ROOT AND BASAL STEM ROT CAUSED BY PHYTOPHTHORA NICOTIANAE ON THYME IN LIGURIA

Root and basal stem rot caused by the soil-borne pathogen Phytophthora nicotianae v. Breda de Haan was recently observed on both Thymus vulgaris L. and T. x citriodorus (Pers.) Schreb. ex Schwei. (cvs. Bertram Anderson, Doone Valley, Silver King and Silver Queen). In Liguria, these species are usually grown in pot and used as ornamental as well as officinal plants. On thyme, P. nicotianae causes collar and root rot, a progressive withering of the branches and wilting of the entire plant. The pathogen was isolated from infected tissues on a selective medium and was identified by morphological, biochemical (i.e. electrophoretic patterns of total mycelial proteins and isozymes on polyacrylamide gels) and molecular characters (i.e. RFLP and sequence analysis if ITS regions of rDNA). Pathogenicity tests and re-isolation of P. nicotianae were carried out to fulfil Koch’s postulates