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POSTERS: Host resistance screening

A sustainable approach to Phytophthora-infested landscape beds: the search for tolerant or resistant annuals and herbaceous perennials
Michelle Henson - North Carolina State University. Suzette Sharpe- North Carolina State University, Inga Meadows- North Carolina State University

Many ornamental nursery crops are susceptible to species of Phytophthora, a genus of fungal-like organisms that can persist in soil for several years. Since chemical applications are not practical in the landscape, knowledge of Phytophthora-resistant or tolerant plant species would provide a sustainable management approach. In 2018, one or two cultivars of 15 annuals and 12 herbaceous perennials were evaluated based on desirability and anecdotal evidence of tolerance or resistance to Phytophthora. Six plant cultivars served as susceptible controls. Three landscape beds were established in North Carolina and infested with three species of Phytophthora: P. nicotianae, P. tropicalis, and P. drechsleri. Plants were regularly rated for disease incidence and appearance and symptomatic plants were assayed to determine the presence of Phytophthora. Ten cultivars of annuals and seven cultivars of herbaceous perennials appeared excellent throughout the season. Phytophthora spp. were recovered from six and five cultivars of the evaluated annuals and herbaceous perennials, respectively. P. nicotianae, P. drechsleri, or P. cryptogea were recovered from each susceptible host. P. tropicalis was recovered from one evaluated plant cultivar. P. cryptogea was recovered from three plant cultivars, although this species was not intentionally introduced in the landscape beds. This study identifies 17 cultivars that can be used as alternatives in landscape beds infested with Phytophthora.