has received minimal attention in ornamental species, repeated isolations of this fungus from dogwood roots and the crown region in field plantings suggest a need to evaluate its impact on flowering dogwood seedlings. Common cultural practices used in
Flowering dogwood is native to the eastern United States from Texas to Massachusetts ( Witte et al., 2000 ). Flowering dogwood continues to be a valuable crop for nursery producers. It is ranked third in total sales value among flowering trees
. Flowering dogwood ( Cornus florida L.) is an important woody ornamental landscaping crop in the United States. They are cultivated in three production systems: field, container, and pot-in-pot production. Relatively, flowering dogwoods do not require large
flowering dogwood ( Cornus florida ) ( Barnard and Gilly, 1986 ; Hodges, 1962 ; Mmbaga et al., 2018 ; Rowan, 1971 ; Seymour, 1969a , 1969b ; Smith and Bega, 1964 ). Macrophomina phaseolina effects on woody hosts are primarily on seedlings and young
Flowering dogwood (Cornus florida L.) is an important tree of forests and urban landscapes in the eastern United States. Currently, there are over 100 cultivars of flowering dogwood commercially available. An identification process based on genotype would be of use to researchers, breeders, and nurserymen, as many cultivars are similar phenotypically. Molecular markers offer a promising way of definitively identifying flowering dogwood cultivars. Amplified fragment length polymorphism (AFLP) is a technique that can be used to generate DNA fingerprints. DNA was isolated from leaves of 17 common cultivars of dogwood and AFLP fingerprints were generated by a Beckman Coulter CEQ™ 8000. Fingerprints were converted to binary data and verified manually. Two drafts of a cultivar identification key were generated based on the corrected, verified binary data and cultivar-specific peaks. Six primer combinations were used to construct all keys and were tested with seven unknown dogwood cultivar samples. Six unknown samples were correctly identified using the keys. Only one unknown, `Cherokee Brave', was unidentifiable with any key. In all cases, some intracultivar variation was observed. A similarity index was calculated and visualized with a tree of genetic relatedness using NTSYSpc. Intracultivar variation was observed in the similarity index as well. This database for cultivar-specific molecular markers will serve as a starting point to which other cultivars can be added and also can be used in breeding applications, patent application and other projects, such as mapping the C. florida genome.
Flowering dogwood (Cornus florida) is a popular flowering tree that is a mainstay of the southeastern U.S. nursery industry. Because cultivars of this species are primarily propagated through budding onto seed-propagated rootstock, a reliable source of seeds is needed. Disease- and weather-related problems may sometimes result in a shortage of dogwood seed. The objective of this study was to develop a method of storing dogwood seed that would allow growers to save seed during years in which good flowering and seed set occur for use when insufficient seed is available. Open-pollinated seeds were collected in Fall 1999, dried to 6%, 10%, and 14% moisture, and stored at -20, 5, and 22 °C. After 1, 2 and 3 years of storage, seed was stratified for 3 months and then planted in the greenhouse. Percent germination was compared to that of a subsample of the seed lot that had been stratified and planted following collection in Fall 1999. After 1 year in storage, seed dried to 10% and 14% moisture and stored at 22 °C failed to germinate; germination of the other samples ranged from 55% to 97% of that of the control sample. After 2 or 3 years in storage, all seed stored at 22 °C and the seed dried to 14% moisture and stored at 5 °C failed to germinate. Germination of the remaining samples ranged from 76% to 97% of the control in year 2, and from 72% to 109% in year 3. After 3 years in storage, seed dried to 6% moisture and stored at 5 °C and seed dried to 10% moisture and stored at -20 °C had the highest germination percentage and best seedling vigor. Development of a seed storage method for dogwood will benefit both dogwood producers and germplasm preservation efforts.
Abstract
Factors affecting natural infestation of flowering dogwoods (Cornus florida L.) by the dogwood borer, Synanthedon scitula Harris (Lepidoptera: Sesiidae), were studied in an urban cemetery in Louisville, Kentucky. Two tree characteristics, severity of trunk wounding and exposure to sun, were most important in determining the probability of borer attack. Degree of crown dieback or color of bloom did not significantly affect the rate of infestation. There was no correlation between tree diameter and probability of attack, but height of attack sites increased linearly with increasing tree size.
A series of experiments was conducted with flowering dogwood (Cornus florida L.) to evaluate in vitro pollen germination both prior to and following storage at various temperatures. For all experiments, pollen was germinated on an agar-solidified medium containing 20% sucrose. Collection method had a significant effect on germination of `Cherokee Chief', `Cherokee Princess', and `Cloud 9' pollen. Pollen obtained from anthers that had been collected prior to dehiscence and allowed to air-dry for 24 hours had a higher germination rate than did pollen that had undergone a desiccation treatment. None of the treated pollen tested, however, had a germination rate >25% of that of freshly collected pollen. The deleterious effect of dehydration could not be reversed by rehydration. Pollen germination was tested after 1, 4, 7, and 108 days at 5, –20, and –196 °C. Pollen stored at –196 and at –20 °C had a better germination rate than that stored at 5 °C. Germination was not significantly affected by length of storage, nor was there any significant temperature × length of storage interaction.
Powdery mildew (Microsphaera pulchra) of flowering dogwood (Cornus florida L.) has become a significant problem of trees in nursery production as well as in the landscapes and forests of the eastern United States. The disease significantly reduces growth and berry production by older established trees and may contribute to the inability of younger trees (liners) in production to survive winter dormancy. Disease resistance in named cultivars is limited to partial resistance found in `Cherokee Brave'—all other cultivars are extremely susceptible. Until now, the only disease control measure was to establish an expensive, labor-intensive, preventive fungicide program. We examined >22,000 seedlings and identified 20 that were extremely resistant to powdery mildew. Three trees with white bracts were selected from the 20 and released as patent-pending cultivars. `Karen's Appalachian Blush' has long, non-overlapping, pink fringed bracts with a delicate appearance. `Kay's Appalachian Mist' has creamy white, slightly overlapping bracts with deeply pigmented clefts. `Jean's Appalachian Snow' has large, strongly overlapping bracts with non-pigmented clefts. The three powdery mildew-resistant cultivars will be entered into an existing breeding program with `Appalachian Spring', a cultivar released by the Tennessee Agriculture Experiment Station and resistant to dogwood anthracnose, in an attempt to produce trees that are resistant to both diseases.
This study was conducted to determine the influence of production methods on the growth of container grown flowering dogwood (Cornus florida). The production practices were: full sun, 40% white shade cloth, 40% black shade cloth, and pot-in-pot. The cultivars studied were: cv. `Welch's Junior Miss', cv. `Barton's White', cv. `Weaver's White', and cv. `Welch's Bay Beauty'. The one variety used was pink. Height and caliper data was collected. Plants grown under white shade cloth had the highest overall height and caliper growth, followed by black shade cloth, full sun, and the pot-in-pot production method. The cultivar `Weaver's White' had the highest overall height and caliper growth and the variety pink had the least, regardless of treatment. The remaining cultivars had similar growth regardless of treatment.