Location: Subtropical Horticulture Research
2022 Annual Report
Objectives
Objective 1: Efficiently and effectively maintain the safety, genetic integrity, health, and viability of subtropical and tropical ornamental genetic resources, and distribute them and associated information worldwide.
Subobjective 1A: Strategically expand and improve collections of priority tropical and subtropical ornamental taxa and associated information.
Subobjective 1B: Conserve, regenerate, and distribute as needed subtropical and tropical ornamental genetic resources and information efficiently and effectively, emphasizing priority genera identified by Crop Germplasm Committees (CGCs).
Objective 2: Develop more effective genetic resource characterization, phylogenetic analyses, and evaluation methods, and apply them to priority subtropical and tropical ornamental genetic resources. Record and disseminate evaluation and characterization data via GRIN-Global and other data sources.
Subobjective 2A: Develop nearly complete whole plastome and low copy nuclear gene sequences to generate well-resolved phylogenies of various clades of Amaryllidaceae.
Subobjective 2B: Elucidate the genetic control of anthocyanin pigmentation in the genera Hippeastrum (amaryllis), Worsleya, and Griffinia, and fragrance production in Hippeastrum.
Objective 3: Guided by new knowledge of the genetic relationships and valuable ornamental traits of poorly-known plants, develop superior new cultivars and genetically-enhanced populations and/or selections of priority subtropical and tropical ornamental crops.
Subobjective 3a. Select, breed, and/or release new cultivars of the subtropical/ tropical shrub Portlandia, the flowering tree genus Tabebuia (inc. Handroanthus), and other tropical/subtropical taxa.
Subobjective 3b: Continue evaluation and selection of Hippeastrum hybrid progeny.
Approach
The long term objectives of this project are to ensure a secure and diverse stream of new genetic variation and enhanced germplasm for the subtropical/tropical ornamental horticulture industry as well as generate and consolidate detailed information about the intrinsic genetic variability, systematic relationships, and ornamental merit of genetic resources via genetic characterization, systematic studies, and field evaluation. These objectives are a combination of hypothesis-driven and non-hypothesis driven research. The objectives form an integrated program of subtropical/tropical ornamental germplasm characterization, enhancement and improved management practices. The program efficiently and effectively maintains the safety, genetic integrity, health, and viability of subtropical and tropical ornamental genetic resources. Collections of priority tropical and subtropical ornamental taxa and associated information will be strategically expanded and improved, distributing them worldwide to customers and stakeholders, emphasizing priority genera identified by appropriate Crop Germplasm Committees.
Nearly complete whole plastomes and many low copy nuclear gene sequences will be obtained to generate well-resolved phylogenies of various clades of Amaryllidaceae. The genetic control of anthocyanin pigmentation in the genera Hippeastrum (amaryllis), Worsleya, and Griffinia, and fragrance production in Hippeastrum will be elucidated.
Guided by new knowledge of the genetic relationships and valuable ornamental traits of poorly-known plants, superior new cultivars and genetically enhanced populations and/or selections of priority subtropical and tropical ornamental crops will be developed, with emphasis on the tropical shrub Portlandia, the flowering tree genus Tabebuia (inc. Handroanthus), and other tropical/subtropical taxa.
The evaluation and selection of Hippeastrum hybrid progeny will be continued. Hybrid progeny from the past few years, many of which are just reaching flowering size, will be evaluated for floral phenotype and flowering behavior, with selections made based on novel flower coloration, patterning, fragrance, and both bud and scape number.
