Skip to main content
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

2018 Annual Report


Objectives
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.


Approach
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 phenotype, 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
This is the final report for 6062-21000-009-00D. To gain basic knowledge about the microbial community composition in roots of different blueberry (Vaccinium (V.) species), two genotypes of each of V. corymbosum, V. virgatum Aiton, V. darrowii Camp (drought tolerant), and V. arboreum Marshall (drought and high soil pH tolerant), were grown in 1-gallon pots in a typical pine bark: peat moss: sand mix (3:1:1). For the microbial community structure analysis, about 0.9 g of roots was collected from each plant and used to extract the microbial DNA using the DNeasy PowerSoil kit. Bacterial and fungal rRNA gene sequencing will be performed using Illumina bacterial 16S rRNA gene libraries and fungal 18S rRNA ITS libraries. To identify the genus and the species of most abundant microorganisms, BLASTN will be used to find homologous sequences in NCBI. To develop blueberry cultivars with resistance to the stem blight pathogens, six isolates of the stem blight pathogens, Botryosphaeria dothidea and Neofusicoccum parvum, were characterized based on comparison of the DNA sequences of internal transcribed spacer (ITS) and elongation factor (EF1-a). The optimum temperature for the growth of the isolates was determined. The efficacy of four fungicides, namely azoxystrobin (Abound), pyraclostrobin + boscalid (Pristine), propiconazole (Orbit), and cyprodinil + fludioxonil (Switch), on growth of the isolates was tested. Furthermore, we conducted pathogenicity tests on 30 cultivars and breeding selections. Of 30, only four southern highbush and three rabbiteye accessions displayed resistance. Results from this study will help us to release blueberry cultivars with resistance to stem blight pathogens. To investigate the host range of the blueberry leaf rust and characterize new sources of resistance to its causative agent (Thekopsora (T.) minima), 15 southern highbush accessions, two interspecific hybrids (Vaccinium spp.), and accessions from five diploid Vaccinium species were inoculated with an isolate of T. minima. Of 15, only two southern highbush accessions displayed resistance, whereas both accessions of V. arboreum displayed immunity against T. minima. Accessions of V. darrowii exhibited necrosis but with limited sporulation, indicating a high level of resistance. Sporulating lesions and brown spots were observed in accessions of V. elliottii and V. tenellum. Brown lesions, large pustules, and abundant sporulation were observed on V. pallidum accessions and their interspecific hybrids. As the lesions expanded, defoliation was observed in V. pallidum accessions. When tested against rabbiteye and southern highbush blueberries, urediniospores of T. minima from overwintering leaves of V. pallidum were found to be virulent, suggesting that T. minima overwinters on V. pallidum. Based on symptoms and scanning electron microscopy of urediniospores, we hypothesize that V. elliottii, V. tenellum, V. pallidum, and V. corymbosum exhibit no host specificity to T. minima. Flow cytometry and chromosome spread were used to determine the ploidy level in different Vaccinium species and interspecific hybrids. Of 77 tested, 11 are diploid, 49 are tetraploid, one pentaploid, and 16 are hexaploid. DNA content was measured for three separate tissue samples from at least three individual plants per taxa for accuracy. Absolute genome sizes varied significantly among ploidy levels, with 2C-value means of 1.09 pg for diploid, 2.10 pg for tetraploid, and 3.60 pg for hexaploid taxa. Hedychiums, also known as ornamental gingers or ginger lilies, are multipurpose plants cultivated as ornamentals because of their multicolor, showy, and scented flowers, and as medicinal plants because their essential oils that have been found to possess antimicrobial, as well as insecticidal properties. There is often taxonomic and botanical confusion about Hedychium species and cultivars because of the apparent existence of more than one cytotype within several Hedychium species, which is most likely due to the ease with which these species hybridize. Nuclear DNA content is the total DNA amount contained in the chromosomes in a single cell of an individual whereas the ploidy is the number of sets of chromosomes in a cell or cells of an organism. DNA content of 23 Hedychium species and hybrids was determined using a flow cytometry machine. We also determined, for the first time, the chromosome number of one species, Hedychium stenopetalum, which was found to be diploid with 2n = 2x = 34 chromosomes. Our results should be helpful not only in clarifying the botanical and taxonomic confusion in Hedychium but also in paving the way for a sound breeding program for this increasingly important ornamental ginger. A new non-patented edible ornamental rabbiteye blueberry cultivar ‘Muffin Man’ was released for homeowners and nursery industry. ‘Muffin Man’ is an ideal choice for edible and ornamental landscape for the USDA hardiness zones 8a thru 9a. ‘Muffin Man’ is characterized by notable fall coloring in leaves, numerous unique pale pink blooms that arise on long reproductive shoots, where berries developed with attractive color ranging from pink to deep blue upon ripening. ‘Muffin Man’ produces berries with small dry stem scars and acceptable aroma and sugar-acid balance. Berry weight, berry size, firmness, pH, Soluble solids content, and titratable acidity of ‘Muffin Man’ are comparable to commercial cultivars ‘Brightwell’ and ‘Alapaha’. A new patented southern highbush blueberry cultivar ‘Gumbo’ was developed by USDA-ARS scientists in Poplarville, Mississippi, and jointly-released with the Mississippi Agricultural and Forestry Experiment Station. The new cultivar has several advantageous attributes for blueberry growers in the Southeastern U.S. and other subtropical regions having more temperate winters. Among these is an earlier ripening period (10-14 days) than the earliest-ripening rabbiteye blueberry cultivars, the predominant blueberry type grown along the U.S. Gulf Coast. In comparison to other southern highbush cultivars with similar chill-hour adaptation to region, ‘Gumbo’ has consistently displayed higher plant vigor and possesses other critically important attributes including good yield potential, resistance to stem blight pathogens, and high fruit quality. Muscadine grape and its wine products are becoming more acceptable due to potential health benefits associated with high concentrations of phenolic compounds. Wines made from eight high-yielding muscadine grape varieties grown in Mississippi were compared for their phenolic composition, antioxidant activity, and other quality parameters during different secondary fermentation periods. During the fermentation, the total content of hydroxybenzoic acid derivatives decreased, while that of hydroxycinnamic acid derivatives increased. Changes in total flavanoids varied depending upon muscadine cultivar. The comparison of wines under different fermentation times from eight muscadine cultivars demonstrated that wine quality and health potential were largely dependent on muscadine genotype and fermentation duration. Relative higher phenolic content and antioxidant capacity were found in ‘Cowart’, ‘Creek’ and ‘Noble’.


