Wheat powdery mildew is a fungal disease caused by Blumeria graminis f. sp. tritici. The disease can be responsible for yield losses up to 25% in Australia. In Western Australia, it has re-emerged as a disease of importance in recent wheat cropping seasons.
The epidemiology of the polycyclic biotrophic disease suggests a high likelihood of significant diversity within the population throughout wheat growing areas of Western Australia (WA). Light air-borne spores, produced prolifically, are easily transported large distances. There are numerous selection factors that can impact genetic diversity within mildew populations including environmental conditions such as temperature, resistance genes deployed in wheat varieties grown and fungicide use or over-use.
Little is known about the diversity of powdery mildew pathotypes in WA. This information is important in the development of wheat lines with effective, enduring resistance and for management strategies of existing commercial varieties.
Recent work undertaken by Golzar et al. (2016) tested a combined mixture of numerous WA pathotypes against a differential set of wheat lines with a suite of resistance genes. The genes Pm2, 3a, 3e, 4a, 13 and 27 were found to be effective in Western Australia through screening plant response at seedling and adult plant growth stage. In our current study, the same suite of differential wheat lines and a sub-set of popular commercially grown wheat varieties are being screened at seedling growth stage against individual isolates with a goal to determine any regional diversity in virulence. In 2016, 15 powdery mildew isolates were collected from locations spanning the WA wheatbelt. Initial testing has confirmed previously identified effective resistance genes, though has not highlighted the expected regional population diversity. This may be due in no small way to the dominance of the susceptible wheat variety “Mace”, which is >60% of all wheat area planted in WA.