Characterization of new sources of resistance to Uromyces viciae-fabae in a germplasm collection of Vicia faba

A collection of 648 accessions of Vicia faba was screened for resistance to faba bean rust (Uromyces viciae-fabae). Two distinct types of resistance w ere identified, both resulting in reduced disease severity (DS) and area un der the disease progress curve (AUDPC), but differing in the expression of hypersensitivity. One should be regarded as incomplete nonhypersensitive re sistance and the other as incomplete resistance with late hypersensitivity. The hypersensitive resistance, which has not been reported before, was not dependent on temperature or plant age. These two types of resistance were characterized by three macroscopic components of resistance: increased late nt period (LP), decreased colony size (CS) and a relatively reduced infecti on frequency (IF), both on seedlings and on adult plants. LP and CS were th e components of nonhypersensitive resistance most highly correlated with DS and AUDPC measured under field conditions. The presence of necrosis was an additional component in the hypersensitive resistant response.