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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research » Research » Research Project #425102

Research Project: Small Fruit and Ornamental Genetic Research for the Mid-South

Location: Southern Horticultural Research

2016 Annual Report

The long-term objective of this project is to develop improved germplasm for woody ornamental and small fruit crops adapted to the Gulf Coast Region where the effects of both biotic and abiotic stresses are exacerbated by frequent weather extremes. Objective 1. Design and apply phenotyping methods to identify and measure traits associated with environmental tolerance in southern-adapted small fruit and woody ornamental crops, especially in underutilized and native germplasm that can be incorporated into existing breeding programs. Objective 2. Identify markers and/or genes that are associated with environmental tolerance in breeding populations and evaluate indirect selection strategies for drought, heat, and poor soil tolerance designed to improve the efficiency and accuracy of selection during breeding. Objective 3. Design and test high throughput sequencing methods to uncover genes differentially expressed in response to environmental stress. Objective 4: Accelerate the genetic improvement and cultivar development for small fruit and woody ornamental genera with the genetic resources developed in Objectives 1, 2, and 3.

Understanding the genetic basis for plant tolerance to environmental stress is critical to protecting agriculture productivity in the U.S. and worldwide. The Thad Cochran Southern Horticultural Laboratory will lead research on the vulnerability of specialty crops to drought, heat, flood and poor soils, and to develop tools to incorporate selection for superior environmental tolerance into existing breeding programs. Scientists will develop innovative and rigorous phenotyping to more quickly and efficiently quantify traits associated with drought and poor mineral soil tolerance in small fruit and woody ornamental crops. Germplasm will be evaluated by modification and refinement of greenhouse methods. Initial focus will be on improved selection in southern adapted blueberry germplasm including existing cultivars. Subsequent efforts will focus on selection criteria for seedling populations to produce criteria directly applicable to southern blueberry breeders. Proposed research is designed to connect phenotypes associated with stress tolerance to specific genotypes allowing rapid, precise selection of traits in existing breeding lines using indirect selection by molecular markers. Molecular studies will also contribute significantly to understanding the genetic basis for environmental tolerance traits and the inheritance and segregation of these traits in existing conventional breeding programs for blueberry. Scientists will also identify novel genes and gene expression patterns associated with severe stress and recovery in native plants exhibiting superior environmental tolerance to drought and flooding to increase our understanding of existing abiotic stress tolerance models. Initial experiments will use Pityopsis ruthii, which is an endangered, native plant that exhibits extreme environmental tolerance. Results from phenotyping, genotyping, and gene expression studies will be incorporated into our conventional breeding programs to enhance efficiency and to advance development and application of new breeding tools. Blueberry parents and seedling populations at all stages of development are available for phenoptype, marker and genotype studies as well as breeding for new, improved cultivars. An extensive blueberry species and cultivar collection is also available on site along with breeding materials from collaborating universities and the National Clonal Germplasm Repository.

Progress Report
Over 200 crosses were made among select rabbiteye and southern highbush blueberry parents and seed were harvested. Seed from 2015 crosses were germinated and are being established for field plantings in 2017. Approximately 5,000 seedlings from 2014 crosses were established in field nursery plantings and approximately 200 selections were made. Selected plants are being propagated by soft wood cuttings for testing at Poplarville and Wiggins, MS locations. An elite rabbiteye blueberry and elite southern highbush blueberry were propagated by tissue culture in preparation their release as new cultivars. Three additional plants were selected for their superior traits and have been submitted to private laboratories for micropropagation in anticipation of their release as new cultivars in the next two years. A grant-supported collaboration between genetics and entomology was established identify potential sources of resistance to the Spotted Winged Drosphilla fruit fly in diverse blueberry germplasm and species. The grant was awarded for the proposal entitled “Screening Small Fruit Germplasm for Resistance to Southern Populations of Spotted Wing Drosophilla” by the NCCC-212 Crop Germplasm Committee. Additionally, a partially seedless muscadine grape with thin skins, crisp pulp, and excellent flavor has been developed and is being tested for its potential as a new fresh-market cultivar. An in vitro screen for pH tolerance in rabbiteye (Vaccinium virgatum) and southern highbush (V. corymbosum) blueberries was initiated as an alternative to the greenhouse method. This in vitro screen for pH tolerance in blueberries has now been completed, and the results of the experiment are currently being analyzed. In addition, an experiment was conducted in the greenhouse to screen for moisture stress in both rabbiteye and southern highbush blueberries. Plant tissue samples were collected at various time intervals and frozen for later use in proline content determination and gene expression studies to potentially identify blueberry varieties that are drought tolerant. A similar experiment is being conducted currently in two diploid species, V. arboreum and V. pallidum. Gene expression data for the model plant Pityopsis ruthii, a native endangered species with extraordinary drought and submergence tolerance, was analyzed to determine the genes that are turned on and off during a drought event. Genes that were turned on during drought were identified by comparing them to genes from other plants. Genes were grouped by networks and pathway to understand how groups of genes were contributing to drought tolerance in Pityopsis ruthii. In order to look at the same genes in other ornamental plants, the genomes for hydrangea and flowering dogwood were sequenced and assembled using funding from a NSF grant.

1. New hibiscus cultivars ‘Hapa White’, ‘Hapa Pink’ and ‘Hapa Red’. USDA-ARS scientists at the Southern Horticulture Research Unit in Poplarville, Mississippi, developed and released three hibiscus cultivars, ‘Hapa White’, ‘Hapa Pink’, and ‘Hapa Red’. All three cultivars are interspecific hybrids resulting from the cross Hibiscus x moscheutos and cold hardy hibiscus. Flowers of ‘Hapa White’ are white and of moderate size with a small red swath of color at the base of each petal producing an eye in combination with surrounding petals. Flowers of ‘Hapa Pink’ are abundant, pink, moderate size with a small red eye. Flowers of ‘Hapa Red’ are red, of moderate size with a small red eye. Plants of all three varieties are generally pest free, moderately vigorous, and compact with a spreading upright growth habit. In cold hardiness zones 7 and 8, plants die to the ground in winter, developing a strong root system that regenerates tops each spring. Plants start flowering in late June. These new hibiscus varieties are well suited to landscape uses such as specimen plants, color accents in shrub borders, contrast plants in mixed landscape plantings or as flowering plants in living screens. Plants perform best in full sun with moderate moisture and fertility. Their broad environmental adaptation and tolerance of common insects and diseases make them ideal plants for low maintenance plantings.


Review Publications
Pounders Jr, C.T., Sakhanokho, H.F. 2015. 'Miss Frances', 'Miss Gail' and 'Miss Sandra' Crapemyrtles. HortScience. 1721-1722.
Rinehart, T.A., Shockey, J.M., Edwards Jr, N.C., Spiers, J.M., Klasson, K.T. 2015. Vernicia fordii ‘Spiers’, a new tung tree for commercial tung oil production in the gulf coast region. HortScience. 50: 1830-1832.