Evaluation of Resistance of Potato Cultivars to Isolates of Alternaria solani the Causal Agent of Early Blight and Study of Total Phenol Contents in Resistance and Susceptible Cultivars

To study the resistance of potato cultivars grown in Markazi Province of Iran to Alternairia solani, five isolates of the pathogen were provided from infected fields of the region. Resistance if nine commercial potato cultivars to these isolates was evaluated in four replications in a factorial model with completely randomized design in greenhouse. Potato cultivars exhibited different responses of resistance and susceptibility. Two resistant and susceptible cultivars and two isolates of the pathogen with high and low virulence were selected for studing the total phenol contents in these two cultivars 2, 4, 6 and 8 days after inoculation with two isolates. Significant differences, related to the resistance of the host, in total phenol contents were detected at different days after inoculation. A significant difference was also observed in total phenol contents of a cultivar in response to different isolates, indicating differences in the pathogenicity of isolates.