Histochemical studies on the accumulation of H2O2 and hypersensitive cell death in the nonhost resistance of pepper against Blumeria graminis f. sp. tritici

Defence reactions between Blumeria graminis f. sp. tritici (Bgt) and pepper cultivar ‘A11’ (nonhost) and susceptible wheat cultivar ‘Shan 225’ were studied histochemically. Conidia of Bgt developed normally on the wheat leaves with limited detectable whole-cell H2O2 accumulation and cell death. In contrast, the germination of conidia on the pepper leaves was delayed. High frequency of H2O2 accumulation and hypersensitive response (HR) were detected in the nonhost interactions. H2O2 accumulation was accompanied by HR and papilla formation. These results indicate that H2O2 and HR play important roles in preventing colonization and disease development of nonhost-pathogen Bgt in pepper plants.

► Nonhost resistance is the most effective and lasting resistance in plants.
► Hypersensitive response is a key defence reaction mechanism in nonhost resistance.
► Nonhost and host resistances are mechanistically interconnected.