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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Horticulture Research

2009 Annual Report

1a. Objectives (from AD-416)
The primary objectives of this project are 1) conserving of tropical/subtropical ornamental crop genetic resourses and associated information important for the evaluation and utilization of that material; 2) the development and application of new or improved horticultural evaluation procedures and genetic marker-based approaches for genetic diversity assessment of the preceding genetic resourses; 3) genetic improvement efforts directed to developing new, superior tropical/subtropical ornamental germplasm; and 4) the transfer of technologiy in the form of tropical/subtropical ormamental crop genetic resourses, associated information, and new, superior tropical/subtropical ornamental germplasm to researchers and breeders worldwide.

1b. Approach (from AD-416)
Collect new accessions of subtropical/tropical ornamental plants that have commerical potential in the U.S. Evaluate newly collected accessions and existing material, primarily flowering trees and shrubs already on site, using phenotypic characters and molecular makers. Organize the information such that it can be used as descriptors for inclusion in the GRIN system. Utilize the molecular and phenotypical analysis to breed improved germplasm in support of the ornamental industry. Communicate and coordinate subtropical/tropical ornamental horticultural research with local and regional industry, universites, and foreign germplasm effort in Florida, Puerto Rico, and Hawaii.

3. Progress Report
New field plantings of Tahina spectabilis (newly described palm from Madgascar), Roystonea oleracea were established. Seed of additional rare palms were purchased from Three dozen additional accessions of tropical conifers have been received through germplasm exchange with the Montgomery Botanical Center and Atlanta Botanical Garden. DNA was extracted from leaf samples of Jamaican Zamia populations, and genotyping with 23 SSR markers has begun. Analysis of the WRKY gene alignments across the palm subtribe Attaleinae (which includes such important ornamentals as coconut and Queen palm) was completed and a manuscript is in review. A final round of evaluation of Turnera diffusa 'Luisa' is underway and release is planned for 2010. Backcrosses of (Hippeastrum papilio x H. brasilianum) to H. brasilianum were successfully made (these should segregate for floral fragrance and will be used for genomic studies of fragrance genes). Leaf samples were received of Zamia populations from the Dominican Republic, from which DNA is being extracted for genotyping. With the assistance of a USDA fellow, the tissue culture lab is functional and micropropagation of Hippeastrum is underway. We have successfully data mined EST databases of Zamia, Lycoris and Alstroemeria for conserved ortholog sequences (COS genes) that can potentially be used for population (SNP) and phylogenetic analyses. A visiting scientist from EMBRAPA is spending the year in our lab through the LABEX program working on the phylogenetics of Brazilian Alstroemeria species.

4. Accomplishments
1. Identification of the closest living ancestor to the coconut. The origins of the coconut have been one of the "abominable mysteries" of science for decades. Using seven independent gene sequences, we investigated the evolutionary relationships of a horticulturally important group of palm trees, including the coconut. We showed that the root of origin for the coconut is in South America and that the genus Syagrus – mostly found in Brazil and an important group or tropical ornamentals - is its closest living relative. Moreover, we present the best supported and most highly resolved tree of life for this group of palms. Syagrus is thus a good choice for investigating functional genes that could confer disease and/or pest resistance to coconut.

2. Genetic relationships among coconut varieties. The genetic relationships among coconut varieties are more complicated than previously supposed. Using 41 molecular markers across 232 coconut individuals representing 10 varieties, we show that most of the previously published studies of genetic diversity in this important crop and tropical landscape ornamental may have presented a false picture of the relationships among these varieties by 1) failing to test for hybrids among the samples and 2) applying only one type of statistical analysis to the data. As a result, theories concerning the origins of the coconut may need to be reappraised.

Review Publications
Maunder, M., Levia, A., Santiago-Valentín, E., Stevenson, D.W., Acevedo-Rodríguez, P., Meerow, A.W., Mejía, M., Clubbe, C., Francisco-Ortega, J. 2008. Plant Conservation in the Caribbean Island Biodiversity Hotspot. Botanical Review. 74:197-207.

Mauro-Herrera, M., Meerow, A.W., Perera, L., Russell, J., Schnell Ii, R.J. 2009. Ambiguous genetic relationships among coconut (Cocos nucifera L.) cultivars: the effects of outcrossing, sample source and size, and method of analysis.. Genetic Resources and Crop Evolution. 57:203-217.

Last Modified: 10/19/2017
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