Investigating successive Australian barley breeding populations for stable resistance to leaf rust
Genome-wide association studies of barley breeding populations identified candidate minor genes for pairing with the adult plant resistance gene Rph20 to provide stable leaf rust resistance across environments.
Stable resistance to barley leaf rust (BLR, caused by Puccinia hordei) was evaluated across environments in barley breeding populations (BPs). To identify genomic regions that can be combined with Rph20 to improve adult plant resistance (APR), two BPs genotyped with the Diversity Arrays Technology genotyping-by-sequencing platform (DArT-seq) were examined for reaction to BLR at both seedling and adult growth stages in Australian environments. An integrated consensus map comprising both first- and second-generation DArT platforms was used to integrate QTL information across two additional BPs, providing a total of four interrelated BPs and 15 phenotypic data sets. This enabled identification of key loci underpinning BLR resistance. The APR gene Rph20 was the only active resistance region consistently detected across BPs. Of the QTL identified, RphQ27 on chromosome 6HL was considered the best candidate for pairing with Rph20. RphQ27 did not align or share proximity with known genes and was detected in three of the four BPs. The combination of RphQ27 and Rph20 was of low frequency in the breeding material; however, strong resistance responses were observed for the lines carrying this pairing. This suggests that the candidate minor gene RphQ27 can interact additively with Rph20 to provide stable resistance to BLR across diverse environments.
KeywordsGenome-wide association studies Hordeum vulgare Puccinia hordei Otth Adult plant resistance Partial resistance Rph20
This research was supported by the Grains Research and Development Corporation of Australia (UQ00056; US00070). The authors give thanks to Ms Julie McKavanagh (DAF), Ms Janet Barsby (DAF), Mr Ryan Fowler (DAF and QAAFI), and Mr Matthew Williams (PBI, University of Sydney) for the technical assistance in the laboratory and field. We would also like to acknowledge statistical support provided by Miss Bethany Macdonald, Mr Eric Dinglasan, and Dr. Kai Voss-Fels.
Author contribution statement
J.D.F., L.T.H., D.R.J., and R.F.P. managed the project; D.R.J., E.S.M., and G.J.P. designed the experiments; J.D.F. provided the plant materials; G.J.P. and D.S. conducted and scored the leaf rust screenings; L.A.Z. and L.T.H. led the data analysis with contributions from E.S.M.; L.A.Z. wrote the manuscript with assistance from all the other authors.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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