The University of Sydney, Plant Breeding Institute, Australia
Vivi Arief, Hanif Miah, Ian H DeLacy, and Harbans S Bariana
Association mapping detects correlations between genotypes and phenotypes in a sample of individuals based on the linkage disequilibrium and can be used to uncover new genetic variation among germplasm collections. Two hundred and five landraces collected by the English botanist A. Watkins in the 1920s were screened for rust response variation under field conditions during three crop seasons. An integrated map of 350 polymorphic DArT markers was developed. Association mapping identified the involvement of several genomic regions in controlling resistance to three rust diseases. Seven, eight and nine genomic regions, respectively, appeared to carry yet uncharacterized leaf rust, stripe rust and stem rust resistance. Three dimensional analyses indicated genetic association of leaf rust and stripe rust resistance in some accessions, whereas no such association was observed between stem rust resistance and resistance to either of the other two rust diseases. A new stripe rust resistance locus, Yr47, has been named.
Department of Plant Sciences, University of California-Davis, USA
M. Rouse, Z. Abate, Y. Jin, and J. Dubcovsky
With the TTKS family of races virulent on most genes currently providing protection against stem rust worldwide, identifying, mapping, and deploying resistance genes effective against these races has become critical. We present here a genetic map of Sr35. Both parents of our diploid mapping population (DV92/G3116, 142 SSD lines) are resistant to TTKSK, but the population segregates for resistance to TRTTF (Yemen) and RKQQC (US). Race analysis suggests that G3116 carries Sr21 and DV92 both Sr21 and Sr35. Resistance to TRTTF and RKQQC was mapped to a 6 cM interval on chromosome 3AmL between markers BF483299 and CJ656351. This interval corresponds to a 178-kb region in Brachypodium which contains only 16 annotated genes and exhibits a small inversion (including 2 genes) and a putative insertion (2 genes) relative to rice and sorghum. This map contains closely-linked markers to Sr35 and provides the initial step for this gene's positional cloning.