Location: Southern Horticultural Research2010 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 with improved fruit production. Blueberry breeding and evaluations continue to focus on early ripening rabbiteye plants. In 2010, 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 made for eventual release as new cultivars. A mapping population to create a genetic linkage map for the crape myrtle genome has been established in collaboration with Texas AgriLife in Dallas, Texas, under an unfunded cooperative agreement. Inheritance of host plant resistance to insects is being analyzed and hybrid populations segregating for resistance are being prepared for evaluation. Disease resistance studies on crape myrtles are also underway. Superior Hibiscus selections have been prepared and released. Evaluations of additional selected hibiscus materials will continue at cooperating nursery sites. New molecular markers are being developed for Hydrangea macrophylla to finish the genetic linkage map. Next generation, high-throughput DNA sequencing is being used to uncover important genes in dogwood as part of “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. Molecular markers that were developed for two native plants, fringe tree and redbud, have been used to assess genetic diversity within cultivated forms. An in vitro assisted breeding program has been established for ornamental ginger, resulting in the development of breeding materials as well as new improved ornamental ginger lines. The breeding materials include artificially created ginger plants with increased chromosome numbers as well as plants with flowers having only the female parts. An increase in chromosome number produced dwarf, compact gingers and the in vitro assisted breeding system created variegated gingers. In-depth studies were conducted on ginger pollen to better understand its biology, viability and storage conditions.
1. ‘USS California’, A New Tropical Hibiscus with Yellow Flowers. ARS Plant Geneticists at the Thad Cochran Southern Horticultural Laboratory recently released Hibiscus rosa-sinensis ‘USS California’, a tropical hibiscus cultivar with superior yellow flowers. Tropical hibiscus is a popular addition to summer landscapes because of bright colorful flowers but some selections have unappealing open growth habits and suffer from insect damage. The objective of the hibiscus breeding program is to introduce new cultivars with enhanced pest resistance in combination with improved production traits and superior landscape performance. ‘USS California’ has uniform, intermediate growth habit and strong flower production in combination with improved pest tolerance. Flowers are large and vibrant yellow. This plant is ideal for landscape use and is adapted to summer heat. Nursery producers will benefit from the strong production traits of this selection including easy propagation and vigorous growth.
2. ‘USS Arizona’, A New Tropical Hibiscus with Orange Flowers. ARS Plant Geneticists at the Thad Cochran Southern Horticultural Laboratory recently released Hibiscus rosa-sinensis ‘USS Arizona’, a tropical hibiscus cultivar with brilliant orange flowers. Tropical hibiscus are known for their bright flowers in a broad range of colors. They are popular shrubs in pots or landscape; however, many have an unsightly, open growth habit and suffer from insect damage. The objective of the hibiscus breeding program is to introduce new cultivars with enhanced pest resistance in combination with improved production traits and superior landscape performance. ‘USS Arizona’ has uniform, intermediate growth habit and strong flower production in combination with improved pest tolerance. Flowers are a unique phosphorescent brilliant orange. This plant is ideal for landscape use and is adapted for hot summer heat. The nursery industry will benefit from the strong production traits of this selection including easy propagation and vigorous growth.
3. New Southern Highbush Blueberry Named ‘Pearl’. ARS Plant Geneticists at the Thad Cochran Southern Horticultural Laboratory recently released ‘Pearl’, a new highbush blueberry cultivar. The objective of the blueberry breeding program is to introduce new cultivars with improved production traits as well as enhanced nutritional value. In addition to yield, one of the key traits for fresh market blueberries is an early ripening period. U.S. fresh market favors early ripening cultivars, which command premium prices. ‘Pearl’ produces ripe berries earlier than the earliest rabbiteye blueberry cultivars in production today. It has good yield potential and produces large, attractive, light blue, firm berries with excellent flavor and small picking scars. ‘Pearl’ has low to moderate chilling requirements and will perform well in the Gulf-coast region and in other areas where southern highbush blueberry cultivars are grown successfully. Growers will benefit from the early ripening and be able to participate in the lucrative early U.S. fresh market where opportunities for marketing rabbiteye blueberries have diminished.
4. ‘Sahara Sunset’, A Variegated Purple Leaf Form of Heat Tolerant African Hibiscus. ARS Plant Geneticists at the Thad Cochran Southern Horticultural Laboratory recently released Hibiscus acetosella ‘Sahara Sunset’, an African hibiscus cultivar with variegated foliage. African hibiscus are known for their heat tolerance and maple-like foliage. Purple and bronze leaf forms are popular annuals in low-maintenance landscapes because they provide striking color contrast. The objective of the hibiscus breeding program is to introduce new cultivars with enhanced pest resistance in combination improved production traits as well as superior landscape performance. ‘Sahara Sunset’ is the first stable variegated form of the purple leaf type and will be protected by a plant patent. The nursery industry will benefit from the unique multicolored foliage that can be used as a specimen plant in landscapes, a color accent in shrub borders, or a contrast plant in mixed annual planters. Heat tolerance and broad environmental adaptation make ‘Sahara Sunset’ an important component of low maintenance, low water plantings. It thrives in summer heat and full sun, has a spreading upright growth habit, and is tolerant of common insects and diseases.Sakhanokho, H.F., Rajasekaran, K., Kelley, R.Y. 2009. Induced Polyploidy in Diploid Ornamental Ginger (Hedychium muluense) Using Colchicine and Oryzalin. HortScience. 44(7):1809-1814.