Location: Southern Horticultural Research2011 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 is focused on the development of new germplasm and cultivars with adaption to the gulf coast region of the U.S. Small fruit research includes conventional breeding to enhance commercial production of blueberries and muscadine grapes. Early ripening, high productivity, and superior fruit quality are the top breeding goals for rabbiteye and southern highbush blueberries. Blueberry breeding also includes improved berry storage and handling, taste and nutritional value. More than 240 crosses were completed among rabbiteye and southern highbush. 120 new selections were planted in field conditions to evaluate performance. Approximately 8,000 blueberry seedlings from the previous season’s breeding efforts were established as progeny for initial selection for fruit quality. Muscadine grape selections, including 200 new seedlings from last year’s breeding efforts, were established in field plantings for evaluation. An elite thornless blackberry selection was propagated via tissue culture in preparation for wide scale testing and release and distribution to nurserymen. Research on ornamental plants includes modern genetic methods, conventional breeding and tissue culture. Because of the diversity within the nursery and greenhouse industry, research is underway on a wide variety of ornamental crops including crapemyrtle, hibiscus, begonia, hydrangea, redbud, fringe tree and dogwood. Elite crapemyrtle selections with improved disease resistance in combination with dark purple, dark red, pink or white flowers were transferred to four nursery companies for evaluation. Ten selections of a wide hybrid crapemyrtle with dark purple flowers have proven root hardy over three winters and were sent to nurseries for additional evaluation. Fourteen Hibiscus selections, including one wide hybrid, are being evaluated by nurseries for possible release. Cold hardy begonia germplasm that was improved to include more desirable horticultural traits has maintained hardiness. As part of a tissue culture strategy to overcome breeding barriers, pollen viability and fertility studies on select begonia were initiated. Two new dwarf variegated ornamental ginger have been developed. One of these two plants is the cultivar ‘Ramata’ for which a patent application was submitted. High throughput sequencing was completed on hydrangea and dogwood and uncovered more than 50,000 genes in these woody landscape crops. Data included an abundance of molecular markers to accelerate conventional breeding for these specialty crops. Further analysis will link the expression of newly discovered genes with important traits. Molecular markers were also developed for two native ornamental trees, fringe tree and redbud. These markers were used to show relatedness between cultivars and species to better understand the resources available for breeding. Markers are also being used to better understand population differences among stands of native trees such as dogwood, redbud and fringe tree. This is especially important for pygmy fringe trees, which are classified as an endangered native tree in Florida.
1. Release of ‘Lufkin White’ and ‘Lufkin Red’ hibiscus cultivars. Hardy hibiscus are useful flowering perennials in full sun landscapes but suffer from disease and pest damage. ARS researchers at Poplarville, Mississippi, released two hardy hibiscus cultivars adapted to the environmental conditions of the South. 'Lufkin Red' was selected for its exceptional red flowers and 'Lufkin White' was selected for its blushed white flowers. Both display outstanding disease resistant foliage. Plants develop rapidly in containers and, in addition to leaf-spot resistance, display good tolerance to other common pests. Under landscape conditions plants should mature to approximately 1.6 meters high x 1.3 meters wide. Flower quality and numbers, as well as growth habit, are improved over the native species which tend to be large plants with loose growth habit. Sales of 'Lufkin Red' and 'Lufkin White' are expected to benefit the nursery industry in USDA cold hardiness zones 4 through 9.
Wang, X., Wadl, P.A., Cabrera, R.I., Pounders Jr, C.T., Scheffler, B.E., Pooler, M.R., Rinehart, T.A., Trigiano, R.N. 2011. Evaluation of genetic diversity and pedigree within crapemyrtle (Lagerstroemia spp.) cultivars using simple sequence repeat (SSR) markers. Journal of the American Society for Horticultural Science. 136(2):116-128.