Evaluation of red raspberry cultivars for resistance to phytophthora rot root

Eighteen red raspberry genotypes originating from breeding programs around the world were tested for resistance to Phytophthora fragariae var. rubi in hydroponic culture under growth chamber conditions. All plants were inoculated with two isolates of P. fragariae var. rubi and evaluated for resistance using qualitative and quantitative measurements of root and shoot symptoms. 'Prelude', 'Anne', 'Caroline', 'Nova', 'Josephine' and NY258 were identified as having high to moderate levels of disease resistance to the pathogen. All of the resistant genotypes tested in this study can be categorized as likely deriving their resistance to R fragariae var. rubi from either 'Latham' or Rubus strigosus Michx. germplasm.