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Molecular cytogenetic characterisation of wheat lines carrying the YrA resistance to stripe rust

Genetic analysis of YrA resistance in Avocet R confirmed two complementary resistance genes. Marker-trait association analysis on a doubled haploid (DH) population derived from Teal/Avocet R mapped one of the genes to chromosome 5BL. A DArT-Seq genetic map for the population indicated the presence of a T5B-7B reciprocal translocation. Fluorescence in situ hybridization (FISH) confirmed the translocation in the susceptible parent Teal relative to Avocet R. Additional FISH examinations on Cappelle Desprez (CD), Chinese Spring (CS) and Avocet S as controls indicated that the translocation in Teal was similar to that in CD. FISH studies also revealed additional polymorphisms in both chromosome 7B arms of Avocet R and Avocet S relative to CS, and that chromosome 5B in Avocet S lacked about 32% of the long arm relative to Avocet R and CS. It was postulated that complementary gene Yr74 was deleted with the missing segment. Australian cultivars Banks, Condor and Egret are also polymorphic for stripe rust response, and intercrosses in earlier studies between the S selections failed to confirm complementary genes. FISH analyses are currently underway to test the hypothesis that the S selections carry the deletion. Results will be reported in the poster.

The University of Sydney, Plant Breeding Institute, Australia
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