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United States Department of Agriculture

Agricultural Research Service


Location: Southern Horticultural Research

2009 Annual Report

1a. Objectives (from AD-416)
Develop improved germplasm for ornamental plants and small fruit crops adapted to the Gulf Coast Region. Research will also determine genetic factors that regulate plant disease, growth characteristics, and tolerance to environmental stress, as well as accelerate the development and release of improved cultivars for production. Develop molecular tools, such as TILLING (Targeting Induced Local Lesions IN Genomes)and/or microarray methods to identify and/or map Quantitative Trait Loci (QTLs), candidate genes, and/or “functional genetic markers” for cold tolerance, drought tolerance, and/or pest and pathogen resistance in priority ornamental genera for the Gulf States, including Cercis (redbud), Cornus (dogwood), and Hydrangea in collaboration with university and U. S. National Arboretum cooperators, to enhance breeding programs of woody landscape plants.

1b. Approach (from AD-416)
Identify desirable traits in small fruit and ornamental plants, develop improved varieties using traditional and modern genetic methods, and release superior germplasm in order to increase profitability of small acreage farms in the Gulf Coast Region. Germplasm from established cultivars, wild clones, and their hybrids will be cooperatively evaluated at USDA-ARS and University Experiment Stations throughout the southeastern United States. Small fruit cultivars that are released will have improved vigor and fruit quality, expanded ripening seasons including earlier harvests, enhanced adaptation, greater productivity with larger yields, improved fresh or processing berry qualities, and enhanced suitability for mechanical harvesting. This research project, combined with cooperative testing and technology transfer efforts with land grant universities, will develop superior cultivars for rabbiteye and southern highbush blueberry, muscadine grapes and other small fruit. Because the ornamental commodity comprises hundreds of plant species, target genera will be selected for improvement from both herbaceous perennials and woody landscape crops. Superior ornamental cultivars that are released will have increased disease resistance and enhanced ornamental qualities including greater aesthetic appeal. In addition to traditional breeding to develop superior ornamental cultivars, this project plan also includes molecular genetic research to accelerate breeding of woody landscape plants by shortening the evaluation, selection, and release cycle. In total, ornamental research described in this plan will impact new cultivar development for crapemyrtle, hibiscus, begonia, butterfly ginger, Dichroa, redbud, fringe tree, and dogwood.

3. Progress Report
Genetics research on small fruits and ornamental plants focuses on seven crops including blueberries, muscadine grapes, crape myrtles, hibiscus, hydrangeas, begonias, and ornamental ginger. Progress includes evaluation and release of new blueberry and muscadine cultivars such as the ‘Prince, a new rabbiteye blueberry cultivar with improved fruit production. Blueberry breeding and evaluations continue to focus on early ripening rabbiteye plants. Over 250 crosses were completed for southern highbush and rabbitteye, approximately 125 crosses for each blueberry type. Replicated field plantings were established for more than 150 plants that were selected based on fruit quality, growth characteristics and productions value. To continue the ongoing evaluation and selection cycle, approximately 8,000 seedlings from last year's breeding efforts were planted in containers and prepared for evaluation and selection. In ornamental plants, evaluation of elite crape mytle breeding lines with dark-colored foliage and an array of flower colors continued and selections have been reduced to superior plants that are likely candidates for release as new cultivars. Inheritance of host plant resistance to metallic flea beetle is being analyzed in collaboration with Texas AgriLife in Dallas, Texas, as part of a new specific cooperative agreement. Disease resistance studies on crape myrtles are also underway. For example, over 2,000 crape myrtle seedlings composed of 26 families generated from 11 commercial clones were screened for field resistance to powdery mildew and cercospora leaf spot for two seasons at Auburn University’s Brewton field station over the last two years. Individual plants displaying resistance were selected and over 100 seedlings were moved to a new plot for additional evaluation. Superior Hibiscus selections have been prepared and released. Evaluations of additional selected hibiscus materials will continue at cooperating nursery sites. Genetic diversity of species related to hydrangea has been published and target species have been successfully incorporated into breeding program at the National Arboretum breeding and in industry. A micropropagation system for ornamental ginger species and cultivars has been published and was used to increase artificial tetraploid plants created from dwarf ginger. Molecular markers were developed for fringe tree and redbud, two new crops that were recently added to the research plan. The genetic diversity of native dogwood populations was also analyzed as part of the subordinate project “Woody Ornamental Genomic Research in the Southeastern United States” (Project No: 6404-2100-008-03S). Dogwood breeding for improved tolerance to anthracnose and new flower colors continued at the University of Tennessee.

