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A glasshouse experiment was conducted to study the responses toStreptomyces scabiesandS. turgidiscabiesin potato cultivars Bellona, Matilda and Sabina (Solanum tuberosum). Potatoes were grown in a peat-sand mixture inoculated with one of the two strains of eitherS. scabiesorS. turgidiscabies.Logit models were used to analyse the data on disease incidence and severity, whereas the data on emergence and yield were tested by analysis of variance.S. turgidiscabies, a recently described potato pathogen in Finland, possessed a high ability to cause superficial, raised and pitted lesions on all three cultivars tested. Symptoms induced byS. turgidiscabieswere similar to those ofS. scabies, regardless of the cultivar, which suggests that the two causal organisms of common scab cannot be distinguished based on symptoms. Infection byS. turgidiscabiesandS. scabiesdelayed emergence, had the tendency to decrease the yield, and increased the proportion of small tubers in the yield, regardless of the potato cultivar. Differences in the levels of resistance to common scab were evident between potato cultivars, since cvs. Matilda and Bellona showed higher disease incidence and more severe scab symptoms than cv. Sabina. [ABSTRACT FROM AUTHOR]