Role of Solanum dulcamara L. in Potato Late Blight Epidemiology

Four sites with naturally growing Solanum dulcamara were surveyed during 2006 and 2007 for the presence of late blight. Despite 2 years of observations, no late blight was detected among natural populations of bittersweet. Nevertheless, repeated infections occurred on few S. dulcamara plants from a collection growing in a botanical garden in the same years. These plants were used to investigate the possibility of survival of the inoculum between seasons. In the respective years, a set of 21 and 52 S. dulcamara accessions inoculated with Phytophthora infestans under field conditions resulted in a wide range of responses to the disease. More susceptible reactions were found among genotypes collected at greater distance from commercial potato fields indicating the possibility of genetic selection caused by P. infestans. However, both scarceness of natural infections and no overwintering, suggest that bittersweet may not play a role in late blight epidemiology.