Accumulation of partial resistance in barley to barley leaf rust and powdery mildew through recurrent selection against susceptibility

Abstract

Two spring barley composites, one based on eight West-European two-rowed cultivars (A) and the other, the predominantly six-rowed composite XXI, based on several thousands of barley cultivars (B), formed the starting point of a recurrent selection procedure. The aim was to study how effective a repeated process of mild selection against susceptibility followed by recombination of the remaining material was in accumulating partial resistance in four host-pathogen situations. i) Only partial resistance is present and the pathogen population is defined (a given race). ii) Partial and major gene resistance both occur and the pathogen population is defined. iii) Only partial resistance is present and the pathogen population is not defined; a mixture of races that varies over the years. iv) Partial and major gene resistance are both present and the pathogen population is not defined.