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New Powdery Mildew Resistant Cultivars of Cornus florida

M. T. Windham1, R. N. Trigiano1, A.S. Windham1 and W. E. Klingeman III2
1Department of Entomology and Plant Pathology and 2Department of Plant Sciences and Landscape Systems
University of Tennessee, Knoxville, TN 37996-4650

A paper from the Proceedings of the 12th Metropolitan Tree Improvement Alliance Conference (METRIA 12), Landscape Plant Symposium: Plant Development And Utilization, held in Asheville, NC, May 23-25, 2002, co-sponsored by the North Carolina State University, North Carolina Division of Forest Resources, USDA Forest Service Southern Region, North Carolina Landscape Association, North Carolina Association of Nurserymen, The Landscape Plant Development Center, The North American Branch of The Maple Society, and The International Ornamental Crabapple Society.


Powdery mildew has drastically increased production costs of flowering dogwood, Cornus florida, since severe epidemics of this disease were first observed in the eastern U.S. in 1994. In 1994 and 1995, seedlings were evaluated for disease resistance in production fields that had been abandoned due to high incidence and severity of powdery mildew. Through field and subsequent greenhouse studies, frequency of resistance in native populations of C. florida was estimated to be one resistant plant in every 1000 plants evaluated (Windham and Witte).

Methods

From the pool of resistant seedlings identified in resistance-frequency experiments described above, three lines were selected for potential release because of early blooming, bloom characteristics and resistance to powdery mildew. These lines were compared with 'Cherokee Brave' (pink cultivar of C. florida that is moderately resistant to powdery mildew) and 'Cherokee Sunset' (cultivar of C. florida that is susceptible to powdery mildew) for reactions to powdery mildew for three years.

Results

All three selections were resistant to powdery mildew in each of the three years they were evaluated. Resistance levels were equal to or better than in 'Cherokee Brave.' The lines have been released by the Tennessee Agricultural Experiment Station as new, powdery mildew resistant cultivars and described below.

Cornus florida 'Jean's Appalachian Snow': The parental lineage of this cultivar is unknown and was discovered in a field planting at a nursery in Decherd, TN. 'Jean's Appalachian Snow' has white bracts that are overlapping and stiff. Bract clefts have either no pigmentation or yellow green pigmentation. US PP13,099 P2.

Cornus florida 'Karen's Appalachian Blush': The parental lineage of this cultivar is unknown and was discovered in a field planting at a nursery in Decherd, TN. 'Karen's Appalachian Blush' has white bracts that have a pink blush suffused along the margin. Bracts are floppy and do not overlap. Clefts are pointed and red-purple in color. US PP13,165 P2.

Cornus florida 'Kay's Appalachian Mist': The parental lineage of this cultivar is unknow and was discovered in a field planting at a nursery in Decherd, TN. 'Kay's Appalachian Mist' has creamy white bracts that are stiff and slightly overlap. Bract clefts are red-purple in color. US PP13,098 P2.

Reference

Windham, M.T. and W.T. Witte. 1998. Naturally occurring resistance to powdery mildew in seedlings of Cornus florida. J. Environ. Hort.16: 173-175.


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