Location: Subtropical Horticulture Research
2023 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
This document presents a summary of Project Number 6038-13210-003-000D, titled "Subtropical and Tropical Ornamental Genetic Resource Management, Characterization, and Genetic Improvement", which began in February 2018 and ended in January 2023. The new Project Number 6038-13210-004-000D, titled "Conservation, Management, Characterization, and Distribution of Subtropical and Tropical Ornamental Genetic Resources", has taken over from the previous project and will continue to provide scientific services to the ornamental horticulture industry. It is scheduled to start in February 2023 and end in January 2028.
The objectives of the terminated project were to ensure a secure and diverse stream of new genetic variation and enhanced germplasm for the subtropical/tropical ornamental horticulture industry. The project also aimed to 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. 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, evaluated, and distributed to various stakeholders. During the project year, over 3,500 propagules (i.e., seeds, budwood, rhizomes, corms) of 380 different ornamental accessions were distributed to 13 states in the U.S. and three international organizations. The researchers completed the analysis of molecular data for 100 species of Amaryllidaceae including the genus Hymenocallis and the tribe Clinantheae. The data include partial DNA sequences of 524 nuclear genes totaling 730,500 base pairs (bp) and partial plastome sequences of about 113,000 bp. The research work 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 was 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 were 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. An updated tree of life analysis of aligned DNA sequences across the Andean Amaryllidaceae that groups both Paramongaia species with three species of Clinanthus were presented. This research advances the taxonomic classification of the Amaryllidaceae. ARS researchers in Miami, Florida also received approval from the Office of Technology Transfer (OTT) for the public domain release of 15 amaryllis hybrid cultivars through the National Plant Germplasm System (NPGS) program.
Interspecific cross progenies of Portlandia grandiflora x P. coccinea ornamental plants were made during this project period. However, they were dramatically reduced by freezes during the winter of 2021 and 2022. They have been clonally propagated and regenerated in container trials under 50% shade in shade house conditions. Seeds of Handroanthus impetiginosus were received from Brazil and seedlings were raised under controlled greenhouse conditions. Due to the long-vacant inactive curator position as well as the retirement of key Investigator, adequate maintenance of ornamental germplasm fields, acquisition, regeneration, plantings, and evaluations have become issues.
Accomplishments
1. 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. From the amaryllis breeding program at the Subtropical Horticulture Research Station, Miami, Florida, approval and release of 15 Hippeastrum x hybridum cultivars were accomplished. The 15 cultivars each have novel characteristics that have not been observed in current commercial varieties. The releases will be provided to commercial nursery producers who request material for production, propagation, and further breeding. Material has been requested by two commercial growers in Florida already. The release of these varieties will expand the current availability of high-quality amaryllis hybrids for the commercial trade, and lead to the expansion of domestic production of this important ornamental crop.
2. ARS scientists in Miami, Florida, described two new species from South America that belong to the amaryllis family (Amaryllidaceae), an important group of ornamental flower bulbs. Clinanthus inflatus and Ismene virescens) are both found in the Andes of Peru. The team also transfer a mis-diagnosed name, Stenomesson rubrum, into Clinanthus as C. ruber. This contribution clarifies the taxonomy of this highly diverse ornamental family and increases our understanding of its biodiversity in the Americas. 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.
3. The research team also released a superior seedling selection of queen’s crape myrtle (Lagerstroemia speciosa ‘Big Pink’) with large pink flowers and precocious flowering habit. Such findings are published in various peer-reviewed scientific articles. This research directly enhances the breeding efforts geared to improve ornamental plants and the availability of high-quality flowering crops for the benefit of the tropical and sub-tropical horticultural industry.
