UMU00038 - Improved Adaptation of Barley to Acid Soils
Soil acidity with high levels of toxic aluminium is the largest (in area) soil constraint limiting sustainable barley production in Australia. Soil acidity impairs the root growth of sensitive crops and hence reduces nutrient acquisition and access to water reserves. As a result, acid soil tolerance is associated with drought tolerance in low-rainfall regions, but is closely associated with waterlogging in the high rainfall regions. Soil acidity is estimated to cost WA grain growers $300 to $400 million annually. Liming has been an important approach to combat acid soils in the past 20 years. Surface liming is costly and is insufficient to decrease acidity in the subsoils because of the slow movement of lime in soil profiles.
Barley has a reputation for a wider adaptation than wheat. However, this is not the case in Australia due to the lack of appropriate variability and breeding selection for abiotic stress tolerance and adaptation. Soil acidity is one of the key limiting factors, with barley much more sensitive to acid soils than wheat. For these reasons, acid soil/Al tolerance was proposed as a genetic solution in combination with lime application and a major breeding target for the BBA-West barley breeding program.
Preliminary results showed that the new acid-soil-tolerant lines out-yield the current malting barley varieties Baudin and Hamelin by more than 20% on acid soils and 30 to 90% on extremely acid soils. National Variety Trial and Agriculture Western Australia Cereal Variety Trials results demonstrated that the area in which barley production is constrained by soil acidity is much bigger than previously suggested, as the new acid-soil-tolerant lines also showed significant yield increases in non-acidic regions. Potential for further improvements in acid-soil tolerance in barley is limited by a lack of germplasm with better or alternative tolerance.
Key issues that must be addressed before developing the next generation of acid-soil-tolerant barley include:
- Barley is very sensitive to acid soils. The current acid-soil-tolerant barley lines are equal to or more sensitive to acid soil conditions than normal wheat and much less tolerant than acid-tolerant wheat.
- There is only one acid-soil-tolerance gene identified in the Australian barley germplasm, although some minor QTLs have been reported.
- There is only one tolerance mechanism identified in barley but at least two mechanisms in other cereal crops.
- Barley is very sensitive to low soil pH and there are no genetic resources identified for tolerance to low pH.
- There is a lack of understanding about the interactions between liming and acid-soil-tolerance genes, although liming has been an important approach to combat acid soils in the past 20 years.
- There is a lack of understanding about the interaction between acid soil and other abiotic stress tolerances, especially acid soil and waterlogging tolerance.
To address the above issues, Murdoch University, Department of Agriculture and Food WA, University of Tasmania and the University of Western Australia formed a consortium to develop a genetic solution for improvement of barley adaptation to acid soils. The consortium includes barley pre-breeders, molecular geneticists, plant physiologists and agronomists.
This project is built on four previous projects:
- Gene interaction of Australian and Chinese barley germplasm for acid soil/Al toxicity tolerance, funded by the Federal Department of Education, Science and Training.
- Bridging the yield gap - Genetic solutions for barley acid soil tolerance, funded by a DAFWA priority funding allocation.
- The past (UT0008) Australia-China barley Germplasm project funded by the GRDC.
- The present (DAW00187) Australia-China barley Germplasm project funded by the GRDC.
Through these projects, more than 300 acid-soil-tolerant barley varieties/lines were introduced from around the world and eight genetic populations have been developed with different sources of acid-soil tolerance.
This genetic material is the key component of this project, which aims to use phenotypic screening, high-throughput molecular marker screening, association mapping and next-generation sequencing techniques to deliver the following outputs.
- Barley germplasm with better acid soil tolerance than current varieties.
- Barley germplasm with different tolerance mechanisms for acid soils including low pH, high aluminium tolerance, seedling and adult plant tolerance and citrate acid and malate acid secretion mechanisms.
- Molecular markers for new genes/QTLs conferring tolerance to low pH and high aluminium toxicity.
- New alleles of the tolerant gene on chromosome 4H.
- Gene-specific molecular markers for acid soil tolerance including malate acid transporter (HvALMT), citrate acid transporter (HvAACT) and other new genes identified in this project.
- Elite barley germplasm with combinations of multiple genes for acid-soil tolerance and acid soil and waterlogging tolerance.
It is anticipated that profitable barley production can be added to the rotation across large areas of WA and in the eastern States through success of this project. The utilisation of acid-soil-tolerant barley in farming systems could improve barley productivity and economic benefit to barley growers. It is estimated that acid-soil-tolerant barley could provide an economic benefit of $30 million annually in WA. The elite barley germplasm and molecular tools developed in this project will improve barley breeding efficiency and accuracy.
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