Position: PhD student
Place of Birth: Australia, Victoria
Scholarships: Australian Postgraduate Award, Grains Research and Development Corporation top up scholarship, Farrer memorial traveling scholarship - 2014/15, Queensland Alliance of Agriculture and Food Innovation (QAAFI) Research higher degree (RHD) travel award - 2016
Advisors: Dr Lee Hickey, Prof. Jerome Frankowiak, Mr Greg Platz, Prof. Robert Park
Leaf rust has been recognised as a significant constraint to barley production in Australia for many years. Recently the first simply inherited gene conferring adult plant resistance to leaf rust was characterised and named; Rph20. This gene contributes resistance to multiple pathotypes and has remained effective against leaf rust for more than 60 years. However, since development of the DNA marker linked to Rph20 and its rapid adoption amongst barley breeders, it is clear that the resistance gene does not confer high levels of resistance when deployed alone. Superior levels of resistance that are stable across environments require the presence of additional ‘minor genes’ or ‘modifiers’.
My project aims to broaden the understanding of the genetic control of adult plant resistance to leaf rust in barley. I will employ a three-pronged approach utilising cutting-edge techniques for dissecting the genetic control of complex traits including; association mapping, selective genotyping and nested association mapping (NAM). I aim to develop molecular markers linked to ‘minor’ genes affecting the expression of Rph20 which will lead to improved efficiency of breeding programs targeting development of resistant cultivars.
Dr Davinder Singh and Laura Ziems performing seedling assessment at the University of Sydney Plant Breeding Institute, Cobbitty, NSW:
Laura Ziems presenting barley leaf rust association mapping work at the Australian Barley Technical Symposium (ABTS) in 2014:
- Identify the ‘minor’ genes influencing expression of Rph20-based resistance in elite breeding material
- Develop useful DNA markers associated with the ‘minor’ genes
- Validate the ‘minor’ gene combinations across diverse environment types and pathotypes of the pathogen
Initial research was performed using elite barley breeding lines representative of the Northern Region Barley Breeding Program (NRBBP) spanning a four year period. These populations were evaluated for resistance to leaf rust at both seedling and adult growth stages. Association mapping was used to map quantitative trait loci (QTL) conferring resistance to leaf rust. Markers and their associated sequences identified across studies will be presented; these are useful tools for pyramiding QTL combinations involving Rph20, to deploy stable resistance to leaf rust in improved barley cultivars.
In the 2011 Hickey et al. study, a potential barley leaf rust adult plant resistance (APR) gene; qRphND, was detected. This QTL was considered promising as when coupled with the known APR gene Rph20, provided stable resistance across environments. The donor of the gene has been crossed to a susceptible standard and an F2:3 population developed to observe segregation patterns in a susceptible background. Selective genotyping was performed at the F2 stage, this involves genotyping individuals that display the most extreme phenotypes, i.e. strongly resistant vs strongly susceptible to detect DNA markers linked to a trait of interest. The selective genotyping paired with segregation patterns should provide information necessary to characterise and designate the gene.
Development of the NAM population is in its final stages. Three barley cultivars preferred for malting and widely grown throughout each of the three mega growing regions of Australia were selected as ‘reference varieties’ and lines that displayed superior phenotypes for APR from the NRBBP were selected as ‘donors’. The F4 plants were genotyped using DArT-seq markers and F4:5 lines sown in five leaf rust nurseries in 2016 (Toowoomba, Gatton, Cobbitty, Horsham and Uruguay). This population will provide a diverse range of leaf rust resistance as no selection pressure was applied throughout line development and will therefore be ideal for examining the gene interactions and genetic background effects for minor APR genes.
Using these three different, but complementary, mapping approaches will provide a thorough dissection of ‘minor’ genes interacting with Rph20.
Ziems, L. A., Hickey, L. T., Hunt, C. H., Mace, E. S., Platz, G. J., Franckowiak, J. D. and Jordan, D. R. (2014) Association mapping of resistance to Puccinia hordei in Australian barley breeding germplasm. Theoretical and Applied Genetics, 127 5: 1199-1212. doi:10.1007/s00122-014-2291-1
Riaz A, Hathorn A, Dinglasan E, Ziems LA, Richard CAI, Singh D, Mitrofanova O, Afanasenko O, Aitken E, Godwin I, Hickey LT (Accepted) Into the vault of the Vavilov wheats: old diversity for new alleles. (Genetic Resources and Crop Evolution 2016)
Ziems LA, Robinson HM, Richard CAI, Franckowiak JD, Platz GJ, Williams R, Park RF, Singh D, Hickey LT (2015) A powerful genetics platform to dissect complex traits in Australian barley, paper presented to the Australian Barley Technical Symposium, Manly, NSW, Australia, 14 – 16 September 2015.
Park RF, Derevnina L, Dracatos P, Elmansour H, Hickey LT, Sandhu K, Ziems LA, SinghD (2015) Rust Resistance in Barley, paper presented to the Australian Barley Technical Symposium, Manly, NSW, Australia, 14 – 16 September 2015.
Ziems LA, Robinson HM, Richard CAI, Franckowiak JD, Platz GJ, Williams R, Park RF, Singh D, Hickey LT (2015) A powerful genetics platform to dissect complex traits in Australian barley, paper presented to the 12th International Barley Genetics Symposium, Minneaplois, Minnesota, United States, 26 – 30 June 2016.
Ziems LA, R Park, Mace ES, Platz GJ, Franckowiak JD, Singh D, Jordan DR, Hickey LT (In Preparation) Minor genes stabilise Rph20 expression to achieve high levels of barley leaf rust resistance consistent across pathotypes and environments. (To be submitted to Theor Appl Genet
Ziems LA, Hickey LT, Platz GJ, Franckowiak JD, Dracatos PM, Singh D, Park RF (In Preparation) Characterisation of Rph24: gene conferring adult plant resistance to Puccinia hordei in barley. (To be submitted to Molecular Breeding)