Researcher on the hunt for phosphorus-efficient wheat

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Photo of Dr Manny Delhaize, a CSIRO Agriculture research scientist

Dr Manny Delhaize from CSIRO is running trials with experimental
wheat lines to determine the difference in the plants’ ability to extract phosphorus from the soil.

PHOTO: Sarah Clarry

Key points

  • Experimental wheat lines developed that maintain root hairs on acid soils
  • Keeping root hairs intact will ensure that wheat is able to take up phosphorus fertiliser efficiently
  • More efficient uptake of phosphorus by wheat cultivars will reduce fertiliser input costs

Dr Manny Delhaize, a research scientist with CSIRO Agriculture, is unlocking the mystery of how wheat grows in acid soils by looking at what happens in the rhizosheath – or the soil surrounding a plant’s roots. Recently his investigations have expanded to include cultivars that are more efficient at exploring soils for phosphorus.

Photo of experimental wheat line with large rhizosheaths grown on acid soil

Figure 1 Experimental wheat lines with large (above)
and small (below) rhizosheaths grown on acid soil.

SOURCE: Dr Manny Helhaize, CSIRO Agriculture

The catalyst for Dr Delhaize’s current GRDC-supported research occurred back in 2004. After years of research with his colleague Dr Peter Ryan which sought to understand how particular wheat cultivars tolerate aluminium, they had a breakthrough with Japanese collaborators that led to the discovery of the major gene that confers aluminium tolerance.

The researchers went on to identify Brazilian wheat cultivars that have aluminium-tolerant root hairs and are efficient at taking up phosphorus from acid soil.

To explore this further, the research moved away from roots and focused on the soil surrounding the roots, known as the rhizosheath (Figure 1, right).

“We used the weight of the rhizosheath as a surrogate to measure root hair length,” he says. “It enabled us to screen and develop experimental wheat lines that were genetically the same but differed only in root hairs when grown on acid soils: short versus long.”

According to Dr Delhaize, the wheat lines with longer root hairs were more efficient in taking up phosphorus in glasshouse trials using acid soils, but the lines needed to be assessed in the field. The most promising field trials were run on some of WA’s sandy acid soils, where phosphorus is more mobile and coincides with where the aluminium toxicity occurs.

Using the single nucleotide polymorphism (SNP) chip genotyping service at La Trobe University, Dr Delhaize found five genetic regions, known as quantitative trait loci, which seem to work together to control the trait for long root hairs in wheat grown on acid soil.

Photo of experimental wheat line with small rhizosheaths grown on acid soil

The SNPs in the genetic regions are being converted into markers that can be used to track the trait in breeding programs.

Dr Delhaize says the trait is being introduced into wheat cultivars, including Mace, Yitpi and Beckom, to develop additional experimental lines and assess the ability of the long root hairs to improve phosphorus use efficiency.

All of these varieties contain the major gene for aluminium tolerance that allows roots to grow effectively on acid soils and it is hoped the aluminium-tolerant root hairs will provide an additional benefit.

Working in collaboration with Perth-based CSIRO Agriculture research scientist Adjunct Professor Jairo Palta, Dr Delhaize says the research group is running further trials with the original experimental lines at Merredin in WA and Tarcutta in New South Wales.

“We want to validate the value of this germplasm in various genetic backgrounds to ultimately convince plant breeders to include the trait in the development of new cultivars that are more efficient in exploring the soil in search of phosphorus,” Dr Delhaize says.

More information:

Dr Manny Delhaize,
02 6246 5047,

manny.delhaize@csiro.au

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GRDC Project Code CSP00165, CFF00009

Region Overseas, South, West