Honeybee-mediated Controlled Pollinations in Cornus florida and C. kousa Intra- and Interspecific Crosses

Flowering (Cornus florida L.) and kousa (C. kousa Hance) dogwoods are ornamental trees valued for their four-season appeal, but also for their importance to retail and wholesale nurseries. The popularity of kousa dogwood has increased in recent years as a result of its resistance to dogwood anthracnose and powdery mildew as compared with flowering dogwood, which is typically susceptible to those diseases. This range of resistance allows the development of intra- and interspecific cultivars with multiple disease resistance or a combination of disease resistance and specific ornamental traits. Breeding requires controlled crosses that are usually done manually, which is a labor-intensive process. Cornus florida and C. kousa have generally been found to be self-incompatible allowing for the breeding process to be made more efficient by not having to emasculate flowers. We have capitalized on the natural ability of honeybees and the self-incompatible nature of dogwood to perform self- and crosspollinations of flowering and kousa dogwood. Self-pollinations were conducted in 2006 and 2007 with C. florida ‘Appalachian Spring’ and ‘Cherokee Brave’ and with C. kousa ‘Blue Shadow’ and Galilean®. The flowering dogwood self-pollinations resulted in no seed production, whereas the kousa dogwood self-pollinations resulted in low seed production, indicating self-incompatibility. Intra- and interspecific crosses of flowering and kousa dogwood cultivars and breeding lines were conducted in 2006 to 2008. Honeybees were effective in facilitating seed production for all intraspecific crosses conducted. Seedling phenotypes of putative intra- and interspecific hybrids are similar and practically indistinguishable, so dogwood-specific simple sequence repeats were used to verify a sample of the putative hybrids. The results demonstrated that honeybees were effective in performing controlled pollinations and that honeybee-mediated pollinations provide an alternative to time-consuming hand pollinations for flowering and kousa dogwood.

A 70-Year History of Arborescent Vegetation of Inwood Park, Manhattan, New York, U.S.

The arborescent vegetation located at three sites within Inwood Park, Manhattan, New York, U.S. was sampled by the quadrat method in October 2004 and May 2005 and compared with the trees present in the same quadrats on a map of trees at Inwood Park prepared by the federal Works Program Administration in 1935. Tulip poplar (Liriodendron tulipifera) was the dominant tree at the Moist Valley and South Slope sites in 1935 and 2005, whereas oak (Quercus) was the dominant genus at Dry Ridge in 1935 and 2005. Dogwood (Cornus florida) was the dominant subcanopy tree in 1935; it was unimportant in 2005, a victim of dogwood anthracnose. In terms of ecologic dominance, there has been no change in the first ranked genera at these sites in the past 70 years. Mean tree diameter (diameter at breast height) has increased from 32.3 cm (12.9 in) to 41.8 cm (16.7 in). The three sites have experienced a parallel pattern of increase in tree size from 1935 to 2005. Nonnative trees were not important in Inwood Park in 2005.

Dogwood Anthracnose: A Threat to Flowering Dogwood

FOR-127, a 3-page illustrated fact sheet by Eric Holzmueller, Shibu Jose, and Alan Long, describes this non-native disease threatening flowering dogwood populations in the eastern United States, signs of the disease, what you can do about it, and references. Published by the UF School of Forest Resources and Conservation, October 2007.