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Development of Flowering Dogwood Cultivars Resistant to Powdery Mildew

M.T. Windham, W.T. Witte and R.N. Trigiano

Tennessee Agricultural Experiment Station, Knoxville, TN 37901-1071

A paper from the Proceedings of the 10th Metropolitan Tree Improvement Alliance (METRIA) Conference held in St. Louis, MO, September 30 and October 1, 1998, co-sponsored by the Landscape Plant Development Center and the Society of Municipal Arborists.

Abstract

Twenty-two thousand flowering dogwood seedlings in two nursery fields were screened in 1994 and 1995 and eighty-four were selected for field resistance to powdery mildew. Most of the selected seedlings were found to be susceptible in controlled greenhouse trials. However, twenty seedlings displayed some resistance to powdery mildew, at least equivalent to 'Cherokee Brave', the only commercial cultivar of Cornus florida with resistance to this disease. These seedlings were evaluated for disease resistance for three years and are now being propagated by rooted cuttings. Six of the trees bloomed prolifically in 1998 and at least four appear to have outstanding floral characteristics. Individual bract length ranges from 5.3 to 5.8 cm (2.1 to 2.3 in) and bract width ranges from 4.1 to 4.8 cm (1.6 to 1.9 in). Bract color was variable and ranged from pure white to a blush pink delicately fading to white at the center. The cleft or notch at the apex of the bracts ranges in color from none to red or purple. Some selections have distinctively overlapping bracts, and lines vary in amount of bract substance or stiffness. A preference trial revealed that men preferred an inflorescence type with the largest bracts whereas women preferred a more delicate blush colored bract. Selected lines will be named and released as one of the 'Appalachian' series of flowering dogwood cultivars


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