4. Accomplishments
1. DNA fingerprint database for hydrangea cultivar identification. Hydrangeas are the fourth most popular flowering shrub and are sold as landscape shrubs, patio plants, greenhouse floral crops, and cut-flowers. Once mislabeled or lost from trade, it is difficult to re-establish cultivar identity based solely on botanical descriptions. There are numerous suspected cases of mislabeling, renaming, and re-discovery of ‘new’ hydrangeas. As part of an in-depth analysis of available and historic H. macrophylla genetic diversity, researchers at the Southern Horticultural Laboratory established a DNA fingerprint database for more than 250 cultivars and demonstrated real-world application of this biotechnology. Applications include detecting mislabeled plants during production and in the marketplace, confirming parentage of self-sown and open-pollinated hybrids, and verifying genetic uniqueness for plant patent protection of select cultivars. Establishing plant breeding rights and exporting protecting material is a complex and time-consuming process. The hydrangea DNA fingerprint database and expertise has been used by 13 nurseries to resolve questions about hydrangea cultivars in the U.S., Belgium, and New Zealand. Recently a large shipment of exclusive breeding material was mixed upon arrival in the Netherlands. DNA fingerprinting technology allowed trading partners to unambiguously sort the genetic material and varieties, keeping the European release on time and saving the multi-year build-up efforts that would otherwise have been delayed.

Review Publications
Sakhanokho, H.F., Kelley, R.Y. 2009. Influence of Salicylic Acid on In Vitro Micropropagation and Salt Tolerance in Two Hibiscus Species, H. acetosella and H. moscheutos (cv ‘Luna Red’). African Journal of Biotechnology 8: 1474-1481.

Stringer, S.J., Spiers, J.M., Draper, A., Marshall, D.A. 2009. Potential new blueberry cultivars for the Gulf Coast region of the U.S. Acta Horticulturae. 810:87-92.

Wang, X., Rinehart, T.A., Wadhl, P.A., Spiers, J.M., Johnson, D., Trigiano, R.N. 2009. A New Electrophoresis Technique to Seperate Microsatellite Alleles Vol.8 (11), pp.2432-2436. African Journal of Biotechnology.

Li, Y., Windham, M.T., Trigiano, R.N., Reed, S.M., Spiers, J.M., Rinehart, T.A. 2009. Bright-field and fluorescence microscopic study of development of Erysiphe polygoni in susceptible and resistant bigleaf Hydrangea. Plant Disease. 93:130-134.

Baird, R.E., Wadl, P.A., Wang, X.W., Hadziabdic, D., Rinehart, T.A., Abbas, H.K., Shier, T., Trigiano, R.N. 2009. Microsatellites from the charcoal rot fungus (Macrophomina phaseolina). Molecular Ecology Resources. 9(3):946-948.

Greer, S.P., Rinehart, T.A. 2009. In Vitro Germination and Dormancy Responses of Hydrangea macrophylla and Hydrangea paniculata Seeds to Ethyl Methane Sulfonate and Cold Treatment. HortScience. 44(3):764-769.

Reed, S.M., Rinehart, T.A. 2009. SSR Marker Analysis of Genetic Relationships within Hydrangea paniculata. HortScience. 44(1):27-31.

Last Modified: 06/22/2017
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