Progress Report
The ornamental horticulture industry in Florida is most demanding and leads a $21.08 billion economy with 203,482 jobs. The population influx to Florida, from other states and countries, and the consequent increase in household landscapes are also increasing the ornamental plant production industry. To satisfy consumer demand, diverse subtropical/tropical plant germplasm requirements are extremely important to the ornamental industry. Being a subtropical environment, the production and use of wide-ranging ornamental germplasms are impacted by disease and pest problems. ARS researchers in Miami, Florida, are effectively conserving and safeguarding invaluable subtropical/tropical plant genetic resources in the form of 2500+ ornamental plants, which are being collected, characterized, and evaluated. During the fiscal year, over 2,010 propagules (i.e., seeds, budwood, rhizomes, corms) of different ornamental accessions were distributed to 13 states in the U.S and three international organizations. Among various subtropical/tropical ornamentals, Lagerstroemia, palms, and plumeria were the three major accessions shared frequently with various national and international stakeholders. Collaborations/consultations were made with diverse specialists to safeguard valuable germplasms (of Enterolobium cyclocarpum against Nectria canker and Adenanthera pavonine against Fuscoporina). For genetic work in Amaryllidaceae, ARS scientists in Miami, Florida, conducted RNA-Seq analysis (with 25-30 GB transcriptome data) using various high throughput bioinformatics tools. The team also successfully generated over 537 million paired transcriptome nucleotide reads for these plants. As less genomic information is available for non-modeled plants, such as Amaryllidaceae, the de novo bioinformatics approach is followed to assemble transcriptome nucleotide reads. Key metabolic enzymes and their isoforms (eg., chalcone isomerase, chalcone synthase, flavanone hydroxylase, phenylalanine ammonia-lyase, etc.) in the anthocyanin biosynthesis pathway for white and purple-colored Amaryllidaceae flowering plants are being identified. The conserved genetic regions in Amaryllis were further validated following polymerase chain reaction and by conducting candidate gene-specific Sanger re-sequencing (used to study a small subset of genes linked to a defined phenotype) experiments. The fragrant white-colored Amaryllidaceae flower shared 88% (Z)-ß-ocimene metabolite concentration as compared to 48% in the non-fragrant purple-colored Amaryllidaceae flower. The gene and genomic information generated in this project will be deposited in the National Center for Biotechnology Information public domain and the data will be shared with the scientific community for further genetic improvement efforts in Amaryllis plants and related ornamental flowering species.
Accomplishments
1. Genetic resource development for ornamental Amaryllidaceae plants. Amaryllidaceae plants are impressive, tough, and reliable bulbs that require minimal maintenance and are primarily distributed in the tropical and sub-tropical regions of the world. They form attractive showy flowers for both indoor and outdoor settings. Despite their great economic, aesthetic, and ecological significance, the extent of their taxonomic classification, genomics, and genetic diversity information remains highly limited. ARS researchers in Miami, Florida, developed molecular resources that help identify two new Amaryllidaceae species. The Amaryllidaceae anthocyanin biosynthesis pathway candidate genes identified as part of this research were compared with other published model plant species and ornamental flowering plants such as grape, lily, onion, garlic, rice, etc. The results highlight gene families that are conserved and comparable across different plant species. Such information provides valuable insights into studying genetic relationships among plant species involving biological processes and molecular functions. These findings directly enhance breeding efforts geared to improve Amaryllidaceae plants for the benefit of the ornamental industry.
Review Publications
Favian-Vega, E., Meerow, A.W., Octavio-Aguilar, P., Iglesias-Andreu, L.G. 2022. Genetic diversity and differentiation in Zamia furfuracea (Zamiaceae): an endangered, endemic and restricted Mexican Cycad. Biodiversity and Conservation Journal. 67(3): 302310.
Campos-Rocha, A., Meerow, A.W., Machado, R.M., Mayer, J.L., Da Mota, R.C., Fontana, A.P., Ribeiro, O.B., Garcia, N.B., Dutilh, J.H. 2022. Out of the mud: two new species of Hippeastrum (Amaryllidaceae) from the Doce and Jequitinhonha River basins, Brazil. Plant Systematics and Evolution. 308:22. https://doi.org/10.1007/s00606-022-01805-3.
Griffith, P., Meerow, A.W., Calonje, M., Gonzalez, E., Nakamura, K., Francisco-Ortega, J. 2022. Genetic patterns of Zamia in Florida are consistent with ancient human influence and recent near extirpation. International Journal of Plant Sciences. 183(3):169-185. https://doi.org /10.1086/717657.
