Frost gene search turns international

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Photo of wheat, blue sky

Wheat showing frost damage

PHOTO: Evan Collis

The common saying in business that ‘you can’t manage what you don’t measure’ applies equally to the business of frost management in cropping systems.

However, until recently, a consistent method had not been applied to the measurement of field frost damage in wheat and barley in different regions, making it difficult to compare frost results. Since 2008, the GRDC has focused frost research on the development of a nationally consistent and coordinated system for measuring field frost damage in wheat and barley. The development and implementation of a national system is currently the responsibility of the GRDC-funded Australian National Frost Program (ANFP), led by the University of Adelaide in collaboration with the Department of Agriculture and Food, Western Australia (DAFWA).  

ANFP researchers have spent the past three years applying an identical method to measure frost tolerance in wheat and barley across Australia.

GRDC Frost initiative regional wheat germplasm resistance targets 

Northern region target

Wheat germplasm with floret sterility equivalent or lower than the barley variety Kapturat – defined as 50 per cent or lower floret sterility when the target germplasm is exposed to minus 6°C temperature at head height during the reproductive stage (GS49-69).

Southern and Western region target

Wheat germplasm with floret sterility equivalent or lower than the barley variety Keel – defined as 50 per cent or lower floret sterility when the target germplasm is exposed to minus 3ºC at head height during the reproductive stage (GS49-69).

The program has been a massive undertaking – spanning the three GRDC growing regions and requiring millions of individual measurements in synchronised field trials across Western Australia, South Australia and New South Wales.

Leader of the western region node of the ANFP Dr Ben Biddulph says the similarity between ANFP field trial results to date and grower experiences with some varieties over many seasons of cultivation provides confidence to apply the method to the search for cereal germplasm with higher frost tolerance.

“We can screen germplasm and breeding lines for frost tolerance in different regions and be confident that the results are accurate and comparable. We can also apply the method to the identification of enhanced germplasm with improved tolerance and to develop molecular markers for tolerance and deliver these to breeding companies to support the development of varieties with reduced frost susceptibility.”

Frost alert

Spring frosts have awoken Dr Biddulph before 4am more than 80 times in the past four years, as automatic weather station equipment installed at his western region ANFP node has triggered an alert to his mobile phone whenever canopy temperatures have fallen below 2°C.

The early morning alerts have allowed Dr Biddulph and his research team to tag flowering wheat and barley plants immediately after a frost event and then follow these plants through to assess the level of frost damage.

The tagging system was replicated across all Australian ANFP research sites.

“Following a frost event, we dissect wheat and barley heads within each plot to determine if the plants are at the flowering stage,” Dr Biddulph says.

“If they are flowering we tag a minimum of 30 flowering heads within each plot and inspect these again at mid-grain-fill to quantify the number of sterile florets within each head.”

From this measure of sterile florets the relative frost tolerance of each breeding line and crop variety in the program is determined.

“About 80,000 heads are tagged and nearly three million individual grains assessed for frost-induced sterility each season.”

One of the issues with past frost research was that measurements were taken at different stages of crop development, making it impossible to compare data from different regions and across different events with any degree of confidence.

“Frost tolerance changes throughout the life of a crop, so measuring plants at the same stage of development is critical to achieving comparable results,” Dr Biddulph says.

The current system is accurate across different environments because the measurements and tolerance comparisons are performed at the same developmental stage, regardless of the variety or when it was sown.

Evaluation of lines nearing commercial release

Since 2012, wheat and barley lines entered into the National Variety Trials program are also being evaluated by the ANFP to determine how floret fertility is affected by frost. The program will assess 30 varieties of wheat and 20 varieties of barley each season to generate information on the relative level of sterility of each line over several seasons and frost events and ultimately how these events impact on yield.

Extending frost resistance

Current Australian wheat varieties show no resistance to frost events below minus 4°C, while the frost resistance of the best barley lines evaluated by Australian frost researchers is several degrees lower.

The GRDC frost initiative is looking to provide Australian wheat breeders with germplasm and selection tools to improve the frost resistance of wheat to at least that of current barley benchmarks, (see targets box on page 5) by identifying frost-resistance traits from international germplasm banks.

“There are literally millions of wheat and wheat relatives, including wild relatives, in genetic resource centres around the world and we want to identify whether any of these contain frost-resistance genes that can be deployed in Australian wheat varieties,” Dr Biddulph explains.

The plan is to use special germplasm sets created via the focused identification of germplasm strategy (FIGS) approach, developed at the International Center for Agricultural Research in the Dry Areas, to highlight potential wheat breeding material that has evolved under frost conditions.

“We will be looking for breeding material from environments where wheat is consistently exposed to low temperatures during flowering and plan to bring in about 4000 lines for frost assessment from 2015. This material will be evaluated in frost trials across Australia and compared with regional barley frost-resistance benchmarks to identify wheat lines with resistance that is equivalent or better.”

However, even if the search for wheat germplasm with increased resistance to frost is successful it will take time for new varieties with higher frost tolerance to reach growers’ paddocks.

“It will take many years, even using the fastest tools available, for Australian breeders to insert any frost-resistance genes we do find into Australian varieties,” Dr Biddulph says.

Researchers hope to have identified frost-resistance genes of interest by 2026, at which point they will start to feed these into Australian crop breeding programs (Figure 1).

Predicted timeline for new frost-tolerance genetics to enter wheat and barley breeding programs

Figure 1: Predicted timeline for new frost-tolerance genetics to enter Australian wheat and barley breeding programs.

More information:

Dr Juan Juttner, senior manager discovery, GRDC,
02 6166 4558,

juan.juttner@grdc.com.au

 

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Gene mix and match to lift frost tolerance

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Focus on frost

GRDC Project Code UA00136, CSP00143

Region National, South, West, North