Powdery mildew (Pm) caused by Blumeria graminis f.sp. tritici (syn. Erysiphe graminis f. sp. tritici) is an important foliar disease of common wheat (Triticum aestivum L.) worldwide. The extensive cultivation of susceptible wheat varieties over the years combined with favourable environmental factors has favoured Pm and its economic importance has become more evident in recent years in Western Australia (WA). Deployment of resistant genes and gene pyramiding for resistance to Pm is desirable to combat rapid changes in pathogen virulence.
The aim of this research was to find QTL for Pm resistance in two double haploid mapping populations (Machete/Magenta and Calingiri/Wyalkatchem). Each population was phenotyped twice during 2012 to 2015.
Trials were conducted under a controlled environment using a randomised complete block design in duplicate. Pm isolates were collected from various locations across WA and a composite inoculum was used for inoculation. The composite of Pm isolates varied for the two phenotyping assessments. Plants were assessed at head emergence for percentage leaf area diseased on flag leaf and the leaf below. Frequency distribution of individuals within each population for various levels of Pm resistance was continuous and a few lines within each population showed higher levels of resistance than both parents indicating additive gene effects. Correlations between assessments made in different years were low to moderate (r = 0.2 to 0.5) possibly due to different inoculum compositions used in different years.
Genetic and QTL analysis showed loci for Pm resistance on chromosomes 2A and 2B in population Machete/Magenta and on 6B and 6D in population Calingiri/Wyalkatchem.