Original ResearchEvaluating the Resistance of Various Potato Genotypes to Early Blight Disease Caused by Alternaria alternata Neda Peymani۱, Ahmadreza Golparvar۱*, Mehdi Nasr-Esfahani۲, Esmaeil Mahmoudi۳, Majid Shams۱۱- Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran۲- Department of Plant Protection Research, Isfahan Agriculture and Natural ResourceResearch and Education Center (AREEO), Isfahan, Iran۳- Department of Plant Pathology, College of Agriculture, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran *Corresponding author E-mail: a.golparvar@khuisf.ac.ir Received: ۱۰ March ۲۰۲۰ Accepted: ۲۲ May ۲۰۲۰ AbstractEarly blight disease (caused by Alternaria alternata (Fr.) Keissler) is one of the most important potato diseases around the world which causes the death of the leaf tissues and sharp decrease in the final yield. Identifying and using resistant potato cultivars is one of the effective methods to deal with this disease. In the current study, the resistance of ۴۶ potato genotypes (including ۲۴ genotypes of Isfahan and ۲۲ common genotypes of Isfahan and Shahrood) were investigated in the field by evaluating the severity of the disease in six levels from ۰ to ۶ (۰-۱۰۰%). The results showed that there were significant differences between the resistances of different potato genotypes. Three resistant genotypes (R۱/۳۳/۱۰, R۲/۳۳/۳ and R۲/۳۳/۲۱) and three sensitive genotypes (۸۷۰۷/۱۰۶, ۸۷۰۳/۸۰۴ and ۸۷۰۷/۱۱۲) were selected to investigate the changes of plant
biomass and were inoculated with the spores of the disease-causing fungus (۱۰۶) in the greenhouse. Biomass parameters showed significant decrease compared to the control samples. The amount of this decrease was much higher in sensitive genotypes than resistant genotypes. The knowledge obtained from this study can be useful for the production of disease-resistant potato cultivars.