Tuber response of six potato cultivars to inoculation with Phytophthora erythroseptica, the causal agent of pink rot

Abstract

Pink rot, caused by Phytophthora erythroseptica, is found in most potato-growing regions of the world. No potato cultivars commonly grown in Canada and the U.S.A. are considered immune to pink rot, but differences in the tolerance of certain cultivars to this disease have been reported. A tuber inoculation study was conducted during a 3-year period (2000–2002) with six potato cultivars ('Russet Burbank', 'Shepody', 'Norland', 'Yukon Gold', 'Butte', and 'Goldrush') and four different pathogen isolates (from Prince Edward Island, Canada, and Maine, U.S.A.) to test for variability in host response to infection and the pathogenicity of isolates. Tuber eyes were inoculated with a zoospore suspension of P. erythroseptica, and tubers were subsequently incubated for 2 weeks at 15 °C prior to rating for disease. Although no cultivars were immune to pink rot, significant (P < 0.001) differences in disease incidence and severity were noted among cultivars. 'Norland' and 'Shepody' were significantly (P = 0.05) more susceptible to pink rot than the other cultivars, according to measurements of surface necrosis, internal discolouration (pinking), and disease incidence. Variations in the response of some cultivars to infection in specific years were noted. Year × cultivar interactions for trials conducted in 2001 and 2002 were significant (P < 0.001). All isolates used in this study were highly pathogenic, and no significant differences in pathogenicity were noted among them. Information on differences in the tolerance of potato cultivars to pink rot may influence the choice of cultivars grown in fields that are poorly drained or with a history of the disease.