Race-specific resistance and cultivar-specific virulence in the barley-leaf rust pathosystem and their consequences for the breeding of leaf rust resistant barley

Abstract

A range of leaf rust (Puccinia hordei) isolates was tested on a series of barley cultivars among which the differential series. No resistance to all isolates seems to exist in the cultivated barley. The barley cultivars appear to carry zero to two race-specific resistance (Pa) genes. The isolates carry from three to eight virulence factors from the eight or nine that could be evaluated. Isolates with wide virulence spectra were most common. The pattern with virulence to Pa, Pa2, Pa4, Pa5, Pa6, and Pa8, and avirulence to Pa3, Pa7 and Pa9 is very common and seems to have a near-global distribution. These isolates, however are not necessarily identical in genotype.