New Research Reveals Wheat Crop Frost Damage Varies Between Types

Australia ( May 10, 2011

New Research Reveals Wheat Crop Frost Damage Varies Between Types

New Research Reveals Wheat Crop Frost Damage Varies Between Types

Scientists have taken a major step towards helping farmers reducing frost damage to wheat crops around Australia, with new data revealing significant differences in tolerance levels among popular varieties.

Estimated to cost the Australian grains industry more than $360 million a year in lost production and management costs, frost has long been considered one of the toughest nuts to crack for plant breeders.

Conventional wisdom dictated that frost damaged all wheat varieties to the same degree, but that belief has been turned on its head following trials conducted at Loxton, South Australia, over the last three years by the University of Adelaide, and supported by the Grains Research and Development Corporation (GRDC).

It is now clear that different varieties have varying levels of frost tolerance, paving the way for the future development of frost susceptibility ratings to guide farmers’ variety selections, and for plant breeders to confidently select germplasm to breed new lines with improved frost resistance.

“From the results we have now, we’re finding there is a range of susceptibility within the current varieties, which is of commercial importance to farmers and plant breeders alike,” University of Adelaide research scientist Tim March said.

“There are some quite popular varieties which have high levels of susceptibility, but there are also several varieties which show promising levels of tolerance.”

In last year’s trials, the level of frost damage from a single event varied from just one per cent grain loss to a whopping 60pc depending on the wheat variety.

But observing this difference has, until recent years, been constrained by the need to find a “reliable and re-producible” method of measuring the level of frost damage in the field (phenotyping).

Over the last decade at the frost-prone site of Loxton in South Australia, the University of Adelaide team has been trialling a frost damage measurement system suitable for evaluating wheat and barley varieties.

The different varieties were sown at times that would see them all flower during early spring, when frosts commonly do the most damage by sterilising reproductive tissues and killing developing grains.

An automated weather station at the trial site was programmed to deliver an SMS alert to the researchers on the mornings of spring frost events, after which they would immediately visit the site to tag all heads that were flowering on that date.

The researchers would then return to the site several weeks later to collect the heads, and count the number of sterile florets within each head.

Following its early success, the trial was last year expanded to incorporate 33 popular wheat varieties as a step towards benchmarking all wheat varieties for frost susceptibility.

What researchers found were results consistent with the earlier small trials, with a good range of susceptibility between the cultivars.

While the 2010 trials provided the team with greater confidence in their early findings, the trials will be repeated again this year to further substantiate the results.

From the benchmarking data so far, Young and EGA Gregory were found to be quite tolerant, while at the other end of the spectrum Wyalkatchem was very susceptible, suffering significantly higher levels of frost damage than many other varieties over several years of trials.

Wheat varieties generally suffered considerably more damage than barley lines, with seed sterility ranging from 1-60pc compared to 1-35pc damage in barley.

The Loxton trials results are considered a major breakthrough, incorporating data from two separate frost events and more than 85,000 individual florets assessed for frost damage.

However the variable nature of frosts and the possibility of regional differences in variety performance mean some caution should be applied in interpreting the results.

The Loxton trials are associated with a national frost trialling program backed by GRDC and also involving Western Australia’s Department of Agriculture and Food (DAFWA), and Queensland’s Department of Employment, Economic Development and Innovation (DEEDI).

Together they have been testing three wheat and seven barley lines as part of a program aimed at developing methods for frost screening which can be applied across the different states.

And with an automatic weather station at each location, they are also gathering data to improve the understanding of climatic conditions, and the interaction between the environment and the genetic disposition of the varieties.

Dr March said frost caused different levels of damage in different grain-growing regions, and researchers were keen to understand the mechanics of climatic factors such as wind, humidity and temperature in the equation.

What is known is that spring radiation frosts typically occur under conditions of clear skies, calm or little wind, temperature inversion, low dew-point temperatures and air temperatures that typically fall below 0°C during the night but are above 0°C during the day.

These conditions allow rapid radiation of heat to the night sky, as well as a drop in temperature of the soil surface and the air surrounding the crop canopy.

“While the level of damage does vary from frost event to frost event, what we’re finding at Loxton is that the ranking of the genotypes is generally consistent regardless of the frost event,” Mr March said.

The GRDC also presently invests in nine frost pre-breeding projects across Australia with a combined budget of approximately $1.3 million a year. One of those projects involves the University of Adelaide which has begun a genetic mapping project to help wheat researchers better understand the genetic factors at play which determine the wide variation in frost susceptibility exposed by the field trials.

And while that research and the related plant breeding programs represent a long-term project, in the short term Mr March believes the foundation has now been laid for conducting on-going national trials to measure frost susceptibility.

This could result in susceptibility ratings being provided as part of the variety information available to farmers, in the same way that disease ratings are currently available on variety guides.

“Some of these varieties which show a high level of susceptibility are also quite high yielding where environmental conditions are favourable,” Mr March said.

“So it’s about providing farmers with the information so they can manage the risk. The more information they have the better informed decisions they can make.”

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