Multiple disease resistance in dogwoods (Cornus spp.) to foliar pathogens.
Disease resistance in several Cornus species and cultivars to three foliar pathogens was evaluated in a 5-year study. Of the 51 accessions evaluated, 20 were of C. kousa, 21 of C. florida, two of C. sericea, two of C. mas, one of C. alternifolia, and five were interspecific hybrids of C. kousa × C. florida. Powdery mildew and spot anthracnose caused by Erysiphe (sect. Microsphaera) pulchra, and Elsinoe corni, respectively, were the most prevalent and severe diseases. Eighteen cultivars of C. kousa, one of C. mas, two of C. sericea, one of C. alternifolia, and four interspecific hybrids were highly resistant to powdery mildew, while 19 C. florida cultivars were susceptible, of which two were moderately resistant. Spot anthracnose was the second most prevalent disease, but its severity was generally low. Three C. kousa cultivars, ten of C. florida, and one of C. mas were mildly susceptible to spot anthracnose. Both cultivars of C. sericea were highly susceptible to Septoria leaf spot (Septoria cornicola), and heavy infections were observed throughout the study. Most C. florida cultivars were highly susceptible to powdery mildew, while most C. kousa cultivars were highly resistant. Results of this study suggest that multiple disease resistance in dogwoods may be achieved through crosses between C. kousa and C. florida.