Seedling and adult plant resistance to powdery mildew in common wheat cultivars and lines

Powdery mildew caused by Blumeria graminis f. sp. tritici is an important disease of wheat throughout the world, especially in areas with maritime and semi-continental climates. In Bulgaria, losses in grain yield due to powdery mildew range from 10 to 30%, and sometimes-higher percentages depending on the resistance of the variety and the degree of attack. Utilization of resistant cultivars is the most effective and environmentally safe means of controlling powdery mildew. The objectives of our study were: (1) identify the resistance of breeding lines, introduced and Bulgarian wheat varieties to a set of isolates; (2) identify age resistance in these cultivars based on field trials. Of the 69 wheat cultivars and lines tested, 42 were susceptible to all isolates. 27 wheat lines and cultivars were found to contain at least one or more resistance genes. The most frequently tested lines and cultivars responded with a persistent response to isolates with marked avirulence with respect to genes Pm 4a and Pm 4b, followed by Pm 8 and Pm 2. Out of 42 selection lines and cultivars showed susceptibility to all isolates on B. graminis. f. sp. tritici in the young phase, 29 respond with a sustained response under field conditions.