Transgressive segregation for enhanced level of adult plant resistance to mildew in the oat cross Mostyn x Maldwyn

Abstract

In the cross Mostyn x (Mostyn x Maldwyn), 87 F6 lines with relatively high levels of adult resistance resulting from selection in previous generations, were field tested for severity to mildew infection in 1980. Of the 74 lines which proved to be homozygous regarding the Mostyn gene (AA or aa), 16 (including three lacking the Mostyn major gene-aa) proved to have significantly lower percentage leaf area infected than the most resistant parent at growth stages ranging from late ‘boot’ to ‘early milk’ ripeness of the grain. Some lines showed 10–15% less mildew than the adult plant resistant parent Maldwyn. There was some evidence to suggest that the presence of the now ‘overcome’ and ineffective major gene in Mostyn may have enhanced the level of partial resistance in this cross even in the presence of the corresponding virulence.