Abstract
Defense reaction of barley cultivars to three nonpathogenic fungi were studied microscopically to clarify whether there are differences among cultivars and the nature of nonhost resistance was discussed by comparing with that of race-specific resistance. In all barley cultivars and non-pathogenic fungi combinations, it is shown that the penetration failure by non-pathogenic fungi was almost associated with papilla formation and cell wall alteration which fluoresced under fluorescence microscopy, of leaf epidermal cells. It is therefore suggested that papilla formation and cell wall alteration associated with defense reaction is major components of nonhost resistance in barley. In addition these components of nonhost resistance are most likely related to the induced resistance caused by previous inoculation with hypo-and hyper-virulent pathogens.
