Cytogenetic studies in wheat XIX. Chromosome location and linkage studies of a gene for leaf rust resistance in the Australian cultivar 'Harrier'

Monosomic analysis indicated that a seedling leaf rust resistance gene pres ent in the Australian wheat cultivar 'Harrier' (tentatively designated LrH) is located on chromosome 2A. LrH segregated independently of the stripe ru st resistance gene Yr1 located in the long arm of that chromosome, but fail ed to recombine with Lr17 located in the short arm. LIN was therefore desig nated Lr17b and the allele formerly known as Lr17 was redesignated as Lr17a . The genes Lr17b and Lr37 showed close repulsion linkage. Tests of allelis m indicated that Lr17b is also present in the English wheats 'Dwarf A' ('Ho bbit Sib'), 'Maris Fundin' and 'Norman'. Virulence for Lr17b occurs in Aust ralia, and pathogenicity studies have also demonstrated virulence in many w estern European isolates of the leaf rust pathogen. Despite this, it is pos sible that the gene may be of value in some regions if used in combination with other leaf rust resistance genes.