Issues facing growers
The discovery of late maturity alpha-amylase in the early 1990s changed the way poor starch viscosity in wheat was viewed, which until then had been attributed to pre-harvest sprouting or poor starch properties. LMA is an enzyme which can degrade grain starch measured by falling number tests at delivery.
LMA is a genetic defect in some wheat varieties and can be triggered by cool temperatures in the middle stages; unlike sprouting triggered by rain at harvest which can result in LMA production.
Unlike sprouting though, there is no evidence of the defect on the grain and so LMA has been difficult to screen for and eliminate.
Managing and eliminating LMA have been high priorities for wheat breeders and the wheat industry. Levels of LMA in wheat varieties vary from high, medium, and low to zero.
By 2004, research funded by the Grains Research and Development Corporation established about 20 per cent of then current varieties and advanced breeding lines were susceptible to LMA.
Doctors Daryl Mares and Kolumbina Mrva of the University of Adelaide identified several genetic loci that control LMA whose molecular markers are being fine-mapped.
Local researchers and UA pre-breeders worked on a GRDC-funded project to develop molecular marker tools to reduce the time it takes to identify wheat lines at low risk of LMA and with enhanced resistance to sprouting and black point.
A GRDC-funded Grains Industry Research Scholarship was also undertaken at UA to provide understanding about how and why the cool temperature shock can produce this undesirable effect on wheat quality.
Results showed cool temperature shock increases sensitivity of the grain to a plant hormone normally present in grains of varieties prone to LMA which in turn lead to changes within the grain resulting in a low falling number.
A 2010-2014 GRDC-funded project through the South Australian Research and Development Institute (SARDI) has been undertaken to establish and provide LMA test kits to scientists and wheat breeders.
In 2013-14, the GRDC licensed the right to use technology for detection of LMA in wheat to UA, with a sub-licence provided to SARDI to produce, maintain, store and distribute antibodies to UA and to Australian breeders to test for LMA. The GRDC sub-licensed UA to provide LMA screening on a cost-recovery basis until June 30, 2018.
In order to assess the risk of LMA occurring in the field in current wheat varieties in different regions, Australia’s wheat breeders are cooperatively running a 20 site by 24 varieties trial spread around the country. GRDC is supporting a survey of varieties across all main season sites in the National Varieties Trials, and LMA testing for both sets of trials.
This will provide evidence on the risk of LMA occurring in a range of environments and identify locations where it poses most risk for which varieties.
As a result of GRDC’s commitment wheat breeders are being equipped with a new understanding about LMA and new tools to assist the development of varieties less likely to be downgraded at harvest due to grain defects.
Research funded by the GRDC has produced new germplasm, screening methods and selection tools to speed up the production of varieties less susceptible to LMA.
LMA test kits (or component reagents) are being made available to scientists and wheat breeding programs in Australia.
The results of the grain defects research are expected to reduce the incidence and severity of defects at harvest, with better varieties becoming available to growers. This will lead to reduced risk and increased or more reliable returns for growers, and flow-on benefits for the marketing of Australian wheat.
GRDC-funded research projects will continue pre-breeding research into grain defects.