Virulence Structure of the Powdery Mildew (Blumeria graminis) Population Occurring on Triticale (x Triticosecale) in Poland

Powdery mildew, caused by B lumeria graminis is an important disease of cereals in many production regions. Until end of the last century triticale had been regarded as a species characterized by high level of resistance for this disease. However, after several years of intensive production on a big area in P oland, G ermany and other E uropean countries it start to be susceptible for many pathogens including B . graminis . Because of this, virulence structure of this pathogen population on triticale in P oland was evaluated across 2008–2010. Leaf samples with symptoms of the powdery mildew disease were collected randomly from nineteen localities. As a total, 1402 B . graminis isolates were collected: 23–25 isolates per locality in each year. Standard differential set of 28 genotypes was used: twenty‐one wheat with known resistance genes and seven triticale. Based on the obtained results it was possible to observe significant differences in virulence structure between years and localities. No virulence's against P m21 ( Y angmai5), and P m3d + 4b ( K adett) were found in any year. All tested isolates were virulent on M oreno and L amberto cultivars. In a total, 36% of tested isolates possessed 9, 11 or 12 virulence's per genotypes. Twenty five percent of tested isolates were virulent to 5 triticale cultivars. Correlation between pathotypes frequency and sampling region were not found what suggest that local epidemics play the most important role in triticale growing regions in P oland.