Bell Pepper Plant Growth, Gas Exchange, Mineral Nutrition, Phytophtora Blight, Fruit Yield, and Postharvest Fruit Decay as Affected by Harpin Protein

Abstract

Harpin protein is an elicitor of hypersensitive response in plants. When applied exogenously, harpin is claimed to control plant diseases, increase plant growth and yield, and reduce postharvest fruit decay. The plant responses to harpin application have been inconsistent. This study was intended to determine the effects of harpin on plant growth, gas exchange, control of Phytophtora blight, fruit yield, and control of postharvest fruit decay in bell pepper (Capsicum annum L.). When applied only before planting, harpin increased marketable yield of bell pepper, but when applied both before and after planting, it reduced marketable and total yields. Harpin had no beneficial effect on plant growth, leaf mineral nutrient content, leaf gas exchange, incidence of Phytophtora blight in the field, and incidence of softrot of fruit after harvest. Harpin had little or no positive effect on most plant attributes in bell pepper in the field or after harvest.