Identification of stem rust and leaf rust resistance genes in Amagalon oats

Studies were undertaken to identify the genes conferring stem rust and leaf rust resistances in Amagalon and to determine the usefulness of this line as a source of rust resistance in oat breeding programs. Amagalon was crossed with certain rust-resistant and rust-susceptible lines and segregating populations were tested with pathotypes of Puccinia graminis avenae and P. coronata avenae . Tests with the widely virulent P. graminis avenae pt 94+ Pg-13 indicated that resistance in Amagalon was governed by the complementary recessive gene complex known as Pg-a . This hypothesis was further substantiated by temperature sensitivity tests and by a test of induced susceptibility to stem rust, known to be unique to lines possessing Pg-a . However, Amagalon yielded a unique source of resistance to leaf rust that was effective against current pathotypes of P. coronata avenae in Australia. This gene, assumed to be Pc91 , was inherited independently of a second leaf rust resistance gene present in cv. Culgoa. It was concluded that Amagalon is a useful source of resistance to leaf rust that should be used in combination with other genes for resistance to prolong its effectiveness.