Frost tolerance search a 'numbers game'

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Dr Tim March surrounded by frost trial plots at the new five-hectare frost nursery at Loxton, South Australia, during the Mallee Sustainable Farming Field Day.

PHOTO: Clarisa Collis

In the ‘numbers game’ of pre-breeding research, new genetic diversity drawn from frost-prone regions around the world has exponentially increased the odds of identifying frost-tolerant wheat lines for delivery to Australian plant breeding companies and, ultimately, grain growers across the country.

Highlighting the importance of this research effort through the GRDC’s $4 million National Frost Initiative (NFI) is the conservative estimate that frost causes $40 million in Australian crop losses a year. A toll expected to rise since historical data shows the frost risk window is widening and frost severity is increasing.

To date, the collaborative research by the University of Adelaide and the Western Australian Department of Primary Industries and Regional Development (DPIRD) has been examining the genetic potential of about 1000 wheat accessions a year, sourced from a spread of countries, particularly in the Mediterranean region, North Africa and the Middle East.

New southern frost nursery

Overseeing the frost nursery established at Loxton, South Australia, in 2016, the University of Adelaide’s Dr Tim March says the new on-farm site – a collaborative farming operation owned by John Gladigau and Robin Schaefer – has helped link frost research findings to local farming systems.

“Our research at the Loxton trial site is better connected to on-farm conditions and has more relevance to growers,” Dr March says. “Hopefully this means more useful research outcomes at a farming level, in terms of varietal options to help minimise frost damage, will lead to increased cropping profitability for growers.”

The five-hectare site at Bulla Burra, three hectares larger than the previous site at the South Australian Research and Development Institute (SARDI) Loxton Research Centre, has also expanded the scope of research exploring the frost susceptibility of wheat and barley across more than 1000 trial plots.

“Plant breeding is a ‘numbers game’, so the larger nursery site means we can test more genetic material, improving our chances of finding frost-tolerant germplasm,” he says.

The leader of the five-year project, University of Adelaide research fellow Dr Tim March, says that of these 1000 wheat lines, each of which is imported to Australia as a single wheat plant to provide seed for multiplication, roughly half – about 500 lines – are selected to optimise the mix of genetic diversity in field trials at frost nurseries across the country.

From these 500 lines, the research team selects just 50 lines a year for ongoing testing based on their regionally specific performance at three frost nurseries representing the southern, western and northern grains regions, at Loxton in South Australia, Dale in WA and Narrabri in NSW.

“Wheat lines from frost-prone regions around the world were selected from international genebanks using a Focused Identification of Germplasm Strategy (FIGS) set up by the University of Western Australia’s Dr Ken Street,” Dr March says. “The theory is that wheat from these regions may have evolved frost tolerance.

“In total, about 3000 wheat lines are being imported into Australia for frost-tolerance evaluation over several years, and if lines showing frost tolerance are identified, they will be introduced to wheat pre-breeding and breeding programs for introgression into Australian cultivars.”

To this end, the research team has been analysing the genetic potential of wheat lines planted at five different sowing times – from 19 April to 22 May – mainly because frost damage during the crop’s reproductive developmental stages, especially post-head-emergence frost (PHEF), generally causes the most severe yield losses. A single frost event damaging stems and killing whole heads can destroy an entire crop.

Breeding for improved PHEF tolerance could help rescue yields in two ways – by decreasing frost damage and by facilitating early sowing to reduce additional crop losses resulting from heat stress and drought late in the growing season.

Speaking at a Mallee Sustainable Farming (MSF) field day, surrounded by trial plots crowded with exotic wheats at the Loxton frost nursery, Dr March said: “Current wheat varieties have a relatively narrow genetic base, but the large number of landraces and varieties from international collections have the potential to reduce frost susceptibility, particularly at reproductive growth stages.

“We don’t expect to discover a line that is completely frost tolerant, but we hope the diversity of crop morphology or plant structure shown in these trials might provide incremental gains in wheat productivity and profitability.”

Another statistical component of the Screening of Frost Tolerance in Cereals project, run through the GRDC-funded Statistics for the Australian Grains Industry (SAGI), has seen researchers rank the frost susceptibility of 73 commercial wheat varieties and 36 barley varieties, based on floret sterility following frost events at the three frost nurseries.

“The floret sterility data is used to generate values for a Frost Value-Plus (FV-Plus) ranking system, which is published on the National Variety Trials (NVT) website and allows growers to compare the relative frost risk of different varieties across different sites and years,” Dr March says.

“However, the frost ranking system is not a tool for selecting varieties. Best practice is for growers to use NVT data to select varieties suited to their region, and this can be overlaid with FV-Plus values to help growers assess seasonal risk and fine-tune their frost management strategies.”

GRDC Research Code UA00162

More information:

Tim March
08 8313 6700
timothy.march@adelaide.edu.au

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