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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Horticulture Research

2012 Annual Report

1a. Objectives (from AD-416):
1. Conserving tropical/subtropical ornamental crop genetic resourses and associated information important for the evaluation and utilization of that material. 2. 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. 4. Transfer of technology in the form of tropical/subtropical ormamental crop genetic resourses, associated information, and new, superior tropical/subtropical ornamental germplasm to researchers and breeders worldwide. 5. Evaluate containerized subtropical/tropical ornamental germplasm for its growth responses to different container media components. Where feasible, estimate for this germplasm the heritabilities and other patterns of genetic variation for adaptation/tolerance to the different container media components.

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:
Germplasm of 12 Bauhinia species have been planted in the field; these were grown from seed requested of the Desert Legume Collection. A particularly floriferous and well-adapted clone of Handroanthus impetiginosus (formely Tabebuia avellandeae) has been identified in the seedling evaluation block that we established. All population of Zamia from Jamaica and Dominican Republic have been genotyped 30 microsatellite loci. Zamia sample collections were completed for the Cayman islands. We have 10 single copy genes that are being used on 10 individual samples of each population genotypes with the simple sequence repeats (SSRs), and the sequencing has been completed for Jamaica, Puerto Rico and Dominican Republic. Analysis of WRKY gene sequences for all other genera of palm tribe Cocoseae (tribes Elaeidinae and Bactridinae) are complete, and a paper is being prepared for publication. analyzed. Patent applications are being prepared for five Hippeastrum hybrid clones and will be submitted to the Technology Transfer patent committee for consideration. We are increasing micropropagated stocks of two diploid Hippeastrum clones to increase attempt chromosome doubling with oryzalin early in 2012. Completed study on alternative potting substrate. Results show composted insect colony waste (CW) substitutions of between 30 and 70% for equal amounts of compost plus peat resulted in plant performance greater than or equal to that observed with a commercial mix. Composted CW is a nutrient rich material that can be used in 50% CW:50% peat mix will have good characteristics for a basic potting substrate for most container grown plants. One peer reviewed publication a second in in-house review). Completed study on ornamental species that have the potential for use in remediation of low-level arsenic contaminated areas. Currently data is being analyzed for manuscript preparation. Data collection on the effect of nitrogen fertilization on coralloid root development in cycads has been completed and these data are being analyzed.

4. Accomplishments
1. New insight into Louisiana iris genetics. The Louisiana iris are a small group of species iris that have been interbred to create a large and popular group of hybrids. Using DNA markers, ARS researchers at Miami, Florida uncovered previously undocumented genetic variation in Louisiana iris populations in Florida. Their analyses support theories of multiple introductions and movement of plants by Native Americans. This research presents data that can be mined by iris breeders to introduce novel genotypes into their program.

2. Genetic diversification within Zamia (Cycadales: Zamiaceae) on Puerto Rico. Three distinctive Zamia species occur on Puerto Rico: Z. erosa on the north coast, and Z. portoricensis and Z. pumila, both in the south. Their relationships are largely unknown. ARS researchers tested a hypothesis of multiple introductions and explored whether the three species show divergent patterns of genetic variation using 31 DNA markers across ten populations. This study is the most intensive population genetics investigation of a cycad to date in terms of number of markers, and one of few microsatellite studies of plants from the Caribbean biodiversity hotspot. Puerto Rican zamias exhibit an amalgam of patterns of genetic differentiation reported for cycads. Zamia erosa exhibits a more than threefold greater degree of population differentiation. Historical gene flow only evident between Z. portoricensis and Z. pumila. Zamia erosa likely represents an independent introduction into Puerto Rico; Z. portoricensis and Z. pumila fit a scenario of allopatric speciation. The study reveals patterns of genetic variation that are of interest to nursery growers of cycads.

3. Insect rearing waste as a substitute potting substrate. A substitute potting substrate using 80% composted solid and semi-solid insect rearing waste (CW) had germination rates and shoot dry weight equal to a commercial mix. No substance in the CW appeared to be detrimental to plant growth. As a potting substrate insect rearing waste was equal to that of the commercial mix.

4. Ornamental plants for bioaccumulation of arsenic. Arsenic applied around nursery structures for rodent control can remove significant acres from production. Switchgrass and the ornamental plants iris, sunflower and marigold grown in hydroponic solution tolerated up to 5.25 ppm arsenic solution and are potential plants for remediation of arsenic contaminated sites.

Review Publications
Meerow, A.W., Gideon, M., Kuhn, D.N., Mopper, S., Nakamura, K. 2011. The genetic mosiac of iris series Hexagonae in Florida: inferences on the Holocene history of the Louisiana irises and anthropogenic effects on their distribution. International Journal of Plant Science. 172(8):1026-1052.

Reed, S.T., Schnell Ii, R.J., Moore, J.M., Dunn, C.B. 2012. Chlorophyll a + b content and chlorophyll fluorescence in avocado. Journal of Agricultural Science. 4(4):29-36.

Oleas, N.H., Meerow, A.W., Francisco-Ortega, J. 2012. Evidence of bottleneck and isolation by distance in an endangered species from the Tropical Andean hotspot. Journal of Heredity. 103(4):557–569.

Meerow, A.W., Krueger, R., Singh, R., Ti, L.L., Ithnin, M., Li, L.O. 2012. Coconut, date and oil palm genomics. In: Schnell, R.J, Priyadarsham, P.M., editors. Genomics of Tree Crops. New York, NY: Springer. p. 299-351.

Chacon, J., De Assis, M.C., Meerow, A.W., Renner, S.S. 2012. From East Gondwana to Central America: Historical biogeography of the Alstroemeriaceae. Journal of Biogeography. DOI: 10.1111/j.1365-2699.2012.02749.x.

Last Modified: 05/22/2017
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