Drought is a major cause of decreased crop production worldwide. In Australian dryland agriculture, grain crop yields are approximately 50% of their potential and are highly unpredictable. The 2006 drought reduced the total Australian wheat yield by 46% (FAO, 2013).
Drought tolerance in cereals is a priority trait considering predicted increases in world population and the accompanying demand for land, food and water. Highly fertile soils will be increasingly occupied by urban areas and agriculture will be marginalized in less favourable environments. Due to the increasing occurrence of heat and drought events particularly in Mediterranean region, the USA, India and Australia, yield improvement under abiotic stress is a major challenge.
Plant tolerance to drought is the ability of a plant to grow and yield under water limited conditions. Yield in low rainfall environments is a complex trait under multigenic control and highly influenced by genotype x environment interactions and plant phenology. Breeding is further complicated since several types of abiotic stress, such as high temperatures, high irradiance and nutrient toxicities or deficiencies can challenge crop plants simultaneously.
The task is particularly challenging in wheat and barley because of the size and complexity of their genomes. However, there is still an opportunity for significant genetic gain using recent technological advances in genomics and genetics.
Our aim is to improve the drought tolerance of wheat and barley varieties by discovering and using new genes and alleles. The aim is not to ‘convert wheat to a cactus’ but to allow wheat and barley to continue to grow and yield grain under water-limited conditions.
We tackle the problem in a multi-disciplinary approach, considering interaction between multiple stresses and plant phenology, and integrating the physiological dissection of drought tolerance traits and genetic and genomics tools. Physiological analysis, population development and phenotyping and the various ‘omics technologies are integrated to support a gene discovery path. Gene functions are then studied and validated using our GM and genome editing platform and our PC2 phenotyping facility.
Australian Grain Technology (South Australia), Barley Program of University of Adelaide (South Australia), InterGrain (Western Australia), INRA Clermont-Ferrand (France), INRA Montpellier (France), John Innes Centre (UK), Kansas University, Longreach (South Australia), University of Minnesota (USA), University of Murdoch (Western Australia), University of Saskatchewan (Canada), University of Tuscia (Italy).
ARC Industrial Transformation Research Hub for genetic diversity and molecular breeding for wheat in a hot and dry climate (IH130200027) (from 2015-2020).
Premier’s Research and Industry Fund’s International Research Grant Program on a molecular diversity drive for precision-engineered wheat (IRGP15), with University of Saskatchewan (Canada) and University of Tuscia (Italy) (2014-2017).
Grain Research and Development Corporation project (UMU00037) on physical mapping of wheat chromosome 7A (since 2011).
Partner on the DROPS European FP7 project on drought-tolerant yielding plants (2009-2015).
ARC International Science Linkage Project linked to EU-FP7 project DROPS: DROught-tolerant yielding PlantS (2009-2015).
Forward genetics programme:
from phenotype to gene
Since 2003, we have intensively studied biparental populations to identify quantitative trait loci (QTL) for drought tolerance. Elite germplasm adapted to the Australian environment were used as parental lines for constructing bi-parental mapping populations. We extensively described morpho-physiological and molecular mechanisms of tolerance in the parents using a semi-controlled phenotyping platform, The Plant Accelerator, and using transcriptomics and metabolomics. This information is used to develop models for QTL analysis and positional cloning by providing functional data to select candidate genes for QTL. We also use data from the International Wheat Genome Sequencing Consortium and the International Barley genome Sequencing Consortium, and whole genome sequencing of our parental lines to fine map QTL and identify candidate genes.
Besides the positional cloning of yield QTL, our research programme now focuses on genetic diversity. New QTL are being identified in wheat using genome wide association mapping in a worldwide diversity panel. We are also developing a large nested association mapping populations using two modern wheat lines (Gladius and Scout) and 76 donor lines with diverse phenotypes for drought and heat tolerance, and broad genetic diversity.
Reverse genetics programme: from gene to phenotype
We investigate classes of genes of known molecular function and determine individually their effect on various drought-related phenotypes. This approach termed “reverse genetics” incorporates recent advances in recombinant DNA technologies and transgenesis. Transgenic plants are assayed under controlled and field conditions for drought tolerance.
Constitutive overexpression of some genes in the drought-responsive network results in unwanted pleiotropic side effects such as delayed development (Morran et al., 2010). To minimize such effects, gene expression in planta has been tailored to overexpress upon drought stress (stress inducible Rab17 promoter).
Parent B, Shahinnia F, Maphosa L, Berger B, Rabie H, Chalmers K, Kovalchuk A, Langridge P, Fleury D. 2015. Combining field performance with controlled environment plant imaging to identify the genetic control of growth and transpiration underlying yield response to water deficit stress in wheat. Journal of Experimental Botany (doi:10.1093/jxb/erv320).
Maphosa L, Langridge P, Taylor H, Parent B, Emebiri LC, Kuchel H, Reynolds MP, Chalmers KJ, Okada A, Edwards J, Mather DE. 2014. Genetic control of grain yield and grain physical characteristics in a bread wheat population grown under a range of environmental conditions. Theoretical and Applied Genetics 127, 1607-1624.
Bonneau J, Taylor J, Parent B, Bennett D, Reynolds M, Feuillet C, Langridge P, Mather D. 2013. Multi-environment analysis and improved mapping of a yield-related QTL on chromosome 3B of wheat. Theoretical and Applied Genetics 126, 747-761.
Bennett D, Izanloo A, Reynolds M, Kuchel H, Langridge P, Schnurbusch T. 2012. Genetic dissection of grain yield and physical grain quality in bread wheat (Triticum aestivum L.) under water-limited environments. Theoretical and Applied Genetics 125, 255-271.
Edwards D, Wilcox S, Barrero RA, Fleury D, Cavanagh CR, Forrest KL, Hayden MJ, Moolhuijzen P, Gagnère GK, Bellgard MI, Lorenc MT, Shang CA, Baumann U, Taylor JM, Morell MK, Langridge P, Appels R, Fitzgerald A. 2012. Bread matters: A national initiative to profile the genetic diversity of Australian wheat. Plant Biotechnology Journal 10:703-708.
Fleury D, Jefferies S, Kuchel H, Langridge P. 2010. Genetic and genomic tools to improve drought tolerance in wheat. Journal of Experimental Botany 61, 3211-3222.
Shinozaki K and Yamaguchi-Shinozaki K. Gene networks involved in drought stress response and tolerance J. Exp. Bot. 2007 58:221-7.
Lopato, S., Bazanova, N., Morran, S., Milligan, A. S., Shirley, N. and Langridge, P. (2006) Isolation of plant transcription factors using a modified yeast one-hybrid system. Plant Methods 2:3-17.
Morran S, Eini O, Pyvovarenko T, Parent B, Singh R, Ismagul A, Eliby S, Shirley N, Langridge P, Lopato S. Improvement of stress tolerance of wheat and barley by modulation of expression of DREB/CBF factors Plant Biotechnol J. 2010 doi:10.1111/j.1467-7652.2010.00547.x