Evaluating the Resistance of Various Potato Genotypes to Early Blight Disease Caused by Alternaria alternata

Early 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 46 potato genotypes (including 24 genotypes of Isfahan and 22 common genotypes of Isfahan and Shahrood) were investigated in the field by evaluating the severity of the disease in six levels from 0 to 6 (0-100%). The results showed that there were significant differences between the resistances of different potato genotypes. Three resistant genotypes (R1/33/10, R2/33/3 and R2/33/21) and three sensitive genotypes (8707/106, 8703/804 and 8707/112) were selected to investigate the changes of plant biomass and were inoculated with the spores of the disease-causing fungus (106) 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.