Breeding Australia breeding program
- NSW Department of Primary Industries (NSW DPI) as part of Dr Kirsty Hobson’s chickpea breeding program.
- Agriculture Victoria DEPI for their lentil and field pea breeding programs.
- South Australian Research and Development Institute (SARDI)
- CSIRO Plant Industry, Perth
- The University of Adelaide for their plant breeding program.
- In collaboration with the University of Tasmania to develop a range of complex populations for breeders of the future using the aSSD platform.
- The platform has also made it possible for PhD students at UWA to study populations of fixed lines within the first year or 18 months of their 3-year research period.
This technology has now become a critical component of the breeding programs as it allows us to fast-track potential variety releases, providing better varieties to growers in a shorter timeframe.
Through rapid, accurate and consistent application of aSSD technology we have been able to quickly access genetically fixed populations relevant to salinity tolerance, vigour, phenology, herbicide tolerance and nematode resistance in chickpea. … a key part of the collaborative success has been the brilliant communication from all members of the UWA team and willingness to understand and accommodate specific needs for each project on which we have worked.
A platform to grow
The aSSD platform includes two phases.
First phase
In the first phase, plant-breeding programs send a population of hybrid seeds representing different combinations of genes from two parents to the team. They are individually planted and tracked through two – four generations in environment-controlled greenhouses, at the UWA’s Plant Growth Facilities. Leaf samples can be sent to collaborators for molecular analysis to determine whether the required gene combination exists in the plant. Plants that hold the desired traits are then maintained and progressed through further generations to fix the trait of interest.
We work in close collaboration with the breeders. This means there is an acceleration in the release of both novel as well as better varieties to the farmers.
The plants begin to flower within 20-30 days, under controlled lighting, airflow, water and temperature conditions.
Second phase
In the second phase, plants are monitored for approximately 18 days after flowering, with an immature seed taken from each plant. Applying research the team has done into seed development and water tolerance, the immature seed is then able to be germinated and grow into a healthy plant of the next generation very quickly.
| Environment | Generations achieved per year (max) | Years required for pure line (approx) |
|---|---|---|
| aSSD platform | 8 | 1 |
| Glasshouse | 3 | 2.6 |
| Field | 1-2 | 4-8 |
Generations achieved per year
This breakthrough significantly reduces breeding times, increases efficiencies and is transformational when compared to glasshouse or field conditions.
Finally, the material is sent to the breeding program who can use the lines for molecular mapping for gene discovery, running field trials to select lines with valuable traits, or as parents in crossing programs.
I get a lot of feedback from farmers as to what the practical problems are on the land and how we can address those through our breeding platforms.
Pure line (aSSD) plants look the same as each other, be similar in height and have the same yield.
A shining ray of light
Plants react to lighting within their environment. The effect of light quality is therefore key to the aSSD platform. The team has developed novel light spectrum regimes integrating specific spectral outputs into the platform to promote rapid flowering and embryonic development.
There has been keen interest in their LED techniques from key breeding companies in Australia and at international conferences.
Commercial LED supplier Valoya have also integrated the research into their range of lighting systems also.
Our new LED technology has been a key mechanism in getting the plants to flower quickly and to develop their seed very quickly as well.
The new LED is a key aspect of the platform
Seed banks
Aside from their work with plant breeders, the team recognise the importance of developing key breeding populations for Australian grown legumes. The team currently produce material from crosses between domestic chickpea and wild relatives. Using a modified aSSD approach, the team is able to quickly develop fixed, pure breeding lines incorporating genes from the wild relatives.The material is sent to the Australian Grains gene bank to improve the diversity that is made available to Australian breeders. Increased diversity of traits in pure seed lines could hold the key to responding to future climate driven production issues.
In 2020, the year of plant health, this UWA team of researchers are working hard to come up with ideas that are key to healthy plant populations and eco systems.
Australian seed banks hold a variety of pulse seed lines
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