Accomplishments
1. Development of a new edible ornamental rabbiteye blueberry cultivar. Homeowners and nursery industry are interested in edible ornamental rabbiteye blueberry cultivars that are well adapted to the region. So far, only three rabbiteye cultivars were released for home gardeners in the USA. ‘Muffin Man’ is a new, non-patented edible ornamental rabbiteye blueberry cultivar developed by the USDA-ARS scientists in Poplarville, Mississippi. ‘Muffin Man’ derived from a cross between T 366 and ‘Brightwell’ which was made in 2003. ‘Muffin Man’ is characterized by notable fall coloring in leaves, numerous unique pale pink blooms that arise on long reproductive shoots, where berries developed with attractive color ranging from pink to deep blue upon ripening. Important attributes of ‘Muffin Man’ include its heat and drought tolerance and extended berry ripening periods which are valuable for homeowners and landscape industry. ‘Muffin Man’ produces berries with small dry stem scars and acceptable aroma and sugar-acid balance. Berry weight, berry size, firmness, soluble solids content, and titratable acidity of ‘Muffin Man’ are comparable to commercial cultivars ‘Brightwell’ and ‘Alapaha’. ‘Muffin Man’ is an ideal choice for edible and ornamental landscape for the USDA hardiness zones 8a thru 9a. ‘Muffin Man’ was released as a public domain cultivar and genetic materials of this cultivar were deposited at the USDA ARS National Clonal Germplasm Repository, Corvallis, Oregon, as PI 687223 for research and breeding purposes.

2. Development of a new southern highbush blueberry cultivar. The native rabbiteye blueberry, have been grown commercially in the southeastern U.S. for well over a century. However, the southern highbush blueberry is continually gaining popularity in much of this geography as well as in subtropical regions due to earlier ripening periods and quality attributes favored by the lucrative early U.S. and worldwide fresh-berry markets. Reluctance of many established Gulf Coast and Mid-South growers to change from rabbiteye blueberries to southern highbush blueberries is in part due the lack of southern highbush blueberry cultivars possessing the zest and vigor to thrive inherent to the native rabbiteye blueberry and to a shorter early-berry market window. ‘Gumbo’ is a new patent southern highbush blueberry cultivar developed by the USDA-ARS scientists in Poplarville, Mississippi, and jointly-released with the Mississippi Agricultural and Forestry Experiment Station. The new cultivar has several advantageous attributes for blueberry growers in the southeastern U.S. and other subtropical regions having more temperate winters. Among these is an earlier ripening period (10-14 days) than the earliest-ripening rabbiteye blueberry cultivars grown along the U.S. Gulf Coast. In comparison to other southern highbush cultivars with similar chill-hour adaptation to region, ‘Gumbo’ has consistently displayed higher plant vigor and possesses other critically important attributes including good yield potential and high fruit quality. ‘Gumbo’ is expected to provide growers along the U.S. Gulf Coast, enhanced opportunities to compete in the lucrative early-fresh-berry market.


Review Publications
Sakhanokho, H.F., Islam-Faridi, N.M., Rajasekaran, K., Pounders Jr, C.T. 2018. Diversity in nuclear DNA content and ploidy level of Hedychium species and hybrids. Journal of Crop Improvement. 32(3):431-439. https://doi.org/10.1080/15427528.2018.1445679).
Sakhanokho, H.F., Rinehart, T.A., Stringer, S.J., Islam-Faridi, M.N., and C.T. Pounders. 2018. Variation in nuclear DNA content and chromosome numbers in blueberry. Sci. Hort. 233:108-113
Gallardo, R.K., Zhang, Q., Klingthong, P., Dossett, M., Polashock, J.J., Rodriguez-Saona, C., Vorsa, N., Edger, P., Scherm, H., Ashrafi, H., Babiker, E.M., Finn, C.E., Iorizzo, M. 2018. Breeding trait priorities of the blueberry industry in the United States and Canada. HortScience. 53(7):1021-1028. https://doi.org/10.21273/HORTSCI12964-18.
Zhang, Y., Chang, S., Stringer, S.J., Zhang, Y. 2017. Characterization of titratable acids, phenolic compounds, and antioxidant activities of wines made from eight Mississippi-grown muscadine varieties during fermentation. LWT - Food Science and Technology. 86:302-311. doi:10.1016/j.lwt.2017.07.038.
Rezazadeh, A., Sampson, B.J., Stafne, E., Shaw, D.A., Stringer, S.J., Hummer, K.E. 2018. Susceptibility of bunch grape and muscadine cultivars to berry splitting and spotted-wing Drosophila oviposition. American Journal of Enology and Viticulture. 69(3):258-269.