Revealing the basis for head-loss in barley (UA721)
START
July 1, 2021
FINISH
November 30, 2022
Summary
Barley head loss prior to harvest causes significant yield loss in some cultivars and environments. This project trialled plant growth regulators (PGRs) and imaging tools to better understand changes in stem traits and in-season strategies to manage the problem. Trials at Tarlee and Millicent showed that PGRs effectively reduced head loss and improved stem strength in susceptible cultivars, though outcomes varied by environment. X-ray computed tomography (CT) scanning showed potential for future phenotyping inner features of barley stems. For growers, careful selection of cultivars and targeted PGR use can reduce yield loss risk, particularly in high wind-prone areas. The research also identified stem traits that could support breeding of more resilient barley varieties.
Background
Head loss in barley can lead to substantial grain yield losses in certain seasons and environments. Previous SAGIT-funded project UA619 developed a delayed harvest method for evaluating head loss susceptibility and indicated plant growth regulators may improve head retention. Further field testing was needed to confirm this under different seasonal conditions and environments. In addition, identifying reliable screening methods, including high throughput imaging technology, could help breeders select more resilient barley cultivars.
Research Aims
The core objectives of the project were to:
- Run one year of field trials at two sites (Tarlee and Millicent) to assess the impact of timing of growth regulator application on stem composition and head retention in barley.
- Assess whether changes in barley stem composition that enhance head retention (found in UA619), could be replicated in a third season.
- Address the suitability of the Australian Plant Phenomics Facility’s mobile FieldExplorer platform as a screening tool for head retention in barley.
In The Field
Field trials were conducted at Tarlee and Millicent using five barley cultivars – Compass, Schooner, RGT Planet, Spartacus CL, and Laperouse – with different head-loss risk profiles. Treatments involved PGR (Moddus Evo) application at different growth stages – GS31, GS37, or GS39.
Plant height and peduncle length were measured at harvest ripeness, and head retention was visually assessed at weekly intervals after physiological maturity. Structural issues such as lodging and brackling affected interpretation of head-loss results, especially at Millicent.
Hyperspectral data was collected at Tarlee with FieldExplorer to assess the spectral separability of heads versus leaves, aiming to automate in-season head counts and head-loss assessments in future research. This was tested on the Spartacus CL cultivar.
Results
PGR application effectively reduced plant height and altered peduncle length, depending on cultivar and application timing.
At Tarlee, PGRs at GS37 were cost-effective for Compass and Schooner, reducing head loss without compromising yield. X-ray scans of treated and untreated peduncles showed accumulation of electron-dense material in peduncles of treated Compass plants, suggesting a structural mechanism for improved head retention.
At Millicent, brackling and lodging reduced the visibility of head loss, complicating analysis. Some PGR strategies (e.g. GS31) led to more exposed heads, increasing susceptibility to wind damage.
Hyperspectral imaging in-field was partially successful: Spartacus CL heads could be spectrally distinguished from leaves with more than 80 per cent accuracy at physiological maturity. However, issues such as lodging and sensor angle limited broader application.
Project Participants
The University of Adelaide: Prof Matthew Tucker, Dr Ghazwan Karem
SARDI: A/Prof Rhiannon Schilling, Melissa McCallum, Brendan Kupke, Dr Kenton Porker
Australian Plant Phenomics Facility: Dr Darren Plett, Dr Kenneth Clarke, Dr Andrew Hennesey
The Problem
Barley cultivars suffer from head loss prior to harvest, potentially leading to significant yield loss, especially under high wind or delayed harvest.
The research
This project tested plant growth regulator strategies and assessed stem traits and spectral tools to better understand and manage barley head loss in South Australia.
More information
Matthew Tucker, The University of Adelaide
T: 08 8313 9241
E: [email protected]
Value for Growers
This research confirmed that PGRs can improve head retention in susceptible barley cultivars like Compass and Schooner, when applied at GS31 or GS37. A detailed dataset of 8 trials over 3 years and multiple SA environments has now been collected.
PGR effectiveness varies by environment. In high-risk zones like the Mid North, PGR use can be cost-effective and help mitigate losses, but in the South-East, structural issues like brackling may limit benefits since they appeared to be insensitive to the tested PGR regimes.
X-ray imaging holds promise for rapid stem phenotyping, but field conditions and cultivar structure must be considered in future research. Ultimately, matching cultivar choice and management strategy to site conditions is essential to reduce yield loss from head shedding.
The project outcomes were communicated at several field days, GRDC updates, SAGIT podcast, and ABC Radio Country Hour.
The work will be continued in new SAGIT project UAD3223 “Screening for genetic components of head-retention in barley”.
