Analysis of a doubled haploid barley population for resistance to powdery mildew

Analysis of the population structure of Erysiphe graminis f.sp. hordei in Ontario revealed virulence to ten race-specific genes (Mla1, Mla3, Mla8, Mlc, Mlg, Mlh, Mlk, Mlp, MlRu2 and Mlnn). In the laboratory, the presence of race-specific genes was determined in parental lines Harrington (Mlg+MlCP) and TR306 (MlTR) with single-spore isolates on seedlings. Mlg+MlCP and MlTR segregated independently in 150 doubled haploid lines and formed four race-specific Groups. Group 1 (Mlg+MlCP+MlTR) and Group 4 (no race-specific genes) were transgressive segregates from the parents: Harrington = Mlg+MlCP and TR306 = MlTR.;In the field, the severity of mildew in hill-plots was scored three times and AUDPC (area under the disease progress curve) calculated. A level of partial resistance was estimated in Group 4 and it accounted for a 14.1% decrease in the leaf area infected.;Air-brush applications of inoculum suspended in fluorinert on seedlings revealed the highest significant regression of AUDPC with Modified Infection Frequency (MIF) in Group 4 (r...